Parker Matthew A
Department of Biological Sciences, State University of New York, Binghamton, NY, 13901.
Evolution. 1988 Mar;42(2):239-247. doi: 10.1111/j.1558-5646.1988.tb04128.x.
Polymorphism existed at 58% of the enzyme loci examined (11/19) in one population of the highly self-pollinated annual legume Amphicarpaea bracteata. Due to extreme gametic disequilibrium among loci, genetic variation in this population was structured into a small number of multilocus genotypes. Over 97% of the plants sampled could be grouped into two classes (biotypes "A" and "B"), each consisting of a few highly similar genotypes. The two classes had mutually exclusive sets of alleles at nine loci. These classes differed sharply in their disease resistance toward one isolate of the specialist fungal pathogen Synchytrium decipiens from their native habitat. All biotype A plants were strongly susceptible, and all biotype B plants were resistant. When plants of both biotypes were exposed to this pathogen in a greenhouse, the resistant biotype (B) exhibited a significantly higher growth rate. The strong association between plant disease-resistance phenotypes and allozyme variants implies that pathogen attack could be a major selective agent influencing the evolution of neutral or near-neutral alleles at enzyme loci in this plant.
在高度自花授粉的一年生豆科植物两型豆的一个种群中，在所检测的19个酶位点中有58%（11/19）存在多态性。由于位点间存在极端的配子不平衡，该种群的遗传变异被构建成少数几个多位点基因型。超过97%的采样植株可分为两类（生物型“A”和“B”），每类由少数高度相似的基因型组成。这两类在9个位点上具有互斥的等位基因组合。这两类对来自其原生栖息地的专性真菌病原体欺骗集壶菌的一个分离株的抗病性差异很大。所有生物型A植株都高度易感，而所有生物型B植株都具有抗性。当在温室中将两种生物型的植株暴露于这种病原体时，抗性生物型（B）表现出显著更高的生长速率。植物抗病表型与等位酶变体之间的强关联意味着病原体攻击可能是影响该植物酶位点中性或近中性等位基因进化的主要选择因子。
