Proceedings of the XLVI Italian Society of Agricultural Genetics - SIGA Annual Congress

Giardini Naxos, Italy - 18/21 September, 2002

ISBN 88-900622-3-1

Oral Communication Abstract - S4c

USE OF PCR-BASED MARKERS FOR PYRAMIDING DISEASE RESISTANCE GENES IN TOMATO “ELITE” LINES

ERCOLANO M.R., LANGELLA R., MUSELLA T., BARONE A., FRUSCIANTE L.

Dept. Soil, Plant and Environmental Sciences, School of Biotechnology Sciences, Via Università 100, 80055 Portici (NA), Italy

disease resistant genes, CAPS marker, tomato, MAS

More than 40 resistant genes have been identified in tomato, and at least twenty have been utilised in conventional breeding programmes. Most of them have also been localised in the tomato RFLP map, and therefore many RFLP markers linked to various resistance genes are now available. The purpose of our research was to identify and use PCR-based markers in order to assist disease resistance gene transfer in tomato lines.

The most suitable primers and restriction enzymes to reveal CAPS markers were selected following three different approaches: 1) the use of previous published markers 2) the exploiting of resistance gene sequences available in GenBank and 3) the conversion of RFLP markers, already reported to be linked to resistant genes. Different markers associated to genes I2 (resistance to Fusarium oxysporum f. sp. lycopersici pat. 1), py-l (resistance to Pyrenochaeta lycopersici), Sw-5 (resistance to TSWV), Tm2a (resistance TMV), Pto (resistance to Pseudomonas syringae pv tomato), Mi (resistance to Meloidogyne spp) were found following one of these approaches. They were preliminary tested in broad tomato germoplasm and only those that clearly distinguished resistant and susceptible alleles were selected to be further used. In fact, the codominant nature of these markers was particularly useful to distinguish dominant from heterozygous resistant plants, as well as to select resistant genotypes when the resistance was due to a recessive allele, as in the case of Pyrenochaeta lycopersici. These DNA markers are now widely used for marker assisted selection in our tomato breeding programme. Twenty lines were genotyped with markers associated to Pto, Sw-5, Tm2a, Mi, py-l and I2. Various breeding programmes were performed to transfer disease resistant genes in both fresh market and processing tomato lines, previously selected for good agronomic traits through pedigree programmes. For two genotypes advanced lines have been obtained in backcross schemes with Stevens, a Sw-5-resistant line. In addition, F₁BC₃ progenies were obtained for 4 different processing lines exhibiting one or two resistance genes. All these progenies will be tested in field to select resistant genotype with good agronomic traits. At the moment, twenty fresh market tomato F₁ hybrids resistant to several pathogens were tested in greenhouse conditions and some of hybrid combinations showed good yield and quality.