Screening of cowpea accessions for cowpea aphid resistance

ABSTRACT Cowpea (Vigna unguiculata) genotypes may preserve important characteristics of potential use for the genetic breeding of this species. This study aimed to characterize sources of genetic resistance to the cowpea aphid (Aphis craccivora), among accessions maintained at the cowpea germplasm bank of the Universidade Federal do Ceará (Brazil), in order to suggest crossing options for obtaining superior cultivars. Twenty-one local accessions were assessed together with two genotypes as resistant checks and two others as susceptible checks. A randomized complete block design, with four replications, was used. Counts of live adults and nymphs per plant were used to evaluate the genotypic resistance and, based on the ranking of these data, the effective resistance was estimated. The applied approach showed to be effective to discriminate the genetic variability for cowpea aphid resistance, identifying antibiosis as the probable resistance mechanism. Four genotypic groups were identified: resistant, intermediate, susceptible and highly susceptible. Thus, for a short-time cultivar release strategy, backcrosses are suggested between the BRS Guariba cultivar (recurrent parental, with good agronomic traits) and aphid-resistant accessions, such as Enrica Pobre (CE-36), Das Almas (CE-07), CE-51 (selected within CE-13) and Ritinha (CE-08). However, for a long-term breeding strategy, crossings between the most dissimilar accessions are suggested, using resistant genitors (e.g. BRS Guariba, Enrica Pobre, Das Almas, CE-51 and Ritinha) and others with good commercial and agronomic attributes.

摘要：豇豆（Vigna unguiculata）种质可保留该物种遗传育种所需的关键性状。本研究以巴西塞阿拉联邦大学（Universidade Federal do Ceará）豇豆种质资源库（germplasm bank）保存的种质为材料，旨在鉴定抗豇豆蚜（Aphis craccivora）的遗传资源，为选育优良豇豆品种提供杂交组合思路。本试验共评估21份地方种质，同时设置2份抗蚜对照种质与2份感蚜对照种质。采用随机完全区组设计（randomized complete block design），设置4次重复。以单株存活成虫及若虫数量作为抗虫性评价指标，基于该数据的分级结果估算各种质的实际抗虫水平。本研究所用方法可有效区分豇豆蚜抗性的遗传变异，并推测抗生性（antibiosis）为该抗虫性的主要作用机制。研究共划分4个抗虫类别：抗虫、中间型、感虫及高感虫。针对短期品种推广策略，建议以兼具优良农艺性状的BRS Guariba品种作为轮回亲本（recurrent parental），与Enrica Pobre（CE-36）、Das Almas（CE-07）、CE-51（CE-13选育品系）及Ritinha（CE-08）等抗蚜种质开展回交（backcrosses）育种。而针对长期育种策略，则建议选用遗传差异最大的抗蚜亲本（如BRS Guariba、Enrica Pobre、Das Almas、CE-51及Ritinha）与其他具备优良商品及农艺性状的种质进行杂交配置。