Determination of self- compatibility levels, physiological disorders, pomology of apples and introduction of 'IRI6' as promising self- compatible cultivar

The level of self-compatibility of the 48 pre-selected apple cultivars, using their own pollen, the genetic capacity of flowering, flower-fruit conversion ratio, multiple fruit fall and bearing preservation during 4 successive biological growth stages were examined through two main treatments of self and cross pollination, in Horticulture Research Station of Kamalshahr in Karaj (Iran). The fruit samples were analyzed via 43 pomological traits and physiological disorders. Six to 10 branches carrying flower buds were labeled within the canopy of the existing, 3 to 6, trees. The labeled branches were isolated by bags, and 5 other open pollinated branches were marked as control for each cultivar or genotype. All branches were submitted to a precise recording of flower buds, young fruits, June drop and mature fruit numbers in 4 different biological stages including 1. bud swelling phase, before balloon stage, 2. two weeks after bloom end, 3. June drop and 4. maturity time. The results showed that there were significant differences between all genotypes and cultivars in the number of produced flowers, flower-fruit conversion ratio, fruit fall and fruit set percent during growth stages and particularly for the self- compatibility level among and within the cultivars. Inbreeding pressure caused appearance of physiological disorders at different levels (based on cultivar), changing the expression of fruit weight, fruit length, fruit diameter, seed number, seed abnormality and other traits. The mean comparisons made by Duncan test confirmed that the promising genotype IRI6, with 6.49% of efficiency in fruit retaining capacity, surpassing the open pollinated treatment as control with 4% of fruit set at the end of the 4^th stage of fruit growth or at harvest time, confirming itself as a completely self-fertile apple genotype. Among the pre-selected self-compatible cultivars, except the 12 off cultivars, all other cultivars demonstrated different and considerable levels of self-compatibility. Complete pomology test of 30 traits was worked out on 10 fruit samples taken from each self and cross treatment belonging to each cultivar and genotype, based on national guideline for the conduct of tests for apple (UPOV), and ulterior biochemical characteristics.