Efficiency of different potato (Solanum tuberosum L) cross combinations in late blight resistance breeding

The complex inheritance pattern and slow clonal multiplication rate makes potato breeding inefficient. An attempt has been made in the present study to analyze the efficiency of breeding potato varieties for late blight resistance at Central Potato Research Institute, Shimla. During last decade, 51 parental lines representing diverse group of genotypes with different geographic origin representing a range of resistance to late blight were utilized for late blight resistance breeding for varietal development. The choice of crosses made for incorporating late blight resistance was skewed towards making crosses among parents having high late blight resistance as maximum crosses belonged to resistant x moderately resistant and resistant x resistant categories. In general, the proportion of resistant progenies produced from any parental combination was low (9.25%) ranging from 1.02% in susceptible x susceptible group to 10.34% in resistant x resistant group. Among individual crosses producing >16% resistant seedling, maximum proportion was observed in the moderately resistant x susceptible parental combination followed by resistant x moderately resistant, resistant x susceptible and resistant x resistant parental combination. The resistant clones were evaluated for various tuber traits and late blight resistance in early clonal generations and a total of 33 clones were advanced to further evaluation trials. Most of the high yielding hybrids belonged to resistant x moderately resistant group and moderately resistant x susceptible group, followed by moderately resistant x moderately resistant and resistant x resistant groups. It appears that the norms for selection of parents in the present resistant breeding programme the high level for late blight resistance can be relaxed to some extent.