DIALLEL ANALYSIS OF TOLERANCE TO DROUGHT IN COWPEA GENOTYPES

ABSTRACT The low use of technologies by farmers and the occurrence of biotic and abiotic stresses are limiting factors for cowpea production in the Brazilian Northeast region. The tolerance of genotypes to drought is an alternative to decrease the negative effects of stresses on cowpea production. Thus, the objective of this work was to identify parents and combinations of cowpea genotypes with high probability of generating segregating populations with tolerance to drought. Six cowpea genotypes were crossed in a complete diallel cross design, totaling 30 F2 populations, which were evaluated together with their parents in an experiment under water deficit at the experimental field of the Embrapa Mid-North, Teresina, State of Piauí, Brazil. A triple lattice incomplete block experiment design was used, with three replications, with experimental plot consisting of six 2-m plant rows. Fifteen plants per plot were sampled to evaluate their agronomic characteristics, whose results were subjected to analysis of variance and means were used to estimate the general and specific combining abilities. The genotypes showed significant differences in all characteristics evaluated, denoting the genetic variability of the population. The additive effects were more important than the non-additive effects, and maternal inheritance was detected. The genotypes BRS Xiquexique, Pingo-de-Ouro-1-2 and MNC99-510F-16-1 were the most promising for use in recurrent selection programs for tolerance to water deficit. The hybrid combinations (1) BRS Paraguaçu X (4) CNCx-698-128G, (2) Pingo-de-Ouro-1-2 X (3) BRS Xiquexique, (3) BRS Xiquexique X (5) Santo-Inácio, (4) CNCx-698-128G X (6) MNC99-510F-16-1 and (5) Santo-Inácio X (4) CNCx-698-128G showed potential for generating superior lineages regarding bean production and tolerance to water deficit.

摘要：巴西东北部地区农户技术应用普及率偏低，生物胁迫与非生物胁迫频发，二者共同构成制约当地豇豆生产的核心限制因素。借助基因型耐旱性以降低胁迫对豇豆生产的负面影响，是当前可行的育种策略。为此，本研究旨在筛选出可创制高概率获得耐旱分离群体的豇豆基因型亲本及杂交组合。本研究采用完全双列杂交设计（complete diallel cross design）对6个豇豆基因型开展杂交，共获得30个F₂群体；随后将上述群体与其亲本一同移植至巴西皮奥伊州特雷西纳市的巴西农业研究公司中北部试验站（Embrapa Mid-North）试验田，开展水分胁迫下的性状鉴定试验。试验采用三重格子不完全区组设计，设置3次重复，每个试验小区包含6行长度为2米的种植行。每个小区选取15株植株进行农艺性状调查，所得数据经方差分析（analysis of variance）后，通过均值估算各亲本的一般配合力（general combining ability）与特殊配合力（specific combining ability）。供试基因型在所有调查性状上均表现出显著差异，表明该群体蕴含丰富的遗传变异。研究结果显示，加性效应相较于非加性效应更为重要，且检测到母性遗传现象。基因型BRS Xiquexique、Pingo-de-Ouro-1-2及MNC99-510F-16-1是用于耐旱水分胁迫的轮回选择育种项目的最优候选亲本。以下5个杂交组合具备培育高产且耐旱优良品系的潜力：(1) BRS Paraguaçu × CNCx-698-128G；(2) Pingo-de-Ouro-1-2 × BRS Xiquexique；(3) BRS Xiquexique × Santo-Inácio；(4) CNCx-698-128G × MNC99-510F-16-1；(5) Santo-Inácio × CNCx-698-128G。