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Title: Diversity among a wide Asian Collection of bitter gourd landraces and their genetic relationships with commercial hybrid cultivars

Author
item DHILLON, NARINDER - The World Vegetable Center (AVRDC) - Taiwan
item SANGUANSIL, SUPANNIKA - The World Vegetable Center (AVRDC) - Taiwan
item SCHAFLEITNER, ROLAND - The World Vegetable Center (AVRDC) - Taiwan
item WANG, YEN-WEI - The World Vegetable Center (AVRDC) - Taiwan
item McCreight, James - Jim

Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/12/2016
Publication Date: 9/1/2016
Citation: Dhillon, N.P., Sanguansil, S., Schafleitner, R., Wang, Y., McCreight, J.D. 2016. Diversity among a wide Asian Collection of bitter gourd landraces and their genetic relationships with commercial hybrid cultivars. Journal of the American Society for Horticultural Science. 141:475–484. doi: 10.21273/JASHS03748-16.

Interpretive Summary: Bitter gourd (Momordica charantia L.) is a commercially and nutritionally important vegetable in Asia, where about 340,000 hectares are cultivated annually. Its cultivation is becoming more popular in Africa for local consumption or for export to Europe and the Middle East to meet the demand of emigrant Asian communities. It is also cultivated in the southern United States, and Australia where Asian hybrid cultivars are grown as a niche product for consumption, chiefly by ethnic communities from Asia. Bitter gourd fruit is a good dietary source of beta-carotene, vitamin C, folic acid, magnesium, phosphorus, and potassium, and has medicinal value. It is often used in folk medicine in Asia to manage Type 2 diabetes, a non-communicable disease that currently affects 347 million people worldwide. Bitter gourd breeders have been effective in improving the bitter gourd crop in the last two decades through development of F1 hybrid varieties with early and high marketable yield, and improvement of traits desired by consumers (fruit color, shape, size, skin pattern), which became strong forces in a reduction of genetic diversity. Emphasis on F1 hybrids leads to reduced genetic diversity through displacement of landrace cultivars and increased vulnerability to disease and insect outbreaks. Plant breeders must make better use of existing bitter gourd diversity to develop improved bitter gourd cultivars that are genetically broad-based. Assessment of the genetic diversity in crop collections, such as the AVRDC bitter gourd holdings, which has a collection of bitter gourd germplasm from more than 15 countries, is a critical for utilization by plant breeders. Here we report our molecular and morphological assessment of the genetic diversity of the AVRDC bitter gourd collection based on polymorphisms at 50 simple sequence repeat (SSR) loci in 114 landraces, breeding lines, and commercial cultivars widely grown in Asia. This germplasm originated from 11 countries in Asia, and represents all the market types of bitter gourd based on fruit size, shape, skin pattern, and color (Table 1).

Technical Abstract: We report here the first genetic characterization of bitter gourd based on polymorphisms at 50 simple sequence repeat loci in 114 accessions that included landraces, breeding lines and commercial cultivars widely grown in Asia. Neighbor-joining (NJ) tree analysis revealed a high level of genetic variability in the collection. The 114 accessions formed three subpopulations represented by five clusters in the NJ tree analysis. 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 and Philippines grouped together. Accessions that originated from Taiwan were genetically distinct and grouped separately. 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 fruits were genetically distinct from those with spindle or elongated fruits. 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. Continued, repeated use of these commercial cultivars for genetic improvement of bitter gourd could limit further genetic gain through breeding, and increase the vulnerability of cultivars to pests and diseases.