Evaluation Of Soybean Resistance To Leaf-Feeding Insects, Cloning Of Insect Resistance Genes And CAPS Analysis

Soybean leaf-feeding insects affect the yield and quality of soybean. One objective of this study was to screen resistant and susceptible soybean accessions. The 58 accessions were tested for the antibiosis to cotton worm (Prodenia litura Fabricius) under inoculation condition according to the 10 days larval and pupal weight. The result indicated that the larval weight and pupal weight were all significantly different among varieties. Low larval and pupal weight indicates the high level of antibiosis. Larval weight was positively related to pupal weight. According to the result of 2001 and 2002, four genotypes, N20922, N21565, N21249 and N21551 were identified to be highly resistant to cotton worm; Three genotypes, N3108, N4029-3 and N3155-1 were identified to be highly susceptible to cotton worm. These genotypes can be used in inheritance study, breeding program and functional study.In this study, Soybean kunitz trypsin inhibitor was cloned through candidate gene homology-based method by specific primers designed on the basis of KTi3. DNA sequence analysis indicates that the cloned DNA fragment composed of 700bp has 99.3%homologies in nucleotide sequence and 99.1% in amino acid sequence respectively compared with previously published sequence. There are three bases differences, which lead to two amino acids changes between sequence of KTI from Larma and 89-29.With the same method, the soybean lectin was also cloned. The sequence from Wan82-178 show that the cloned fragment is 999bp. Like most plant lectin genes, there is no intron in the amplified sequence. The open reading frame of the fragment codes a 31KD polypeptide, which contains 285 amino acid residues. There is a signal sequence with 31 amino acid residues at its NH2 terminus. The cloned DNA fragment has 99.6% and 99.3%homologies in nucleotide sequence and amino acid sequence compared with Led. Molecular evolution studies of Lec reveals that Lec clusteres with legumes first, thenclusteres with Gram ineae and mustard family. This shows the genetic relationship among plants and suggests that the inference is reliable about the function of the product of gene. The sequence from Tong Shan bo pi huang dou jia show that the cloned fragment is 1000bp. The open reading frame contains 253 amino acid residues. Structure analysis show that it only contains Legume lectin beta domain. And the sequence from Wan 82-17S contains Legume lectin beta domain and Legume lectin beta domain. These changes maybe affect the activity of polypeptide. But this requires further study to be carried out.The soybean trypsin inhibitor was obtained from two parents of recombinant inbred population (RIL) from the cross of kefeng No 1 (resistance) and 1138-2(susceptible). DNA sequence analysis indicates that the cloned fragment is 1376bp with an 835bp intron. After the BstB I digestion, the digestion products showed polymorphism between the two parents. 104 lines were screened randomly from RIL to digest the PCR products with BstB I. The data analysis showed that the current CAPS marker data are not relevant to the resistance data. This requires further study to be carried out...