1Central Potato Research Institute, Shimla-171 001, (H.P.).
2Department of Agricultural Botany, Meerut University, Meerut-250 005, (U.P.).
*Part of the Ph.D thesis of Sr. author (1993).
Genetic divergence studied in fifty two tuberosum, andigena and andigena-tuberosum potato cultures on the basis of 11 characters revealed considerable genetic diversity in the Indian potato varieties in comparison to the advance pre release hybrids indicating their development from a narrow genetic base. The tuberosum and andigena cultures fell in different clusters indicating genetic diversity between them and possibility of getting heterotic effects on crossing. The cultures with wild species in their pedigree showed high genetic diversity, in contrast to cultures with common species in their pedigree or the cultures developed either from the same parentage or involving one common parent. Fifteen diverse parents selected from above were crossed in all possible combinations (half diallel) and were studied for combining ability of 10 characters important in raising crop from TPS. Cultures EX/A-680-16 and EX/B-687 (andigena) and VB-8. Katahdin and Kufri Jyoti (tuberosum) were identified good combiners for most of the characters. A positive correlation between GCA effects for total, marketable and per cent marketable yield and between total yield and average tuber weight was observed. No relationship between the GCA effects of the parents and the SCA effect of crosses was noticed for all the cnaracters indicating selection of parents on the basis of combining ability will not limit the use of SCA effects for improvement of these characters. The good crosses for yield and tuber uniformity involved both tuberosum and andigena parents and generally showed positive and significant SCA effect for yield when tuberosum cultures were used as females and andigena as males. The high SCA values for yield and uniformity were associated with crosses involving parents with intermediate genetic distance in contrast to parents from same cluster or closely related clusters and also from distant clusters suggesting that genetically related or widely divergent parents should not be involved in crosses meant for developing TPS populations with high yield and uniformity of tuber characters.
