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Narinder P.S. Dhillon, Supannika Sanguansil, Roland Schafleitner, Yen-Wei Wang and James D. McCreight

We report here the genetic characterization of bitter gourd (Momordica charantia) based on polymorphisms of 50 simple sequence repeat (SSR) loci in 114 accessions that included landraces, breeding lines, and commercial open-pollinated and F1 hybrid cultivars widely grown in Asia. Neighbor-joining tree analysis revealed a high level of genetic variability in the collection. The 114 accessions formed three subpopulations represented by five clusters. Distribution of accessions across the five clusters reflected their geographic origin to a large extent. South Asian accessions originating from India, Bangladesh, and Pakistan were more closely related to each other than to any other geographical group. Likewise, southeast Asian accessions that originated from Cambodia, Vietnam, Indonesia, and Philippines were grouped together. Accessions that originated from Taiwan were genetically distinct and grouped separately. A landrace from Laos was genetically close to the accessions from Thailand and genetically distinct from the rest of the accessions. White-fruited genotypes were genetically distinct from green- and dark green–fruited genotypes. Low- and medium-bitter accessions were more similar to each other than to the high-bitter genotypes. Accessions with cylindrical fruit were genetically distinct from those with spindle or elongated fruit. Commercial cultivars in each cluster were closely related, which indicated a narrowing of the bitter gourd genetic base in Asia in response to market demands for uniformity and yield. Use of diverse germplasm resources in bitter gourd breeding will help in sustainable breeding and production.

Open access

Derek W. Barchenger, Sopana Yule, Nakarin Jeeatid, Shih-wen Lin, Yen-wei Wang, Tsung-han Lin, Yuan-li Chan and Lawrence Kenyon

Chile pepper (Capsicum annuum L.) is an increasingly important vegetable and spice crop. Among the most devastating chile pepper–infecting viruses, especially in tropical and subtropical regions, are members of the whitefly transmitted Begomovirus, which cause pepper yellow leaf curl (PYLC). An effective PYLC management strategy is the development of resistant cultivars. However, genetic recombination, acquisition of extra DNA components, and synergistic interactions among different begomoviruses have resulted in the rapid emergence of new viruses that can infect new hosts, cause new disease symptoms, and overcome host resistance. In this project, 98 Capsicum entries comprising breeding lines, open pollinated varieties, genebank accessions, and wild species were screened for resistance to strains of Pepper yellow leaf curl Thailand virus (PepYLCThV). We used a randomized complete block design with three replications and 10 plants per replication in field net-houses at two locations (Khon Kaen and Kamphaeng Saen, Thailand) using augmented inoculation by viruliferous whiteflies. Scoring was done at ≈60, 90, and 120 days after inoculation using a standardized 6-point scale (1 = no symptoms to 6 = very severe symptoms), and the average of the scores of 10 plants within each replication was used for analysis. Although no entry was immune to the disease, the breeding line 9852-123 was highly resistant. Several accessions and lines were moderately resistant at both locations, although a high level of variability within these entries was observed. Overall, the disease severity at the Khon Kaen location was greater compared with Kamphaeng Saen, highlighting the importance of multilocation testing for disease resistance. The resistant entry identified here can be used to study gene action and to move resistance genes into well-adapted germplasm.

Open access

Derek W. Barchenger, Khin Thandar, Thain Gi Myint, Tran Ngoc Hung, Nguyen Quoc Hung, Shih-wen Lin, Yen-wei Wang and Tsung-han Lin

Chile pepper (Capsicum annuum) is an increasingly important crop worldwide, and Vietnam and Myanmar are major producing countries. The chile pepper markets in Myanmar and Vietnam are different, with production primarily for domestic consumption in Myanmar and for the export market in Vietnam. However, there is an overall lack of domestically developed cultivars in both countries. The objective of this study was to identify high-performing chile pepper entries, adapted to local conditions, for use in domestic breeding programs or direct release. Fruit length, width, weight, and yield were measured during two seasons (2016–17 and 2018–19), and the same entries were evaluated in Hanoi, Vietnam, and Nay Pyi Taw, Myanmar. However, different entries were tested in each season. During the 2016–17 season, AVPP1324 grown in Hanoi had the overall highest yield (15.3 t·ha–1), followed by AVPP1330 (15.0 t·ha–1 in Hanoi) and AVPP1111 (14.4 and 14.9 t·ha–1 in Hanoi and Nay Pyi Taw, respectively). AVPP0303 had the greatest fruit length, fruit width, and fruit weight in both Hanoi and Nay Pyi Taw during the 2016–17 season. During the 2018–19 season, AVPP1345 (24.8 t·ha–1) followed by AVPP9905 (22.5 t·ha–1) in Nay Pyi Taw, and AVPP1245 (17.4 t·ha–1) in Hanoi had the highest yield. AVPP9905 had the greatest fruit weight and width in both locations. AVPP1345 and AVPP9905 had the greatest fruit length during the 2018–19 season. There is an obvious need for domestically produced cultivars in Myanmar and Vietnam that meet local farmer and consumer preferences and that are adapted to the pests, diseases, and stress in each country. Several high-performing lines were identified that can be used as direct release or incorporated in local breeding programs for the development of inbred or F1 hybrid cultivars. This research also provides a basis for future studies on stability of yield and yield components in Southeast Asia.