Zhu Jinming, Mickelson Suzanne M, Kaeppler Shawn M, Lynch Jonathan P
Department of Horticulture, Pennsylvania State University, University Park, PA 16802, USA.
Theor Appl Genet. 2006 Jun;113(1):1-10. doi: 10.1007/s00122-006-0260-z. Epub 2006 May 3.
Suboptimal phosphorus availability is a primary constraint for terrestrial plant growth. Seminal roots play an important role in acquisition of nutrients by plant seedlings. The length and number of seminal roots may be particularly important in acquisition of immobile nutrients such as phosphorus by increasing soil exploration. The objective of this study was to identify quantitative trait loci (QTL) controlling seminal root growth in response to phosphorus stress in maize, and to characterize epistatic interactions among QTL. Seminal root length and number were evaluated in 162 recombinant inbred lines derived from a cross between B73 and Mo17 in seedlings grown in a controlled environment. B73 and Mo17 significantly differed for seminal root length under low phosphorus, but not under adequate phosphorus conditions. Seminal root length of the population grown under low phosphorus ranged from 0 to 79.2 cm with a mean of 32.3 cm; while seminal root length of plants grown under high phosphorus ranged from 0.67 to 59.0 cm with a mean of 23.4 cm. Under low phosphorus, one main-effect QTL was associated with seminal root length and three QTL with seminal root number; under high phosphorus, two QTL with seminal root length and three QTL for seminal root number. These accounted for 11, 25.4, 22.8, and 24.1% of the phenotypic variations for seminal root length and number at low phosphorus, and seminal root length and number at high phosphorus, respectively. Di-genic epistatic loci were detected for seminal root length at low phosphorus (two pairs) seminal root number at low phosphorus (eight pairs), seminal root length at high phosphorus (four pairs), and seminal root number at high phosphorus (two pairs), which accounted for 23.2, 50.6, 32.2, and 20.3% of the total variations, respectively. Seminal root traits observed here were positively yet weakly correlated with shoot biomass in the field under low phosphorus, although no coincident QTL were detected. These results suggest that epistatic interactions are important in controlling genotypic variation associated with seedling seminal root traits.
磷有效性欠佳是陆地植物生长的主要限制因素。种子根在植物幼苗获取养分过程中发挥重要作用。种子根的长度和数量对于通过增加土壤探索来获取诸如磷等难以移动的养分可能尤为重要。本研究的目的是鉴定控制玉米种子根生长以响应磷胁迫的数量性状位点（QTL），并表征QTL之间的上位性相互作用。在可控环境中生长的幼苗中，对由B73和Mo17杂交产生的162个重组自交系的种子根长度和数量进行了评估。在低磷条件下，B73和Mo17的种子根长度存在显著差异，但在磷充足条件下则无显著差异。低磷条件下生长的群体种子根长度范围为0至79.2厘米，平均为32.3厘米；而高磷条件下生长的植株种子根长度范围为0.67至59.0厘米，平均为23.4厘米。在低磷条件下，一个主效QTL与种子根长度相关，三个QTL与种子根数量相关；在高磷条件下，两个QTL与种子根长度相关，三个QTL与种子根数量相关。这些分别占低磷条件下种子根长度和数量以及高磷条件下种子根长度和数量表型变异的11%、25.4%、22.8%和24.1%。在低磷条件下检测到两对控制种子根长度的双基因上位性位点、八对控制低磷条件下种子根数量的双基因上位性位点、四对控制高磷条件下种子根长度的双基因上位性位点以及两对控制高磷条件下种子根数量的双基因上位性位点，它们分别占总变异的23.2%、50.6%、32.2%和20.3%。尽管未检测到重合的QTL，但此处观察到的种子根性状在低磷田间条件下与地上部生物量呈正相关但相关性较弱。这些结果表明，上位性相互作用在控制与幼苗种子根性状相关的基因型变异中很重要。
