Study on pollination activity of pistillate and staminate flowers in walnut excellent varieties

Stigma receptivity and pollen viability during walnut flowering can determine the fruit set percentage and the yield of current year directly. In this study, representative walnut cultivars—‘Wen185’, ‘Chandler’ and ‘QingXiang’ were observed. The morphological changes of stigma were recorded during pollination and fertilization, the stigma receptivity and optimal pollination period were studied by benzidine\|H2O2 method, and the period and conditions for keeping highest pollen viability were detected by MTT staining method. The results showed that the stigma receptivity period was ranging from the stigma slightly open to it with brown stripes. The best period for pollination was 3-5 days after the split stigma opened. The pollen can be stored for 96 hours under natural conditions and the viability decreased quickly to 33% after 4 hours. The pollen viability was the highest when the walnut anthers shedding，reaching 95%. Pollen viability could be reinforced at 4 ℃ and the average viability was 633% after 120 hours.