Evaluation And Inheritance Of Resistance To Whitefly Bemisia Tabaci Gennadius In Soybean

Whitefly (Bemisia tabaci Genn) is one kind of agricultural pests with wide occurrence, severe harm, strong virulence in soybean around the world, so it is an effective way to breed resistant soybean varieties to control whitefly. The objective of this study was to select resistant soybean germplasm; establish a resistance identification system to whitefly; reveal the inheritance, molecular genetic mechinism, non-preference, antibiosis of resistance to whitefly on soybean, and provide information for soybean breeding.The main conclusions are as follows:1. A dynamic resistance identification system to whitefly in soybean was established.Whitefly nympha is more harmful than adult on soybean, because the population of nympha is big than adult, and nympha produce dew that will cause mildew. So the number of whitefly nympha on per leaflet and per plant was identified, using 419 foreign and Chinese soybean germplasm in Jinan and Guanxian in 2004 and 2007. And the relationship between different resistance indices including mean of whitefly nympha per leaflet, minimum of whitefly nympha per leaflet, maximum of whitefly nympha per leaflet, and total of nympha per plant were comprehensively analyzed. The results showed that the mean of whitefly nympha per leaflet(MWPL) was suitable for as the main index to identify the resistance,because MWPL was significantly corelated with other indices. And it is relatively consistent for the most varieties, althouth MWPL of soybean varities were significantly different at different locations and in different years. Four varieties with the highest resistance including Huapidou, Dongxuan1, Hedou12 and Henghe, and four varieties with the highest susceptibility consisting Qihuang26, Ludou10, Ludou12 and Qihuang28 were screened as the standard varieties. The resistant criterion was made as follows:when MWPL<(a+d), the resistance of soybean variety was high resistant;≥(a+d)-<(a+3d) was resistant;≥(a+3d)-<(a+5d) was medium;≥(a+5d)-<(a+7d) was susceptible; and≥(a+7d) was high susceptible. Meanwhile the results revealed that top leaves were suitable for the resistance identification of determinate soybean varieties, and middle leaves for that of semi-determinate and in-determinate soybean varieties.2. The inheritance of resistance to whitefly was controlled by main genes and polygenes in soybean3 crosses RB1(Qihuang26×Huapidou),RB2(Huapidou×Qihuang26),and RB3(Dongxuanl×Qihuang26) were made with two of the highest resistant Germplasm Huapidou and Dongxuanl,and one of the highest susceptible germplasm Qihuang26. From the 3 crosses,12 populations were derived that included 5 populations JRB1F1,JRB1F2, JRB2 F1,JRB2F2, and JRB2F2:3 in Jinan;and 7 populations LRB1F1, LRB1F2, LRB2 F1, LRB2F2, LRB2F2:3, LRB3 F1, and LRB3F2 in Guanxian. The MWPL of all the populations were identified. Genetic analysis was performed under the Major gene+ polygene mixed inheritance model in the P1, P2, F1, F2, and F2:3 populations. The results suggested that resistance to whitefly were controlled by two major genes and plus polygenes, with the major genes inheritabilty of 86.41%,85.72%,95.90%,95.26%, and 73.18%, and Polygene heritability of 1.09%,10.78%,0.88%, and 23.76% respectively.3. QTL resistant to whitefly was Mapped in soybeanThe resistance identification was difficult and time-consuming, so MAS is the best way to breed whitefly resistant soybean variety. Based on the genetic research above, QTL mapping for resistance to whitefly was carried out as following. The JRB1F2 population with 170 plants was used to construct a genetic linkage map that contained 73 SSR markers, spanning 18 lingkage groups (LG) at a total distance of1035.6cM, with an average distance of 14.19cM between the flanking markers by using MAPMAKER/EXP 3.0 procedure. By using of the both composite interval mapping (CIM) of the software Win QTL Cartographer Version 2.5, QTLs were mapped on resistance in JRB1F2:3 populations derived from JRB1F2 population. One QTL qRwf-d2-1 associated with whitefly resistance was mapped on D2 linkage group. It was mapped on the linkage group D2 between satt186 and satt₀31, the LOD score was 2.7, explaining 12.47%.4. Resistant mechanism to whitefly in soybeanThere are 3 kind of resistant mechanism to pests in plant. It includes non-preference, antibiosis, and toleranee.Non-preference depends on the structure of a plant, antibiosis depends on its chemical composition, and the tolerence depends on its physiological reaction. The resistance to whitefly in soybean should base on the non-preference, antibiosis, and toleranee too. In this study the relationships between resistance to whitefly and pubescences traits, chemical composition, and agronomic traits of soybean were analyzed with SPSS 16.0 used 213 Chinese and foreign soybean germplasms.The results suggested that the correlation between MWPL and pubescences length, watersolutable protein content, stem diameter were significant at 0.01 level,the pearson corelations were 0.740**,0.909**,0.282**; and correlations between MWPL and pubescences angle, seed protein content, seed weight per plant were significant at 0.05 level,the pearson corelation were 0.626*,0.166*, and 0.165*. And the correlations between MWPL and seed coat color, cotyledon color, branch number, seeds fat content, pod length, and pod width were insignificant. Meanwhile the MWPL of soybean varieties with different stem termination were significant difference at 0.05 level. The MWPL were determinate varieties> semi-determinate> indeterminate. So the resistance to whitefly was affected by pubescences structure, quality, and agronomic traits of soybean. There are non-preference, antibiosis, and tolerance to whitefly in soybean.