A MALE-FERTILE LYCOPERSICON-ESCULENTUM X SOLANUM-LYCOPERSICOIDES HYBRID ENABLES DIRECT BACKCROSSING TO TOMATO AT THE DIPLOID LEVEL

Solanum lycopersicoides Dun. is a wild nightshade native to Chile and Peru that possesses many traits of potential interest to tomato breede rs, including environmental stress tolerance, resistances to disease a nd insect pests, and certain fruit quality characteristics. Sexual and somatic hybrids with the cultivated tomato (Lycopersicon esculentum M ill.) are readily obtained, yet have a strong tendency towards male-st erility combined with unilateral incompatibility, barriers that have d eterred breeding efforts in the past. We report herein the synthesis o f a partially male-fertile F-1 hybrid by sexual crosses between tomato and a recently collected population of S. lycopersicoides. Over 280 B C1 plants were obtained by direct backcrossing to tomato at the diploi d level, of which 58 were sufficiently fertile to permit selfing or ad ditional backcrosses. The transmission of S. lycopersicoides genetic m arkers into a uniform L. esculentum background was confirmed with 24 i sozyme or morphological loci on 11 of the 12 alien chromosomes. Potent ially useful tolerance to gray mold (Botrytis cinerea) was demonstrate d by inoculation of stem cuttings with mycelial plugs: at 6 days post- inoculation, the intergeneric hybrid showed little evidence of disease progression and the length of stem lesions averaged only one third th at of susceptible controls.