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Differential Biochemical Responses of Resistant and Susceptible Genotypes of Chili to Pepper Yellow Leaf Curl Thailand Virus
(2025-09-01)
Mueangkhong, Manthana
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Suwor, Patcharaporn
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Techawongstien, Suchila
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Teerarak, Montinee
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Tsai, Wen Shi
Chili (Capsicum annuum L.) production is threatened by the pepper yellow leaf curl virus (PepLCV), transmitted by whiteflies, leading to reduced yields. This study investigated the biochemical changes in two chili genotypes, PEP6 (tolerant to PepLCV) and Homsuphan (susceptible to PepLCV), following inoculation with the Thailand strain of PepLCV (known as Pepper Yellow Leaf Curl Thailand Virus, PepYLCTHV). Inoculation was performed using whitefly transmission (WF) and graft transmission (GT) methods, and disease severity was evaluated using a standardized index. The level of total phenolic compounds and the activities of peroxidase (POD) and polyphenol oxidase (PPO) enzymes were analyzed in virus-infected plants and compared with those in uninoculated controls. Both chili genotypes exhibited a more rapid increase in disease severity when inoculated with WF than with GT. In PEP6, disease severity was lower than Homsuphan in both WF and GT inoculations. Disease severity in WT-inoculated PEP6 plants increased gradually, reaching 100% by day 36, whereas Homsuphan plants had a more rapid progression, attaining 100% by day 21. The GT method led to slower disease severity progression in both genotypes, reaching 80–85% by day 36. In PEP6 plants, total phenolic compound content increased significantly following WF, indicating an active defense response, whereas levels remained stable in GT plants. Phenolic content in the tolerant genotype Homsuphan remained stable across all conditions. Notably, peroxidase (POD) activity was elevated in GT plants of both genotypes, which correlated with reduced disease severity. Polyphenol oxidase (PPO) activity was lowest in control plants, but WT and GT increased the PPO level. Among the treatments, GT induced the highest PPO activity, which was associated with the lowest disease severity. These findings suggest that GT may enhance disease resistance by modulating phenolic compound accumulation and increasing POD and PPO activity.
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Effect of Trichoderma harzianum against Fusarium oxysporum in resistant and susceptible tomato cultivars
(2025-01-01)
Suwor, Patcharaporn
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Mueangkhong, Manthana
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Kawicha, Praphat
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Thanyasiriwat, Thanwanit
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Techawongstien, Suchila
Fusarium wilt disease presents a substantial challenge to tomato production, especially in an open field environment. The peroxidase (POD) activity and total phenolic compounds (TPCs) play a crucial role in measuring the antioxidant capacity of plants. Understanding the variations in the POD and TPC levels during disease-induced stress becomes important for effectively managing Fusarium wilt and enhancing tomato production. This study investigates the impacts of Trichoderma harzianum inoculation through the root drip method on five tomato cultivars. It compares these cultivars to their non-treated counterparts when they are subjected to infection by Fusarium oxysporum f. sp. lycopersici (Fol). The results showed that the level of resistance to Fol is based on the specific tomato cultivar. Notably, 'MT26' exhibited the lowest disease severity index (DSI), indicating a strong response, whereas 'CLN3682F' showed notable susceptibility. Regarding the POD and TPC activity, its exhibition differed in compatibility with the response of each tomato cultivar to Fusarium wilt disease. The resistant cultivars increased the POD activity after the Trichoderma induction before the Fol inoculation, and this activity was further boosted when exposed to disease conditions. Consequently, enhancing the POD and TPC levels during the initial stages could potentially serve as a systemic defence mechanism of tomatoes against the Fusarium wilt disease.
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Combining ability analysis in anthracnose-resistant introgression inbreds and developing improved resistant lines of pepper (Capsicum annuum L.)
(2025-01-01)
Saengarun, Patcharapan
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Suwor, Patcharaporn
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Inprasert, Hathaipat
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Kumsee, Nattika
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Tsai, Wen Shi
Chili peppers (C. annuum L.) are a commercial spice crop in the tropics. In Thailand, chili pepper is a cash crop for farmers and has cultural significance in Thai cuisine. Anthracnose disease caused by Colletotrichum spp. is responsible for a significant reduction in the marketable fruit yield of chili peppers. In this study, we tested the combining abilities of anthracnose-resistant chili pepper lines possessing resistance introgression genome segments from C. chinense (PBC932) and C. baccatum (PBC80). Six parental inbreds developed from two resistant donors PBC80 and PBC932 were crossed in a haft-diallel fashion to develop 15 cross combinations during 2018. In 2019, seeds of 21 genotypes comprising six parents and 15 F<inf>1</inf> s were planted in Randomized Complete Block Design (RCBD) and data on plant characteristics, fruit yield and yield components were recorded. Detached fruits were screened against anthracnose causing aggressive species (C. acutatum). ANT4 showed the lowest disease lesion size and lowest GCA value at green and red fruit stages, containing resistance from PBC80. Additionally, the general combining ability (GCA) and specific combining ability (SCA) were significantly different at the green fruit stage, with the SCA component greater than GCA. Based on GCA and SCA estimates, ANT4 was selected and crossed to three highly susceptible cultivars (Yodsonkeam 80, Num, and Jindanil 80). The crosses were advanced and 10 F<inf>5</inf> lines were developed through marker-assisted selection (MAS) for resistance genes. The MAS was more useful for selecting resistance at the green fruit stage. We also found that MAS was more effective in F<inf>2</inf> progenies compared to F<inf>5</inf> progenies. Finally, we selected 10 new pure lines and evaluated them at the farmer's field. AF1, AF6, and AF7 were highly resistant to anthracnose, a more desirable good fruit type and high yield.
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Improving Pepper Inbreds for Resistance to Pepper Yellow Leaf Curl Thailand Virus (PepYLCTHV) through Challenged Inoculations
(2024-09-01)
Kumsee, Nattika
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Suwor, Patcharaporn
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Teerarak, Montinee
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Tsai, Wen Shi
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Techawongstien, Suchila
Chili peppers (Capsicum annuum L.) are an economically important crop worldwide. Pepper yellow leaf curl Thailand virus (PepYLCTHV), a Begomovirus causing yellow leaf mosaic disease of chili pepper, has been reported to incur 95% economic loss under epiphytotic conditions. Thirty-one chili genotypes were screened for resistance to PepYLCTHV disease through inoculation using 10–15 viruliferous whiteflies per plant. We purified two resistant lines (PEP6 and PEP12) through four generations of selfing and selection. At 28 days after inoculations, two chili genotypes (PEP6 and PEP12) had low disease severity and percentage of disease incidence (DI) compared to four susceptible checks, viz., Yodsonkeam80, Homsupan, Huareau12, and Pong Charian, which had a disease severity score of 5 with 100% DI. Thirty initial plants of PEP6 showed an average disease severity of 3.64 with 69.33% DI, and PEP12 showed an average disease severity of 3.83 with 77.67% DI. From these populations, we selected nine highly resistant plant of PEP6 and seven plants of PEP12 having a disease severity of 0 through pure-line selection for four selfing generations. The ratio of resistance (R) to susceptibility (S) consequently decreased. In PEP6, the ratio decreased from 1R:2S to 1R:1S, while in PEP12 the ratio decreased from 1R:3S to 1R:1S. These lines have potential for release as resistant lines for improving chili pepper resistance to PepYLCTHV and for developing makers associated with the resistant trait.
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Chili (Capsicum annuum L.) genotypes resistant to Pepper yellow leaf curl Thailand virus (PepYLCTHV)
(2021-01-01)
Suwor, Patcharaporn
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Masirayanan, Tawatchai
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Khingkumpungk, Hathairat
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Tsai, Wen Shi
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Saetiew, Kanjana
Pepper yellow leaf curl Thailand virus (PepYLCTHV) causes leaf curl disease in chili production regions of the tropics and subtropics. Information on PepYLCTHV disease severity and resistance in chili pepper is still limited in Thailand. This study reports PepYLCTHV disease severity through graft inoculation and selection of single resistant plants for use in a chili breeding program. Twenty-one chili genotypes consisting of the local cultivar (5) collected from Thailand, breeding lines (9) developed at Khon Kaen University (KKU), Thailand and improved lines (7) obtained from the World Vegetable Center, Taiwan were used in this study. Forty-five-day-old seedlings of all the genotypes were graft inoculated with PepYLCTHV in a randomized complete block design (RCBD) with three replications and 10 plants per replication and kept in a plastic net house. Disease symptoms were scored at 20, 27, 34, 41 48, and 55 days after graft/inoculation (DAI). Disease severity was visually recorded using 0−5 scores. Results showed that the disease severity of 21 chili genotypes significantly differed at 48 days after grafting. High resistance and stability were shown by 9853-123 genotypes. Two genotypes, PSP11-7 and PSP11-10-1, showed resistant reaction with disease severity scores of 1.9 and 1.8, respectively. However, among 21 chili genotypes or 630 grafted plants, 302 plants were successfully grafted inoculated plants. Therefore, from the results of this work, highly resistant plants (69 single plants) can be selected, selfed and advanced for breeding.

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