RELATIONSHIP BETWEEN SEED AND BUD CHILLING REQUIREMENT OF PERSIAN WALNUT

Abstract

In this work, the effect of stratification on germination and growth of Persian walnut seeds and correlation between seed and bud chilling requirement was studied. In 2006 and 2007, mature seeds of five walnut cultivars and promising genotypes (`Serr', 'Lara', 'Rond de Montignac', 'Z 63 ' and `Z 53 ') were stratified at 7°C for eight stratification periods (0, 1, 2, 3, 4, 5, 6, 7 and 8 weeks). At the end of each chilling treatment period, the seeds were transferred to a greenhouse with a natural photoperiod and temperature between 17 to 26°C. The number of germinated seeds and time of emergence of the first root primordia from the seedlings were recorded weekly for each treatment. After two months, the seedling's heights were recorded for each treatment. The results showed that the seed stratification period could affect the growth (from 119 mm in all cultivars and genotypes for the control to 288 mm with eight weeks of stratification) and time of emergence of first root primordia (from 14.15 days in the control compared with 6.27 days with eight weeks of stratification) and percentage of seed germination (from 36.8% for the control compared with 86.3% with eight weeks of stratification). According to the chilling requirement of buds of the studied cultivars and genotypes which were measured in previous studies, the relationship between chilling requirement of buds and some germination related traits of seeds were evaluated. The chilling requirement of seeds was higher in late flowering (with high chilling requirement of buds) cultivars/genotypes ('Z63' and 'Lara'), in comparison with the earlier ones ('Rond de Montignac' and 'Serr').