Balyejusa Kizito Elizabeth, Rönnberg-Wästljung Ann-Christin, Egwang Thomas, Gullberg Urban, Fregene Martin, Westerbergh Anna
Department of Plant Biology and Forest Genetics, Swedish University of Agricultural Sciences, Uppsala, Sweden.
Hereditas. 2007 Sep;144(4):129-36. doi: 10.1111/j.2007.0018-0661.01975.x.
Cassava (Manihot esculenta Crantz) is a starchy root crop grown in the tropics mainly by small-scale farmers even though agro-industrial processing is rapidly increasing. For this processing market improved varieties with high dry matter root content (DMC) is required. Potentially toxic cyanogenic glucosides are synthesized in the leaves and translocated to the roots. Selection for varieties with low cyanogenic glucoside potential (CNP) and high DMC is among the principal objectives in cassava breeding programs. However, these traits are highly influenced by the environmental conditions and the genetic control of these traits is not well understood. An S(1) population derived from a cross between two bred cassava varieties (MCOL 1684 and Rayong 1) that differ in CNP and DMC was used to study the heritability and genetic basis of these traits. A broad-sense heritability of 0.43 and 0.42 was found for CNP and DMC, respectively. The moderate heritabilities for DMC and CNP indicate that the phenotypic variation of these traits is explained by a genetic component. We found two quantitative trait loci (QTL) on two different linkage groups controlling CNP and six QTL on four different linkage groups controlling DMC. One QTL for CNP and one QTL for DMC mapped near each other, suggesting pleiotrophy and/or linkage of QTL. The two QTL for CNP showed additive effects while the six QTL for DMC showed additive effect, dominance or overdominance. This study is a first step towards developing molecular marker tools for efficient breeding of CNP and DMC in cassava.
木薯（Manihot esculenta Crantz）是一种块根富含淀粉的作物，主要由热带地区的小规模农户种植，尽管其农产工业加工正在迅速增长。对于这个加工市场而言，需要具有高干物质根含量（DMC）的改良品种。潜在有毒的氰基糖苷在叶片中合成并转运到根部。选择具有低氰基糖苷潜力（CNP）和高DMC的品种是木薯育种计划的主要目标之一。然而，这些性状受环境条件的影响很大，并且对这些性状的遗传控制尚未完全了解。利用两个在CNP和DMC方面存在差异的木薯育成品种（MCOL 1684和Rayong 1）杂交产生的S(1)群体，研究这些性状的遗传力和遗传基础。发现CNP和DMC的广义遗传力分别为0.43和0.42。DMC和CNP的中等遗传力表明这些性状的表型变异由遗传成分解释。我们在两个不同的连锁群上发现了两个控制CNP的数量性状位点（QTL），在四个不同的连锁群上发现了六个控制DMC的QTL。一个控制CNP的QTL和一个控制DMC的QTL彼此靠近定位，表明QTL存在多效性和/或连锁关系。两个控制CNP的QTL表现出加性效应，而六个控制DMC的QTL表现出加性效应、显性效应或超显性效应。本研究是开发用于木薯CNP和DMC高效育种的分子标记工具的第一步。
