Yongbo WANG, Yaru WANG, Xiao LI, Yingtao WANG, Hongbao WANG, Jin WANG, Yong LI

Shijiazhuang Fruit Research Institute, Hebei Academy of Agricultural and Forestry Sciences, Shijiazhuang 050061, China

Abstract ‘Jixiu’ is a new early ripening pear variety bred by ‘Jimi’בXinhang’, and its fruit quality is excellent. It has performed well in central and southern Hebei. This paper introduces its botanical characteristics, growth phenology, growth and fruiting habits, pollination characteristics and disease resistance in central and southern Hebei. A set of suitable cultivation techniques for Jixiu pear were summarized, including pruning, fruit thinning and bagging, water and fertilizer management, pest and disease control and so on, which provided theoretical support for the popularization and demonstration of this new variety.

Key words Pear, New varieties, Jixiu, Precocity

1 Introduction

China’s pear cultivation area and yield rank first in the world[1]. Pear industry plays an important role in China’s national economy and has become an important industry for rural revitalization and farmers’ income increase. The vast number of pear breeding researchers have made great contribution, and have successively bred more than 100 new pear varieties with their own characteristics, such as ‘Cuiguan’, ‘Huangguan’, ‘Yuluxiang’, ‘Ningxia’ and ‘Xialu’. The market contribution rate of new varieties is over 40%, which promotes the rapid and sustainable development of pear industry. However, there are still some problems in pear industry in China, such as unreasonable variety structure, excessive proportion of middle and late maturing varieties and lack of early maturing varieties[3]. China has a vast territory and diverse climatic conditions. Breeding excellent early-maturing pear varieties suitable for local ecological conditions is the key to giving full play to variety advantages and promoting industrial development[4]. ‘Jixiu’ is a new early-maturing pear variety bred by Shijiazhuang Fruit Research Institute of Hebei Academy of Agricultural and Forestry Sciences through cross breeding (Fig. 1), which was approved by Hebei Forest Variety Approval Committee in 2020.

2 Breeding process

‘Jixiu’ was bred by crossing ‘Jimi’ (Xuehuali×Huanghua) as female parent and ‘Xinhang’ (Shinseiki×Hangqing) as male parent, and its original code name was 08-1-52-2. Sexual hybridization was carried out in 2005, and 1 050 hybrid seeds were harvested, which were sown in spring of 2006 after low temperature stratification treatment. In 2007, the seedlings were pre-selected, and in the spring of 2008, 412 seedlings were planted in the seedling selection nursery of Shijiazhuang Fruit Research Institute of Hebei Academy of Agricultural and Forestry Sciences in the "cluster" cultivation mode (4 plants in one hole).

In 2010, the strain numbered 08-1-52-2 began to bear fruit, showing the characteristics of early maturity, smooth and beautiful fruit surface and excellent quality, and was listed as the best primary plant. After 3 years of re-selection, it was confirmed that 08-1-52-2 had early ripening period and excellent comprehensive quality. In 2013, a pilot garden was established in Shijiazhuang Fruit Research Institute of Hebei Academy of Agricultura and Forestry Sciences, and three regional pilot gardens were established in Jinzhou, Shenzhou and Handan, Hebei Province. After years of continuous observation, the genetic traits of this strain were stable and the cultivation traits were good. In 2019, after on-site testing by experts recommended by Hebei Forest Variety Approval Committee, it passed the examination and approval in April 2020 and was officially named ‘Jixiu’.

Fig.1 A new pear variety ‘Jixiu’

3 Investigation on traits in the breeding process

3.1 Botanical characteristics‘Jixiu’ tree vigor was moderate; trunk and perennial branches were grayish brown with smooth bark; annual branches were yellow-brown, with small and dense lenticels and internode length of 3.48 cm; leaf buds were adnate, and flower buds were conical; young leaves were maroon, mature leaves were dark green, oval, 10.3 cm long and 6.7 cm wide; the leaves were revolute, the leaf base was wide and wedge-shaped, the tip was sharp, the leaf margin was sharply serrated, and there were prickly awns; buds were white, petals were elliptic, overlapping; each flower had 5-10 petals, with white corolla, purple anther, and there were 7-9 flowers per inflorescence.

3.2 Economic characters of fruit‘Jixiu’ was ripened in early August, and its fruit was oval, with an average single fruit weight of 210 g; the fruit surface was green and yellow, the peel was thin, the fruit dot was small and dense, and there were obvious fleshy "protuberances" at the fruit stems; the pulp was white, the meat was fine, crisp, juicy, sweet and sour and fragrant; the fruit core was small, there were few stone cells and residues, and the content of soluble solids was 12.98%; the comprehensive quality was excellent and there was good storage resistance.

3.3 Biological characteristics

3.3.1Main phenological periods. In Shijiazhuang, ‘Jixiu’ sprouted in the first half of March, initially bloomed in early April, and fully bloomed in early April, with a flowering period of about 8 d; the ripening period of fruit was early August; the new shoots began to grow in mid-April and stopped growing in the middle and late June; the leaf falling period was November (Table 1).

Table 1 Main phenological periods of different pear varieties in Shijiazhuang (2018)

3.3.2Growth and fruiting habits. Young trees were strong and grew vigorously, and the tree vigor was moderate in the full fruiting period; the germination rate was high (71.43%) and the branching ability was at medium level; short fruit branches mainly bore fruit; two side shoots of each fruit spur were produced, and the side shoots of fruit spur had strong continuous fruiting ability; under natural pollination, the average number of fruits per inflorescence was 3.2 (Table 2).

Table 2 Investigation on growth and fruiting habits of ‘Jixiu’

Under normal management conditions, the fruit can be obtained after 2-3 years of planting, and the yield of 4-year-old trees can reach 8 253.0 kg/ha; after planting for 7 years, the yield can reach 330 000.0 kg/ha, without great fluctuations, and it has high and stable yield performance (Table 3).

3.4 Pollination characteristicsPollination experiments of different varieties on ‘Jixiu’ were carried out for three consecutive years from 2016 to 2018. The fruit setting rates were: 70.6% for Jixiu×Zaoguan Jixiu×Zaoguan; 72.3% for Jixiu×Huangguan Jixiu×Huangguan; 85.1% for Jixiu×Zhongli 1 Jixiu×Zhongli 1; 75.9% for Jixiu×Yali Jixiu×Yali; 76.6% for Jixiu×Xuehuali Jixiu×Xuehuali. The results showed that the fruit setting rate of inflorescence was more than 70.0% for different pollination combinations.

3.5 Disease resistance and adaptability‘Jixiu’ has strong stress resistance, and no harm of scab, black spot and anthracnose has been found in field investigation for many years; in extreme low temperature years, there was no freezing damage; the requirements for soil are not strict, and it can be planted on flat land and beach, which is resistant to high temperature and humidity; at extreme high temperature (above 38 ℃), leaves have slight sunburn, and no fruit cracking occurs under drought conditions.

4 Cultivation techniques

4.1 Planting density and pollinating treeThe optimum planting density was 2.5 m×4.5 m. ‘Huangguan’, ‘Zaoguan’, ‘Zhongli 1’ and ‘Yali’ were selected as pollinating varieties, and the ratio of ‘Jixiu’ to pollinating varieties was (4-5)∶1.

4.2 Shaping and trimmingThe tree form can be single-layer heart, the tree in dense planting garden can be cylindrical or spindle-shaped, and the "transformed" tree can be open-heart-shaped. It is necessary to pull branches and shape them in young trees, and the opening angle of main branches should be 60°-70°. At full fruiting stage, attention should be paid to the renewal of fruiting branches, weeping branches and thin and weak fruit branches.

4.3 Tree load and baggingThe fruit setting rate of ‘Jixiu’ under natural pollination was high, but the average fruit weight was slightly lower, so flower thinning and fruit thinning should be carried out strictly, and the load should be adjusted by flower thinning and fruit thinning. A single fruit per inflorescence was kept, and the space distance between young fruits was 20-25 cm. It is necessary to keep low order fruits (2-3) to ensure good fruit shape and excellent varieties. According to the measurement of internal and external quality of ‘Jixiu’ by different paper bag types, it is recommended to use single-layer white wax paper bag as the preferred fruit bag (Table 4).

4.4 Fertilizer and water managementIn autumn, 60 000-70 000 kg/ha of high-quality organic fertilizer and proper amount of compound fertilizer were applied; appropriate amount of quick-acting fertilizer was applied according to different periods in the growing season to meet the needs of tree and fruit growth; at the full fruiting stage, 1.0 kg of available N fertilizer was applied to each plant after flowering, and P and K compound fertilizer was applied once in early July. Water management was based on the principle of early guarantee and late control, and drainage work in rainy season should be done well in low-lying gardens.

4.5 Pest and disease controlThe main disease is ring spot, and the main pests are oriental peach moth, pear leaf sucker, yellow meal worm,P.comstockiKuwanaand so on. In the production, we should first pay special attention to the agricultural control measures such as clearing the garden, and scraping bark in dormant period. Spraying 3°-5° stone sulfur mixture once in the whole garden before germination in spring is very important to killing overwintering eggs. It is necessary to pay attention to comprehensive prevention and control. On the basis of doing a good job in agricultural prevention and control, we should select biological pesticides, mineral pesticides and new chemicals with high efficiency, low toxicity and low residue, such as mancozeb, thiophanate-methyl, carbendazim, imidacloprid, abamectin, beta-cypermethrin and diflubenzuron.