Mapping Quantitative Trait Loci (QTL) for Resistance to Late Blight in Tomato.

Dilip R Panthee,Ragy Ibrahem,Ann Piotrowski

doi:10.3390/ijms18071589

Dilip R Panthee, Ragy Ibrahem + Show 1 more

Open Access

https://doi.org/10.3390/ijms18071589

Copy DOI

Abstract

Late blight caused by Phytophthora infestans (Montagne, Bary) is a devastating disease of tomato worldwide. There are three known major genes, Ph-1, Ph-2, and Ph-3, conferring resistance to late blight. In addition to these three genes, it is also believed that there are additional factors or quantitative trait loci (QTL) conferring resistance to late blight. Precise molecular mapping of all those major genes and potential QTL is important in the development of suitable molecular markers and hence, marker-assisted selection (MAS). The objective of the present study was to map the genes and QTL associated with late blight resistance in a tomato population derived from intra-specific crosses. To achieve this objective, a population, derived from the crossings of NC 1CELBR × Fla. 7775, consisting of 250 individuals at F2 and F2-derived families, were evaluated in replicated trials. These were conducted at Mountain Horticultural Crops Reseach & Extension Center (MHCREC) at Mills River, NC, and Mountain Research Staion (MRS) at Waynesville, NC in 2011, 2014, and 2015. There were two major QTL associated with late blight resistance located on chromosomes 9 and 10 with likelihood of odd (LOD) scores of more than 42 and 6, explaining 67% and 14% of the total phenotypic variation, respectively. The major QTLs are probably caused by the Ph-2 and Ph-3 genes. Furthermore, there was a minor QTL on chromosomes 12, which has not been reported before. This minor QTL may be novel and may be worth investigating further. Source of resistance to Ph-2, Ph-3, and this minor QTL traces back to line L3707, or Richter’s Wild Tomato. The combination of major genes and minor QTL may provide a durable resistance to late blight in tomato.

Highlights

Late blight (LB), caused by the oomycete Phytophthora infestans, (Montagne, Bary) is one of the most potentially devastating diseases of tomato in areas with high humidity and cool temperatures and can cause 100% crop loss in unprotected tomato fields or greenhouses
Genetic resistance to LB in tomato has been of interest for many years, and three major resistance genes have been identified in the red-fruited tomato wild species S. pimpinellifolium, including Ph-1, Ph-2, and Ph-3, which have been mapped to tomato chromosomes 7, 10, and 9, respectively
The objective of the present study was to map the genes and quantitative trait loci (QTL) associated with late blight resistance in a tomato population derived from intra-specific crosses

Summary

Introduction

Late blight (LB), caused by the oomycete Phytophthora infestans, (Montagne, Bary) is one of the most potentially devastating diseases of tomato in areas with high humidity and cool temperatures and can cause 100% crop loss in unprotected tomato fields or greenhouses. Genetic resistance to LB in tomato has been of interest for many years, and three major resistance genes have been identified in the red-fruited tomato wild species S. pimpinellifolium, including Ph-1, Ph-2, and Ph-3, which have been mapped to tomato chromosomes 7, 10, and 9, respectively. Ph-1 was mapped to the distal end of chromosome 7 using morphological markers [1]. No molecular marker associated with this resistance gene has been reported. Other genes Ph-4, and Ph-5-1 and Ph-5-2 have been reported originating from LA1033 [2] and PSLP153 [3], respectively. P. infestans race T-1 predominates, rendering the resistance conferred by Ph-1 ineffective

Objectives

Methods

Results

Conclusion