Detection of novel QTLs for foxglove aphid resistance in soybean.

The Raso2 , novel QTL for Korea biotype foxglove aphid resistance in soybean from PI 366121 was identified on chromosome 7 using GoldenGate SNP microarray. Foxglove aphid, Aulacorthum solani (Kaltenbach), is a hemipteran insect that infects a wide variety of plants worldwide and causes serious yield losses in crops. The objective of this study was to identify the putative QTL for foxglove aphid resistance in wild soybean, PI 366121, (Glycine soja Sieb. and Zucc.). One hundred and forty-one F4-derived F8 recombinant inbred lines developed from a cross of susceptible Williams 82 and PI 366121 were used. The phenotyping of antibiosis and antixenosis resistance was done through choice and no-choice tests with total plant damage and primary infestation leaf damage; a genome-wide molecular linkage map was constructed with 504 single-nucleotide polymorphism markers utilizing a GoldenGate assay. Using inclusive composite interval mapping analysis for foxglove aphid resistance, one major candidate QTL on chromosome 7 and three minor QTL regions on chromosomes 3, 6 and 18 were identified. The major QTL on chromosome 7 showed both antixenosis and antibiosis resistance responses. However, the minor QTLs showed only antixenosis resistance response. The major QTL mapped to a different chromosome than the previously identified foxglove aphid resistance QTL, Raso1, from the cultivar Adams. Also, the responses to the Korea biotype foxglove aphid were different for Raso1, and the gene from PI 366121 against the Korea biotype foxglove aphid was different. Thus, the foxglove aphid resistance gene from PI 366121 was determined to be an independent gene from Raso1 and was designated as Raso2. This result could be useful in breeding for new foxglove aphid-resistant soybean cultivars.