Department of Horticultural Sciences, University of Florida, Gainesville, FL 32611, USA.
Theor Appl Genet. 2010 Jun;121(1):37-46. doi: 10.1007/s00122-010-1289-6. Epub 2010 Feb 24.
Bacterial spot, one of the most damaging diseases of pepper, is caused by Xanthomonas euvesicatoria. This pathogen has worldwide distribution and it is particularly devastating in tropical and sub-tropical regions where high temperatures and frequent precipitation provide ideal conditions for disease development. Three dominant resistance genes have been deployed singly and in combination in commercial cultivars, but have been rendered ineffectual by the high mutation rate or deletion of the corresponding cognate effector genes. These genes are missing in race P6, and their absence makes this race virulent on all commercial pepper cultivars. The breeding line ECW12346 is the only source of resistance to race P6 in Capsicum annuum, and displays a non-hypersensitive type of resistance. Characterization of this resistance has identified two recessive genes: bs5 and bs6. Individual analysis of these genes revealed that bs5 confers a greater level of resistance than bs6 at 25 degrees C, but in combination they confer full resistance to P6 indicating at least additive gene action. Tests carried out at 30 degrees C showed that both resistances are compromised to a significant extent, but in combination they provide almost full resistance to race P6 indicating a positive epistatic interaction at high temperatures. A scan of the pepper genome with restriction fragment length polymorphism and AFLP markers led to the identification of a set of AFLP markers for bs5. Allele-specific primers for a PCR-based bs5-marker have been developed to facilitate the genetic manipulation of this gene.
辣椒细菌性斑点病是一种危害严重的病害，由丁香假单胞菌辣椒致病变种引起。该病原菌分布广泛，在高温和频繁降雨的热带和亚热带地区尤其具有破坏性，为病害的发展提供了理想的条件。三个主要的抗性基因已被单独或组合应用于商业品种中，但由于相应效应子基因的高突变率或缺失而失效。这些基因在 P6 菌系中缺失，这使得该菌系对所有商业辣椒品种都具有毒性。ECW12346 品系是辣椒中对 P6 菌系唯一具有抗性的来源，表现出非超敏性的抗性类型。对这种抗性的特征分析确定了两个隐性基因：bs5 和 bs6。对这些基因的单独分析表明，bs5 在 25°C 时比 bs6 具有更高的抗性水平，但两者结合可使 P6 完全具有抗性，表明至少存在加性基因作用。在 30°C 下进行的测试表明，这两种抗性都受到了很大程度的削弱，但两者结合提供了对 P6 菌系几乎完全的抗性，表明在高温下存在正上位性相互作用。利用限制性片段长度多态性和 AFLP 标记对辣椒基因组进行扫描，确定了一组用于 bs5 的 AFLP 标记。已经开发出用于基于 PCR 的 bs5 标记的等位基因特异性引物，以促进该基因的遗传操作。
