Preliminary field screening of newly developed bitter gourd breeding lines against cucurbit powdery mildew and for key fruit traits
2019
Laenoi, S. | Srimat, S. | Dhillon, N. P. S.
Bitter gourd (Momordica charnatia L.) is an economically important crop with high nutritional value. Cucurbit powdery mildew (CPM) caused by Podosphaera xanthii (Px) is a serious disease of bitter gourd that results in defoliation and high yield losses. Five bitter gourd breeding lines resistant to CPM were developed in 2014 at the World Vegetable Center (WorldVeg) and seed was made available to interested stakeholders in the private seed sector and public institutions. In addition, we also developed 23 CPM-resistant bitter gourd S6 lines by selecting within segregating populations of 23 landraces originating from India (4), Bangladesh (8), the Philippines (9) and Vietnam (2). The 23 lines were evaluated for resistance to CPM in the field and for key fruit traits (fruit weight, length, width, color, shape and bitterness) during May-August 2017 when CPM is epidemic in bitter gourd fields at the Research and Training Station of the World Vegetable Center, East and Southeast Asia, Kamphaeng Saen, Thailand. Lines were grown in a single plot of 5 plants per entry. WorldVeg line THMC 144 developed 100% CPM disease in the field during this period and rows of this susceptible check were grown on both sides of each entry. Each plant was rated 60-days after transplanting for CPM reaction using a 0 (no disease symptoms) to 5 (>75% disease symptoms on individual leaves) disease severity scale. The 23 lines were resistant (score 0) to the local isolate of Px and the susceptible check was 100% susceptible to Px (score 5). Three distinct fruit skin colors were observed among entries: green, light green, and dark green. Average fruit weights ranged from 10 to 193 g. These 23 lines will be tested against local Px isolates in future multi-location trials in Asia.
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