中国西南水稻白叶枯病菌遗传多样性垂直分布格局

针对我国西南稻区特有的立体气候和农业生态系统,利用rep-PCR和IS-PCR技术构建不同海拔稻区白叶枯病菌的DNA指纹图谱,聚类分析病菌的遗传多样性。结果表明:1西南稻区白叶枯病菌的遗传多样性十分丰富,共包含56种分子谱型,不同海拔稻区病菌的分子谱型种类明显不同;2白叶枯病菌的遗传多样性指数和丰富度指数在不同海拔稻区存在显著差异,其以中海拔稻区最高,低海拔稻区次之,高海拔稻区最低;3不同气候带白叶枯病菌的遗传多样性呈现出随着气候带温度降低而逐步减小的趋势;4聚类分析结果显示,56种分子谱型可分为9个遗传家系,低海拔稻区的菌株主要集中在lineage1和lineage2,中海拔稻区的菌株主要集中在lineage3~lineage6,而高海拔的主要集中在lineage3~lineage5。不同海拔稻区的菌株在变异程度上存在明显不同,因此,根据病菌致病型布局抗性基因时,应充分考虑菌株间遗传多样性的差异以及地区间病菌的变异强度,以减缓病菌在寄主选择压力下的变异速度,避免品种抗性丧失的周期过短。

Vertical distribution patterns of genetic diversity of Xanthomonas oryzae pv. oryzae in Southwest China

Based on the specific agro-ecological system and vertical climate in Southwest China, two polymerase chain reaction- based assays (rep-PCR and IS-PCR) were used to evaluate the population structure of Xanthomonas oryzae pv. oryzae (Xoo) from different elevation ranges (150 to 2 600 m) in Southwest China, which belong to six climate zones - north tropical climate zone, south subtropical climate zone, central subtropical climate zone, north subtropical climate zone, south temperate climate zone and cold temperate zone. A total of 218 isolates were tested in the research, out of which 73 isolates were collected from low elevation range (150?1 200 m), 90 isolates from medium elevation range (1 200?1 800 m) and 55 isolates from high elevation range (1 800? 2 600 m). The genetic diversity of Xoo was high in Southwest China, a total of 56 haplotypes were identified. The Xoo haplotypes in different elevation ranges were different, of which 18 were tested in high elevation range, 28 in low elevation range and 34 in medium elevation range. Although genetic diversity of Xoo was high, only H10 and H39 of haplotypes were tested in all the three different elevation ranges. Significant differences in the genetic diversity (Shannon Wiener index) of Xoo were observed among different elevation ranges. According to t-test, Shannon Wiener index in low and medium elevation ranges was significantly higher (P < 0.05) than that in high elevation range. However, no significant difference (P > 0.05) existed between medium and low elevation ranges. The genetic diversity of Xoo gradually reduced with decreasing temperature in different climate zones. Basis on cluster analysis of UPGMA, the 56 haplotypes of Xoo strains constituted nine putative genetic lineages. While strains from low elevation occurred under lineage 1 and lineage 2, strains from medium and high elevations occurred under lineage 3 to lineage 6 and lineage 3 to lineage 5. There were visible differences in Xoo strains from different elevation ranges. It was therefore recommended to take into account genetic diversity and variation degree of Xoo when laying out resistant genes based on haplotypes. This could slow down the rate of variability of Xoo strains on host selection pressure and avoid rapid lose of rice resistance.