JIA-2018-09

2071 ZHANG Shuai et al. Journal of Integrative Agriculture 2018, 17(9): 2066–2073 markers, we found that A . gossypii populations in northern China exhibited greater genotypic diversity, and the 31 populations in northern China could be classified into one of 3 biotypes according to host species (Luo et al. 2016). Unlike in other places, the microsatellite loci had high diversity in northern China, making it difficult to practically use. Based on complete mitochondrial sequences, a molecular marker with 5 single-nucleotide polymorphisms within Cytb and 16S genes was identified to distinguish the biotypes, and 2 biotypes of A . gossypii specializing on cotton and cucurbits in northern China were identified (Wang et al. 2016). Other studies also showed that the mitochondrial Cytb gene can be used to distinguish A . gossypii from related species in many places (Carletto et al. 2009a; Kim et al. 2011). In this study, we used single-nucleotide polymorphisms within Cytb and 16S genes beyond the 5 single-nucleotide polymorphisms used to distinguish A . gossypii biotypes, and these may be used in studying the life cycle of different host biotypes of A . gossypii in northern China. The cucurbit host-race A . gossypii has been well studied, and has been assigned to genetic clusters I, II, and III according to Vat resistance of Cucumis melo (Boissot et al. 2016; Thomas et al. 2016). Type 1 A. gossypii exactly corresponded to the cucurbit host-race. Type 1 contained 3 haplotypes in northern China, and was only found on zucchini, kidney bean, cucumber and muskmelon. No primary hosts were found in this study. Zucchini and kidney bean have been shown in previous studies to serve as hosts without consideration of the host-race of A . gossypii (Wu et al. 2013). Results indicated that cucurbit host-race can be anholocyclic or holocylic lineages and originating from wild plants that had never been previously sampled (Thomas et al. 2012). The haplotypes that contained more than 2 individuals were chosen to construct a NJ tree and to identify A . gossypii biotypes, as less abundant haplotypes could be derived from nucleotide incorporation mistakes that occurred during the PCR or sequencing procedure (Biles and Connolly 2004). Unlike the cucurbit host-race that was not found on cotton, 3 out of 4 biotypes considered in the cotton host- race of A . gossypii were on cucurbits. In melon-growing areas of France, Bayesian Structure results showed that a cluster contained some multilocus genotypes (MLGs) that specialized on Cucurbitaceae and some specialized on Malvaceae (Thomas et al. 2012). In this study, zucchini was planted near cotton and Cucurbitaceae fields, and the cotton host-race may have transferred from cotton to Cucurbitaceae with zucchini as a bridge plant (Wu et al. 2013). A large scale field experiment in a Cucurbitaceae plant field is needed in order to confirm this hypothesis. A . gossypii can be holocyclic in northern China. The other 4 biotypes in the cotton host-race have this lifecycle because all of them have both primary and summer hosts. Those primary hosts are not only hibiscus, pomegranate, and Chinese prickly ash , but also S. japonica , which was reported for the first time in China to our knowledge. Using classification with the mitochondrial gene, pomegranate was the host of the cotton host-race, and when using SSR, the population on pomegranate was classified with populations collected on cotton (Luo et al. 2016). The Chinese prickly ash (Rutaceae) is one of the most ancient cultivated economic trees in Chinese mountainous regions, and is of major agricultural importance as sources of spices and traditional medicine (Feng et al. 2015). All 4 biotypes of A . gossypii can be found on Chinese prickly ash, with Type 5 being on cotton and Chinese prickly ash. The highest haplotype diversity value was observed in populations on Chinese prickly ash, but populations from globally distributed hibiscus had lower diversity. Since Chinese prickly ash originated fromChina and has a narrow range, the A . gossypii immigrant colony may host on this plant, leading to a Table 2 Genetic diversity of 19 Aphis gossypii geographic populations in China revealed by mitochondrial genes 1) Collection locations 2) n Nh π (%) Hd Shandong Province SDCW 21 2 0.017 0.095 SDCX 12 3 0.058 0.318 SDJX 16 5 0.222 0.767 SDLL 5 1 0 0 SDLQ 31 3 0.096 0.471 SDXJ 11 2 0.076 0.436 SDSX 31 1 0 0 SDWC 6 2 0.092 0.533 Hebei Province HBWX 33 2 0.011 0.061 HBLZ 23 1 0 0 HBNP 26 2 0.088 0.508 HBQX 13 2 0.027 0.154 HBQZ 18 2 0.019 0.111 HBZQ 29 2 0.090 0.517 Henan Province HNSQ 30 2 0.050 0.287 HNWS 16 2 0.079 0.458 HNXH 22 3 0.109 0.567 HNLY 37 2 0.066 0.378 HNYL 23 4 0.112 0.447 Total 403 10 0.093 0.484 1) Nh, number of haplotypes; π, nucleotide diversity; Hd, haplotype diversity. 2) SDCW, Chengwu in Shandong Province; SDCX, Caoxian in Shandong Province; SDJX, Jinxiang in Shandong Province; SDLL, Laoling in Shandong Province; SDLQ, Linqing in Shandong Province, SDXJ, Xiajing in Shandong Province; SDSX, Shanxian in Shandong Province; SDWC, Wucheng in Shandong Province; HBWX, Weixian in Hebei Province; HBLZ, Linzhang in Hebei Province; HBNP, Nanpi in Hebei Province; HBQX, Qiuxian in Hebei Province; HBQZ, Quzhou in Hebei Province; HBZQ, Zhaoqiang in Hebei Province; HNSQ, Shangqiu in Henan Province; HNWS, Weishi in Henan Province; HNXH, Xihua in Henan Province; HNLY, Luyi in Henan Province; HNYL, Yanling in Henan Province.