Production of Somatic Hybrids between Tomato (Lycopersicon esculentum) and Night Shade (Solanum lycopersicoides) by Electrofusion

Abstract

Mesophyll protoplasts of tomato (Lycopersicon esculentum Mill. cv. 'Ohgata Zuiko') and Solanum lycopersicoides were fused by electrofusion method to develop fertile tetraploid somatic hybrids. Following electrofusion the protoplasts were plated in modified TM2 (MTM2) medium in which S. Iycopersicoides protoplast could not form callus. The putative hybrid calli were regenerated on MS3ZG regeneration medium in which tomato protoplasts derived calli could not regenerate shoots. Tomato protoplasts were partially inactivated with iodoacetamide (IOA) for the easy selection of heterokaryons. Three hundred regenerated plants were grovvn to maturity in a green house. The hybridity of the plants was argued by morphological, isozyme and random amplified polymorphic DNA (RAPD) analyses. All plants were heterotic in their growth, expressing an erect stem with a prominent internode like tomato, as well as days to flowering, perennial habit, free anther without sterile tip like S. Iycopersicoides. Several traits, such as leaf margin, inflorescence, flower and fruit color were intermediate between both parents. The electrophoretic pattern of PGI (.phosphoglucoisomerase), GOT (.glutamate oxaloacetate transaminase) and PG[M (phosphoglucomutase) confirmed the hybrid nature of the nuclei of all the tested plants. RAPD markers generated from 35 randomly selected plants, using eight decamer primers reconfirmed the hybrid nature of their nuclear genomes. Cyt.ological study of 20 randomly selected plants revealed 60 %of them had euploid chromosome numbers (2x=4n= 48). Tetraploid plants produced fertile pollen and developed fruits and viable seeds upon self pollination. About two thirds of the tested somatic hybrid plants survived in the winter-cold temperature (Average minimum -1.25°C) to maximum 5.3°C).