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Cucurbit powdery mildew (CPM) caused by Podosphaera xanthii (Px) is an economically important disease of bitter gourd (BG; Momordica charantia) in Asia. Highlevel resistance to CPM is known in various BG accessions that have been used to develop BG breeding lines that originated in different countries. BG breeding lines THMC 113 (Belize), THMC 143 (India), THMC 153 (Thailand), THMC 167 (India), and THMC 170 (Taiwan) possess high-level resistance to BG Px race (BG-CPM), designated Mc-1 from a field at Kamphaeng Saen, Thailand, whereas THMC 144 (India) is susceptible. Our objective was to determine the inheritance of resistance to BG-CPM race Mc-1. To that end, THMC 144 (India) was crossed with the five resistant lines. The parents and their respective F1, F2, backcross progenies were evaluated for BG-CPM disease severity in inoculated field and growth chamber tests. Resistance to BG-CPM race Mc-1 in the five resistant lines was controlled by at least two independent, recessive genes. Intercrosses of the BG-CPM-resistant lines revealed allelic resistances in four of the breeding lines: THMC 113, THMC 153, THMC 167, and THMC 170. Resistance in THMC 143 was clearly non-allelic for resistance to BG-CPM with the other four BG-CPM-resistant lines. [ABSTRACT FROM AUTHOR]

Bitter gourd, Momordica charantia L., is an important commercial cucurbitaceous vegetable of enormous medicinal value in Asia because of its secondary metabolite content. We report here the characterization and evaluation of open-pollinated (OP) edible South Asian and Southeast Asian types of bitter gourd breeding lines, developed at the World Vegetable Center, for horticultural traits (11 OP) and secondary metabolites (10 OP) and their comparisons with commercial OP and F1 hybrid cultivars. Marketable yields of South Asian and Southeast Asian type breeding lines were comparable to the OP ‘BARI Karella 1’ and the hybrid ‘Benteng’, respectively. The bitter gourd cultivars and breeding lines included in this study exhibited specific patterns for five secondary metabolites (saponins, carotenoids, chlorophyll a and b, and vitamin C): in general the two cultivars and South Asian type breeding lines contained higher levels of secondary metabolites, e.g. carotenoids, than the Southeast Asian bitter gourd breeding lines. Some of these bitter gourd lines will be released to Asian home and school gardeners after conducting multi-location trials across Asia to improve vegetable consumption as a main task of bitter gourd breeding. [ABSTRACT FROM AUTHOR]

Bitter gourd (Momordica charantia L.) is a commercially and nutritionally important market vegetable in Asia cultivated mainly by smallholder farmers. Cucurbit powdery mildew (CPM) caused by Podosphaera xanthii (Px) is a nearly ubiquitous and serious fungal disease of bitter gourd. Five bitter gourd breeding lines (THMC 113, THMC 143, THMC 153, THMC 167, and THMC 170) were selected at the World Vegetable Center for resistance to a local isolate of Px in Kamphaeng Saen, Thailand. We evaluated the resistance potential of these five inbred lines against local isolates of Px at 12 locations in five Asian countries. Plants were inoculated with the respective local Px isolate 15 and 30 days after transplanting and additional Px-infected plants of the inoculated control were interplanted throughout each test. Plants were rated 60 days after transplanting forCPM reaction using a 0 (no evidence of infection) to 5 (>75% infection evident on individual leaves) disease severity scale. THMC 153 and THMC 167 were resistant to the local race of Px in all locations, whereas THMC 143 was observed resistant in all test locations except one in China. THMC 113 was resistant in each location except one in India. THMC 170 was susceptible in three locations in India. The multilocation tests revealed four unique Px races on bitter gourd in different Asian countries and sources of resistance for breeding CPM-resistant bitter gourd cultivars. Six strains of Px isolated from other cucurbits (Cucumis and Cucurbita) and representing five melon CPM races were unable to infect the susceptible M. charantia accession THMC 144 and the five resistant breeding lines, indicating pathotype differences between them and an isolate of M. charantia origin typed as race 1 on melon. THMC 143 and THMC 167, which originated from India, exhibited good yield potential in trials conducted in Thailand, Myanmar, Vietnam, and Bangladesh. [ABSTRACT FROM AUTHOR]