A COMPARISON OF PROGENY FROM DIALLELE CROSSES OF DIPLOID POTATO WITH REGARD TO THE FREQUENCIES OF 2N-POLLEN GRAINS

Selection of diploid potato genotypes that produce high frequencies of 2n-pollen grains in different environments is an important requiremen t for analytic breeding as well as for true potato seed production. In this context, quantitative estimates of 2n-pollen formation were made in two type of diploid potato populations. One population set consist ed of the progeny from diallel crosses of five well-known diploid pota to clones (A = US-W 5293.3, B = US-W 5295.7, C = US-W 5337.3, D = US-W 7589.2 and E = 772102-37). Another population set was obtained by pol linating three genotypes of Solanum phureja, IvP35, IvP48 and IvP101 w ith clones A, C and E. It was observed that the behaviour of the paren tal clones with respect to 2n-pollen grains formation in different env ironments, such as in Europe and China, was stable. The correlation co efficient between means of 2n-pollen grains frequency of combinations and percentage of genotypes with more than 5% 2n-pollen grains in a gi ven combination were estimated and that between mean and maximum frequ ency of 2n-pollen grains formation in each combination. The results sh owed that the former coefficients were significant whereas the latter were not. The combining ability analysis revealed variation in 2n-poll en grains formation between families. Specific combining ability (SCA) effects contributed much more than general combining ability (GCA) to the variation in 2n-pollen grains formation. The broad-sense heritabi lity of 2n-pollen grains formation was estimated to vary between 0.45 and 0.53 and the narrow-sense heritability was calculated to be 0.15 a nd 0.20 in the two types of populations. This means that additive vari ance was relatively low. Two to four genes were estimated to control t he inheritance of 2n-pollen grains formation.