Grain discolouration has been noticed in rice over the years in Guyana. The disease has been a serious problem in affecting quality and yield of rice. A study was carried out to identify the causal agent of grain discolouration and to develop suitable disease management practices in rice. The initial identification revealed that Curvularia spp. was predominant in rice grains with expression of symptoms of grain discolouration from samples collected from various locations of Guyana. The Centre for Agriculture and Biosciences International (CABI) of the UK has confirmed the pathogen as Curvularia lunata, based on the amplification and sequence analysis of internal transcribed spacer (ITS) region of the rDNA. Pathogenicity test has proved that C. lunata is responsible for the cause of grain discolouration. Eight new-generation fungicides were tested against C. lunata under in vitro and field conditions. All fungicides recorded a significant inhibition of mycelial growth of the C. lunata under in vitro. Fungicides that exhibited higher than 70% inhibition of mycelial growth of C. lunata compared to the untreated control were further evaluated in multiple field trials. Application of Amistar Xtra 28 SC (Triazol, Estrobilurtina, Cyproconazol, Azoxystrobin) 1.5 mL L⁻¹; Glory 75 WG (Mancozeb + Azoxystrobin) at 3.0 g L⁻¹; Antracol 70WP (Propineb) at 5.0 g L⁻¹; and Carbendazim 50SC (Carbendazim 50%) at 1.5 mL L⁻¹ showed more than 50% reduction in the incidence of grain discolouration. The efficacy of Amistar Xtra 28 SC; Glory 75 WG; Antracol 70WP; and Carbendazim 50SC were further demonstrated in field trials established with three replicates and an individual plot size of 225 m² at farmers’ holdings in regions 2, 3, 4, 5 and 6 of Guyana. A significant reduction in grain discolouration was noticed from 48.58 to 92.85% in field demonstrations. In addition, these four fungicides have enhanced number of filled grains, 1000 grain weight and grain yield compared to control.

中文翻译：

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水稻病因鉴定和谷物变色处理

圭亚那多年来已经注意到稻米中的谷物变色。该病已成为影响稻米质量和产量的严重问题。进行了一项研究，以查明谷物变色的病因，并开发出适合水稻的疾病管理方法。初步鉴定显示该弯曲菌属。在从圭亚那各地采集的样品中，谷粒中主要表现出谷粒变色的症状。英国农业和生物科学国际中心（CABI）根据rDNA内部转录间隔区（ITS）区域的扩增和序列分析，已确认该病原体为弯弯曲菌。致病性试验证明了月球梭菌是造成谷物变色的原因。在体外和野外条件下测试了八种新一代杀真菌剂对月球梭菌的抗药性。在体外，所有杀菌剂均记录了对月球梭菌菌丝体生长的显着抑制。与未经处理的对照相比，对月球梭菌的菌丝体生长抑制作用高于70％的杀菌剂在多个田间试验中进行了进一步评估。Amistar Xtra 28 SC（Triazol，Estrobilurtina，Cyproconazol，Azoxystrobin）的应用1.5 mL L ^-1；在3.0 g L ^-1时的Glory 75 WG（Mancozeb + Azoxystrobin）；浓度为5.0 g L ^-1的Antracol 70WP（Propineb）；和多菌灵50SC（多菌灵50％）在1.5 mL L ^-1下显示出谷物变色的发生率降低了50％以上。Amistar Xtra 28 SC的功效；荣耀75 WG; Antracol 70WP；圭亚那第2、3、4、5和6区的农民所持土地上的三份重复样本和225 m ²的个体土地面积进一步证实了田间试验和Carbendazim 50SC 。在实地演示中，发现谷物变色从48.58大大降低到92.85％。此外，与对照相比，这四种杀菌剂的填充谷物数量增加，1000谷物重量和谷物产量提高。