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Sudarsono and Ronald G. Goldy

Four muscadine grape (Vitis rotundifolia Michx.) cultivars (Carlos, Noble, Regale, and Tarheel) were evaluated for their ability to be cultured in vitro. Axillary buds were placed on Murashige and Skoog medium as modified by Chee. Different levels of benzylaminopurine [(BA) 0.5 to 10.0 μm], kinetin [(KIN) 0.5 to 5.0 μm], and thidiazuron [(TDZ) 0.5 to 11.3 μm], and different explant positions were evaluated for their effect on in vitro explant establishment and shoot production. Thidiazuron (2.3 to 4.5 μm) alone or in combination with BA (1.0 to 5.0 μm) or KIN (1.0 or 5.0 μm) was effective for establishing axillary buds. Similar levels were also effective for promoting shoot proliferation. Explants originating from the 10 basal nodes of a shoot with at least 25 nodes gave better shoot proliferation than explants originating from the 10 distal nodes. Chemical names used: 6-benzylaminopurine, 6-furfurylaminopu. rine (kinetin):N -phenyl-N'-l,2,3 -thiadiazol-5-y lurea (thidiazuron).

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Mathieu Ngouajio, Guangyao Wang, and Ronald G. Goldy

Field studies were conducted in 2003 and 2004 to determine effects of withholding irrigation on pepper (Capsicum annuum) plant height, leaf chlorophyll content, yield, and irrigation water use efficiency. Irrigation treatments were initiated at pepper transplanting (S0), after transplant establishment (S1), at first flower (S2), at first fruit (S3), or at fruit ripening (S4). The control treatment received only enough water to apply fertigation (FT). Withholding irrigation did not affect pepper plant height except FT treatment, but increased leaf chlorophyll content. Withholding irrigation until S4 saved 50% and 41% of irrigation water in 2003 and 2004, respectively, without affecting fruit yield compared with the treatment where irrigation started at transplanting. However, yield in the FT treatment was significantly reduced. Irrigation water use efficiency (pepper yield per unit area per millimeter of water applied) was maximum at S4 (59.1 kg·ha−1 per millimeter) and S3 (24.1 kg·ha−1 per millimeter) in 2003 and 2004, respectively. Similar trends in response of pepper to the irrigation treatments were observed in 2003 and 2004 even though there were large differences in rainfall, and pepper yield between years. This suggests that withholding irrigation until first fruit may help to maintain pepper yield while reducing irrigation costs. However, it is important to have adequate soil moisture at transplanting to insure adequate transplant establishment.