Laboratoire de Biologie des Invertébrés, Institut National de la Recherche Agronomique, B.P. 2078, 06606, Antibes Cedex, France.
Theor Appl Genet. 1996 May;92(7):873-9. doi: 10.1007/BF00221900.
The inheritance of resistance of the self-incompatible Myrobalan plum Prunus cerasifera to the root-knot nematode Meloidogyne arenaria was studied using first a diallel cross between five parents of variable host suitability (including two highly resistant clones P.1079 and P.2175, a moderate host P.2032, a good host P.2646 and an excellent host P.16.5), followed by the G2 crosses P.16.5 × (P.2646 × P.1079) and P.2646 × (P.16.5 × P.1079). A total of 355 G1 and 72 G2 clones obtained from hard-wood cuttings sampled from trees in the field experimental design, then rooted in the nursery and inoculated individually in containers (5-10 replicates per clone) under greenhouse conditions, were evaluated for their host suitability based on a 0-5 gall-index rating under a high and durable inoculum pressure of the nematode. In the crosses involving the resistant P.1079 and P.2175 and the hosts P.2646 and P.16.5: (1) all of the G1 crosses of P.1079 were resistant while the G2 crosses segregated 1 resistant to 1 host, (2) the G1 crosses between P.2175 and either P.2646 or P.16.5 segregated 1 resistant to 1 host, and (3) all of the G1 progeny between P.2646 and P.16.5 were host. These results indicate that resistance is conferred by a single major dominant resistance gene (homozygous) in P.1079, and the same, or an allelic or a different, major dominant gene (heterozygous) in P.2175, and that P.2646 and P.16.5 are recessive for this (these) major resistance gene(s). As expected according to the hypothesis of a recessive genotype for P.2032, all of its hybrids with P.1079 were resistant, all of its hybrids with P.2646 and P.16.5 were host, and its hybrids with P.2175 segregated for resistance. Nevertheless, the 3∶2 segregation ratio of these latter hybrids suggests that clones bearing the P.2175 gene would have a selective advantage. Both resistance genes are completely dominant and confer a non-host behaviour that totally prevents the multiplication of the nematode. This is the first reported evidence of major nematode resistance genes towards M. arenaria in a species of the subgenus Prunophora in the genus Prunus. The symbols Ma1 for the P.2175 gene and Ma2 for the P.1079 gene are proposed.
利用五个不同适合度亲本（包括两个高度抗性克隆 P.1079 和 P.2175、一个中度适合度亲本 P.2032、一个良好适合度亲本 P.2646 和一个极好适合度亲本 P.16.5）进行自交不亲和西洋李李属樱桃对根结线虫 Meloidogyne arenaria 抗性的遗传研究，然后进行 P.16.5×(P.2646×P.1079)和 P.2646×(P.16.5×P.1079)的 G2 杂交。从田间试验设计的树木中采集硬木插条，获得了 355 个 G1 和 72 个 G2 克隆，然后在苗圃中生根，并在温室条件下单独接种到容器中（每个克隆 5-10 个重复），根据线虫高持久接种压力下的 0-5 个瘿指数评分评估其适合度。在涉及抗性 P.1079 和 P.2175 以及宿主 P.2646 和 P.16.5 的杂交中：(1) P.1079 的所有 G1 杂交均为抗性，而 G2 杂交则分离出 1 个抗性到 1 个宿主；(2) P.2175 与 P.2646 或 P.16.5 之间的 G1 杂交分离出 1 个抗性到 1 个宿主；(3) P.2646 和 P.16.5 之间的所有 G1 后代均为宿主。这些结果表明，P.1079 中的抗性由单个主要显性抗性基因（纯合）赋予，而 P.2175 中的相同、等位或不同的主要显性基因（杂合）赋予，P.2646 和 P.16.5 为该（这些）主要抗性基因的隐性。根据 P.2032 基因型为隐性的假设，其与 P.1079 的所有杂种均为抗性，与 P.2646 和 P.16.5 的所有杂种均为宿主，与 P.2175 的杂种则分离出抗性。然而，这些后者杂种的 3∶2 分离比表明，携带 P.2175 基因的克隆将具有选择优势。这两个抗性基因均完全显性，赋予非宿主行为，完全阻止线虫的繁殖。这是首次在李属西洋李属的一个种中报道对抗线虫 M. arenaria 的主要线虫抗性基因的证据。建议使用 P.2175 基因的 Ma1 和 P.1079 基因的 Ma2 符号。
