Late Blight of Tomato - Translational Genomics for Crop Breeding: Biotic Stress - page 241

Chapter 13

LateBlight of Tomato

MarcinNowicki,ElzbietaU.Kozik,and MajidR.Foolad

Abstract

Late blight (LB), caused by the oomycete Phytophthora infestans (Mont.) de Bary, is one of the most
destructive diseases of tomato ( Solanum lycopersicum L.) and potato ( S. tuberosum L.) worldwide,
causing significant economic losses annually. The success of P. infestans as a pathogen originates
from its effective asexual and sexual life cycles, as well as its remarkable capacity to rapidly overcome
plant resistance genes, a result of its high evolutionary potential. The most sustainable strategy to
manage tomato LB would be to deploy an integrated system including cultural practices, fungicide
application, and the use of cultivars with broad-spectrum genetic resistance against LB. Prior to the
reemergence of LB in the late 1980s, cultural practices in combination with fungicide applications
were highly effective measures to control the tomato LB. However, with the appearance of new and
more aggressive isolates of P. infestans , many of which are resistant to LB-specific systemic fungicides,
the greatest contribution to tomato LB control in the future will have to be through the development
of cultivars with improved genetic resistance. Thus far, a number of major LB-resistance genes and
quantitative trait loci (QTLs) have been identified in tomato and several breeding lines and cultivars,
with improved resistance developed. Research is also underway to identify additional resistance genes
or QTLs and to pyramid multiple resistance factors in order to develop stronger and more durable
resistance. Further, as exemplified by the fast progress in potato LB research and conservation of
LB signaling pathways between potato and tomato, detailed knowledge of the pathogen effectors in
combination with high-throughput genomics technology will facilitate a better understanding of the
LB disease and host-pathogen interactions, which in turn may lead to development of tomatoes with
more durable resistance.

in the Andean region of South America, now
encompassed by parts of Peru, Chile, Colom-
bia, Ecuador, and Bolivia (Jenkins 1948; Rick
1978), and domesticated in Mexico (Rick 1976).
Although a tropical plant, it is grown in almost
every corner of the world (see below). The broad

Introduction

Tomato, Solanum lycopersicum L. (formerly
known as Lycopersicon esculentum Mill.) is
a major vegetable crop worldwide (FAOSTAT
2011). Tomato is thought to have originated