Watermelon [Citrullus lanatus (Thunb.) Matsum and Nakai] is one of the economically most important fruit crops of the Cucurbitaceae family. Among different watermelon traits, disease resistance and fruit quality are the important traits for growers and consumers. The single nucleotide polymorphism (SNP) markers similar to those traits can potentially and cost-effectively distinguish the genetic variations among these traits. Consequently, we developed 33 SNP makers linked to different watermelon traits associated with fruit quality and disease resistance, and validated in the genetic resources of watermelon and F1 breeding lines using ‘Fluidigm SNP Genotyping’ assay. Most of the SNP markers distinguished the alleles into three different types such as reference allele, alternative allele and heterozygous from watermelon genotypes for various traits. The SNP markers ‘ZymFL-T81P’ (ZYMV- resistance), ‘FON1-U161’ and ‘FON1-S075’ (Fusarium wilt-resistance), ‘Pmr21-Cla831’ (PM-resistance), and ‘ClGBS-J168’ and ‘GBS-GC230’ (GSB-resistance) can successfully differentiate resistant (R), susceptible (S) and heterozygous watermelon genotypes. Similarly, the SNP marker associated with sugar content, citrulline content, arginine content, rind hardness, flesh firmness, fruit shape, rind strip pattern of watermelon fruit and seed coat colour can successfully distinguished the watermelon genetic resources and F1 breeding lines as reference allele (A) type, alternative allele (B) type and heterozygous (H). These SNP markers could be utilized for marker assisted selection as well as screening of a large number of watermelon germplasm for fruit quality and disease resistance. However, further validation like artificial inoculation of pathogens for the traits related to disease resistance is required in watermelon crops.

Powdery mildew (PM), caused by the biotrophic fungus Podosphaera xanthii, drastically reduces the yield and quality of melon (Cucumis melo L.). Knowledge of the genetic control and high throughput molecular markers linked with resistance against this disease are essential for breeding programs. The bioassay study of the F1 and F2 populations derived from the parents, ‘PMR 5’ (♂) and ‘SCNU1154’ (♀) revealed a monogenic dominant nature of resistance to the devastating race, race 5. Besides, we developed three SNP based high resolution melting markers, PMm-HRM-1, PMm-HRM-2, and PMm-HRM-3, based on the previously identified SNPs on chromosome 12 and validated them using 8 melon lines and 137 F2 populations. Among these, the SNP of marker PMm-HRM-1 causes a missense mutation in the LRR region of MELO3C002393 and we were able to distinguish the resistant vs susceptible genotypes from eight diverse melon accessions and the segregating F2 population with more than 90% genotyping efficiency. The other two markers were based on intergenic SNPs and had more than 80% genotyping efficiency in F2 population. These markers will be helpful to melon breeders to develop melon cultivars resistant to P. xanthii race 5 via marker assisted breeding programs.

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• Developing DNA Markers based on Male-Specific Chromosomal Regions for Selecting Male Plants in Hop (Humulus lupulus)
  Tae hyun Ha, Jae Il Lyu, So Young Yi, Si-Yong Kang
  Plant Breeding and Biotechnology.2024;[Epub]     CrossRef
• Identification of Gene Responsible for Conferring Resistance against Race KN2 of Podosphaera xanthii in Melon
  Sopheak Kheng, San-Ha Choe, Nihar Sahu, Jong-In Park, Hoy-Taek Kim
  International Journal of Molecular Sciences.2024; 25(2): 1134.     CrossRef

Viral diseases in squash are damaging during the early stages of development and cause loss of crop yield and economic value. To reduce the damage caused by viral diseases, resistant cultivars should be bred. The
objective
of this study was to determine whether there was a relationship between virus resistance and a basic helix-loop-helix (bHLH) gene in squash (Cucurbita pepo L.). To do this, the bHLH transcription factor, known to be related to virus resistance, was isolated and analyzed using C. pepo individuals that were resistant or susceptible to zucchini yellow mosaic virus (ZYMV) and watermelon mosaic virus (WMV). The results showed that a three bp (GAC) deletion in the nucleotide sequences were found in the regulatory region of the CpbHLH gene in susceptible lines. It was confirmed that the deletion region was located near the binding site of the MYB transcription factor associated with the bHLH gene. It could be hypothesized that the susceptibility of susceptible lines may have been due to the lack of important sequences near the transcription factor binding region due to the deletion in the regulatory region, thus suppressing the expression of the gene. Quantitative real-time PCR (qRT-PCR) revealed that the expression level of the bHLH gene in resistant lines was 2.17 times higher than in susceptible lines.

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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• A survey of Podosphaera xanthii races in melon-producing regions in Rio Grande do Norte State, Brazil
  Anânkia de Oliveira Ricarte Marinho, Adriano Ferreira Martins, Francisco Linco de Souza Tomaz, Elaíne Welk Lopes Pereira Nunes, Denilson Eduardo Silva Dantas, Geovanna Alicia Dantas Gomes, Edicleide Macedo da Silva, Glauber Henrique de Sousa Nunes
  Journal of Plant Pathology.2025; 108(1): 777.     CrossRef
• Status, Gaps and Perspectives of Powdery Mildew Resistance Research and Breeding in Cucurbits
  Aleš Lebeda, Eva Křístková, Barbora Mieslerová, Narinder P. S. Dhillon, James D. McCreight
  Critical Reviews in Plant Sciences.2024; 43(4): 211.     CrossRef
• Identification of powdery mildew resistance quantitative trait loci in melon and development of resistant near-isogenic lines through marker-assisted backcrossing
  Chun-San Wang, Ssu-Yu Lin, Jin-Hsing Huang, Hsin-Yi Chang, Di-Kuan Lew, Yu-Hua Wang, Kae-Kang Hwu, Yung-Fen Huang
  Botanical Studies.2024;[Epub]     CrossRef
• Identification of Gene Responsible for Conferring Resistance against Race KN2 of Podosphaera xanthii in Melon
  Sopheak Kheng, San-Ha Choe, Nihar Sahu, Jong-In Park, Hoy-Taek Kim
  International Journal of Molecular Sciences.2024; 25(2): 1134.     CrossRef
• Fine mapping and identification of candidate genes associated with powdery mildew resistance in melon (Cucumis melo L.)
  Xiaoyu Duan, Yue Yuan, Núria Real, Mi Tang, Jian Ren, Jiaqi Wei, Bin Liu, Xuejun Zhang
  Horticulture Research.2024;[Epub]     CrossRef
• Inheritance of Resistance to Race 5 of Powdery Mildew Fungus Podosphaera xanthii in Melon and Development of Race 5-Specific High Resolution Melting Markers
  Jeong-Eui Hong, Mohammad Rashed Hossain, Hee-Jeong Jung, Ill-Sup Nou
  Plant Breeding and Biotechnology.2022; 10(4): 272.     CrossRef
• Development of powdery mildew race 5-specific SNP markers in Cucumis melo L. using whole-genome resequencing
  Jewel Howlader, Yeji Hong, Sathishkumar Natarajan, Kanij Rukshana Sumi, Hoy-Taek Kim, Jong-In Park, Ill-Sup Nou
  Horticulture, Environment, and Biotechnology.2020; 61(2): 347.     CrossRef
• Genetic Mapping and Nucleotide Diversity of Two Powdery Mildew Resistance Loci in Melon (Cucumis melo)
  Cui Haonan, Ding Zhuo, Fan Chao, Zhu Zicheng, Zhang Hao, Gao Peng, Luan Feishi
  Phytopathology®.2020; 110(12): 1970.     CrossRef
• PCR-Based InDel Marker Associated with Powdery Mildew-Resistant MR-1
  Yu-Ri Choi, Jae Yong Lee, Seongbin Hwang, Hyun Uk Kim
  Agronomy.2020; 10(9): 1274.     CrossRef
• Identification of Two New Races of Podosphaera xanthii Causing Powdery Mildew in Melon in South Korea
  Ye-Ji Hong, Mohammad Rashed Hossain, Hoy-Taek Kim, Jong-In Park, Ill-Sup Nou
  The Plant Pathology Journal.2018; 34(3): 182.     CrossRef

Powdery mildew (PM) is a severe fungal disease for melon cultivation worldwide. Stress resistance related genes could be important tools to address this problem. In this study, we retrieved defense related peroxidase and glucan synthase genes from Melon Genome Database ‘Melonomics’. Thereafter, we analyzed the genes in silico. We conducted protein blast in the NCBI database and found a high degree of homology among them. Based on the highest protein homology we named two isoforms of Cucumis melo peroxidase 2-like genes (CmPrx2-1 and CmPrx2-2) and one glucan synthase1-like gene (CmGLS1). In reverse transcription- polymerase chain reaction (PCR), all 3 genes showed organ specific expression in a C. melo line, SCNU1154. Real-time quantitative PCR expression of these 3 genes was conducted in the infected leaf samples by PM fungus Podosphaera xanthii and also treated leaf samples by exogenous phytohormones (salicylic acid and methyl jasmonate). The CmPrx2-2 gene was up-regulated in response to all seven races of PM fungus whereas up-regulation or down-regulation of CmPrx2-1 gene was race-specific. The CmGLS1 gene was down-regulated in response to all races except one race. The CmPrx2-1, CmPrx2-2, and CmGLS1 genes were up-regulated under both salicylic acid and methyl jasmonate treatments but their level of expression was higher in salicylic acid treated plants compared to methyl jasmonate. Therefore, we speculate that defense response of the three tested genes is largely mediated by the salicylic acid signaling pathway under PM infection. Taken together, the data presented herein may be useful resources in the development of PM stress resistant in C. melo L.

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• Induction of defense related enzymatic and non-enzymatic antioxidants and their gene expression imparts resistance to muskmelon against Fusarium oxysporum f. sp. melonis infection
  Chahak Jain, Shilpa Gupta, Sat Pal Sharma, Manjeet Kaur Sangha, Navraj Kaur Sarao, Anu Kalia, Shabda Verma
  Journal of Plant Biochemistry and Biotechnology.2025; 34(4): 941.     CrossRef
• Magnaporthe grisea infection modifies expression of anti-oxidant genes in finger millet [Eleusine coracana (L.) Gaertn.]
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  Journal of Plant Pathology.2019; 101(1): 129.     CrossRef

A panel of 65 melon germplasm was used to screen for resistance to Fusarium oxysporum f. sp. melonis (Fom) and Monosporascus cannonballus. The screening test revealed 35 accessions that are highly resistant to Fom race 1 and 11 accessions with high resistance to M. cannonballus. A total of four accessions, ‘K134068’, ‘K133069’, ‘Wondae’ and ‘PI 414723’, showing resistance to both pathogens were selected as candidates for melon rootstock. Yield and quality of fruits harvested from ‘Earl’s elite’ (Muskmelon, Reticulatus Group) grafted onto the selected melon rootstocks were found comparable to or better than those of non-grafted melons. Nearly negligible incidence of fruit fermentation was observed when ‘Homerunstar’ (Honeydew type, Inodorus Group) was grafted with the selected melon rootstocks, unlike when it was grafted onto ’Shintozwa’ (Cucurbita spp.) rootstock. The selected melon accessions with resistance to Fusarium wilt and Monosporascus root rot are considered to be potential and valuable genetic resources for breeding program of melon.

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• Molecular identification and phylogenetic analysis of different races of Fusarium oxysporum f.sp. Melonis in muskmelon using RAPD markers under Punjab conditions
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