Abstract Pigeonpea (Cajanus cajan) originated in India and is now a major source of protein in countries in tropical and subtropical regions worldwide. However, little is known about the effect on crop yields of inoculation with appropriate rhizobia strains. The objective of this study was to explore the possibility of improving pigeonpea yields in the Caribbean region, by inoculating with selected N-fixing symbionts. To achieve the study objective, we selected three elite strains of the genus Bradyrhizobium isolated from root nodules of pigeonpea in the Dominican Republic, we formulated them using innovative carriers, and finally we tested the formulated inoculant on eight farms located in the Dominican Republic. Three different carriers (sewage sludge, pine bark biochar and poultry litter) plus perlite as control were tested for the formulation. The first step was to test bacterial survival in the different carriers at different times up to one year (shelf-life). Pine bark biochar and the control resulted in the best shelf-life and were selected for the field experiment. The experimental design comprised two pigeonpea cultivars and five fertilisation strategies: Inoculation with three Bradyrhizobium strains without nitrogen (N) fertilisation, plus two non-inoculated controls one of them fertilised with 125 and 210 kg N ha−1 in non-irrigated and irrigated fields respectively. Nodule occupancy by the inoculated bacterial strain depended solely on the level of soil native nodulating bacteria and not on the bacterial strain or the carrier. Inoculation produced, on average, a significant yield increase compared to the non-inoculated non-N-fertilised control. Furthermore, the yield with the inoculated treatments did not significantly differ from the yield of the N-fertilised control. However, either inoculation or N-fertilisation were ineffective in two out of the eight fields with more than 104 nodulating bacteria g soil−1, compared to the non-inoculated non-N-fertilised control. Yield was neither significantly affected by the bacterial strain nor by the cultivar-strain interaction, and therefore, the two cultivars can be considered promiscuous. Neither carrier had a significant effect on yield. Thus, inoculants based on strains of Bradyrhizobia isolated from the root nodules of pigeonpea, formulated with pine bark biochar or perlite as carrier, are recommended as a good strategy to ensure food security in tropical agroecosystems with pigeonpea.

中文翻译：

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接种以生物炭为载体配制的天然慢生根瘤菌菌株可提高木豆 (Cajanus cajan L.) 的性能

摘要 鸽豆（Cajanus cajan）起源于印度，现在是世界热带和亚热带地区国家的主要蛋白质来源。然而，关于接种合适的根瘤菌菌株对作物产量的影响知之甚少。本研究的目的是探索通过接种选定的固氮共生体来提高加勒比地区木豆产量的可能性。为实现研究目标，我们选择了从多米尼加共和国木豆根瘤中分离出的慢生根瘤菌属的三个优良菌株，我们使用创新载体对其进行了配制，最后我们在位于多米尼加共和国的八个农场中测试了配制的接种剂。三种不同的载体（污水污泥、松树皮生物炭和家禽垫料）加上作为对照的珍珠岩对配方进行了测试。第一步是在长达一年的不同时间（保质期）测试不同载体中的细菌存活率。松树皮生物炭和对照品的保质期最好，并被选作田间试验。实验设计包括两个木豆栽培品种和五种施肥策略：接种三个不施氮 (N) 的慢生根瘤菌菌株，加上两个未接种的对照，其中一个在非灌溉和灌溉田中分别用 125 和 210 kg N ha-1 施肥分别。接种细菌菌株的根瘤占有率仅取决于土壤天然根瘤菌的水平，而不取决于菌株或载体。与未接种的未施氮肥的对照相比，接种平均产生显着的产量增加。此外，接种处理的产量与施氮对照的产量没有显着差异。然而，与未接种未施氮肥的对照相比，接种或施氮肥在 8 个土壤中超过 104 个根瘤菌 g 土壤-1 的两个田间无效。产量既不受细菌菌株的显着影响，也不受栽培品种-菌株相互作用的显着影响，因此，两个栽培品种可以被认为是混杂的。两种载体都对产量没有显着影响。因此，基于从木豆根瘤中分离出的慢生根瘤菌菌株，以松树皮生物炭或珍珠岩为载体配制的接种剂被推荐为确保木豆热带农业生态系统粮食安全的良好策略。