Younghoon Park

This study systematically evaluated cultivation requirements, host range, and chemical control options for Cercospora citrullina causing watermelon spot disease. Among 11 chemically defined media tested, Corn Meal Agar (CMA) medium supported optimal mycelial growth of C. citrullina, with an average radial growth rate of 56.72 ± 1.45 mm under controlled conditions (25°C, darkness). Host range determination via artificial inoculation of 19 plant species confirmed the host range of strain UNL090101 is limited to the Cucurbitaceae species tested., with watermelon (Citrullus lanatus) exhibiting the highest susceptibility, followed by melon (Cucumis melo), and cucumber (Cucumis sativus). Fungicide screening of 17 commercial formulations identified 40% iminoctadine tris (albesilate) WP (EC₅₀ = 2.82 μg·L⁻¹) and 64% mancozeb + 8% cymoxanil (WS) (EC₅₀ = 48.75 μg·L⁻¹) as the most effective treatments, achieving control efficacies of 74.47% and 58.62%, respectively. These findings provide actionable guidelines for optimizing crop rotation, inter-cropping strategies, and fungicide selection in watermelon production systems.

Mohammad Hadi Yunus ･Gaeun Jang ･Jagyeong Shin ･Jungjae Han ･Junyoung Jang ･Juan Li ･Wooseong Ahn ･ Namju Ahn ･Younghoon Park. J Plant Biotechnol 2025;52:163-73. https://doi.org/10.5010/JPB.2025.52.019.163

Melon (Cucumis melo L.) is a globally grown crop renowned for its juice and flavor. Despite growth in production, the melon industry faces several challenges owing to a wide range of biotic and abiotic stresses throughout the growth and development of melon. The aim of the review article is to consolidate current knowledge on the genetic mechanism of both biotic and abiotic stress in melon, facilitating the development of robust, disease-resistant melon varieties. A comprehensive literature review was performed, focusing on recent genetic and molecular advancements related to biotic and abiotic stress responses in melons. The review emphasizes the identification and analysis of quantitative trait loci (QTLs), functional genes, and molecular markers in two sections. The initial section provides a comprehensive summary of the QTLs and major and minor functional genes, and the establishment of molecular markers associated with biotic (viral, bacterial, and fungal pathogens, and nematodes) and abiotic stress (cold/chilling, drought, salt, and toxic compounds). The latter section briefly outlines the molecular markers employed to facilitate marker-assisted backcrossing (MABC) and identify cultivars resistant to biotic and abiotic stressors, emphasizing their relevance in strategic marker-assisted melon breeding. These insights could guide the incorporation of specific traits, culminating in developing novel varieties, equipped to withstand diseases and environmental stresses by targeted breeding, that meet both consumer preferences and the needs of melon breeders.

The fruit flesh of watermelons differs depending on the distinct carotenoid composition. Orange-colored flesh relates to the accumulation of β-carotene, which is beneficial to human health. Canary-yellow-fleshed OTO-DAH and orange-β-fleshed (orange-fleshed with high β-carotene) NB-DAH near-isogenic lines (NILs) were used to determine the genetic mechanism attributed to orange watermelon flesh. For genetic mapping, an F₂ population was developed by crossing the two NILs. The segregation ratio of flesh color in the F₂ population indicated that the orange-β flesh of the NB-DAH NIL was controlled by a single incompletely dominant gene. Through a comparative analysis of the whole-genome sequences of the parent lines and NILs, a major introgression region unique to the NB-DAH NIL was detected on Chr. 1; this was considered a candidate region for harboring genes that distinguish orange from canary-yellow and red flesh. Among the 13 genes involved in the carotenoid metabolic pathway in watermelons, only ClPSY1 (ClCG01G008470), which encodes phytoene synthase 1, was located within the introgression region. The genotyping of F₂ plants using a cleaved amplified polymorphic sequence marker developed from a non-synonymous SNP in ClPSY1 revealed its relationship with orange-β flesh. The insights gained in this study can be applied to marker-assisted breeding for this desirable trait.

Melon (Cucumis melo L.) is an important crop that is cultivated worldwide for its fleshy fruit. Understanding the genetic basis of a plant’s qualitative and quantitative traits is essential for developing consumer-favored varieties. This review presents genetic and molecular advances related to qualitative and quantitative phenotypic traits and biochemical compounds in melons. This information guides trait incorporation and the production of novel varieties with desirable horticultural and economic characteristics and yield performance. This review summarizes the quantitative trait loci, candidate genes, and development of molecular markers related to plant architecture, branching patterns, floral attributes (sex expression and male sterility), fruit attributes (shape, rind and flesh color, yield, biochemical compounds, sugar content, and netting), and seed attributes (seed coat color and size). The findings discussed in this review will enhance demand-driven breeding to produce cultivars that benefit consumers and melon breeders.

The flesh color of watermelon is an important trait that is determined by carotenoid composition and affects consumers’ fruit desirability. Although a complete dominant control by C locus (Cllcyb) for canary yellow flesh (CY) over red flesh has been reported, red and CY colors frequently appear as a mixed pattern in the same flesh (incomplete canary yellow, ICY) in F₁ and inbred lines carrying dominant C alleles. Therefore, we examined the genetic control of the mixed color pattern in ICY using whole-genome resequencing of three ICY (ICY group) and three CY inbred lines (CY group), as well as genetic linkage mapping of an F₂ population. The segregation pattern in 135 F₂ plants indicated that CY is controlled by a single locus (named C₂) dominant over ICY. The whole-genome resequencing of ICY and CY inbred lines revealed an ICY/CY-specific region of approximately 27.60–27.88 Mb on Chr. 2 that was polymorphic between the ICY and CY groups. Our genetic map, using nine cleaved amplified polymorphic sequence markers developed based on the single-nucleotide polymorphisms from the ICY/CY-specific region, confirmed that C₂ is located on Chr. 2 and cosegregated with the marker (M7) derived from a non-synonymous single-nucleotide polymorphism of the pentatricopeptide repeat (PPR) gene (ClPPR, Cla97C02G039880). Additionally, 27 watermelon inbred lines of ICY, CY, and red flesh were evaluated using previously reported Cllcyb (C locus)-based markers and our C₂ locus-linked ClPPR-based marker (M7). As a result, dominant alleles at the C₂ locus were required to produce CY, in addition to dominant alleles at the C locus, while a recessive homozygous genotype at the C locus gave the red flesh irrespective of the genotype at the C₂ locus. Using a ClPPR-based cleaved amplified polymorphic sequence developed in this study and Cllcyb-based markers, watermelon cultivars with CY, ICY, and red flesh could be successfully discerned, implying that the combined use of these markers will be efficient for marker-assisted selection of flesh color in watermelon breeding.