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No sources of resistance to Xanthomonas campestris pv. cucurbitae (X.c.c.) in the Cucurbita species have been reported. Cultivars, breeding lines, landraces, and PI lines of 5 Cucurbita species were screened for resistance to X.c.c. in 3 greenhouse tests (GH). A `florist`s frog' was used to inoculate the first fully expanded leaves using a X.c.c. suspension (107 CFU/ml). The disease reaction was recorded as the percentage of inoculated leaf area with necrotic lesions and/or chlorosis. Butternut (b n) breeding lines were also evaluated for reaction to X.c.c. under uniform natural in feetion in 2 field (F) trials. A randomized complete block design was used in all GH and F experiments. C. moschata Nebr. BN PM1-88-8 and C. martinezii had high resistance to X.c.c. All other entries in all tests were susceptible. BN PM-88-8 is an early maturing small stable (no crookneck fruit) near-round BN type squash. The fruit are resistant to black–rot, but the leaves are susceptible to powdery mildew. BN PM-88-8 is ideal for microwave cooking because of its near-round shape permitting more uniform cooking. Release is expected in 1990.
Bean golden mosaic (BGM), rust (RU), web blight (WB), and common blight (CB) are major constraints affecting bean yields in the Dominican Republic (DR). The objectives of the USAID DR supported project were to educate graduate students, improve research facilities and equipment, institutionalize the project, and develop a comprehensive bean disease management program. The project trained 25 researchers. A national center for bean improvement (CIAS) was established. Facilities for plant pathology, germplasm storage, and screenhouses were built and equipment and vehicles were acquired. The high-yielding rust-resistant red mottled bean variety `PC-50' was introduced and grown on about 60% of the hectarage. However, BGM became a serious problem with the increase of the white fly population (vector of BGMV) due to increased vegetable production. Under severe BGM, yields were low in plantings made after 15 Dec. The combination of the use of `PC-50', along with a fallow period with delayed planting until early November, reduced the populations of white fly, BGM, RU, and CB and led to a dramatic yield increase of beans and to self sufficiency in beans in the DR. PC-50 became damaged by a new RU race and a resistant line PC-21-SMA (UPR) was released. New bean lines with resistance to BGM, WB, RU, and CBB are being tested for release.