Interspecific Hybridization in Potato by Unilateral Sexual Polyploidization

This work was carried out in the Laboratory of Plant Biotechnology at University of Passo Fundo, in South Brazil. The objective of these experiments was to test, for local condition, the hybridization technique strategy by sexual unilateral polyploidization in potato in order to transfer genes from wild diploid into the tetraploid cultivated species. Initially, the temperature effect on the occurrence of unreduced (2n) pollen grains in two diploid clones at temperature of 10, 15, 20, 25, 30 and 35 degrees C was evaluated. The highest frequency of unreduced pollen grains was observed in temperatures of 15 degrees C with an average of 30.7% for one clone and 7.6% for the other. Both clones were used as male parents in crosses with tetraploid cultivars. A total of 109 crosses were performed, and in 14 of them, 2,4-D was applied after pollinations. After pollination, three fruits were obtained from 14 flowers that were treated with 2,4D. However, only one of them was fertile, producing five plants, which presented morphological traits from both parents, eliminating the self-pollination hypothesis. The number of mitotic chromosomes of F-1 plants was 48. This tetraploid ploidy level shows that the tetraploid cultivar oosfere was fertilized by the unreduced pollen of diploid species. This indicated the overcoming of a critical restriction for the genes transference between plants with different ploidy levels had occurred. Although this strategy needs to be optimized, this work shows the possibility of using non reduced pollen grain as a bridge to transfer desirable traits from wild gene pool to the cultivated one under our conditions. This enlarges the genetic variability of the crop, increasing the potential of developing new potato cultivars having disease resistance, good eating quality and superior agronomic traits.