Evaluating Quantitative Trait Locus Resistance in Tomato to Multiple Xanthomonas spp.

Abstract

Bacterial spot of tomato is a foliar disease caused by four Xanthomonas species. Identifying genetic resistance in wild tomatoes and subsequent breeding of varieties has been a strategy to reduce the loss from this disease because control using pesticides has been ineffective. Three independent sources of resistance have been identified with quantitative trait loci (QTL) mapping to the centromeric region on chromosome 11. These sources are derived from Hawaii 7998 (QTL-11A), PI 114490 (QTL-11B), and LA2533 (QTL-11C). To determine which QTL introgression from chromosome 11 provides the greatest resistance to multiple species, we developed near-isogenic lines (NILs) using marker-assisted backcrossing. In parallel, we developed an NIL that contains Rx-4/Xv3, which provides major gene resistance to Xanthomonas perforans. Additionally, we combined Rx-4/Xv3 resistance with QTL-11A. These sources of resistance were independently introduced into the susceptible parent, OH88119. During a 3-year period from 2016 to 2018, we evaluated backcross-derived families and NILs from each source in independent field trials inoculated with X. perforans, X. euvesicatoria, or X. gardneri. Our results suggest that both QTL-11C and QTL-11A combined with Rx-4/Xv3 provide effective genetic resistance against multiple Xanthomonas species. In addition, we provide evidence for additive to dominant genetic action for the QTL introgressions.

Tomato SlPUB24 enhances resistance to Xanthomonas euvesicatoria pv. perforans race T3

“…As a tomato source with broad-spectrum resistance to bacterial spot, PI 114490 has been used in various breeding programs to develop new lines with partial resistance to different species and races of Xanthomonas [8][9][10]36 . Several studies have shown that the common locus QTL-11b on chromosome 11 is responsible for the resistance to multiple species and races of Xanthomonas 7,9,10,12,13 . The phenotypic variation explained by the locus varies from 12.5 to 29.4% depending on the population of plants and the species of the pathogen used for genetic analyses 10,12,13 .…”

“…Previous studies indicate that the locus QTL-11B from the resistant line PI 114490 confers resistance to races T1-T4 7,9 . To check whether SlPub24 was also resistant to races T1, T2, and T4, PI 114490, OH 88119, and Slpub24 mutants and transgenic lines overexpressing SlPub24 were subjected to disease evaluation.…”

“…Several studies have indicated that Solanum lycopersicum var. cerasiforme accession PI 114490 may provide broad-spectrum resistance to all species and races of Xanthomonas causing bacterial spot in tomato [7][8][9] . The resistance to races T1-T4 and X. cynarae pv.…”

“…The resistance to races T1-T4 and X. cynarae pv. gardneri in PI 114490 is quantitatively inherited, and several quantitative trait loci (QTLs) have been reported [7][8][9][10][11][12][13] . Classical genetic analyses based on segregation of resistance in F 2 and inbred backcross (IBC) populations derived from PI 114490 suggest that its resistance to race T2 is conditioned by two to four loci 8 .…”

“…Recent studies indicate that the common locus on chromosome 11, designated QTL-11B, confers resistance to races T1-T4 and X. cynarae pv. gardneri 7,9 . All these data suggest that QTL-11B in PI 114490 confers resistance to all races and species.…”