Identification of QTLs for Ralstonia solanacearum race 3-phylotype II resistance in tomato

Abstract

Resistance against a Ralstonia solanacearum race 3-phylotype II strain JT516 was assessed in a F(2:3) and a population of inbred lines (RIL), both derived from a cross between L. esculentum cv. Hawaii 7996 (partially resistant) and L. pimpinellifolium WVa700 (susceptible). Resistance criteria used were the percentage of wilted plants to calculate the AUDPC value, and bacterial colonization scores in roots and stem (hypocotyl and epicotyl) assessed in two independent greenhouse experiments conducted during the cool and hot seasons in Réunion Island, France. Symptoms were more severe during the cool season trials. Heritability estimates in individual seasons ranged from 0.82 to 0.88, depending on resistance criterion. A set of 76 molecular markers was used for quantitative trait loci (QTL) mapping using the single- and composite- interval mapping methods, as well as ANOVA. Four QTLs, named Bwr- followed by a number indicating their map location, were identified. They explained from 3.2 to 29.8% of the phenotypic variation, depending on the resistance criterion and the season. A major QTL, Bwr-6, and a minor one, Bwr-3, were detected in each season for all resistance criteria. Both QTLs showed stronger effects in the hot season than in the cool one. Their role in resistance to R. solanacearum race 3-phylotype II was subsequently confirmed in the RIL population derived from the same cross. Two other QTLs, Bwr-4 and Bwr-8, with intermediate and minor effects, respectively, were only detected in the hot season, demonstrating that environmental factors may strongly influence the expression of resistance against the race 3-phylotype II strain JT516. These QTLs were compared with those detected in the RIL population against race 1-phylotype I strain JT519 as well as those detected in other previous studies in the same genetic background against other race 1-phylotype I and II strains. This comparison revealed the possible occurrence of some phylotype-specific resistance QTLs in Hawaii 7996.

Bacterial Wilt Resistance in Tomato, Pepper, and Eggplant: Genetic Resources Respond to Diverse Strains in the Ralstonia solanacearum Species Complex

“…Hence, virulence patterns are generally not phylotype specific, although phylotype-specific resistance QTLs were identified by Carmeille et al (8) on the basis of two strains belonging to two phylotypes. Phylotype classification is indicative of the evolutionary past of the organism (9,10,22) because it was established from sequence variations observed in different housekeeping genes.…”

“…The resistance of tomato (reference accession Hawaii 7996) is controlled by several mapped quantitative train loci (QTLs) with major or minor and broad-spectrum or strain-specific effects (5,8,56,70,71,76). For eggplant, different patterns of genetic control have been described (14,74) whereas, for pepper, the expression of resistance is quantitative (45).…”

Genetic mapping of a major dominant gene for resistance to Ralstonia solanacearum in eggplant

“…Resistance in tomato was described as monogenic or polygenic with recessive to dominant effects, depending on the genetic material used and environmental conditions (Gonzalez and Summers 1995;Grimault et al 1995;Hanson et al 1996;Mohamed et al 1997;Scott et al 1988). Mapping studies have shown the involvement of generalist as well as strain-specific quantitative trait loci (QTLs) in S. lycopersicum Hawaii 7996 (Carmeille et al 2006;Mangin et al 1999;Thoquet et al 1996;Wang et al 2000). In addition, bulked segregant analysis has shown the presence of two incompletely dominant genes associated with resistance in tomato cultivar T51A (Miao et al 2009).…”

QTL Analysis for Resistance to Ralstonia solanacearum in Capsicum Accession ‘LS2341’

“…The resistance is described as polygenic, except for some tobacco accessions, and is largely dependent on environmental conditions, such as air and soil temperature and humidity (Hayward, 1991;Nishi et al, 2003). Several quantitative trait loci (QTLs) affecting BW resistance are located on several chromosomes in tomato (Carmeille et al, 2006;Danesh et al, 1994;Wang et al, 2000). Most of the resistance to viruses or bacterial diseases is mediated through hypersensitive reactions, and rejects intrusion of the pathogen (Boukema, 1980;Huang and Knopp, 1998); however, the pathogen of BW can enter resistant plant tissues and spread to some extent.…”