西瓜种质资源瓜氨酸含量分析及评价

李蒙蒙，路绪强，赵胜杰，何楠，尚建立，刘文革^﹡

（中国农业科学院郑州果树研究所，郑州 450009）

摘  要：【目的】通过对195份供试西瓜材料果实中瓜氨酸含量的测定，以期对西瓜种质资源总体瓜氨酸含量有较为全面的了解。根据瓜氨酸含量高低，将195份西瓜种质资源划分为瓜氨酸含量不同的类群，研究不同瓤色（白、黄、粉、红）以及不同西瓜类型（野生西瓜、粘籽西瓜、籽瓜、地方品种、选育品种、国外引进的固定品种）在各个西瓜类群中的分布规律，筛选出高瓜氨酸含量的西瓜种质，为选育高瓜氨酸西瓜品种奠定基础。【方法】以195份西瓜种质资源为材料，用分光光度法测定成熟果实中瓜氨酸含量(鲜重)，通过聚类分析将195份西瓜资源分为不同的类群，进行资源分类与筛选。【结果】195份西瓜种质资源瓜氨酸含量瓜氨酸含量平均值为1.45 g/kg∙FW，呈近似正态分布，大多数品种集中分布在0.84-2.10 g/kg∙FW之间。根据聚类分析，195份西瓜种质资源可划分为4个类群（极低型（Ⅰ）、低型（Ⅱ）、高型（Ⅲ）、极高型（Ⅳ））。白瓤西瓜主要集中在含量较低的Ⅰ类群，黄瓤、粉瓤、红瓤西瓜主要分布在瓜氨酸含量较高的Ⅲ类群中，黄瓤、粉瓤、红瓤三种瓤色西瓜瓜氨酸含量无显著差异，但显著高于白瓤西瓜品种。地方品种、选育品种以及国外引进的固定品种主要集中在瓜氨酸含量较高的Ⅲ类群中；粘籽西瓜主要分布在Ⅰ和Ⅱ类群中，而野生西瓜和籽瓜则主要分布在含量极低的Ⅰ类群中。地方品种、选育品种以及国外引进的固定品种瓜氨酸含量差异不显著，但均显著高于野生西瓜、粘籽西瓜和籽瓜。【结论】195份西瓜种质资源瓜氨酸含量范围为0.49-2.55 （g/kg∙FW），变异系数为0.30。黄瓤、粉瓤、黄瓤三种瓤色西瓜品种瓜氨酸含量显著高于白瓤西瓜，而地方品种、选育品种以及国外引进的固定品种瓜氨酸含量显著高于野生西瓜，粘籽西瓜、籽瓜，西瓜瓜氨酸含量与西瓜瓤色以及类型有关，不同瓤色和类型西瓜瓜氨酸含量差异可能是由于人们对西瓜的选择、驯化造成的。筛选高瓜氨酸品种的亲本材料时，除了选育品种，还可以从地方品种和国外引进的固定品种中筛选，丰富了育种材料。本试验筛选出了23份高瓜氨酸含量西瓜种质资源（包括14份选育品种、4份地方品种以及5份国外引进的固定品种），可作为选育高瓜氨酸西瓜品种的亲本材料。

关键词：西瓜种质资源；瓜氨酸；西瓜类型；瓤色

Analysis and Evaluation of Citrulline Content in Watermelon Germplasm Resources

LI Meng-meng, LU Xu-qiang, ZHAO Sheng-jie, HE Nan, SHANG jian-li, LIU Wen-ge

(Zhengzhou Fruit Research Institute, Chinese Academy of Agricultural Sciences, Zhengzhou 450009)

Abstract:【Objective】L-citrulline is a naturally amino acid that function in detoxification of catabolic ammonia and is a key element in production of the vasodialator, nitric oxide. Watermelon is considered to be a natural source for citrulline because of the large amount of citrulline in the flesh and rind. With the improvement of people 's living standard, functional food have been valued, the watermelon varieties with higher citrulline have been bred by breeders.In recent years, the content of citrulline in different varieties, flesh colors, and organs, ploidy, fruit development stages in watermelon had been determined. However, a problem that will be solved in these researches is the lack of comparability of citrulline content due to few varieties and different growing environment and different locations, In this work, the contents of citrulline in 195 watermelon germplasm resources planted in the same location were measured. According to the citrulline content level, 195 watermelon germplasm resources were divided into different groups, then the distribution pattern of different flesh color (white, yellow, pink, red) and different watermelon types (wild watermelon; egusi watermelon; edible seed watermelon; the landrace cultivar; bred cultivar and the cultivar from foreign) in different groups were evaluated. In recent years, most of the traditional varieties(wild watermelon; egusi watermelon; edible seed watermelon; the landrace cultivar) are replaced by hybrids and modern cultivars which display higher yields and strong tolerance. So in this work,195 watermelon germplasm resources were evaluated in order to recover the use of some varieties and increase agrobiodiversity, some excellent germplasm resources for breeders were screened out, some supports might be provided for breeding high citrulline watermelon cultivars. 【Method】Totally 195 watermelon germplasm resources were planted in Henan Province under the same planting conditions, the central flesh from ripe fruit was used to measure the citrulline contents, and the tissues were immediately frozen in liquid nitrogenand quickly, stored at -80℃ till use. Citrulline was extracted by Methanol-Hcl in 55℃ waterbath 30 min after watermelon tissues was homogenated, then decolorized the solution by activated carbon, under the action of a mixture of phosphoric acid and sulfuric acid, boiled 30min in the dark, colorreaction by the diacetyl monoxime. The UV-visible spectrophotometric method was used to determine the citrulline content of watermelon fruit indirectly, all data were repeated three times【Result】This study showed that the mean content of 195 watermelon germplasm resources was 1.45g/kg∙FW, the variation coefficient was 0.30. The bred cultivar ‘98A13’with red flesh showed the highest citrulline concentration( 2.55 g/kg∙FW), while the wild watermelon‘PI 296341’ with white flesh performed the lowest citrulline concentration(0.49 g/kg∙FW). A skewed normal distribution was found in the citrulline contents of watermelon. The citrulline content of most of the varieties were concentrated in 0.84-2.10g/kg∙FW, accounted for 82.56% of all tested watermelon germplasm resources. Cluster analysis showed that the 195 watermelon germplasm resources could be divided into four categories, which were very low group (I), low group (II), high group (III), extremely high group (IV) respectively. Group III contained the largest number of watermelon germplasm resources, included 85 varieties, accounted for 43.59% of all the tested materials; followed by group II contained 52 varieties, accounted for 26.67%; group I contained 35 varieties, accounted for 17.95%; while group IV contained the minimum numbers of watermelon germplasm resources, included 23 varieties, accounted for 11.79% . The citrulline contents of group IV were the highest in 4 groups, ranged from 2.02 to 2.55 g/kg∙FW, while the citrulline content of group I was the lowest, ranged from 0.49 to 0.99 g/kg∙FW. The citrulline contents in group II ranged from 1.02 to 1.37 g/kg∙FW and groups III ranged from 1.39 to1.99 g/kg∙FW. The results of this study suggested that the citrulline contents of each groups all appeared great variation. From the study about the distribution pattern of different flesh color watermelon in the four groups, it was found that the citrulline contents of white flesh watermelon was very low, mainly distributed in group I, accounted for 51.28% of all white flesh watermelon, while the yellow flesh , the pink flesh and red flesh watermelon were mainly concentrated in group III, accounted for 50.0%, 58.06%, 48.42% respectively. Although there was no significantly difference among the citrulline contents of yellow flesh, pink flesh and red flesh watermelon, the citrulline concents of brightly flesh color watermelon (yellow, pink, red) were significantly higher than white flesh ones. The distribution of different watermelon types in 4 groups showed that the citrulline contents of wild watermelon, egusi watermelon and edible seed watermelon were relatively lower, all of them only distributed in group I, II and III, wild watermelon and edible seed watermelon mainly distributed in I group, accounted for 60.0%, 50.0% of the corresponded test varieties respectively, while the egusi watermelon mainly in I and II, accounted for 40.0% respectively. However, the landrace cultivar, bred cultivar and cultivar from abroad could be found all of the 4 groups, the citrulline contents of them were relatively higher and all of them were concentrated in group III, accounted for 44.44%, 50.0% and 55.0% respectively. Although there was no significant differences between the citrulline contents of landrace cultivar, bred cultivar and cultivar from foreign, but they were significant higher than wild watermelon, egusi watermelon and edible seed watermelon.【Conclusion】The results showed that the citrulline content of 195 watermelon germplasm resources ranged from 0.49 to 2.55 g/kg∙FW, exhibited large variation. According to citrulline contents, the 195 watermelon germplasm resources were devied into 4 groups. The citrulline concents of brightly flesh color watermelon (yellow, pink, red) were significantly higher than white flesh ones; the citrulline contents of the landrace cultivars, bred cultivars and cultivars from foreign countries were significant higher than wild types, egusi watermelon and edible seed watermelon. The citrulline contents might be affected by the watermelon flesh color and type, the difference of the citrulline contents of different types and flesh colour are most influenced by artificial selection and domestication of watermelon. Not only bred cultivars but also the landrace cultivars and the cultivars from foregin could be selected when the varieties of high citrulline contents were needed. 23 watermelon germplasm resources with high citrulline contents were screened out to provide valuable material supports for breeding and germplasm innovation.

Keywords: Watermelon germplasm resources; Citrulline; Watermelon types; Flesh colours.