PHENOTYPE, INHERITANCE, AND REGULATION OF EXPRESSION OF A NEW VIRESCENT MUTANT IN WATERMELON - JUVENILE ALBINO

Juvenile albino gene symbol ja, is a spontaneous virescent mutant, fir st observed in 'Dixielee' and an F-2 population of 'G17AB' (msms) x 'D ixielee' in 1992. Hypocotyls, new young leaves, shoot tips, tendrils a nd flowers on the main shoot of the ja mutant are all albino during ea rly spring. The interior portions of albino leaves gradually become gr een, while the margins remain albino. Fruit rind color of the mutant i s variegated, Growth of the ja mutant is severely impaired in the earl y spring. However 'the mutant grows at a rate comparable to wild-type in the summer, and produces fruit of almost normal size, Genetic analy sis of F-1, F-2, and BC1 populations derived from the ja mutant showed that the gene for the ja mutant is inherited as a single, recessive, nuclear gene, Segregation ratios in the F-2 and BC1 progenies derived from the cross between the previously reported delayed green virescent mutant and the ja mutant indicate independent inheritance of the gene s dg and ja. Temperature and red/far-red light had no differential eff ect on mutant and the wild-type plants, An increase of daylength from 8 to 15 hours increased fresh weight and chlorophyll content more in t he ja mutant than in the wild-type, The mutant had a higher chlorophyl l a : b ratio than the wild-type under long days. Chlorophyll synthesi s or accumulation in the mutant is severely impaired under short days. This is the only virescent mutant in the family Cucurbitaceae whose e xpression is regulated by daylength.