Institute of Agricultural Sciences, ETH Zurich, Plant Nutrition group, Eschikon 33, CH-8315, Lindau, Switzerland.
Research Institute of Organic Agriculture (FiBL), Ackerstrasse 113, CH-5070, Frick, Switzerland.
Appl Microbiol Biotechnol. 2018 Jun;102(12):5265-5278. doi: 10.1007/s00253-018-9005-6. Epub 2018 Apr 25.
Cowpea N fixation and yield can be enhanced by selecting competitive and efficient indigenous rhizobia. Strains from contrasting agro-ecologies of Kilifi and Mbeere (Kenya) were screened. Two pot experiments were established consisting of 13 Bradyrhizobium strains; experiment 1 (11 Mbeere + CBA + BK1 from Burkina Faso), experiment 2 (12 Kilifi + CBA). Symbiotic effectiveness was assessed (shoot biomass, SPAD index and N uptake). Nodule occupancy of 13 simultaneously co-inoculated strains in each experiment was analyzed by matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectrometry (MS) to assess competitiveness. Strains varied in effectiveness and competitiveness. The four most efficient strains were further evaluated in a field trial in Mbeere during the 2014 short rains. Strains from bacteroids of cowpea nodules from pot and field experiments were accurately identified as Bradyrhizobium by MALDI-TOF based on the SARAMIS™ database. In the field, abundant indigenous populations 7.10 × 10 rhizobia g soil, outcompeted introduced strains. As revealed by MALDI-TOF, indigenous strains clustered into six distinct groups (I, II, III, IV, V and VI), group III were most abundant occupying 80% of nodules analyzed. MALDI-TOF was rapid, affordable and reliable to identify Bradyrhizobium strains directly from nodule suspensions in competition pot assays and in the field with abundant indigenous strains thus, its suitability for future competition assays. Evaluating strain competitiveness and then symbiotic efficacy is proposed in bioprospecting for potential cowpea inoculant strains.
豇豆的固氮和产量可以通过选择有竞争力和高效的本土根瘤菌来提高。从肯尼亚基利菲和姆贝雷（肯尼亚）的对比农业生态区筛选了菌株。建立了两个盆栽实验，包括 13 个慢生根瘤菌菌株；实验 1（11 个姆贝雷+CBA+来自布基纳法索的 BK1），实验 2（12 个基利菲+CBA）。通过基质辅助激光解吸/电离飞行时间（MALDI-TOF）质谱（MS）分析同时共接种的 13 种菌株在每个实验中的共生有效性（生物量、SPAD 指数和 N 吸收）。在 2014 年短雨季的姆贝雷田间试验中，进一步评估了 4 种最有效的菌株。在盆栽和田间实验中，从豇豆根瘤固氮菌中提取的菌株，通过 MALDI-TOF 基于 SARAMIS™数据库，准确鉴定为慢生根瘤菌。在田间，丰富的土著种群 7.10×10 根瘤菌 g 土壤，竞争过引入的菌株。MALDI-TOF 显示，土著菌株聚类成六个不同的组（I、II、III、IV、V 和 VI），第三组最丰富，占分析的 80%的根瘤。MALDI-TOF 快速、经济实惠且可靠，可直接从竞争盆栽试验和丰富土著种群的田间的根瘤悬浮液中鉴定慢生根瘤菌菌株，因此，它适合未来的竞争试验。在生物勘探中，建议评估菌株的竞争力，然后评估共生功效，以寻找潜在的豇豆接种菌株。
