FLOWERING BEHAVIOR, MALE-STERILITY AND BERRY SETTING IN TETRAPLOID SOLANUM-TUBEROSUM GERMPLASM

Six hundred and seventy six accessions of cultivated potato (Solanum t uberosum ssp. tuberosum) from 25 countries, were studied for flowering and fruiting behaviour under long days (12-14 h). Flowering intensity ranged from dropping of floral buds just after initiation to profuse blooming. The majority (58.3%) of the accessions bloomed profusely, th ough 20.4% of the accessions did not bloom at all. 'Weeks to flowering ' ranged from 6 to 15 and the majority (66.5%) of the flowering access ions bloomed within 8 to 9 weeks after planting. 'Duration of flowerin g' ranged from 1 to 10 weeks and the majority (68.1%) of the flowering accessions bloomed for 1 to 4 weeks only. Twentythree per cent of the flowering accessions were completely male sterile. Maximum male ferti lity was 90% only. No berry setting was observed in 31.8% of the flowe ring accessions. Only 54.3 per cent of the accessions were found to be fertile in all respects and could be used both as male and female par ents. Premature bud abscission was the major cause of sterility. Peru was the best source of profuse-flowering genotypes, Poland was the bes t source of early flowering genotypes and Mexico was the best source o f long duration flowering and good berry setting genotypes. The result s suggested that flower bud formation; the growth and development of m ature flowers; weeks to flowering and duration of flowering are indepe ndent characters controlled by different genes of quantitative nature. Berry setting and duration of flowering were closely associated (r = 0.95). Genetic as well as environmental factors interfered with the de velopmental process leading to flower production and berry setting at different times in different genotypes. The practical implications of these results for true potato seed production are discussed.