Genetic differences and cluster analysis of pollens from different male kiwifruit germplasm resources

Abstract:【Objective】Most cultivated species of kiwifruit (Actinidia Lindl.) were functional dioecy. Fruitsetting, fruit size, flesh color and fruit production mostly depended on whether the flowers were fully polli-nated. Selection of male strains with abundant pollens strong germination rate was the primary premise ofsuccessful commercial orchard. Most domestic kiwifruit breeding research focuse on female plant screen-ing. Little attention has been paid on selecting superior male strains for improving commercial quality offruits and characteristics of descendants. So far, more than one hundred female cultivated species andstrains have been reported and published. However, there are only a few of accompanying male strains be-ing in use such as‘Tomuri'‘Matua', and‘Moshan 4'. Meanwhile, with the development of mechanicalpollination of kiwifruit, excellent male strains are urgently needed in the mass production of kiwifruit forcutting labor costs.【Methods】To verify the genetic differences of pollens from different male strains, varia-tion analysis of the pollen size, pollen quantity and germination characteristics were carried out on 100 kiwifruit male strains. They were F1 progenies of Actinidia diliciosa(‘Xuxiang'בTaihangxiongying 2',‘Hayward'בTaihangxiongying',‘Mibao'בTaihangxiongying'and‘Miliang 1'בTaihangxiongy-ing') plants generated from the seeds of ‘Qiongjiang' (A. chinensis) treated with space radiation andplants developed from the wild seeds of A. chinensis, respectively. Experimental materials were all collect-ed from germplasm resources nursery of Zhengzhou Fruit Research Institute, Chinese Academy of Agricul-tural Sciences and included one hundred male seedling strains obtained in 2006 and top grafting malestrains collected from different places in 2010. And all pollens were collected in the same year. Among allthe experimental materials, individual plants of F1 progenies accounted for 55%, seedlings of‘Qiongji-ang'treated with space mutation accounted for 12%, and other materials accounted for 33%.【Results】Anther number per flower, pollen quantity per anther, pollen quantity per flower, pollen germination rate,pollen tube length and pollen major axis were obviously varied with different male strains. Variation number of anther per flower was 36 to 379, pollen quantity per anther was 11 581 to 265 502, pollen quantityper flower was 1 390 704 to 31 677 957, pollen germination rate was 10.85% to 90.60%, pollen tubelength was 49.66 μm to 446.96 μm, and pollen major axis 26.60 μm to 55.20 μm, respectively. Variation coefficients of the same F1 progenies and males of A. diliciosa were: anther number per flower 26.75%, pollen quantity per anther 52.91%, pollen quantity per flower 49.10%, pollen germination rate 50.42%, pol-len tube length 62.77% and pollen major axis 8.10% respectively. Variation coefficients between differentmale strains were: anther number per flower 20.94%, pollen quantity per anther 45.94%, pollen quantityper flower 51.47%, pollen germination rate 40.94%, pollen tube length 59.49% and pollen major axis4.57%, respectively. Variation coefficients of the plants generated from the seeds of‘Qiongjiang'(A. chinensis) treated with space radiation were: anther number per flower 10.33%, pollen quantity per anther57.69%, pollen quantity per flower 50.45%, pollen germination rate 28.99%, pollen tube length 36.98%and pollen major axis 11.65% respectively. Variation coefficients between different male strains were: an-ther number per flower 17.31%, pollen quantity per anther 70.86%, pollen quantity per flower 74.66%,pollen germination rate 54.64%, pollen tube length 77.37% and pollen major axis 6.88%, respectively.Variation coefficient of anther number of A. diliciosa was higher than that of A. chinensis, pollen quantityper anther of A. chinensis was higher than that of A. diliciosa. Except for pollen quantity per flower, variation coefficients of other parameters were higher in F1 progenies than that of different strains of A. diliciosa. Except for pollen major axis, variation coefficients of other parameters were all lower in‘Qiongjiang'seedlings generated from the seeds of‘Qiongjiang' (A. chinensis) treated with space radiation than that ofdifferent individual strains of A. chinensis. Cluster analysis based on above parameters showed that anthernumber of A. diliciosa was higher than that of A. diliciosa and A. argute obviously. Three parameters: pollen quantity per flower, pollen germination rate and pollen tube length above the mean value took up major contribution rates in A. diliciosa. Seven male strains with high pollen germination rate(73.93%) andrapid pollen tube growth were obtained.【Conclusion】This study confirmed the genetic differences of pol-lens from different male strains of kiwifruit and provided scientific basis for male variety breeding.