遗传搭车与方差分析在水稻定向选择群体的抗旱性位点分析中的初步应用

水稻抗旱性属于复杂性状，近年的遗传研究日益关注胁迫下的产量相关位点。选用来自同一抗旱性较好的供体亲本（BG300），具有两种遗传背景（IR64和特青）和两种选择条件（低地和旱地）的4个水稻高代回交（BC₂）抗旱性定向选择导入系群体。通过SSR分子标记，检测群体中供体等位基因的导入频率，分析了选择条件和遗传背景对供体等位基因导入频率的影响。在此基础上，利用基于遗传搭车原理的卡方检验对等位基因导入频率的偏离进行检测，同时结合表型-基因型方差分析（ANOVA）的方法，对上述群体进行了和抗旱性相关位点的QTL分析。共检测到显著位点24个，其中卡方检验发现20个，方差分析检测到8个。有4个被这两种方法都检测到，很可能是与胁迫下的产量直接相关的位点。同时也对非胁迫下的产量位点进行了检测，发现上述抗旱性位点与非胁迫下产量的关系不大。还就选择条件和遗传背景的效应等对目标性状QTL定位的影响进行了讨论。研究结果将为进一步的水稻抗旱性分子育种研究提供有用的信息和材料。     

Observed and predicted changes over eight years in frequency of barley powdery mildew avirulent to spring barley in France and Denmark

Aerial populations of Blumeria graminis f.sp. hordei were studied in two French and two Danish regions from 1991 to 1999, at a time of year when only winter barley was present. A high frequency of genotypes not able to grow on the spring-sown crop of the previous growing season (denoted 'spring-avirulent') was observed in most years and regions. This frequency increased with increasing proportion of winter barley; it was highest in France and decreased in general over the 8-year period. Most of the spring-avirulent genotypes possessed the V _{a 22} virulence gene, matching a resistance that has never been present in barley cultivars grown in Europe. A hypothetical cropping system, including winter- and spring-sown crops with three resistance genes altogether, was constructed to mimic the utilization of host cultivars in the four regions. Results from a mathematical model simulating changes in the composition of the pathogen population in this system, demonstrated that selection solely due to host resistance genes, i.e. without assuming any cost of virulence, might lead to such results as those observed. The changes in frequency of spring-avirulent genotypes and the frequency of unnecessary virulence genes may be predicted from the proportion of the barley area sown with winter barley, the use of resistance genes in the cultivars, the initial composition of the pathogen population, and hitch-hiking due to gametic disequilibria.