Study and Evaluation of spring frost effects on yield fluctuations of apricot cultivars

Spring frost injury is the most limitation factor of apricot production in Kurdistan province, Iran. In order to evaluation apricot varieties under spring frost condition, an experiment was conducted on 8 commercial cultivars accompany with 18 local genotypes of apricot in a RCBD arrange with 3 rep. in Grizeh research station (sanandaj) during 2005-2008. Date of blooming, flowering period, relative water content (RWC), proline and K+ contents in pistil of flower, severity of frost injury in flowers, fruit set, date of fruit ripe, yield, fruit weight, fruit size and total soluble solids of fruit were measured and determined in this experiment. Combined analysis variance of data showed a significant difference (p0.01) between apricot varieties for all evaluated charachteristics. Different Years showed significant difference (p0.01) in date of blooming, flowering period, relative water content (RWC), proline and K+ contents in pistil of flower, severity of frost injury in flowers, fruit set, date of fruit ripe and yield. The reciprocal effects of variety and year was significant for Date of blooming, flowering period, severity of frost injury, date of fruit ripe, yield, proline and K+ contents in pistil of flower at level %1. Means comparison showed that "Dorosht-Malayer" cultivar had the earliest blooming and the longest flowering period compared with other varieties. "Ghermez-Shahroud" was the most sensitive cultivar against spring frosts and showed the highest injury compared with other varieties.The highest fruit set (%22.88) was observed in local genotype "Jahangiri". The commercial cultivar "Tilton" had the highest yield (22.63 kg/tree) whereas the local genotype "Ghamishlou" had the lowest fruit set ( % 4.87) and the lowest yield ( 2.67 kg/tree) . There was a significant and positive correlations (p0.01) between fruit set with yield, proline and K+ contents in pistil of flower. A positive and significant correlation was observed between yield and proline content in pistil of flower. Also a positive and significant correlation at level %1 was observed between date of fruit ripe and TSS.