Breeding of a new sand pear cultivar Jinhuazao

Abstract:Jinhuazao is an excellent strain of local sand pear (Pyrus pyrifolia) cultivars in Shangfeng town, She county, Anhui province. In 2008, we surveyed the sand pear germplasm resources in Anhui province and discovered five distinct self-rooted mother trees with moderate fruit size, round fruit shape and outstanding fruit quality, as well as tolerance to early defoliation disease and long storage period. During the preliminary selection, it was temporarily named as Jinhuazao pear. To confirm the hypothesis that these five plants were unprecedented local pear cultivars, we re-investigated the local sand pear germplasm resources during 2009—2010 and successfully constructed a SRAP genetic map for them. According to the phylogenetic tree analysis and DNA electrophoresis results, we revealed that these five plants were distinctive from other surveyed pear strains. Therefore, we subsequently consulted the relevant information and conducted fruit quality evaluation and genetic molecular identification on them, and two of them were selected for further study. After that, we monitored and comparatively analyzed the biological and physiological characteristics and resistance to abiotic stresses between the two selected strains and other pear strains. Fortunately, we obtained a new excellent local sand pear cultivar, which was early maturing, highly yielding, strongly adaptable and more tolerant to early defoliation disease. These support our assumption that Jinhuazao was a characteristic local pear variety that was unrecorded before in Anhui province. A regional evaluation was performed from 2015 to 2020 in Anhuiprovince, and the biological characteristics, phenological period and main economic traits of Jinhuazao were systematically investigated. The results showed that Jinhuazao was a kind of strong and upright pear tree, which was recognized by its strong branching potential but weak branching power in the field. Jiangzaohua sprouted on March 10, and the flowers began to open on March 20, full bloom occurred on March 24, and flowering ended on March 30. Their flowers consisted of 5−6 white petals, where the internal stamens were date-red or red, with 20−22 individual whorled filaments. In addition, corymb-shaped clusters were observed in full bloom, which was composed of 5−7 flowers. At the same time, we found that the 1- year- old branches of Jinhuazao were brown, and were spirally attached by green and oblong oval- shaped leaves, which were distinguishable by their long and acute leaf tips, rounded leaf bases, and bluntly serrated leaf margins. Moreover, we noticed that the leaf surface was smooth and glossy, slightly curved inward on both sides, and the pedicels were thin. The transverse and the vertical diameters of the leaves were approximately 12.59 cm and 7.52 cm, respectively, while the petiole length of them was roughly 4.22 cm. Beyond those, we discovered that Jinhuazao was highly fruit-setting, whose fruits matured earlier than other local pear varieties in Anhui province, and in the Huangshan region of Anhui province, the fruit maturity occurred in late August. The fruit of Jinhuazao was round, and the flesh was creamy white and compact with a 5-ventricle-denoted medium fruit core. It displayed medium hardness and exhibited a green pericarp accompanied by brown rust spots on the shoulder. According to our analysis, the average fruit weight was 350.6 g, the soluble solid content of the fruit was 10.8%, and the organic acid content was 0.05%. Importantly, compared to the local pear cultivars Chuwhangbae and Housui, Jiangzaohua seemed to be more tolerant to the early defoliation disease that arose on November 2 in the field, and the fruit was equipped with a better storage property, with a storage period of approximately 30 days at room temperature. Jinhuazao could be grafted on the Duli rootstock to achieve greater economic value. The planting density in the orchard should be set as 2 m between trees and 4 m between rows. The trees should be trained into sparsely-layered or open-central system. To guarantee the yields of the coming year, the structure of the canopy and the composition of the branches should be strictly controlled through winter pruning, which ought to be performed between 20−25 days after leaf drop. If available, bees can be released at full bloom period to promote pollen dispersal, hence improving the fruit set. As for fertilizer management, sufficient fertilizer must be applied to the trees in the juvenile period, with a single-use of fast-acting fertilizer before the emergence of new shoots. During this period, foliar fertilizer can be sprayed to promote the growth of branch tips. Upon entering adulthood, special attention should be paid to the application of basal, pre-flowering and fruit-harvesting fertilizers, where organic manure should be the main fertilizer, and its reasonable combination with medium-, and trace-elements is needed. Noteworthily, the amount of organic manure application should account for more than 70% of the annual amount of fertilizer. However, despite the strong resistance of Jinhuazao to multiple diseases, more attention should still be paid to prevent it from disease in the field in the southern rainy season, with an emphasis on the governance towards the black spot, anthracnose and Gymnosporangium asiaticum of pear. To reduce the rate of pests and diseases, prediction and forecasting should be strengthened, and agricultural, biological, physical and chemical control should be integrated and adopted under the principle of“prevention first, green governance”. The grafted trees of Jinhuazao could bear abundant fruit in the fourth year and harvested in the fifth year after grafting, the yield of grafted trees was consistent and highly productive, and it reached more than 2 125.2 kg per 666.7 m2 , which is higher than that of Chuwhangbae and Housui. It is appropriate for cultivation in the Yangtze River basin and mountainous area of southern Anhui, and it can grow wellin any area where it is warm and humid with cool summers. In 2021, it was approved by the Anhui Forest Variety Approval Committee (Accession No.: Wan S-SV-PP-004-2021).