Lettuce genotype resistance to "soft rot" caused by Pectobacterium carotovorum subsp. carotovorum

Kátia Cilene Da Silva Felix,Willams José De Oliveira,Rosa De Lima Ramos Mariano,Elineide Barbosa De Souza

doi:10.1590/0103-9016-2013-0301

Kátia Cilene Da Silva Felix, Willams José De Oliveira + Show 2 more

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https://doi.org/10.1590/0103-9016-2013-0301

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Journal: Scientia Agricola	Publication Date: Aug 1, 2014
Citations: 8	License type: cc-by

Affiliation: Universidade Federal Rural de Pernambuco

Abstract

Soft rot, caused by Pectobacterium carotovorum subsp. carotovorum (Pcc), is the main bacterial disease affecting lettuce (Lactuca sativa L.) crops in Brazil and leads to significant yield losses. This study aimed to assess the reaction of lettuce genotypes to soft rot induced by a virulent isolate and the stability of the resistance to three isolates varying in virulence. Using a descriptive ordinal scale ranging from 1 to 9 a classification system was defined: class 1 = resistant (R): severity (Sev) < 1.5; class 2 = moderately resistant (MR): 1.5 < Sev < 2.5; class 3 = susceptible (S): 2.5 < Sev < 3.5; class 4 = highly susceptible (HS): Sev > 3.5). Of the 41 tested genotypes, 14 were classified as MR and 27 as S when inoculated with a Pcc isolate of intermediate virulence. Eleven of these genotypes (four S and seven MR) were selected to test their resistance stability against three other isolates with an increasing degree of virulence (Pcc36 < Pcc-A1.1 < Pcc-23). Out of the 11 genotypes eight retained the original classification and three moved from S to MR resistant class when challenged with the least virulent isolate. Vitória de Santo Antão was the only genotype classified as MR for all tested isolates and is a promising candidate for durable soft rot resistance breeding.

Highlights

Lettuce (Lactuca sativa L.) is one of the most widely consumed leafy vegetables and is cultivated all over Brazil during different periods throughout the year
Soft rot caused by Pectobacterium carotovorum subsp. carotovorum (Jones) Hauben et al is considered the main bacterial disease of several economically important crops in Brazil and worldwide (Charkowski, 2006; Zhang et al, 2012), including lettuce (Cariddi and Sanzani, 2013)
Because soft rot may be a strong limiting factor for lettuce production in some areas, the present study aimed to identify sources of resistance to soft rot caused by P. carotovorum subsp. carotovorum in a collection of lettuce genotypes and to assess the resistance stability of selected genotypes to isolates varying in virulence

Summary

Introduction

Lettuce (Lactuca sativa L.) is one of the most widely consumed leafy vegetables (in the form of salad) and is cultivated all over Brazil during different periods throughout the year. It is among the six most economically important vegetables and is the eighth largest in terms of volume produced (Sala and Costa, 2012). In the state of Pernambuco, in the northeast of Brazil, lettuce production is concentrated in the municipality of Vitória de Santo Antão, where it is usually planted with successive crops throughout the year, and soft rot can cause extensive losses, mainly under high temperature and humidity conditions. The use of resistant cultivars is considered the most cost-effective and technically feasible control method as compared with the use of pesticides that, in some cases, may lead to pesticide resistance in the pathogenic populations and accumulate in the consumable product as harmful residues

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