Z. Gui’s research while affiliated with Nanchang University and other places

Acarus siro L., a common acaroid mite in China, is one of the main pest mites damaging the stored products, economic crops and edible fungi. The mite is widely studied due to its economic importance. In this paper, the genetic structure and genetic diversity of A. siro in four geographic populations were studied by using ISSR marker. 18 primers were selected for their ability to produce clear and reproducible patterns of polymorphic bands. Those primers were then used for analysing genetic diversity within and among populations of A. siro collected in Nanchang city, Jiujiang city in Jiangxi province and Hefei city, Caohu city in Anhui province (NC, JJ, HF, CH). A total of 136 DNA bands were yielded, 107 of which were polymorphic and PPB was 78.68%. The levels of genetic diversity of four population could be ordered in abundance as JJ> NC> HF> CH and the JJ population was the highest level. The value of Gst was 0.6283, indicating high level of genetic differentiation among populations. Nei's genetic diversity analysis showed that the level of gene flow (Nm=0.3717) was lower than that among populations (Nm=0.29). Dendrogram constructed using the UPMGA method and Nei's unbias genetic distance showed the same location could be clustered together to form a specific clade. Geographic difference caused great differentiation. Moreover, there was no significant correlation between the genetic distance and geographic distance, indicating that geographic isolation was not the main factors inducing genetic difference.

Genetic relationships among 26 alfalfa cultivars, of which, 12 were of high resistance to common leaf spot (CLS), were assessed using sequence-related amplified polymorphism (SRAP) markers. 34 SRAP primer combinations were selected for fingerprinting of these cultivars and a total of 281 bands were observed, among which 115 were polymorphic (40.93%). Based on molecular data, 26 cultivars were classified into 5 groups. Group I included 12 Chinese cultivars, most of which had a low CLS resistance and were planted in cold and/or drought region in China, while 10 of 11 cultivars with a high CLS resistance were put in group II or group IV respectively. Furthermore, the clustering pattern was, on the whole, consistent with their CLS resistance or geographic origins. In addition, there was a low genetic diversity among alfalfa cultivars from China. In conclusion, SRAP markers may serve as a quick tool to analyze the genetic relationships and genetic diversity among alfalfa cultivars in conjunction with DNA bulking method. The information produced by this study on the genetic relationships and genetic diversity among 26 cultivars could be useful to select parents in a CLS resistance breeding program of alfalfa.