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Abstract

Chinese cabbage (Brassica campestris L. ssp. pekinensis) transplants grown under a protective, wax-coated paper cover were subjected to various degrees of defoliation (0%, 25%, and 50% of the foliar length) to determine the effect on the incidence of premature bolting and transplant shock recovery. Various transplant sizes (3–4, 5–6, and 7–8 true leaves) were used to determine differences in vernalization sensitivity and bolting ability. Protective tunnels significantly reduced the percentage of bolters. Olders transplants (7–8 leaves) without protection were superior in preventing bolting. The 5–6 transplants grown under tunnels produced the best overall yield. Partial defoliation failed to show consistent results on all parameters measured from year to year and from soil to soil.

Open Access
Authors: and

Abstract

Raised bed culture and different population densities were studied to determine their effect on bacterial soft rot (Erwinia carotovora ssp. carotovora) during summer production of Chinese cabbage (Brassica campestris L. Group pekinensis). Seeds were sown on different dates to determine the relationship between head formation and the occurrence of soft rot. Tropical (heat-tolerant) cultivars were evaluated for summer production potential in raised-bed and flat-culture systems. Raised beds were, in some instances, beneficial in reducing the incidence and progression of soft rot. Phyllosphere air temperatures on raised beds were slightly lower than on flat culture; however, the effect on reducing soft rot incidence is unclear. Plants grown at 30-cm within-row spacing produced fewer marketable heads than plants at 46, 61, or 76 cm. Plants from seed sown after mid June had a significantly higher incidence of soft rot when compared to earlier planting dates.

Open Access

Pea root rot is a serious economic threat to pea production in the Great Lakes region. The primary causal organism is Aphanomyces euteiches Drechs., which is responsible for an estimated 10% annual crop loss. A fall oat (Avena sativa) rotation before spring pea planting reduces disease severity. To better understand the beneficial effect of oat on A. euteiches, isolated individual pathogen lifecycle stages of zoospores, mycelium, and oospores were treated in culture with oat extract. Resulting mycelial mats were dried and weighed. Treatment with 90%, 70%, 50%, and 30% oat extract resulted in significant spore germination and mycelial growth of A. euteiches. In the presence of nutrient solution, oat extract concentrations of 90%, 70%, 50%, and 30% significantly enhanced spore germination and mycelial growth of the pathogen. These results demonstrate that the use of oat extract results in dosage dependent germination and growth of A. euteiches.

Free access

Glucosinolates are a class of nitrogen (N) and sulfur (S) containing compounds shown to have cancer-preventing properties in animal models and widely found in cruciferous plants. The overall objective of this study was to determine whether N and S fertility affects glucosinolate concentrations in cabbage (Brassica oleracea L. Capitata group). Field studies on a sandy soil low in available N and S were conducted over a 2-year period with both green (`Grand Slam') and red (`Vorox') cabbage cultivars. Treatments evaluated each year were the interactive effects of N (125 and 250 kg·ha–1) and S (0, and 110 kg·ha–1) fertilizer application. Yield of both cabbage cultivars increased with increasing N and S in the second year of the study, but not in the first. Tissue N concentrations in heads at harvest increased with N application and tissue S concentrations increased with S application. When S was not applied, tissue S decreased significantly as N rate increased, while N rate had no effect on tissue S concentrations when S was applied. The dominant glucosinolate detected in both cabbage cultivars was glucobrassicin, with indole forms accounting for about 80% of the total glucosinolates regardless of treatment. Tissue N was negatively correlated and tissue S and S to N ratio were positively correlated with total glucosinolate concentration, although all correlations were generally weak (r 2 < 0.5). Total glucosinolates and glucobrassicin concentrations were maximized in both cultivars at the low N and high S application rates. Except for sinigrin in one of the 2 years, all glucosinolates detected were higher in Vorox than in `Grand Slam'. Based on these results, glucosinolates in cabbage can be manipulated by cultural management practices as well as genetics.

Free access