Phenotypic characterization of maize landraces from Sahel and Coastal West Africa reveals marked diversity and potential for genetic improvement

Landraces of maize (<i>Zea mays</i> L.) are invaluable sources of genetic variability for improving agronomic traits, and they hold great promise in developing new maize varieties with enhanced resilience to stresses. Even though phenotypic characterization is an inexpensive approach for elucidating variation hidden in genetic resources, information on the genetic diversity patterns in large collections of landraces remains limited and this constitutes a major impediment for their optimal utilization in modern maize breeding programs. We investigated the extent of phenotypic diversity among 196 maize landraces, representing gene pools from Burkina Faso, Ghana and Togo, and 14 improved populations/varieties from the Maize Improvement Program of International Institute of Tropical Agriculture (IITA-MIP). The germplasm was assessed for 26 agronomic traits. Highly significant differences (<i>P ) were observed among the accessions for all measured traits. Cluster analysis separated the maize germplasm into five major groups, differentiated largely by phenology and overall phenotypic appeal, enabling identification of outstanding genotypes for further screening for stress tolerance. Wide genetic diversity was observed between Burkinabe and improved gene pools, suggesting that the original Sahelian gene pool might not have contributed much to modern cultivars. This gene pool offers opportunities for pre-breeding by providing novel alleles for enriching elite maize germplasm. Shannon-Weaver diversity index (H’) revealed high genetic variability among the landraces (H’ = 0.73) and a narrow genetic base in the improved populations and varieties (H’ = 0.46). These results provide new insights into the potential of tropical maize landraces for genetic improvement of maize.</i>

玉米（Zea mays L.）地方品种是改良农艺性状的宝贵遗传变异资源，在培育抗逆性提升的玉米新品种方面具有巨大应用潜力。尽管表型鉴定是解析遗传资源中隐藏变异的低成本手段，但针对大型地方品种种质集合的遗传多样性模式的相关信息仍较为匮乏，这成为其在现代玉米育种项目中最优利用的主要阻碍。本研究对196份玉米地方品种的表型多样性程度展开分析，这些材料涵盖布基纳法索、加纳与多哥的本土基因库，以及来自国际热带农业研究所玉米改良项目（IITA-MIP）的14个改良种群/品种。对该种质资源的26个农艺性状进行了表型鉴定，结果显示所有被测性状在各供试材料间均存在极显著差异（P）。聚类分析将供试玉米种质划分为5个主要类群，类群间主要以物候期与整体表型性状差异为区分依据，据此可筛选出优异种质用于后续抗逆性鉴定。布基纳法索本土基因库与改良基因库间存在广泛的遗传多样性，这表明原始萨赫勒基因库对现代玉米品种的遗传贡献相对有限。该本土基因库可通过提供新的等位基因以丰富优良玉米种质资源，为玉米预育种工作提供新的机遇。香农-威纳多样性指数（Shannon-Weaver diversity index, H’）分析结果显示，地方品种间的遗传变异程度较高（H’=0.73），而改良种群与品种的遗传基础相对狭窄（H’=0.46）。本研究结果为热带玉米地方品种在玉米遗传改良中的应用潜力提供了新的理论依据与研究视角。