A Study On Molecular Marker For Resistance To Bacterial Wilt In Peanut(Arachis Hypogaea L.)

Peanut (Arachis hypogaea L.) is an important oilseed and cash crop in the world. It is an important source of vegetable oil and protein in certain developing countries. Worldwide, China is the largest country in terms of peanut production, consumption and export trade. Development of peanut production is crucial for farmer's income and national food security. Bacterial wilt, caused by Ralstonia solanacearum, is among the key biotic constraints affecting peanut production. In China, the annual groundnut area naturally infested with Rsolanacearm is over 400,000 hm2. Planting peanut cultivars with resistance is the most important strategy for controlling bacterial wilt. However, due to narrow genetic basis of resistant parents, peanut breeding for resistance to bacterial wilt has progressed slowly in recent years. Meanwhile, the conventional method for selecting resistance to bacterial wilt in breeding has been based on the survival ratio in naturally diseased nurseries in which environmental factors could have great influence. Resistance identification and selection in natural nurseries is also time and labor consuming. It is highly necessary to broaden the genetic background of breeding parents and establish new technologies for resistance identification for enhancing the breeding efficienc. In this study, the genetic diversity of selected peanut germplasm lines with resistance to bacterial wilt was investigated by AFLP approach. Molecular marker for bacterial wilt resistance was identified by AFLP analysis of recombined inbred lines (RILs) derived from a cross combination of "Zhonghua 5 ×Yuanza 9102". The results are as following:1. The AFLP fingerprints of 24 peanut accessions with resistance to bacterial wilt were established. Seventeen of the 24 accessions could be detected by using 4 primer pairs and all the 24 lines could be distinguished by using 6 primer pairs including P1M62, P4M55, P8M52, P9M51, P5M48 and P2M47. The fingerprints provide a valuable tool for identifying the resistant germplasm lines at the AFLP level.2. In addition to previous investigation on genetic diversity among the bacterial wilt resistant peanut germplasm collection in China based on morphological observation, the AFLP analysis in this study further confirmed such diversity. At the AFLP level, there is systematic differentiation between var.hirsuta and var. vulgaris which are the two botanic avieties with largest evolutional difference of the cultivated peanut. Two peanut accessions in vai.vulgaris with high level resistance to bacterial wilt and largest genetic heterogeneity, "Yuanza 9102" and "89-15048", were identified and might be used as core parent for resistance.3. For the first time in the world, two AFLP markers linkaged with resistance to bacterial wilt in peanut (P1M58 and P3M59) were identified by resistance identification and BSA analysis of RILs derived from "Zhonghua 5 × Yuanza 9102 ". The genetic distance between the P1M58 and P3M59 and the resistance is 13.93cM and 8.73cM respectively.4. Ten peanut genotypes with resistance to bacterial wilt were used to verify the reliability of the resistance markers. The marker P3M59 was amplified in 7 resistant genotype while P1M58 was amplified in 5 genotypes. The results indicated these markers could be useful in identifying resistance genes in most resistant germplasm lines and their hybrid progenies.