Pollination compatibility and pollen xenia of Xinjiang pear cultivars with ‘Kuerlexiangli' pear

Abstract: 【Objective】‘Kuerlexiangli'pear is famous at home and abroad for its thin skin, crispy flesh, juicy and sweet taste, endurable storage, rich nutrition and other characteristics.‘Kuerlexiangli'pear is a kind of self-incompatible fruit whose quality and quantity is strongly influenced by the pollens of the pollinators.‘Dangshansuli'and‘Yali'have shown disadvantages as pollinating trees for‘Kuerlexiangli'pear for inducing poor quality and small fruits. It is necessary to screen more suitable pollinating cultivars. The germplasm resources of Xinjiang pear are rich and their flowering phenology is close to‘Kuerlexiangli'pear. However, these cultivars are only preserved in National Germplasm Resource Nurseries and horticultural experiment stations, and are seldom utilized in commercial orchards. In order to provide practical guidance and scientific basis for improving yield, fruit quality and further research of‘Kuerlexiangli'pear, the pollination compatibility and Metaxenia of Xinjiang pear cultivars on‘Kuerlexiangli'pear were studied.【Methods】Nine Xinjiang pear cultivars including‘Luntai Jujuli'‘Hese Jujuli'‘Aiwenqieke'‘Kuqa Amut'‘Huocheng Donghuangli'‘Heisuanli'‘Korla Huangsuanli'‘Lüli', ‘Aksu Jujuli'and introduced cultivar‘Dangshansuli'were used as pollinators for‘Kuerlexiangli'pear. Pollen germination and growth of different pollination combinations on the stigma of‘Kuerlexiangli'pear were observed after in vivo pollination. Fruit setting rates were counted after the second physiological fruit drop period after castration pollination at the popcorn stage. The appearance quality (fruit weight, fruit shape index) and internal quality (fruit firmness, soluble solids, soluble sugar, titratable acid and vitamin C) and seed number of different pollination combinations were analyzed when the fruits ripened. The pollination compatibility of different pollination combinations and the xenia effect were analyzed, and the optimal pollination combinations were selected according to the results.【Results】The percentage of pollen tube elongation of‘Lüli' (50%) and‘Dangshansuli' (55%) to the style base of‘Kuerlexiangli'pear were higher after 96 h of pollination, followed by‘Kuqa Amut' (28%) and‘Aksu Jujuli' (28%) . The pollen tube of‘Kuerlexiangli'pear and other cultivars could not reach or seldom reached the style base of‘Kuerlexiangli'pear at 96 h after pollination.‘Lüli' (34.31% ± 1.87%) , ‘Dangshansuli' (31.22% ± 1.89%) and‘Aksu Jujuli' (26.95% ± 1.36%) had higher fruit setting rates, followed by‘Kuqa Amut' (8.41%±0.94%) . The fruit setting rate of self-pollination was 2.56%±0.03% and the fruit setting rate of‘Luntai Jujuli'‘Hese Jujuli'and‘Heisuanli'was zero, showing self-incompatibility and cross-incompatibility. Pollination compatibility was significantly positively correlated with single fruit weight but negatively correlated with fruit shape index of hybrid fruit.The single fruit weight of‘Kuerlexiangli'pear was the larger when‘Kuqa Amut' (135.00 ± 1.78 g) , ‘Aiwenqieke' (124.17±2.95 g) and‘Lüli' (122.50±5.05 g) were used as pollinators, compared with that of‘Dangshansuli' (106.70±2.84 g) and other pollinating combinations. The fruit shape indexes of‘Kuerlexiangli'pear were larger when self pollinated (1.26±0.02) or‘Huocheng Donghuangli' (1.25±0.02) was used as pollinator compared with those when‘Dangshansuli' (1.10 ± 0.01) , ‘Lüli' (1.14 ±0.02) and‘Aksu Jujuli' (1.14 ± 0.02) were used as pollinators. The fruit firmness of‘Kuerlexiangli'pear was the higher when‘Dangshansuli' (8.03±0.30 kg · cm-2) and‘Aiwenqieke' (7.66±0.23 kg · cm-2) were used as pollinators, compared with those when‘Lüli' (6.56±0.25 kg · cm-2) was used as pollinator.The sugar-acid ratios of‘Kuerlexiangli'pear higher when‘Kuqa Amut' (15.96 ± 0.20) and‘Korla Huangsuanli' (16.08 ± 0.38) were used as pollinators compared with those when‘Aksu Jujuli' (8.75 ±0.18) and‘Huocheng Donghuangli' (9.03±0.28) were used as pollinators. The fruits of‘Kuerlexiangli'pear had the highest soluble solids content when they were pollinated by‘Kuqa Amut' (14.14% ±0.14%) , and the lowest soluble solids content when they were pollinated by‘Aiwenqieke (12.18 ±0.21%) and‘Huocheng Donghuangli' (12.26% ± 0.37%) . The Vitamin C contents of‘Kuerlexiangli'pear varied with the pollinators. They were 3.83±0.09 mg · 100 g-1 (self-pollinated) , 3.55±0.02 mg · 100 g-1 (pollinated by‘Aksu Jujuli') , 2.84 ± 0.06 mg · 100 g-1 (pollinated by‘Dangshansuli') , (2.84 ± 0.05 mg ·100 g-1 (pollinated by‘Huocheng Donghuangli') , respectively. The number of normal seeds of‘Kuerlexiangli'pear were 8.68 (‘Lüli'used as pollinator) , 8.94 (‘Dangshansuli'used as pollinator) and 2.33 (‘Huocheng Donghuangli'used as pollinator) . Seed number of hybrid fruit was negatively correlated with fruit shape index; pollinizer pollen xenia had a significant positive effect on fruit shape index of‘Kuerlexiangli'pear.【Conclusion】‘Lüli'could be a suitable pollinizer for‘Kuerlexiangli'pear because it was highly compatible with‘Kuerlexiangli'pear and would increase the fruit weight, reduce fruit firmness and fruit shape index, and lead to perfect sugar-acid ratio, and medium contents of soluble solids and Vitamin C of th efruits of‘Kuerlexiangli'pear.