Fruit phenotypic characters diversity analysis of pear native varieties in Yunnan

Abstract:【Objective】The abundance of germplasm resources of pear in Yunnan is notable. In excess of 200 distinct pear varieties (types) have been domesticated and adapted to varying climatic conditions over long periods of cultivation, attesting to their diversity and adaptability. Despite the abundance of genetic resources, research on fruit traits of local pear varieties in Yunnan is still limited. Therefore, the aim of this study was to investigate the fruit characteristics and diversity of these varieties in order to provide valuable references for their exploitation and utilization in the future.【Methods】In this study, a total of 61 distinct local pear varieties were collected from primary pear-growing areas in Yunnan. A comprehensive assessment of sixteen descriptive traits and seven quantitative characters of the fruit were conducted to evaluate the diversity and variant types of the species. The sixteen descriptive phenotypic traits included fruit shape, ground color, dot-obviousness, smoothness of the fruit skin, stalk-cavity depth, eye- basin depth, relief of area around eye basin, flesh color, texture, texture-type, fruit-core size, stone-cell amount, juiciness-of-flesh, flavor, astringency, and fruit maturity date. The seven quantitative characteristics were fruit-single weight, fruit- vertical diameter, fruit- transverse diameter, fruit-shape index, fruit-stalk length, fruit-stalk roughness, and soluble-solid content. Furthermore, electronicnose detection of fruit aroma was performed, and principal-component-analysis was applied to analyze the data. The electronic nose incorporated a sensor array detecting the chemical compounds in an aroma mixture, and then converted electronic output signals from all sensors. Collectively, these signals generated a unique digital pattern known as the Electronic Aroma Signature Pattern (EASP) highly specific to the gas mixture being analyzed. Consequently, the instrument output generated a distinctive aroma signature or smell-print useful in identifying the particular type and variety of fruit.【Results】The phenotypic traits of 61 pear local varieties exhibited a wide range of variation , and totally 63 variations were observed. On average, 4.0 variations per trait were identified. The diversity index (H’) ranged from 0.45 to 1.88, indicating the high level of diversity presented in these varieties. The diversity of fruit shape and ripening stage were notably apparent among the various types. Obovate, Oblate, and Globose were the most common fruit shape observed. The majority of fruit ripening dates occurred between mid-August and September, comprising 81.96% of the total ripening dates. A total of nineteen local pear varieties had been identified, with distinct kinds of red-skin, such as bright red, light red, pink or dark red. Out of the seven local pears, including Huizehuopiaoli, Miduhuobali, Miduhongxiangsu, Miduxiaohongli, Weishanhongxueli, Weishanhuobali, and Eryuanhuobali, notably standed out for their bright red skin, offering an excellent resource for the selection and breeding of red-skinned pear. The coefficient of variation for seven quantitative traits ranged between 11.25% and 61.79%, while the diversity index (H’) varied from 1.676 to 2.080. The coefficient of variation of the single fruit weight was extremely high, 61.79%. The heaviest single fruit was Weishanshiquandameili, with a weight of 519.78 g. Conversely, the smallest fruit was Jianshuixiaotianli, with a weight of 22.02 g. The fruit vertical and transverse diameter, fruit shape index, stalk length, and soluble solids content showed a high degree of diversity with H’values exceeding 2.0. Among the local varieties, the largest vertical fruit diameter was observed in Weishanlaomanli, while the longest transverse fruit diameter was observed in Weishanshiquandameili. In contrast, Jianshuixiaotianli exhibited the smallest vertical and transverse diameters. Xiangyunbendili 2 possessed the highest soluble solids content, with a value of 13.59%, while Yongpinglaopinzhongli exhibited the lowest value, with only 7.63%. The results from electronic nose technology revealed that WIW (hydrogen sulfide sensor), W5S (NOx compound sensor), and W2W (organic sulfide sensor) were very important in pattern recognition. The principal component analysis showed that it was possible to distinguish all cultivars through analyzing specific aroma compounds.【Conclusion】61 pear local varieties in Yunnan are rich in fruit descriptive traits and have high diversity index of quantitative traits. Seven varieties with bright red peels, including Huizehuopiaoli, could be used as excellent resources for red-skin pear breeding. The electronic nose technology could be used as an auxiliary means for local variety identification.