Evaluation of Breeding Strategies for Pistachio Male Genotypes Based on Flowering Index, Pollen Traits, and Female Yield Elements

This study was carried out in the Khatam, Yazd province, Iran from the beginning of 2014 to the end of 2015.  Phenological traits and pollen properties of some male pistachio genotypes ‘A1’, ‘A2’, ‘A3’, ‘A4’, ‘A5’, ‘A6’, ‘A7’, ‘A8’, ‘A9’, ‘N1’, ‘Mh1’, ‘G1’, ‘M1’, ‘M2’, and ‘F1’ were surveyed. To find the effect of pollen source on the nut traits of the resulting seeds as well as the initial fruit set, Xenia and Metaxenia were evaluated. Moreover, pistillate flowers of the ‘Akbari’ cultivar were crossed with different pollen sources. Results showed that pollen germination of male pistachio genotypes was various. Among all of the pistachio male genotypes, the highest pollen germination percentage was obtained from ‘M1’ (92.66%) followed by ‘Mh1’ (86.66%) and ‘G1’ (86.00%). There were also significant differences between cluster and pollen weight of different pollen sources. Based on our findings, among the studied genotypes, ‘M1’ had the longest pollen tube 391.6 (μm), as well as the maximum pollen tube growth rate of 39 (μm h-1). The longest flowering periods were recorded to be 10 days in ‘M1’ and 7 days in ‘Mh1’, while the shortest period was 4 days in genotype ‘A5’ and ‘A3’. A significant correlation was found between pollen grain characteristics and initial fruit set, pistachio ounce, nut blanking, and as well malformed fruits. Based on the results pollens of genotype ‘M1’ decreased the nut blanking and malformed fruits in ‘Akbari’ cultivar, pollens of genotype ‘Mh1’ improved the pistachio ounce, and genotype ‘G1’ increased the initial fruit set.