Analysis of morphological diversity of Pyrus calleryana Dcne. in Southern China

Abstract: 【Objective】The objective of the study was to investigte the distribution of Pyrus calleryana Dcne. and assess morphological diversity of the species in southern China.【Methods】We refered to the floras of China, floras of several provinces and articles published in recent 10 years on the resources of wild fruit trees, and the data of Chinese Virtual Herbarium for selecting the regions to investigate. From September 3 to 16, September 23 to October 1, and October 30 to November 16, 2017, we went to Zhejiang, Hunan, Hubei, Guangdong, Guangxi and Jiangxi provinces and collected 78 P. calleryana resources. Variance analysis, principal component analysis, cluster analysis and Duncan's multiple comparative analysis were carried out to study 19 morphological traits of the leaves and fruits of the species.【Results】The results showed that there were abundant morphological diversity of P. calleryana in southern China. The diversity index of the eleven descriptive traits of branches, leaves and fruits was 0.56-1.04, among them the diversity indices of the shape of leaf base (1.04) , the leaf extension state (0.96) , and the fruit core position (0.93) were higher. The diversity indices of the annual branch color (0.87) , the leaf bud attitude (0.63) , the leaf bud apical feature (0.30) , the leaf shape (0.75) , the leaf apex shape (0.56) , the leaf margin (0.82) , the fruit shape (0.71) and the fruit bottom color (0.88) were relatively lower. Among the eight quantitative traits, the difference of the length of carpopodium and fruit shape index among the populations reached a very significant level, indicating that there were wide differences in the lengthes of carpopodium stalk and fruit shape indices among the populations, and the differences of fruit transverse diameter and fruit longitudinal diameter within and between populations reached significant levels, indicating that there were wide variations in the fruit transverse diameter and the fruit longitudinal diameter in the groups and between the populations. The F values among populations were higher than those within populations in all quantitative traits. There were more genetic variation between the populations of P. calleryana than those within the populations. The average coefficient of variations of the eight quantitative traits was 19.85, among them the length of petiole was the largest (37.48%) , followed by the length of carpopodium (19.75%) and the leaf width (19.40%) , and the fruit shape index was the smallest (8.1%) . The morphological diversity of the populations varied greatly. The average coefficient of variations of the populations collected from Guangxi and Hubei was the largest, 18.47% and18.61% respectively, indicating that the dispersal degree of each traits index of the population was larger, while the average coefficient of variations of the populations collected from Guangdong was the smallest, only 11.93%, indicating that the variation of Guangdong population was small. The results of multiple comparative analysis of 8 quantitative traits showed that the leaf length and the leaf width of the populations collected from Hubei were significantly larger than those of other populations, indicating that there were mostly large leaf individuals of P. calleryana in Hubei. The leaf shape index of Hubei population was significantlylarger than that of Zhejiang population, suggesting that the leaves of P.calleryana from Hunan and Hubei were mostly oblong, while those from Zhejiang were mostly short circle, and the Length of petiole of Hubei population was significantly larger than that of Guangdong population. The fruit shape indices of Zhejiang and Hubei populations were significantly higher than that of Hunan, Jiangxi, Guangdong and Guangxi, populayions, indicating that the fruits of P. calleryana in Zhejiang and Hubei were mostly oblong, while those from Hunan, Jiangxi, Guangdong and Guangxi were mostly oblate. The Length of petiole of Zhejiang populations was significantly longer than that of other populations, indicating that the petioles of P. calleryana in Zhejiang were longer than that of the populayions from other areas. The principal component analysis of 8 quantitative traits showed that the Eigenvalue of the first seven principal components were all over 1, and the cumulative contribution rate was 70.804, indicating that the first seven principal components could better explain all the genetic information of the all variables. The cluster analysis of 19 phenotypic characters of 78 P. calleryana showed that when the distance coefficient was 9.9, 78 P. calleryana could be grouped into five categories.The first category consisted of the materials from Hubei and Zhejiang; the second category consisted of the materials from Hunan; the third category included all the materials from Jiangxi and the materials from Quanzhou county of Guangxi; the fourth category included the materials from Guangdong;and the fifth category included the materials from Huanjiang County, Yizhou City, Bama County and Ningming County of Guangxi.【Conclusion】The coefficient of variation of different characters varied greatly, and there were abundant variations among different populations of P. calleryana resources.