Marker assisted selection (MAS) for disease resistance is widely applied in practical tomato breeding program both in public and private sectors. Due to the commercial value and the importance as a model crop system, tomato has taken the lead in MAS among the other horticultural crops. A wide range of disease resistance genes were identified and the mechanism of the resistances has been explored in tomatoes. In the case of disease resistance Tomato yellow leaf curl virus (TYLCV) is one of the major threats for tomato production worldwide, and several resistance sources for TYLCV resistance have been identified among wild tomato species. Ty1/3 resistance gene has been recently identified as a DFDGD-class RNA dependent RNA polymerase (RDR). Late blight (LB) in tomato is caused by Phythophthora infestans, and several resistances sources have been applied in the practical breeding program. Ph3 resistance, a LB resistance against a wide-range of P. infestans isolates, has been reported as a gene coding a CC-NBS-LRR gene on chromosome 9. In this study, we developed reliable and comprehensive molecular markers based on the single nucleotide polymorphisms (SNPs) or insertion/deletion (InDel) directly responsible for the resistance phenotype. These functional molecular markers are expected to enhance the effectivity and accuracy of MAS for disease resistance in tomato breeding programs.

본 연구는 우리나라 벼흰잎마름병 균주에 대한 인디카형과 자포니카형의 단일 저항성 유전자의 반응과 이들의 집적 효과를 비교 분석하고 자포니카형의 유망 조합을 제시하여 향후 우리나라 환경 여건에 효과적인 저항성 품종을 육성하고자 수행하였다. 단일 저항성 유전자 계통중 Xa1, Xa3, Xa21은 생태형 간에 차이가 없었으나 Xa4와 xa5는 자포니카에 비해 인디카형에서 저항성이 강하였다. 인디카형과 자포니카형에서 모두 저항성 유전자가 집적되었을 경우에 단일 또는 두 개의 저항성 유전자에 비해 저항성이 정도가 증가하거나, 저항성 수준이 높은 유전자가 저항성 수준이 낮거나 균계 특이적 이병성을 나타내는 저항성 유전자를 보완하는 효과를 나타냈다. 자포니카형에서 새롭게 확인된 저항성 유전자 집적 조합인 Xa3+Xa21, xa5+Xa21과 Xa3+xa5+Xa21은 우리나라 우점 균주와 16개 균주에 대해서 저항성이었으며 현재 우리나라 벼흰잎마름병 저항성 육종에서 주력 저항성 조합으로 이용되고 있는 Xa3+xa5 보다 높은 수준의 저항성을 나타냈다. 이들 저항성 유전자 집적 조합은 균계 분화 등에 따른 저항성 붕괴에 안정적으로 대응할 수 있고 저항성을 효과적으로 강화할 수 있는 유망 조합으로 생각되어 자포니카 벼흰잎마름병 저항성 증진을 위한 목표 조합으로 설정하여 육종사업을 수행하겠다. 

Japonica rice cultivars exhibit high susceptibility to bacterial blight(BB) disease due to genetic vulnerability in Korea. Korean japonica resistant rice cultivars mainly possess one of the genes, Xa1 or Xa3 for BB resistance. These resistance genes are becoming susceptible to K3a, resulting in serious rice yield reduction. This study was carried out to confirm the effect of xa13 gene pyramiding for developing of japonica rice cultivars resistant to BB pathogen breaking down Xa1 or Xa3. IRBB4 conferring Xa4 gene was resistant to K1(HB01013), K2(HB01014), K3(HB01015), and moderately resistant to K3a(HB01009). IRBB5 having xa5 gene was resistant to K1, K2, K3, and K3a. The recessive gene xa13 was resistant to K1 race but susceptible to K2, K3, and K3a. But Xa21 gene is susceptible to predominant K1 race but resistant to other races such as K2, K3, and K3a. Two genes Xa3 and xa13 were susceptible and Xa4 gene was moderate resistant to 24 isolates. xa5 and Xa21 genes were resistant to all isolates including K3a. When xa13 gene combined Xa4, xa5 and Xa21 genes, effect of xa13 gene pyramiding showed higher resistant reaction than that having singe gene out of Xa4, xa5, and Xa21. The order of resistance against 24 isolates breaking down Xa3 gene was IRBB55(xa13+Xa21) > IRBB53 (xa5+xa13) > IRBB51 (Xa4+xa13).

Grain weight (GW) or grain size is the most important target not only as a major component of grain yield, but also associated with the cooking quality in rice breeding program. In a previous study, two loci for grain weight, gw8 and gw9, have been fine map to about 306.4kb and 37.4kb, respectively, in backcross populations derived from a cross between the Korean japonica cultivar Hwaseongbyeo and Oryza rufipigon (IRGC 105491). Both O.rufipogon alleles increased GW in the Hwaseongbyeo background despite the fact that O. rufipogon was the small-seeded parent. To test the effect of pyramiding the QTLs for grain weight, an F2 population consisted of 226 individuals was developed derived from the cross between the two QTLs (gw8 and gw9), and used MAS to select nearly isgenic lines for two QTLs and a pyramiding line. Molecular genotyping of F2 population revealed the existence of interaction between gw8 and gw9. Moreover, the interaction was also confirmed by phenotypic analysis of four QTL-NILs. The results suggest that epistasis interaction is important genetic basis in determining yield traits in rice.

Conventional breeding method was used to pyramid three bacterial blight resistance genes, Xa1,Xa2and Xa3. Breeding lines with two and three resistance genes were developed and tested for resistance to the bacterial blight pathogen. Homozygous Fplants with

서광벼/밀양5004, HR 1619-6-2-1-2-2 /밀양5004 및 55061/IR 19735-5-2-3-2-1등 3개 조합의 F1 잡종과 이들 양친품종들의 혼묘를 각각 도열병 race IA-61, IB-47, IC-13 및 IH-1 등의 단독 race와 IC-13과 IA-61, IC-13과 IB-47 및 IC-13과 IH-1 등 2 race씩의 혼합 inoculum으로 접종시켜 이들의 잎도열병 발병반을을 검토하였다. 3개 조합의 양친품종들은 단독 race에 대해서 서로 다른 반응을 보여 각각 서로 다른 저항성 유전자의 지배를 받는 것으로 나타났다. 이들 서로 다른 정항성 유진자를 가진 양친품종들은 반응이 다른 2 race 씩의 혼합 inoculum에 대해서 모두 이병성이었으나 이들간의 F1 잡종은 모두 저항성이었다. 저항성 유전자가 서로 다른 양친품종간의 F1 잡종은 저항성 유전자의 집적효과로 인해 양친보다 광범한한 저항성을 나타내었다.