• Exp. Agric. (IF 2.089) Pub Date : 2019-02-28
Manuel Iván Gómez; Andrea Barragán; Stanislav Magnitskiy; Luis Ernesto Rodríguez

Remote sensors permit forecasting the nutrient status and yields in crops of economic importance in Colombia. The objective of this study was to determine the relationships between normalized difference vegetation index (NDVI) and yield as well as concentrations of ${\rm {N - NO}}_3^ -$ and K+ in stem sap of potato cultivars Diacol Capiro and Pastusa Suprema (Solanum tuberosum L., Group Andigenum) in relation to different fertilizer rates. Increasing doses (0, 1450, 1900 and 2375 kg ha–1) of macro- and micronutrient fertilizers were applied to determine NDVI behavior at 55, 75, 100, 125 and 150 days after planting. For Capiro, significant differences in NDVI readings (0.84–0.88) were found between phenological stages. In both cultivars, NDVI correlated positively with yield and K+ concentrations in stem sap during tuber filling and maturation, while in Capiro no correlation was established between NDVI values and ${\rm {N - NO}}_3^ -$ concentrations in stem sap. The NDVI readings could be used to forecast productivity and K status in potato Group Andigenum.

更新日期：2020-01-24
• Am. J. Potato Res. (IF 1.095) Pub Date : 2020-01-22
Jonathan A. D. Neilson, Colby J. Robertson, Emily W. Snowdon, Dmytro P. Yevtushenko

Abstract Fumigants are used to reduce disease pressure and there is some evidence of benefits through promotion of beneficial microorganisms. The current study examined the effect of fumigation and a soil freshener implement, as recommended by the fumigant manufacturer, on the microbial community in a potato field in Southern Alberta. Fumigation did not greatly reduce microbial species abundance or diversity, though there were changes to the community structure. Fumigation and use of the soil freshener increased tuber size profiles, but not marketable yield. Fumigation was effective at reducing wilt ratings, but there was no added benefit to using the soil freshener in the current study. This research highlights the need for management tools to decide whether fumigation and application method will increase profitability within a given production system.

更新日期：2020-01-23
• Am. J. Potato Res. (IF 1.095) Pub Date : 2019-12-24
Graham D. Ellis, Lisa O. Knowles, N. Richard Knowles

Abstract The vigorous growth phenotype of ‘Bondi’ is characteristic of high endogenous gibberellins, making it ideal for evaluating the efficacy of gibberellin biosynthesis inhibitors to improve allometric partitioning and production efficiency in potato. Foliar applications of prohexadione-calcium decreased foliar growth with no effects on tuber number, size, or yield. In contrast, when applied pre-tuberization, paclobutrazol decreased maximum foliar growth from 91 to 63 MT ha−1, increased tubers plant−1 from 6.4 to 8.9, and decreased average tuber fresh weight from 296 to 188 g tuber−1 with no reduction in tuber yield, which effectively increased the harvest index. However, when applied post-tuberization, PBZ reduced maximum foliar growth from 91 to 72 MT ha−1 with no effects on tuber number, size, or yield. Paclobutrazol can alter source/sink relationships in potato to increase production efficiency and this may translate to reduced agronomic inputs. Application timing and concentration are important for modulating tuber set and size.

更新日期：2020-01-04
• Am. J. Potato Res. (IF 1.095) Pub Date : 2019-12-20
James S. Busse, Paul C. Bethke

Abstract Attractive appearance is highly desirable for fresh market red-skinned potatoes. Red potatoes derive their skin color from anthocyanins. Some growers attempt to enhance red potato skin color by treating vines with the synthetic auxin 2,4-D. In this study, 2,4-D was applied twice at early bloom stage to ‘Red Norland’ potatoes and tubers were harvested weekly until plants senesced. 2,4-D rapidly increased anthocyanin quantity and altered anthocyanin composition. Average tuber mass at the final harvest was less for the 2,4-D-treatment than untreated controls. Elevated anthocyanin content resulting from 2,4-D persisted through 3 months storage. 2,4-D-treated potatoes did not differ from untreated controls in the number and depth of red pigmented cells in the phellem. Thus, changes in periderm cell division and expansion may not contribute to the 2,4-D response of ‘Red Norland’. Instead, the data suggest that 2,4-D application initiated a rapid change in anthocyanin accumulation that persisted into storage.

更新日期：2020-01-04
• Am. J. Potato Res. (IF 1.095) Pub Date : 2019-12-17
Maria A. Slugina, Alexey A. Meleshin, Elena Z. Kochieva, Anna V. Shchennikova

Abstract Starch turnover is important for plant response to abiotic stresses and plastidic starch phosphorylase Pho1a is a key enzyme regulating starch metabolism. In this study, we identified Pho1a coding sequences in seven wild tuber-bearing potato species. In Solanum tuberosum cv. Nadezhda grown at normal conditions, Pho1a transcription was low; it was detected in stems, leaves, flowers, and roots. After harvest, Pho1a expression in tubers of 16 S. tuberosum cultivars was either absent or low but progressively increased during storage at +4 °C, which corresponded to an increase in the content of reducing sugars. In the leaves of both cultivated and wild potato species, exposure to short-term cold stress downregulated Pho1a expression, especially at night, and stimulated starch degradation, but there was no uniform diurnal pattern in Pho1a expression dynamics. These findings indicate that Pho1a may have different functions in storage and photosynthetic organs of potato.

更新日期：2020-01-04
• Am. J. Potato Res. (IF 1.095) Pub Date : 2019-12-16
Dong Chil Chang, Ji Hong Cho, Chung Gi Cheon, Su Jeong Kim, Jung Hwan Nam, Yong Ik Jin

Abstract The objective of this study was to assess the efficacy of pre-plant light-sprouting (chitting) on hastening the maturation of potato. Four cultivars with different maturities (‘Superior’, ‘Haryeong’, ‘Seohong’, and ‘Jayoung’) were used over three different growing seasons from 2016 to 2018. Different degrees of physiological age were obtained by exposing the seed lots of each cultivar to sprout-inducing conditions (13–15 °C temperature and 40–50% relative humidity (RH) in 11–20 μmol m−2 s−1 of diffuse light), for 0, 2–4, 6–7, and 10–11 weeks before planting. As the sprout-inducing periods increased, seeds physiologically aged, as evidenced by the increase in the percent sprouted eyes and sprout length per tuber, and the resulting stem numbers per plant. Moreover, in a longer the chitting duration, the increase in the number of stems was highly correlated with the tendency to have more tubers per plant. Physiologically aged seed significantly hastened plant growth through the decreased number of days to emergence, tuberization, and canopy development for all cultivars regardless of the growing season. The accelerated growth of shoots and tubers resulted in an increase in the harvest index, yield, and specific gravity of tubers, with no effect on second growth. However, there were practically no consistent benefits in the early-maturing cultivar Superior. That made it possible for the crop, especially medium- and late-maturing cultivars, to be harvested earlier in the short growing season environment. The magnitude of light-sprouting-induced effects depended on the chitting duration regimes, the maturities of cultivars, and the growing season environments.

更新日期：2020-01-04
• Am. J. Potato Res. (IF 1.095) Pub Date : 2019-12-16
Karen Hills, Harold Collins, Georgine Yorgey, Andrew McGuire, Chad Kruger

Abstract Many factors are driving interest in improving soil health in potato production systems in the U.S. Pacific Northwest and beyond, including the need for enhanced sustainability and economic viability, and consumer preferences. Potato production poses a particular challenge in terms of soil health due to intensive tillage, minimal residue left on fields, short rotations, and the importance of managing soilborne pathogens. This review discusses existing soil health assessment methods and their relevance for the region and summarizes results of studies conducted in the Pacific Northwest and beyond, examining practices aimed at improving soil health and their effects on soil health, soilborne pathogens, yield and quality of potatoes, and net returns in potato production systems. These practices include reducing tillage; adjusting crop rotation length and species composition; reducing fumigation; and using cover crops, green manures, and organic amendments.

更新日期：2020-01-04
• Am. J. Potato Res. (IF 1.095) Pub Date : 2019-12-16
Raven A. Bough, David G. Holm, Sastry S. Jayanty

Fifteen potato genotypes were evaluated for flavor and related components using sensory analysis, metabolite analysis, and an instrumental measurement of hardness over two growing seasons. Bake and boil cooking methods were also compared. Several sensory attributes had a significant variation in both years, where positive or negative correlations to overall quality determined desirable or undesirable attributes, respectively. Desirable attributes in both years were potato-like and mealy texture, while undesirable attributes were bitter, earthy, and other off-flavors. Significant desirable attributes limited to a single season were buttery, creamy, and sweet. Significant undesirable attributes restricted to a single season were aroma intensity and woody. Relative amounts of metabolites across genotype and cooking methods were significantly different for 14 metabolites in 2015 and 30 metabolites in 2016. Metabolites consisted of hydrocarbons, terpenes, alcohols, an acid, furans, aldehydes, ketones, as well as halogenic, nitrogenous, and sulfurous compounds. Flavor is an inherently complex phenotypic trait that is difficult to assess without subjective sensory analysis, however, flavor biomarkers may enable objective high-throughput flavor phenotyping. Candidate metabolites for potato flavor biomarkers found in this study include furfural for buttery, potato-like, and umami; 2-ethylfuran, 2-pentylfuran, isomenthone, methional, 2-phenylacetaldehyde, dimethyl trisfulfide, and 2,2,3,4-tetramethylpentane for potato-like; 3-methylpentane for aroma intensity, bitter, earthy, woody, and other off-flavors; 2-methoxy-3-propan-2-ylpyrazine for aroma intensity; 3,4,5-trimethyl-2-cyclopenten-1-one for bitter; pentan-1-ol for earthy; 2-pentylfuran, (E)-hept-2-enal, pentanal, and (E)-2-methylpent-2-en-1-ol for woody; and 5-methylhexan-2-one for other off-flavors. Further, instrumental measurements of hardness were negatively correlated to mealy texture. Biomarkers, if validated, have the potential to enable objective flavor phenotyping, which would allow for more efficient flavor improvement within conventional breeding programs.

更新日期：2020-01-04
• Am. J. Potato Res. (IF 1.095) Pub Date : 2019-12-16
Dominika Boguszewska-Mańkowska, Krystyna Zarzyńska, Artur Nosalewicz

Abstract Potato plants are often exposed to soil drought, which results in crop losses, because potato root system is shallow. The aim of our study was to examine the relationship between root system architecture and drought tolerance. We measured rooting depth, total length, surface area, average diameter, and dry weight of the root system every 20 cm of soil depth. We examined four potato cultivars, two that were more tolerant to drought (Gwiazda and Tajfun), and two that were more sensitive (Oberon and Cekin). Our results showed different responses by the tested cultivars to drought. The root dry mass decreased in response to drought and this decrease was smaller in the more drought-tolerant cultivars. In response to drought, the more drought-tolerant cultivars developed elongated roots, but the roots of the less-tolerant cultivars remained the same length. The decrease in root diameter was also smaller in the more drought-tolerant cultivars.

更新日期：2020-01-04
• Am. J. Potato Res. (IF 1.095) Pub Date : 2019-12-12
John Bamberg

The potato crop has much exotic related germplasm, so optimizing the techniques for obtaining hybrid seeds from interspecific crosses is of interest to potato researchers and breeders, especially when the cross of interest is very difficult and few hybrid seeds are expected per pollination. A model plant of Solanum verrucosum (a particularly useful wild bridge species) was selected to have very uniform and robust flower and seed production in natural crosses as a backdrop for detecting effects of different emasculation techniques. For three uniform buds in single inflorescences, one was pollinated naturally (N) after no emasculation, one was emasculated by gently opening the corolla and plucking out only the immature anthers (A) with a tweezer, and one had total (T) removal of the sepals, corolla and anthers with a tweezers. Pollen of a highly fertile diploid tuberosum male was applied uniformly to all three buds within an inflorescence one day later. No pistil abortion occurred, excluding that as a limiting factor for getting hybrid seed. But both average fruit weight and average seeds per fruit were highly significantly reduced by emasculation in the pattern T < A < N, suggesting that the increasing physical trauma of emasculation progressively reduces seedset in S. verrucosum. In contrast, in similar crosses made within tuberosum cultivar females, pistil abortion was the only significant factor limiting hybrid seedset. We conclude that it could be valuable to find alternatives to physical emasculation for preventing selfing.

更新日期：2020-01-04
• Am. J. Potato Res. (IF 1.095) Pub Date : 2019-12-11
Guodong Zhang, Ruimin Tang, Suyan Niu, Huaijun Si, Qing Yang, Benoit Bizimungu, Sharon Regan, Xiu-Qing Li

Abstract Heat stress can seriously reduce the tuber yield of potato (Solanum tuberosum). Early maturing cultivars are usually less affected by heat than late cultivars, which is explained by the avoidance of long exposure to summer temperatures due to the short growing time of early maturing cultivars. To determine whether there are other mechanisms involved in heat tolerance of early cultivars, we conducted correlation analysis between field earliness and growth performance of 50 potato cultivars under both heat-stressed (HS, day/night 35 °C/28 °C) and control conditions (CK, day/night 22 °C/18 °C). We classified the 50 cultivars into 8 scales of earliness and grouped them into early, intermediate and late groups based on the information on field plant maturity in Canada. We found that cultivars known to be early in the field grew similar to late cultivars under heat stress in the greenhouse in terms of traits evaluated, such as chlorophyll content and plant height. Compared with late cultivars, the early cultivars did not show any sign of early maturity under heat stress conditions. The HS/CK ratios of chlorophyll content, plant height, and largest tuber weight (tuber size) were all significantly greater in early cultivars than in late cultivars. Tuber size and field earliness were negatively correlated in CK but positively correlated under heat stress. Clearly, in addition to avoidance, other mechanisms (such as pleiotropic effects of earliness genes) were involved in the better performance of early cultivars under heat stress. These results indicated that the cultivars reprogramed their plant maturity and development under heat stress.

更新日期：2020-01-04
• Am. J. Potato Res. (IF 1.095) Pub Date : 2019-12-04
Ying Su, Marcela Viquez-Zamora, Danielle den Uil, Jarno Sinnige, Hein Kruyt, Jack Vossen, Pim Lindhout, Sjaak van Heusden

Abstract Potato is playing an increasingly important role in food production. The development of new varieties is slow due to the genetic complexity of potato and the inefficient breeding process. Modern techniques, such as hybrid breeding and the introduction of new traits in specific, existing elite material, have not been reported in the development of new and improved potato varieties. This paper describes the first example of marker-assisted introgression of four different Phytophthora infestans resistance genes in selected highly homozygous, diploid potato lines. After two backcrosses and one selfing, the original line can be recovered with Phytophthora resistance, thus providing added value. After crossing two diploid lines, each with a different resistance gene, hybrids were obtained and tested for resistance to Phytophthora in small field trials. In these experiments, the hybrids with two resistance genes were more resistant than the plants with only one of the two resistance genes.

更新日期：2020-01-04
• Am. J. Potato Res. (IF 1.095) Pub Date : 2019-11-29
Melanie Kalischuk, John Hachey, Dallas Thomas, Dan Johnson, Lawrence Kawchuk

Pectobacterium atrosepticum is a pectolytic enterobacterium that causes blackleg in plants. Bacteriophage Peat2 was isolated from P. atrosepticum infected potato tissue and its genome sequenced. Analysis of the 48,659 bp genome revealed that Peat2 resembles the Myoviridae family Klebsiella pneumoniae bacteriophage JD001 and includes a CRISPR Cas 4 RecB-like nuclease. A lytic bacteriophage, Peat2 details provide important information for application as a biocontrol agent of disease caused by phytopathogenic P. atrosepticum.

更新日期：2020-01-04
• Am. J. Potato Res. (IF 1.095) Pub Date : 2019-11-22
David M. Spooner, Philipp Simon, John B. Bamberg, Kenneth M. Cameron

The Potato Introduction Station in Sturgeon Bay Wisconsin has maintained herbarium specimens as part of its operations. These specimens mostly were grown from seeds in the field plots or greenhouses, but also include original specimens made during germplasm collecting expeditions. The herbarium of the Station (herbarium acronym PTIS) has been transferred from the potato genebank in Sturgeon Bay Wisconsin to the Wisconsin State Herbarium (acronym WIS) in Birge Hall, University of Wisconsin-Madison where it is now fully integrated and curated and funded by WIS; PTIS is discontinued and is no longer maintained as a separate herbarium. Separately, maps and taxonomic literature that were used by the potato taxonomist in Madison were transferred to the Potato Station in Sturgeon Bay.

更新日期：2020-01-04
• Am. J. Potato Res. (IF 1.095) Pub Date : 2019-11-30
B. Gundersen, Debra Ann Inglis, M. Pavek, A. V. Karasev

Five fresh market potato cultivars commonly grown in western Washington were evaluated against Potato virus Y (PVY) O, NTN, and N-Wi using inoculated PVY-free plantlets in the greenhouse in 2015 and successive generations of seed tubers from foliar inoculated plants in 2016, 2017, and 2018. Mosaic displayed strongly on all cultivar by strain combinations, except All Blue by PVYO. Russet Burbank and Yukon Gold infected with PVYO had highest area under symptom progress curve values for leaf drop across all cultivars and years. Yields mostly were lowest for PVYO. More cracked tubers developed on G3 tubers in the field than greenhouse G2 or G1 plants. Chieftain infected with PVYO and PVYNTN, and Yukon Gold with PVYN-Wi had marked increases in tuber cracking by 2018. Cracking began at early plant growth stages; seed tuberborne rather than current season infections had higher cracking incidence; cracking became prevalent with succeeding seed tuber generations; cracking did not contribute to tuber weight loss during storage; and, PVY and tuber cracking substantially impacted yield.

更新日期：2020-01-04
• Am. J. Potato Res. (IF 1.095) Pub Date : 2019-11-22
Jaebum Park, Christine A. Hackett, Louise-Marie Dandurand, Xiaohong Wang, Walter S. De Jong

Abstract The golden and white potato cyst nematodes (Globodera rostochiensis and G. pallida, respectively) are devastating quarantine pests of potatoes. The most widely distributed pathotype of the golden nematode, Ro1, is well controlled by the H1 resistance gene. A pathotype that overcomes H1, Ro2, has been detected on several farms in New York State. To map Ro2 resistance gene(s), two autotetraploid parental clones – NY121 (Ro2 resistant) and NY115 (susceptible) – along with 182 F1 offspring were genotyped with 8303 SNP markers, and the resistance of each clone to Ro2 was assessed with a greenhouse pot assay. Analysis with TetraploidSNPMap identified two Ro2 resistance QTL on chromosome 5: one QTL was located at 26 cM and explained 24.4% of the variation for resistance, while the second at 59 cM co-localized with a marker (57R) known to be tightly linked to H1 and explained 23.8% of the residual variation. Subsequent inoculation with G. pallida revealed that the chromosome 5 locus at 26 cM also conferred some resistance against pathotype Pa2/3, explaining 9.2% of the variation. A second QTL that increased susceptibility to Pa2/3 was located at 15 cM on chromosome 10 and explained 6.9% of the variation. The resistance gene(s) at 26 cM on chromosome 5 may correspond to previously described Grp1; a marker diagnostic for this region would be useful for applied potato breeding.

更新日期：2020-01-04
• Am. J. Potato Res. (IF 1.095) Pub Date : 2019-11-26
Agnieszka Węgierek-Maciejewska, Aleksander Masny, Tomasz Wołkowicz, Agata Jagiełło, Edward Arseniuk

The published data indicate that the bacterium Clavibacter michiganensis subsp. sepedonicus (Cms) shows a notably low degree of intraspecific variation, and most of the molecular diagnostic methods could differentiate among subspecies groups but lacked the resolution to detect genetic diversity within subspecies. The present study describes effective differentiation of 50 isolates of C. michiganensis subsp. sepedonicus by the PCR MP method using five restriction enzymes (ApaI, PstI, BamHI, XmaI, HindIII). By analysing the electrophoretic patterns obtained by the PCR MP method performed with the applied restriction enzymes, each of the 50 tested isolates could be identified and distinguished from the remaining isolates. The PCR MP method of bacterial strain identification can be used in epidemiological studies, particularly for excluding the isolates of C. michiganensis subsp. sepedonicus as a source of primary infection.

更新日期：2020-01-04
• Am. J. Potato Res. (IF 1.095) Pub Date : 2019-12-02
Jeffrey A. Lojewski, Erik J. Wenninger

Abstract The efficacy of insecticides is often assessed in small-plot field trials that compare insect damage and yield loss relative to an untreated check, typically in a randomized complete block (RCB) design. When insect damage is not uniformly distributed across a field, differences among treatments might reflect differences in local pest pressure rather than differences in treatment efficacy. One potential way to account for patchy distributions is to use a “running check” in which each plot contains an insecticide treatment and its own untreated check. Any benefits of this approach must be weighed against the additional labor involved. Wireworms (Coleoptera: Elateridae) are soil-dwelling insects that typically exhibit patchy distributions that can confound insecticide efficacy trials. Several species of wireworms feed on potato tubers, causing damage that makes the tubers unmarketable and, aside from crop rotation, insecticides remain a cornerstone of wireworm management in potato. The current investigation evaluated insecticide efficacy trials targeting wireworms in potato by comparing two different analyses for the same data sets spanning five years and seven different studies. Data collected using the running check approach were analyzed using analysis of covariance and compared with analysis of variance as if the experiment were designed as a RCB. In a majority of cases, both methods resulted in similar levels of statistical power and similar conclusions; however, including data from the running check as a covariate did sometimes eliminate or reveal differences between treatments compared to ANOVA. Overall, given the similarity of the results and the additional labor involved in using running checks, the standard RCB design would have been appropriate for the experiments assessed here. However, for wireworms and other pests that exhibit patchy distributions, care must be taken when designing experiments and interpreting results.

更新日期：2020-01-04
• Am. J. Potato Res. (IF 1.095) Pub Date : 2019-11-29
Guoqi Wen, Athyna N. Cambouris, Noura Ziadi, Annick Bertrand, Mohamed Khelifi

Abstract Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say), is an important pest of potato crops. Potato foliar amino acids play essential roles in CPB growth. In this study, amino acids were classified into four groups according to their different roles in promoting CPB growth. Then, nitrogen (N) rate effects on the concentrations of amino acid groups were investigated under field conditions. Experiments were carried out with five N rates of 0, 60, 120, 180, and 240 kg N ha−1 in a randomized complete block design. Twenty leaves were collected at 40, 54, 68, and 82 days after planting (DAP) for amino acids analysis. Results showed that N rate had no significant effect on concentrations of each amino acid group at 40 DAP. However, their concentrations linearly increased as N rate increased at 54, 68, and 82 DAP, suggesting that higher N rates could potentially favor CPB growth after potato enters tuber initiation stage.

更新日期：2020-01-04
• Am. J. Potato Res. (IF 1.095) Pub Date : 2019-11-30
Olga Escuredo, Ana Seijo-Rodríguez, Laura Meno, María Shantal Rodríguez-Flores, María Carmen Seijo

Early blight caused mainly by Alternaria solani Soraeur and Alternaria alternata (Fr.) Keissl is one of the main diseases of potato. To improve forecasting of disease risk and to provide useful tools for a good decision support system, knowledge about the influence of environmental conditions on the Alternaria species, is necessary. The pattern distribution of the Alternaria spores during eight potato growing cycles in “A Limia” (north-west Spain), and the relationships between Alternaria levels and meteorological parameters were analyzed. Also, the phenology of the potato plants and the meteorological conditions during the study were monitored. Higher Alternaria peaks were found during plant senescence. Nevertheless, extremely high levels can appear starting the plant flowering, when the disease is more destructive. Statistical analysis showed a close relationship between temperature and relative humidity with the concentration of Alternaria in the air. Higher Alternaria levels were observed with a mean temperature above 20 °C and a mean relative humidity below 70%. It is also important to highlight that lower temperature and higher relative humidity during the night, favours the formation of Alternaria spores during the day. The present study showed how differences in weather can be related with the presence of Alternaria spores in the atmosphere of potato crop, and how climate change could affect the development of this agricultural crop. If Spain continues to experience increases in temperature events, longer duration and increasing intensity of early blight epidemics in potato crops are expected in future years.

更新日期：2020-01-04
• Am. J. Potato Res. (IF 1.095) Pub Date : 2019-11-29
Joseph B. DeShields, Natalia Moroz, Lauren E. Braley, Guadalupe Arlene Mora-Romero, Kiwamu Tanaka

The amplification of specific nucleic acid sequences with high specificity and sensitivity is an essential technique for pathogen detection. Recombinase polymerase amplification (RPA) is a rapid isothermal amplification method. Here, we demonstrate the end-point and real-time detection of Spongospora subterranea f. sp. subterranea (Sss) using RPA and potato mop-top virus (PMTV) using reverse transcription (RT)-RPA. Oligonucleotide primers were designed for amplification that target the internal transcribed spacer 1 (ITS1) region and the coat protein readthrough (CP-RT) domain for the detection of Sss and PMTV, respectively. Our data showed that real-time RPA can detect 100 of Sss sporosori per gram of soil, while real-time RT-RPA could detect in ~1 ng total RNA of the PMTV-infected tuber. For Sss detection, the R2 value for real-time RPA and real-time PCR was 98.0% by linear regression analysis in the concentration range of 100–34,000 sporosori per gram of soil. The developed RPA assay here may provide a useful alternative tool for the rapid, simple and reliable detection of Sss and PMTV in diagnostic laboratories and in-field testing.

更新日期：2020-01-04
• Am. J. Potato Res. (IF 1.095) Pub Date : 2019-11-27
Curtis M. Frederick, Paul C. Bethke

Abstract Chipping potatoes are bred for their ability to produce light-colored, defect-free chips. Chips with stem-end chip defect (SECD) have dark blemishes and are undesirable to consumers and chip processors. The heritability of SECD is not known and genetic loci linked to defect formation have not been identified. Chip processing varieties ‘Wauseon’ and ‘Lenape’ were crossed and tubers from parents and 191 progeny were evaluated over four years for chip color descriptors L*, a*, and b* and SECD score in January, March, and May. Broad sense heritability for SECD was 0.64 or greater at each sampling time. Genotype data were used to construct a 1282 cM linkage map. Nine quantitative trait loci (QTL) for SECD were detected, and seven overlapped QTL for chip color traits. The QTL identified are starting points for developing molecular markers that are used to select genotypes that produce light-colored chips and have resistance to SECD formation.

更新日期：2020-01-04
• Exp. Agric. (IF 2.089) Pub Date : 2019-02-05
C. M. Zimmer; I. P. Ubert; M. T. Pacheco; L. C. Federizzi

Multiflorous spikelets are found in oat Avena sativa L. subsp. nudisativa, which is characterised by elongated rachilla and variable number of florets per spikelet. One of the main factors limiting the exploration of multiflorous spikelets in oats, aiming to produce naked grains, is its variable expressivity. This work aimed to detect the environmental influence on the variable expressivity of multiflorous spikelet formation in oats and to estimate the heritability of this trait by analysing its expression in lower, middle and upper third of the panicle in 94 inbred lines of two crosses each. Two populations of recombinant inbred lines were screened for the spikelet formation in 2 years and sowing dates under field experiments. The results demonstrate that the variable expressivity of the multiflorous spikelet formation was highly influenced by the environmental conditions. The variable expressivity varied according to the genetic background, as well as the panicle third where spikelets were produced. The upper third of the panicle showed greater stability for the multiflorous spikelet formation, which is confirmed by the highest heritability coefficients observed in this third, regardless of the assessed population. Our results provide substantial evidences of the contribution exerted by environmental conditions in multiflorous spikelet formation in oats.

更新日期：2020-01-04
• Exp. Agric. (IF 2.089) Pub Date : 2019-01-31
Min Huang; Shengliang Fang; Shuanglü Shan; Yingbin Zou

The development of mechanised large-scale farming has led to changes in rice production systems. Increases in time of farming operations often occur under large-scale farming conditions, which can lead to delayed transplanting (DTP). In this study, field experiments were conducted in the late rice-growing season in 2016 and 2017 to compare the growth stages, growing-season temperature and yield attributes between normal transplanting with 15- to 20-day-old seedlings and DTP with 30-day-old seedlings of two rice cultivars. DTP resulted in 6- and 12-day delays in heading stage for both cultivars in 2016 and 2017, respectively. As a consequence, low temperature stress occurred at anthesis under DTP in both years, which led to significantly reduced spikelet filling and grain yield under DTP for both cultivars. These results confirm that DTP can reduce spikelet filling and grain yield due to low temperature stress at anthesis in machine-transplanted late-season rice. This finding highlights that greater efforts should be made to develop high-yielding short-duration rice cultivars to meet the development of mechanised large-scale rice farming.

更新日期：2020-01-04
• Exp. Agric. (IF 2.089) Pub Date : 2019-02-06
Judith Riedel; Nora Kägi; Laura Armengot; Monika Schneider

Overaged full-sun cacao plantations and the need for sustainable production systems call for combining rehabilitation of plantations with the establishment of agroforestry. We tested the effect of drastic rehabilitation pruning of old cacao tree stock and the introduction of both high- and low-diversity agroforestry on survival, growth and yield of T. cacao in a commercial plantation in peninsular Malaysia over a period of 5 years. We further determined the incidence of pests and diseases of cacao pods and assessed the performance of the whole system for smallholder farmers, including yields of by-crops. Rehabilitation pruning negatively affected cacao tree development and short-term yield. No more effects of pruning on cacao yield were observed starting in the third year on in the monoculture and starting in the fourth year on in low-diversity agroforestry. We found similar cacao tree development and yield in the low-diversity agroforestry and a common practice monoculture, suggesting that the implementation of agroforestry is a commercially feasible strategy, due to additional income generated through timber production. Reduced cacao tree development and yield in the high-diversity agroforestry were compensated by additional harvests of cassava and banana compared to monoculture. Incidence of cocoa pod borer (Conopomorpha cramerella) was lower in the agroforestry systems, especially the high-diversity system, while the incidence of black pod disease (Phytophthora spp.) did not differ between agroforestry and monoculture. The findings highlight the potential of agroforestry to reconcile ecologically sustainable land use with natural, cost-effective pest management. While pruning needs to be done with timing and disease pressure in mind to minimize short-term yield losses, this measure proved to be a feasible strategy for establishing agroforestry on extant plantations.

更新日期：2020-01-04
• Exp. Agric. (IF 2.089) Pub Date : 2018-12-27
Ingrid A. N. Lino; Danielle K. A. Da Silva; Júlio C. R. Martins; Everardo V. S. B. Sampaio; Leonor C. Maia

We evaluated the effects of cattle manure and inoculation with arbuscular mycorrhizal fungi (AMF) in maize plants growing in a semiarid area of Brazilian north-east in 2012 and 2013. Three isolates of AMF (Acaulosporalongula URM-FMA 07 and URM-FMA 03, Claroideoglomusetunicatum UNIVASF 06A) were used, with or without the application of cattle manure, during two growing cycles. In the first year, significant effects of inoculation were detected for straw yield only when the manure was applied. In the second year, there was an interaction between fertilisation and inoculation for plant height and grain yield, with the highest values in the fertilised treatments. Inoculation with A. longula demonstrated that mycorrhizal inoculation in field-grown plants could be an alternative management for improving plant growth and grain yield, reducing the use of cattle manure. The AMF sporulation and mycorrhizal colonisation were improved after inoculation, and A. longula URM-FMA 07 increased sporulation by more than 15 times while inoculation with C. etunicatum increased sporulation by more than 3 times. The mycorrhizal inoculation is a management practice that can be useful for recovering or maintaining AMF infective propagules in soil, showing potential to be used in large-scale field conditions in Brazilian semiarid. Although mycorrhisation presents high agricultural relevance due to benefits promoted to the soil and plants, the knowledge about the factors influencing the interactions among microorganisms, soil and plants need to be broadened aiming to achieve successful crop management in semiarid regions.

更新日期：2020-01-04
• Exp. Agric. (IF 2.089) Pub Date : 2019-01-31

Weedy rice species exhibit differential competitive ability and cause significant losses to rice yield. The present study was conducted to evaluate the competing ability of weedy rice accessions collected from foothills of eastern Himalayas and coastal Odisha grown in the presence of cultivated indica rice var. Swarna. The competitive ability of Swarna and weedy rices were estimated on the basis of (i) Swarna yield reduction under different durations of competition with weedy rice; and (ii) nutrient uptake by Swarna and weedy rice in competitive environment. There was significant yield reduction (18%) when competition was allowed until 6 weeks after emergence (WAE) compared to competition until 2 WAE, which was due to vigorous growth of weedy rice at early vegetative stage. The biomass accumulation and tiller number of weedy rice were significantly higher compared to Swarna. Odisha weedy rice accession recorded about 18, 57 and 24% higher N, P and K uptake, respectively, than Swarna. The highest yield reduction (22%) in Swarna was recorded when grown with OA1 and the lowest impact (7.7%) was recorded with AA2. As conclusion, management practices should be implemented within 2–4 weeks of emergence considering 5–10% acceptable yield loss of Swarna, and grain yield of cultivated rice was reduced significantly by high N and K uptake by weedy rice under a competitive environment.

更新日期：2020-01-04
• Exp. Agric. (IF 2.089) Pub Date : 2019-01-18
Oyakhilomen Oyinbo; Joseph James Mbavai; Mohammad Bello Shitu; Alpha Yaya Kamara; Tahirou Abdoulaye; Omadachi Ogbodo Ugbabe

In order to ensure sustainability of maize production in short-season environments of Nigeria, the Sudan savanna taskforce of Kano–Katsina–Maradi (KKM) Pilot Learning Site promoted short-season maize varieties in 2008 via Innovation Platforms (IPs). In the light of the promoted varieties, we evaluated the adoption and net benefits (productivity and income) of the maize varieties. We used cross-sectional household data elicited from 600 sampled households, double-hurdle model and propensity score matching. There was a remarkable increase in the adoption of short-season maize varieties in 2014 compared to what was obtained in a baseline conducted in 2008. Our empirical findings revealed that the adoption of the short-season maize varieties promoted through the IPs had significant productivity and income increasing effects. This implies that policy interventions to ensure sustainable maize intensification in the face of environmental limitations, such as early and late season drought, should intensify the promotion of short-season varieties in Sudan savannas. This will require well-concerted agricultural extension that can leverage IPs in view of its potentials.

更新日期：2020-01-04
• Exp. Agric. (IF 2.089) Pub Date : 2019-01-07

Establishment of young cacao trees in West Africa can be severely impeded by the onset of the dry season. To address this issue, a field experiment was conducted in Ghana to examine whether different mulch treatments and irrigation applied during the dry season combined with overhead shade could improve survival, early growth and yield of cacao. The mulch treatments used were polyethylene film and coffee husks placed around the young plants. Irrigation was used as a positive control, and no mulching or irrigation was a negative control. Three shade regimes were provided through different arrangements of Gliricidia sepium and plantains. Four different cacao clones were used in the study in a replicated split-plot design. Early growth of cacao was stimulated under the irrigation and plastic mulch treatments. Higher rates of photosynthesis during the dry season appeared to underlie these increases. Significantly higher early yields were also observed under the irrigation and coffee mulch treatments compared with the control. Plant survival varied significantly between treatments; irrigation was associated with the highest plant survival (94%), followed by the plastic mulch treatment (91%), coffee husk (82%) and the control (70%). There was also an increase in survival when more intense shading was used. Under zero mulch conditions, differences in survival were observed between clones. The clones P 30 [POS] and SCA 6 were more sensitive to drought (in terms of survival) than PA 150 and T 79/501. It is concluded that relatively simple mulching techniques or controlled irrigation in conjunction with appropriate shade management can significantly improve early establishment and cropping of cacao.

更新日期：2020-01-04
• Exp. Agric. (IF 2.089) Pub Date : 2019-01-21
Daniel Silveira Pinto Nassif; Leandro Garcia da Costa; Murilo dos Santos Vianna; Kassio dos Santos Carvalho; Fabio Ricardo Marin

The expansion of sugarcane crop to regions with lower water supply in Brazil has increased the importance of correct estimation of crop water requirements. Currently, the irrigation management is generally done using the crop coefficient (Kc) based on the FAO 56 bulletin. Kc is used to determine the potential water demand of the crop for a given period of time and is considered constant for each crop stage. However, some recent studies have shown that Kc can be significantly variable under different evapotranspiration (ETo) rates. This paper aimed to analyse sugarcane water consumption at different scales: plant (sap flow measurements by energy balance method); canopy (Bowen ratio energy balance method); and plant–atmosphere coupling (infrared gas analyser) to reduce the uncertainties on the irrigation practices. Measurements were taken at two experimental sites, where a modern Brazilian cultivar CTC 12 was grown under drip irrigation and an old main Brazilian cultivar (RB867515) was grown under sprinkler irrigation by a central pivot. The mean crop evapotranspiration (ETc) values by the Bowen ratio energy balance method were 2.92 and 3.68 mm d−1 for RB867515 and CTC 12, respectively, resulting in a mean Kc of 0.99 at the full vegetative growth stage. Kc values were dependent on ETo and varied between 0.2 and 1.7 for both cultivars. This occurred in a crop coupled to the atmosphere (Ω = 0.37) and was the same found in other coupled crops such as coffee and citrus. In conclusion, the sugarcane Kc for southeast Brazil presented temporal variability due to coupling conditions according to reference evapotranspiration, and this should be considered in irrigation management.

更新日期：2020-01-04
• Exp. Agric. (IF 2.089) Pub Date : 2019-02-20
Nidheesh Kammadavil Sahodaran; Abju K. Arun; Joseph George Ray

An experiment was carried out to assess the benefits of native arbuscular mycorrhizal fungi (AMF) for banana plants cv. ‘Nendran’. The AMF species applied were Funneliformis mosseae and Glomus microcarpum, which were identified in a previous survey as the most common root associates of Musa spp. in traditional monoculture banana fields. Spores of both the AMF species isolated from the natural banana fields were mono-cultured and used in the experiment, individually and in combination, at two inoculum spore levels (2500 or 5000 spores). We evaluated the root colonising potential of AMFs and their effects on plant height, chlorophyll content and leaf N, P and K concentrations at regular intervals up to 90 days after inoculation. All the inoculated plants showed more than 80% root colonisation. Increase in chlorophyll content in the leaves was found significant in all treatments, with the exception of the combination of 5000 spores of F. mosseae and 5000 spores of G. microcarpum each. Increases in leaf N, P and K were found in all the inoculated plants as compared to control (sterile soil without any AMF). While a significant reduction in soil available nitrogen and soil pH was observed in all treatments with inoculation, the soil available phosphorus and soil total organic carbon were increased by inoculation. Overall data revealed positive effects of AMF species in banana, especially during its early growth. As AMF species were isolated from fields differing in relation to banana variety and soil type and have positive effects in banana nutrition, an integrated soil fertility management using AMF appears promising.

更新日期：2020-01-04
• Exp. Agric. (IF 2.089) Pub Date : 2019-03-04
Muhyideen Oyekunle; Shehu G. Ado; Inuwa S. Usman; Rekiya O. Abdulmalik; Hauwa O. Ahmed; Lateefat B. Hassan; Muhammad A. Yahaya

Maize (Zea mays L.) grain yield is severely constrained by drought and this study was conducted to assess gains in grain yield and other traits of released maize cultivars. Twenty-three maize cultivars plus a check were evaluated under drought and well-watered conditions at Zaria and Kadawa during 2015/2016 and 2016/2017 dry seasons. The 24 cultivars were evaluated using 6 x 4 lattice design with three replications. Genotypes differed significantly for all measured traits except anthesis-silking interval (ASI), husk cover, and number of ears per plant under drought, and ASI, husk cover, and ear aspect under well-watered conditions. Under drought, grain yield ranged from 2251 kg ha−1 for SAMMAZ 31 to 4938 kg ha−1 for SAMMAZ 19, with a genetic gain of 1.93% yr−1. Under well-watered conditions, grain yield varied from 3082 kg ha−1 for SAMMAZ 37 to 5689 kg ha−1 for SAMMAZ 51, with the same genetic gain found under drought conditions. Grain yield reduction as a result of drought was 28.4% and performance under drought predicted performance under well-watered conditions better than vice versa with regression coefficient value of 0.8. Grain yield had significant correlations with all measured traits under both water conditions, except for husk cover, plant and ear heights under drought. Our data revealed that substantial genetic gains have been made in breeding for high grain yield cultivars under drought and well-watered conditions over a period of 16 years in Nigeria.

更新日期：2020-01-04
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