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This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.Plant Breed. Biotech. 2016 (May) 4(2):225~233 http://dx.ABSTRACT Powdery mildew disease caused by an obligatory parasitic fungus Podosphaera xanthii is a serious problem of melon (Cucumis melo L.) production worldwide. Severity of problem is further associated with emergence of new races over the years. In this study a new race of powdery mildew fungus was discovered from Ibaraki, Japan. The race was different from all other existing races of P. xanthii occurring in Japan. Phenotypic and genetic analysis established the new fungus type as a new race, N5. Ten melon lines were infected with a total of eight fungal races including the new N5 race and it was found that all melon lines had different disease reactions against the new race compared to other seven races. Only four melon genotypes were found resistant out of 42 commercial cultivars and lines were tested. Disease reactions of two sets of F2 populations and one set of backcross population revealed that two separate epistatic gene loci located in two different linkage groups (LG), LG II and LG XII, interact together for the resistant or susceptible reaction of melon lines. A total of six simple sequence repeat (SSR) markers were found polymorphic in melon lines out of 16 tested in response to N5 race. Two different sets of F2 populations between resistant and susceptible melon lines were assessed with two polymorphic SSR markers located in two different groups, LG II and LG XII. SSR genotyping yielded 78% and 94% expected polymerase chain reaction fragments in favor of resistance or susceptibility of F2 populations of CM17187×PMR5 and PMR45×PMR5 of melon lines, respectively.

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멜론 흰가루병의 race 분화 및 저항성 계통 선발을 위한 분자마커 개발김회택 ･ 박종인 ･ 石川 友子 ･ 葛谷 真輝 ･ 堀井 学 ･ 八城 和敏 ･ 노일섭 Development of molecular marker to select resistant lines and to differentiate the races related to powdery mildew in melon (Cucumis melo L.) Abstract Powdery mildew (Podosphaera xanthii) commonly occurs in cultivated fields of melon (Cucumis melo L.). It inflicts a lot of damages. Therefore, breeding resistant lines is essential. Development of a resistant line by integrating resistance gene takes a long time. In addition, break down of developed resistance by generating new virulent fungus strains increases disease susceptibility. This phenomenon was related to races of powdery mildew. Therefore, it is important to develop a DNA marker to genetically analyze race-specific resistance genes of melon powdery mildew to breed resistant lines. To date, a total of 28 races of Podosphaera xanthii have been reported in the literature. In Japan, 10 races have been reported in the Ibaraki region. We developed a system to characterize the races of Podosphaera xanthii and confirmed eight out of those 10 races in the Ibaraki region. In Korea, only one race has been characterized to date. However, some different races were detected. Through genetic analysis of resistant lines and susceptible lines of powdery mildew, resistance genes of race1 (Pm-X, PXB, and Pm-R 1), race N1 (PXA), race 2 (Pm-w and Pm-R 2), race 3 (Pm-X3), and race 5 (Pm-X5 and Pm-R5) were identified in melon. These related genes of race 1, 3, N1, 5, and race 1, 2, 5 were located at linkage group II and V, respectively. In race 1, resistance gene was located in the linkage group XII. In addition, each race-specific marker related to specific resistance gene was developed. Using race information and race selection system obtained in this study, resistant line can be bred to develop resistant cultivar for several areas. Furthermore, this will make it more easily and economically to breed resistant lines by using selected markers.