Determination of Self and Cross Compatible Genotypes Obtained from Almond Breeding Program

Self-incompatibility is one of the most prominent inhibiting factors in almond production which reduces fruit set, making orchard management difficult. Therefore, breeding of almond to produce self-compatible genotypes is indispensably important. In this research work, pollen tube growth rate was studied in 38 genotypes obtained from crossing between Touno (male parent)‎ and Shahrood 12 (female parent)‎. Flowers of each progeny was self pollinated. Then, pollen tube growth was studied through fluorescent microscopy. Fruit set was also determined. To study pollen tube growth rate, a number of four branches of any one tree were bagged in stage D. Flowers were hand pollinated with their own pollen, using a camel brush. Percentages of initial vs. final fruit set were determined 15, 30, 45and 60 days past pollination, respectively. In addition, one branch was left for open pollination to be compared with self pollinated ones. Results indicated that genotype number 23 was self-compatible by a fruit set of 18.23%. On the other hand, cross-pollination increased fruit set of self-compatible genotypes.For a microscopic study, flowers were harvested at 24, 72 and 120 hr following hand pollination. Results of a two year (2009 and 2010) study showed that 24 and 72 hr were not enough for pollen tube to reach the base of style, while a 120 hr duration was a suitable time. At 120 hr following pollination in 2010, 39.47% of the genotypes were self-incompatible, 23.68% were doubtful, 26.32% were self-compatible and 10.53% recognized as highly self-compatible. Pollen tube growth was also studied following a cross pollination of the 38 genotypes using pollen of cultivar Sahand. Flower samples were harvested at 120 hr after hand pollination. Results indicated that two genotypes were cross-incompatible, four doubtful, 10 were cross-compatible while 22 genotypes recognized as highly cross-compatible. Results of microscopic observations were in the same line with fruit set measurements in both cases of self and cross-pollination. Therefore, pollen tube growth observation through fluorescent microscopy proved to be a useful and practical method to discriminate between self, and cross-compatible genotypes.