Open Access(13) Comparative Mapping of Early Blight Resistance QTLs and Candidate Resistance Genes in F2, F3, F4 and a RIL Population of Tomato
Author(s) -
Hamid Ashrafi,
Arun Sharma,
D. Niño-Liu,
Liping Zhang,
Majid R. Foolad
Publication year - 2005
Publication title -
hortscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.518
H-Index - 90
eISSN - 2327-9834
pISSN - 0018-5345
DOI - 10.21273/hortsci.40.4.1040b
Subject(s) - biology , population , genetics , blight , quantitative trait locus , plant disease resistance , candidate gene , restriction fragment length polymorphism , cultivar , gene , resistance (ecology) , gene mapping , horticulture , genotype , agronomy , chromosome , medicine , environmental health
Most cultivars of tomato ( Lycopersiconesculentum ) are susceptible to early blight (EB), a devastating fungal ( Alternariasolani ) disease of tomato in the northeast and eastern part of the U.S. The most economic and durable measure of disease control is by using genetic resistance. There is limited EB resistance within the cultivated tomato. However, genetic sources of resistance exist within the tomato-related wild species L. hirsutum and L. pimpinellifolium . Early blight resistance does not follow the gene-for-gene model of host–pathogen interaction. Mapping QTLs conferring horizontal resistance is an effective approach for studying complex resistance traits such as EB. We have developed F 2 , F 3 , F 4 , and an F 2:7 derived RIL population of a L. esculentum × L. pimpinellifolium cross and evaluated them for EB resistance under field conditions. Genetic maps were constructed based on the F 2 (including 256 RFLP, EST and RGA markers) as well as the RIL population (including over 220 RFLP and EST markers). In each of the F 2 , F 3 , and F 4 population, an average of seven QTLs were identified for resistance, which were highly consistent across populations. Mapping of EB resistance QTLs in the RILs is underway. Co-localizations of QTLs with several ESTs and RGAs were observed, suggesting potential involvement of the latter markers with EB resistance. Furthermore, co-localizations were observed among QTLs, ESTs, and RGAs and several known tomato vertical disease resistance genes. Possible occurrence of such co-localization in the RIL population will be reported. It is speculated that candidate-gene approach is an effective way of identifying and mapping new R genes in tomato. This study may lead to the identification of genes underlying EB resistance in tomato.