Processing tomato selection for corky root resistance in Italian environment

Abstract

The study reports the results of a breeding program to transfer resistance to Pyrenochaeta lycopersici to new processing tomato lines. This program involved the Californian variety 'UC 82', as recurrent parent susceptibleto the fungal pathogen, and the fresh market tomato cultivars Victorio, Nikita and Rezano, as donors of partial resistance, repeatedly observed in these varieties under field conditions in southern Italy. The materials were selected with three self-fertilisation cycles following three backcrosses, on the basis of greenhouse fungal partial resistance in early growth stages and field evaluation of agronomic and quality features. The greenhouse selection examined i) taproot discoloration; ii) plant growth on infected soil as compared to control; iii) production of adventitious roots following taproot discoloration; iv) presence/absence of necrosis on adventitious roots. At the end of the breeding program, five selected lines had a significantly higher growth performance than 'UC 82' on standard and highly infected soil. The resistance of improved lines was due to several traits; high adventitious root production following taproot discoloration and improved root tissue resistance to discoloration were the most evident.