Variation among 41 Genotypes of Tomato (Lycopersicon esculentumMill.) for Crossability toL. peruvianum(L.) Mill.

Abstract

Even with the aid of tissue culture, crosses betweenLycopersicon esculentum(E) andL. peruvianum(P) typically yield few progeny. To determine whether some E genotypes produce more progeny per fruit that others when crossed with P, 41 E genotypes were crossed with pollen bulked from five P accessions. This first experiment (expt 1) was replicated over 2 years. In a second experiment (expt 2), differences among three genotypes each of E and P, and among individual plants within E genotypes were investigated. The E genotypes for expt 2 were chosen for relatively high and low crossability based on results of expt 1. The P genotypes for expt 2 were from different accessions than those used in expt 1. For both experiments, the 15 largest ovules from each ripe fruit were cultured aseptically for 1 month. Out of 1228 fruit, 753 hybrids were obtained. For expt 1, significant genotype by year interactions were observed. Within each year, there were significant differences among E genotypes for crossability. In expt 2, significant effects were found for E genotypes, but not for interactions between E and P genotypes, P genotypes, nor plants within E genotypes. Moreover, general crossability for E genotypes using bulked pollen (expt 1) was indicative of general crossability with three P accessions not present in the bulk (expt 2). Thus, selecting E genotypes of high crossability to P is the key to obtaining progeny for gene introgression. Rare production of E×P seed which was large and had brown seed coats typical of E seed indicated strong selection pressure to maintain separate species, but gene exchange in nature may be possible albeit at a low rate over long periods of time.