Department of Plant Pathology, University of California, Davis 95616, USA.
Phytopathology. 2013 Sep;103(9):935-40. doi: 10.1094/PHYTO-03-13-0074-R.
The root-knot nematode Meloidogyne hapla can reproduce on a wide range of crop species but there is variability in host range and pathogenicity both within and between isolates. The inbred strain VW9 causes galling but does not reproduce on Solanum bulbocastanum clone SB22 whereas strain VW8 causes little galling and reproduces poorly on this host. Comparison of reproduction on SB22 of nematode F2 lines generated from hybrids between strains VW8 and VW9 revealed that, whereas over half the lines produced no progeny, some lines reproduced to higher levels than did either parental strain. Using a genetic map previously generated using the same set of F2 lines, three quantitative trait loci (QTLs) were identified and positioned on linkage groups. A combination of two QTL alleles from one parent and one from the other was highly represented in F2 lines that exhibited higher reproduction than either parental strain but was absent from lines that failed to reproduce on SB22. This result suggests that sexual hybridization and assortment of opposing alleles leads to segregation of individuals with improved reproductive ability on a particular host. The genome sequence and integrated genetic and physical linkage map of M. hapla provide resources for identification of genes responsible for the identified QTL.
豌豆根结线虫能够在广泛的作物物种上繁殖，但在种内和种间，其寄主范围和致病性存在变异性。近交系 VW9 引起结瘤，但不能在 SB22 克隆上繁殖；而 VW8 则引起较少的结瘤，在该寄主上繁殖不良。比较 VW8 和 VW9 杂交产生的 F2 系在 SB22 上的繁殖情况表明，尽管超过一半的系没有产生后代，但有些系的繁殖水平高于亲本系。利用之前使用相同的 F2 系生成的遗传图谱，鉴定并定位了三个数量性状位点（QTL）到连锁群上。在表现出比亲本系更高繁殖力的 F2 系中，来自一个亲本的两个 QTL 等位基因和来自另一个亲本的一个等位基因的组合高度存在，但在不能在 SB22 上繁殖的系中不存在。这一结果表明，有性杂交和对立等位基因的重组导致了在特定寄主上具有改良繁殖能力的个体的分离。豌豆根结线虫的基因组序列和整合的遗传和物理连锁图谱为鉴定所鉴定的 QTL 相关基因提供了资源。
