). Near anthesis, B. oleracea stems elongate rapidly. In many Brassica species this elongation (bolting) is regulated by GA independently from its role in reproductive induction ( Mandel et al., 1992 ). Here, we test whether GA can trigger that process
Plants in the family Brassicaceae play integral roles in the diets of the world's population. Brassica oleracea , for example, includes the following staple food cultivars: cabbage, broccoli, cauliflower, kale, kohlrabi, and brussels sprouts
vegetative and reproductive tissues of canola and sunflower plants grown in nutrient solution Plant Soil 243 243 252 Booij, R. 2000 Effects of nitrogen on yield components of Brussels sprouts ( Brassica oleracea L. var. gemmifera DC) European Journal of
Peduncle explants from 12 Brassica oleracea L. lines representing five varieties [broccoli (italica), cabbage (capitata), cauliflower (botrytis), Chinese broccoli (alboglabra), and rapid-cycling B. oleracea] readily regenerated shoots in vitro. Average regeneration rates of more than 75% were obtained for most lines, with up to 35 shoots per explant. Shoots were visible within 7 to 10 days. Initial regeneration was polarized, occurring mainly from the basal end of explants. Linsmaier-Skoog-based medium containing 1 mg BA/liter was suitable for shoot regeneration from all 12 lines tested. Plants were rooted on hormone-free medium and transferred to soil. Chemical name used: benzyladenine (BA).
Segregation for annual vs. biennial flowering habit was observed in F2 progenies from crosses of early and late-maturing broccoli (Brassica oleracea L. Italica Group) inbred lines with cabbage (B. oleracea L. Capitata Group), kohlrabi (B. oleracea L. Gongyloides Group), collards (B. oleracea L. Acephala Group), kale (B. oleracea L. Acephala Group), and brussels sprouts (B. oleracea L. Gemmifera Group). F, progenies were usually completely annual. F2 progenies from crosses involving late broccoli contained two to five times as many biennials as F2 progenies from early broccoli crosses. Maturity factors carried by the biennial parents also appeared to affect expression of flowering habit. Annual habit is dominant over biennial and is controlled by several major genes with a strong effect of modifiers from both the annual and biennial parent. Time of heading of annual plants in F2 progenies appeared to be controlled by quantitative, mainly additive, factors. Distribution of heading dates for the F1 and annual broccoli parents showed a large environmental or cultural effect. It appears that the biennial parents, especially brussels sprouts and collards, contributed strong factors for late maturity.
Plant culture. On 19 June 2006, seeds of a rapid cycling Brassica oleracea L. population (Crucifer Genetics Cooperative, Department of Plant Pathology, University of Wisconsin, Madison, WI) were sown in growing cubes (Smithers-Oasis, Kent, OH
petiole sap in vegetables. Petiole sap nitrate-nitrogen (PSNN) levels associated with maximum growth rate or yield have been determined for vegetable crops like cabbage ( Brassica oleracea L. Capitata group) ( Gardner, 1989a ; Schulbach et al., 2007
Water loss in relation to the wax associated with the surface of leaves of Brassica oleracea was investigated. Varieties of Brussels sprouts, broccoli, cauliflower and collards were found to possess highly significant differences in regard to stomatal transpiration, cuticular transpiration and quantity of wax per unit area of leaf surface. Rubbing away the waxy bloom increased the cuticular transpiration rate. There was little correlation between the quantity of wax and the water loss per unit area of leaf surface either during the daytime or nighttime experiments. It appears inadvisable to attempt to breed for drought resistance in Brassica oleracea by selecting for the presence of a heavy waxy bloom or high levels of wax per unit area of leaf surface.
Resistance of a Brassica oleracea germplasm collection (broccoli, Italica Group; cauliflower, Botrytis Group; and collard and kale, Acephala Group) to silverleaf whitefly (SLW; Bemisia argentifolii Bellows and Perring) infestation was evaluated using several measures of insect infestation (including adult vs. nymph counts) taken at plant growth stages ranging from seedling to mature plant. An initial study was conducted in an outdoor screen cage artificially infested with the SLW adults; subsequent field trials relied on natural infestations. The glossy-leaved lines (`Broc3' broccoli, `Green Glaze' collard, and `SC Glaze' collard) had low SLW infestations in cage and field tests. SLW adult counts were less variable than similar comparisons using nymphal counts, although adult and nymph counts were positively and significantly correlated at late plant stages. Based on this study, comparing relative SLW adult populations would be a preferred criterion for identifying B. oleracea resistance to this insect.
The relative resistance of 18 cultivars of Brassica oleracea L. to attack by the sweetpotato whitefly [Bemisia tabaci (Gennadius)] was studied in screen cage (spring), field (autumn), and laboratory tests. The B. oleracea entries consisted of six types, including 16 green and two red cultivars. Cabbage (Capitata Group) and broccoli (Boytrytis Group) were less infested than other crops in a screen cage test, with kale, collard (Acephala Group), and brussels sprouts (Germmiter Group) experiencing relatively high and kohlrabi (Gongtlodes Group) intermediate infestations. Relative ranking of crops was similar in an autumn field study, with the exception of brussels sprouts, which had an intermediate level of infestation. Differences in numbers of whiteflies among cultivars within crops were negligible or inconsistent, except that red cultivars of brussels sprouts (`Rubine') and cabbage (`Red Acre') were much less infested than green cultivars. In a laboratory test, differences of whitefly oviposition and nymphal survival and development were small, indicating that nonpreference factors, rather than antibiosis, are the best explanations for differences in the numbers of whiteflies among the B. oleracea cultivars that were tested,