COMMENTS ON DEGENERATION AND BEHAVIOR AT DIFFERENT PLANTING DATES OF FOUR POTATO (Solanum tuberosum L.) VARIETIES

Abstract

The four potato varieties DELTA-A, HANSA, HYDRA and TONDRA were tested in the dry and in the rainy season of 1971, in Goiânia. Imported certified seed potatoes were used for the first planting and the harvested tubers, for the second. All varieties, except DELTA-A, yielded more in the rainy than in the dry season. This difference was found to be caused by the better water supply during the rainy season. There was no significant influence of the season on the production of DELTA-A. HANSA produced in both seasons significantly more in total weight than the other varieties and more marketable potatoes (over 33 mm) in the rainy season. But the large tubers (over 40 mm) harvested in this season became nearly worthless because of the intensive occurrence of internal dark and scattered spots, associated to enlarged lenticels. HYDRA was the best variety in producing large potatoes, mainly in the dry season. In both seasons, however, most of the potatoes were lost for the market, due to the strong attack of common scab (Streptomyces scabies). TONDRA showed the greatest difference between yields of different seasons. Production of marketable tubers increased twice and that of large tubers, almost three times, in the rainy season. This variety had no trouble similar to that of the other ones and in the rainy season, its yield of large potatoes was not significantly lower than that of HANSA and HYDRA.