Creation of triploid germplasm of longan by inducing 2n male gametes
Longan (Dimocarpus longan Lour.) is an important economic fruit tree with good flavor and rich nutrition in southern China. It is important to make progress in breeding a seedless cultivar by triploid induction because of its small fruit, low edible rate and lack of seedless germplasm. In this study, we created a stable triploid through sexual hybridization by using 2n male gametes of the longan major cultivar Shixia. To determine the best induction stage corresponding with the male flower bud size, we studied the correlation between the microspore mother cell meiosis stages and male flower bud diameters. The result showed that when the diameters of the flower buds were between 1.5 to 1.8 mm, the microspore mother cells were at the pachytene to diakinesis. At this best induction stage, the male flower buds were treated with colchicine with different concentrations and times to maximize the rate of the 2n male gates. The 2n pollen percentage of male flower buds treated with 0.9% colchicine for 2 days was the highest, reaching 19.46%. In the blooming stage of female flowers, the collected 2n pollens were pollinated to female flowers artificially. The ploidy of 878 Shixia self-cross seedlings was identified by chromosome counting using root tip and leaf. Three self-cross seedlings were identified as triploid with 45 chromosomes (2n=3x=45). The induction efficiency of 2n male gates was related to the treatment concentration and days of colchicine, while also tied to the weather.
Xiong, H., Mao, X., Gan, J., Hu, G., Liu, C. and Fu, J. (2020). Creation of triploid germplasm of longan by inducing 2n male gametes. Acta Hortic. 1293, 113-120
longan, triploid, 2n male gamete, meiosis