Effects of Late Spring Frost on Fruit Yield and Some Physiological Traits of Apricot in Kurdistan Province in Iran

One of the major problem in apricot production is serious damages of flower buds and developing fruits due to late spring frost. Selection of cultivars with lower yield fluctuation in spring frost prone areas is important. Therefore, the objective of this research was to evaluate the effects of late spring frost on fruit yield, phenological and physiological traits of 26 apricot cultivars in orchard conditions. The experiment was carried out in randomized complete block design with three replications in Garizeh agricultural reseach station, Sanandaj, Iran, in 2007 and 2008 growing seasons. Spring frost damage was observed as blackening of flower pistil and young fruit seed. Results showed significant (p < 0.01) differences among cultivars in all measured traits. “Dorosht-e-Malayer” cultivar had the earliest flowering time and the longest flowering period as compared with other cultivars. “Ghermez-e-Shahroud” cultivar showed the highest frost injury. Although “Jahangiri” showed the highest fruitset (%22.88), but “Tilton” had the highest fruit yield (22.66 kg tree-1). “Ghamishlu” cultivar had the latest flowering time, the lowest fruitset (4.87%) and fruit yield (2.67 kg tree-1). Results also indicated that the range of flowering date among apricot cultivars was narrow (7 days), and late flowering cultivars had lower fruit yield. Fruit set showed significantly (p < 0.01) positive correlation with yield, proline and K+ contents. Cultivars with higher proline and K+ contents showed higher fruit sets and lower yield fluctuations under spring frost conditions, perhaps due to higher cold hardiness. “Tilton”, “Royal”, “Dorosht-e-Malayer”, “Ghorban-e-Malayer”, “Hashtalui”, “Khorramta 1” and “Khorramta 2” apricot cultivars are suitable for spring frosts prone areas.