Cowpea (Vigna unguiculata L. Walp.) is a key climate-resilient legume for food security, especially in sub-Saharan Africa. Cowpea yields are limited by edaphic stresses including drought and low phosphorus (P) availability. Identifying genotypes with advantageous root phenotypes can facilitate breeding for improved yield in marginal environments. We evaluated 50 elite genotypes from African and U.S. sources for seedling root architecture and root hair length and density. Significant genotypic variation was detected for all phenes, and high heritability was observed for architectural phenotypes including primary root length (77%), basal root number (72%), and taproot branching density (67%). Moderate heritability was detected for root hair length and density among different root classes (34 to 63%), which were positively associated with each other. Principal component analysis identified three clusters, primarily defined by seed dimension and seedling root architecture. Genotypes were identified with longer root hairs (TVu-7778, Vita7, and Sanzi) and longer taproots (IT96D-610, IT98K-111-1, and IT97K-499-35), as potential parents. Root phenotypes, grain, and fodder yield were assessed on a subset of 20 genotypes under contrasting P availability in the field. Some seedling root phenotypes were significantly related to mature plant dry fodder weight (taproot hair density) and to grain yield (lateral root hair density) under low P. Root hairs are positively related to plant productivity under low P. We suggest selection for longer primary roots, as more basal and lateral root roots may be beneficial for cowpea in drought and low P environments. These findings suggest seedling root phenotypes can support cowpea breeding for suboptimal environments.

中文翻译：

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对豇豆幼苗根系结构进行表型分析揭示了对培育磷高效品种很重要的根系

豇豆（豇豆）L. Walp.) 是粮食安全的关键气候适应豆类，特别是在撒哈拉以南非洲地区。豇豆产量受到土壤胁迫的限制，包括干旱和低磷 (P) 可用性。识别具有有利根表型的基因型可以促进在边缘环境中提高产量的育种。我们评估了来自非洲和美国的 50 种优良基因型的幼苗根结构和根毛长度和密度。检测到所有表型的显着基因型变异，并且观察到结构表型的高遗传性，包括初生根长度 (77%)、基根数 (72%) 和主根分枝密度 (67%)。不同根类（34％至63％）的根毛长度和密度检测到中等遗传力，它们彼此呈正相关。主成分分析确定了三个集群，主要由种子维度和幼苗根结构定义。将具有较长根毛（TVu-7778、Vita7 和 Sanzi）和较长主根（IT96D-610、IT98K-111-1 和 IT97K-499-35）的基因型鉴定为潜在亲本。根表型、谷物和饲料产量在田间对比 P 可用性下对 20 个基因型的一个子集进行了评估。一些幼苗根表型与成熟植物干饲料重量（直根毛密度）和低磷下的籽粒产量（侧根毛密度）显着相关。根毛与低磷下的植物生产力呈正相关。我们建议选择更长的初级根，因为在干旱和低磷环境中，更多的基部和侧根可能对豇豆有益。