Recent climate changes have resulted in high temperatures, a greater frequency of flooding, and outbreaks of various plant diseases and insect pests, the latter of which has been characterized by a change in pest type from crop chewing to sap-sucking insects. To date, however, there has been limited study of plant resistance to sap-sucking insects. This study was carried out to evaluate the resistance and genetic patterns of the foxglove aphid Aulacorthum solani, a sap-sucking pest of soybean. We investigated the growth and reproduction of the foxglove aphid on five different varieties of soybean showing either susceptibility or resistance to this aphid in a non-choice test. Genetic analysis was conducted using the two F₂ populations derived from Daepung (susceptible to foxglove aphid)×IT104704 (resistant to foxglove aphid) and Daepung×IT188399 (resistant to foxglove aphid) crosses, which were evaluated for their responses to foxglove aphids. Differences in the responses of resistant and susceptible varieties were confirmed by monitoring aphid growth and reproduction. Although the two resistant germplasms (IT104704 and IT188399) have a strong antibiosis effect, they showed a slight difference with respect to aphid viability. Genetic analysis of foxglove aphid resistance showed that resistance was governed by a single dominant gene in IT104704 (3:1, p=0.11). We accordingly identified two resistant resources showing antibiosis to foxglove aphid, which is reported here for the first time, and also detected differences in genetic behavior. These results could be useful not only with respect to securing materials showing resistance to the foxglove aphid but also in the breeding of new foxglove aphid-resistant soybean cultivars.

Gayabyeo, a Tongil-type rice variety, has been known to be resistant to the brown planthopper (BPH) in Korea. For genetic analysis of BPH resistance of Gayabyeo, we developed an F2 and F3 population derived from a cross between Gayabyeo and Taebaegbyeo which is a Tongil-type BPH susceptible rice variety. Based on the previously detected 284,501 putative SNPs between Gayabyeo and Taebaegbyeo, 99 cleaved amplified polymorphic sequences (CAPS) markers were developed, and they have been used for genotyping 180 F2 plants. By comparison of resequencing data of Gayabyeo and the sequences of already reported BPH resistance genes (Bph3, BPH9, Bph14, BPH18, BPH26), it was revealed that Gayabyeo has Bph3 and BPH26 resistance genes. Two InDel markers, Bph3IND and BPH26IND, were developed, which can be used as selection markers in breeding program aiming at introducing BPH resistance genes of Gayabyeo into Korean high quality japonica rice varieties. In addition, BPH bioassay was performed with 180 F3 lines for BPH resistance QTL analysis. Two major QTLs were found on chromosome 4 and 12. The regions of these two QTLs included Bph3 and BPH26, which also supported that Gayabyeo has Bph3 and BPH26 resistance genes. These results would be useful in accelerating development of various BPH-resistant high quality japonica rice varieties in Korea.

As a first step of mapping genes conferring resistance to the brown planthopper, Nilaparvata lugens Stål, in Gayabyeo using a population derived from a cross between Gayabyeo and Taebaegbyeo, we performed the whole genome resequencing of these two Tongil-type rice varieties. The amount of raw sequence data was about 18.5X10⁹ bp and 17.9X10⁹ bp in Gayabyeo and Taebaegbyeo, respectively. After quality trimming and read mapping onto Nipponbare reference genome sequence, 9.3X10⁹ bp was mapped in Gayabyeo with mapping depth of 25.0X, and 9.5X10⁹ bp was mapped in Taebaegbyeo with mapping depth of 25.5X. Between Gayabyeo and Nipponbare, 1,585,880 SNPs were detected, while 1,416,898 SNPs were detected between Taebaegbyeo and Nipponbare. Between Gayabyeo and Taebaegbyeo, 284,501 SNPs were detected. Among the SNPs between Gayabyeo and Taebaegbyeo, 21.2% were in genic region and 78.8% were in intergenic region. In CDS region, 15,924 SNPs were detected, among which synonymous SNPs covered 47.3% and non-synonymous SNPs covered 52.7%. We designed Cleaved Amplified Polymorphic Sequences (CAPS) markers with SNPs in the restriction enzyme recognition sites, and 20 CAPS markers were tested. Of the 20 markers, 19 markers showed polymorphism and one marker showed monomorphism between Gayabyeo and Taebaegbyeo. It is expected that sufficient DNA markers for mapping genes with a population derived from a cross between Gayabyeo and Taebaegbyeo can be developed based on the results of the study.