Table_1_A Genome-Wide Association Study Dissects the Genetic Architecture of the Metaxylem Vessel Number in Maize Brace Roots.XLSX

Metaxylem vessels in maize brace roots are key tissue, and their number (MVN) affects plant water and inorganic salt transportation and lodging resistance. Dissecting the genetic basis of MVN in maize brace roots can help guide the genetic improvement of maize drought resistance and lodging resistance during late developmental stages. In this study, we used 508 inbred lines with tropical, subtropical, and temperate backgrounds to analyze the genetic architecture of MVN in maize brace roots. The phenotypic variation in MVN in brace roots was evaluated in three environments, which revealed broad natural variation and relative low levels of heritability (h2 = 0.42). Stiff-stalk lines with a temperate background tended to have higher MVNs than plants in other genetic backgrounds. MVN was significantly positively correlated with plant height, tassel maximum axis length, ear length, and kernel number per row, which indicates that MVN may affect plant morphological development and yield. In addition, MVN was extremely significantly negatively correlated with brace root radius, but significantly positively correlated with brace root angle (BRA), diameter, and number, thus suggesting that the morphological function of some brace root traits may be essentially determined by MVN. Association analysis of MVN in brace roots combined 1,253,814 single nucleotide polymorphisms (SNPs) using FarmCPU revealed a total of nine SNPs significantly associated with MVN at P < 7.96 × 10–7. Five candidate genes for MVN that may participate in secondary wall formation (GRMZM2G168365, GRMZM2G470499, and GRMZM2G028982) and regulate flowering time (GRMZM2G381691 and GRMZM2G449165). These results provide useful information for understanding the genetic basis of MVN in brace root development. Further functional studies of identified candidate genes should help elucidate the molecular pathways that regulate MVN in maize brace roots.

玉米支柱根（maize brace roots）中的后生木质部导管（metaxylem vessels）是关键组织，其数量（MVN）可影响植株水分与无机盐的运输及抗倒伏能力。解析玉米支柱根后生木质部导管数量的遗传基础，有助于指导玉米生育后期抗旱性与抗倒伏性的遗传改良。本研究选取508份具有热带、亚热带及温带遗传背景的玉米自交系，对玉米支柱根后生木质部导管数量的遗传结构进行分析。在3个环境下对支柱根后生木质部导管数量的表型变异进行评估，结果显示其存在广泛的自然变异，且遗传力相对较低（h²=0.42）。具有温带遗传背景的硬秆自交系，其MVN数量通常高于其他遗传背景的材料。MVN与株高、雄穗主轴长、穗长及行粒数均呈显著正相关，这表明MVN可能会影响植株的形态发育与产量。此外，MVN与支柱根半径呈极显著负相关，而与支柱根角度（BRA，brace root angle）、直径及数量呈显著正相关，这提示部分支柱根性状的形态功能本质上可能由MVN决定。本研究结合1,253,814个单核苷酸多态性（single nucleotide polymorphisms, SNPs），采用FarmCPU方法对玉米支柱根MVN进行关联分析，共鉴定出9个在P<7.96×10^-7水平下与MVN显著关联的SNP位点。筛选得到5个MVN候选基因，其中3个（GRMZM2G168365、GRMZM2G470499及GRMZM2G028982）可能参与次生细胞壁形成，另外2个（GRMZM2G381691及GRMZM2G449165）可调控开花时间。上述结果为解析玉米支柱根发育过程中MVN的遗传基础提供了有益参考。对筛选得到的候选基因开展进一步功能研究，将有助于阐明调控玉米支柱根MVN的分子通路。