Characterization of two recessive genes controlling resistance to all races of bacterial spot in peppers

Abstract

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.

Molecular mapping of a recessive stripe rust resistance gene yrMY37 in Chinese wheat cultivar Mianmai 37

“…Similarly, a small number of recessive genes have also been found to be involved in resistance reactions against powdery mildew including Pm5, Pm9, Pm26 and pm42 (Hua et al 2009;Hsam et al 2001) and leaf rust Lr30 (Dyck and Kerber 1981) and Lr48 (Saini et al 2002). Although a few types of recessive resistance genes are documented in crops, the resistance mechanism, which is generally distinct from that of dominant resistance genes, has remained unknown (Antony et al 2010;Piffanelli et al 2004;Vallejos et al 2010;Yan and Chen 2006).…”

The Genetic and Molecular Basis of Plant Resistance to Pathogens

“…In addition to the above mentioned classification for mostly dominant resistance genes, several recessive resistance genes have been identified in plants. For example, two recessive genes, bs5 and bs6, which control resistance to all known races of Xanthomonas euvesicatoria in peppers, have been characterized (Vallejos et al, 2010). In rice, a novel recessive resistance gene, xa34, was mapped to a 204-kb interval and confers resistance against Xanthomonas oryzae pv.…”

Research Article Multiple genetic resistances in Capsicum spp.

“…The latter is the most effective among the control measures. Several studies have aimed to understand the interaction between Capsicum and Xanthomonas (Jones et al, 2004;Vallejos et al, 2010;Ryan et al, 2011;Potnis et al, 2012), seeking for resistance sources (Costa et al, 2002;Riva-Souza et al, 2009;Moreira et al, 2013) by characterization of the gene expression (Jones et al, 1998;Riva et al, 2004b;Kiss et al, 2016), genetic inheritance (Riva et al, 2004a), developing molecular markers for resistance genes (Holdsworth and Mazourek, 2015), and use of transgenics (Zipfel and Jones, 2015). Despite these studies, few pure line cultivars that are resistant to BS are available in the seed market.…”