VARIATION AMONG 41 GENOTYPES OF TOMATO (LYCOPERSICON-ESCULENTUM MILL.) FOR CROSSABILITY TO LYCOPERSICON-PERUVIANUM (L.) MILL

Even with the aid of tissue culture, crosses between Lycopersicon escu lentum (E) and L. peruvianum (P) typically yield few progeny. To deter mine whether some E genotypes produce more progeny per fruit that othe rs 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 thre e genotypes each of E and P, and among individual plants within E geno types were investigated. The E genotypes for expt 2 were chosen for re latively high and low crossability based on results of expt 1. The P g enotypes for expt 2 were from different accessions than those used in expt 1. For both experiments, the 15 largest ovules from each ripe fru it were cultured aseptically for 1 month. Out of 1228 fruit, 753 hybri ds were obtained. For expt 1, significant genotype by year interaction s were observed. Within each year, there were significant differences among E genotypes for crossability. In expt 2, significant effects wer e found for E genotypes, but not for interactions between E and P geno types, P genotypes, nor plants within E genotypes. Moreover, general c rossability for E genotypes using bulked pollen (expt 1) was indicativ e of general crossability with three P accessions not present in the b ulk (expt 2). Thus, selecting E genotypes of high crossability to P is the key to obtaining progeny for gene introgression. Rare production of E x P seed which was large and had brown seed coals typical of E se ed indicated strong selection pressure to maintain separate species, b ut gene exchange in nature may be possible albeit at a low rate over l ong periods of time. (C) 1997 Annals of Botany Company.