Thesis (M. Agr. Sc.) -- Lincoln University, 2008. / "'Pasja' is considered both as a species and cultivar in this document as it [is] marketed as such in New Zealand. Technically 'Pasja' is a leaf turnip"--Abstract. Also available via the World Wide Web.

Additive weed competition experiments were undertaken to study the effect of lamb's-quarters (Chenopodium album) interference on direct seeded broccoli. Lamb's-quarters (3, 8, 10, 12, and 15 plants m⁻²) began to affect broccoli growth 28 to 36 days after seeding. Decreases in crop growth increased with weed density as time after seeding increased. Yield data were fitted to a rectangular hyperbolic model which indicated that even one lamb's-quarters plant m⁻² could reduce total yield by 18 to 20 percent and marketable yield (head >10 cm across) by 22 to 37 percent. Lamb's-quarters reduced total yield by reducing average head weight and not by lowering the number of heads per plot. On the other hand, the weed reduced marketable yield by reducing both the average head weight and the number of heads per plot. The feasibility of using liquid ammonium nitrate as a post-emergent weed control spray in cole crops was studied. The relative susceptibility of different weed species grown by themselves (1989) and with two crops (broccoli and onion; 1987) to ammonium nitrate (800 L ha⁻¹; 0, 7.5, 10, 15, 20 percent N) burning was investigated. The fertilizer controlled shepherd's-purse (Capsella bursa-pastoris), chickweed (Stellaria media), cudweed {Gnaphalium uliginosum), and redroot pigweed (Amaranthus retroflexus), but not lamb's-quarters, purslane (Portulaca oleracea), and annual bluegrass (Poa annua). Corn spurry (Spergula arvensis) varied in its tolerance. Although weed populations were reduced by 70 percent in 1987, the remaining weeds competed so strongly with the onion and broccoli that the crop plants did not reach a harvestable size. The large initial weed population (799 plants m⁻²), the large number of tolerant weeds present, and the possible recovery of some of the susceptible weeds may all have been factors responsible for crop failure. The effect of different shepherd's-purse densities (52 to 988 plants m⁻²) on the degree of ammonium nitrate (800 L ha⁻¹; 20 percent N) control in broccoli was also studied. The initial weed control achieved was reduced over time either because some weeds counted as dead had recovered or new plants were being recruited to the population through seed germination. Although the maximum density of shepherd's-purse plants that survived was 219 plants m⁻², these plants did not significantly reduce crop yield possibly because shepherd's-purse is not a very competitive species and all the surviving weeds had been damaged to varying degrees, further reducing their competitive ability. The relative susceptibility of various crop cultivars to ammonium nitrate (800 L ha⁻¹; 0, 10, 15, 20 percent N) burning was also studied. In 1987, the growth rates of 'Lunet' (Brussels sprouts), ‘SGI' (broccoli), 'Elgon' (cauliflower), and 'Matra' (cauliflower) initially decreased but the plants recovered; they were largely unaffected in 1988. The growth rates of 'White Lisbon' (onion), 'Emperor' (broccoli), and 'Early Marvel' (cabbage) were largely unaffected in either year. Although some cultivars had shown initial signs of lower growth rates, there was no decrease in crop yield. Leaf surfaces of tolerant and susceptible crop and weed species were examined by scanning electron microscopy to determine the basis of ammonium nitrate selectivity. Leaf surfaces of tolerant species were completely covered with a crystalline wax layer, while susceptible species had little or no epicuticular wax. Cellulose acetate was used to remove the epicuticular wax from cabbage leaves. The stripped leaves showed far greater ammonium nitrate retention and salt injury than unstripped leaves, demonstrating the importance of the epicuticular wax in providing protection against ammonium nitrate injury. Trichomes, observed on the leaf surfaces of some susceptible species, may further increase ammonium nitrate retention and, therefore, salt injury. / Land and Food Systems, Faculty of / Graduate

No description available.

Experimental plots were overlaid on commercial fields of broccoli (Brassica oleraceae L. var. Italica) and cauliflower (Brassica oleraceae L. var. botrytis L.) to evaluate legume species as interseedings in vegetable production. White clover (Trifolium repens L.), red clover (T. pratense L.), yellow sweet clover (Melilotus officinalis L.), hairy vetch (Vicia villosa Roth.) and crimson clover (T. incarnatum L.) were seeded 4-5 weeks after an early planting of broccoli and a late planting of cauliflower. Crop yields, forage biomass, weed biomass and percent fall ground cover were recorded. / A dry year coupled with difficulties in applying the treatments resulted in low forage biomass. Hairy vetch yielded the most within the early broccoli planting system. High rainfall the next year resulted in high biomass yields. Over the two year study, hairy vetch and crimson clover emerged as the two most productive species. Significant effects on fall weed biomass were observed with broccoli in the second year of the study, where interseeded plots reduced weed populations by at least 66%. No evidence was seen of weed suppression by interseedings prior to harvest. Crop yields were not affected by interseedings. All interseeded treatments provided the minimum of 30% ground cover required to help reduce erosion.

Thesis(M.S.)--Auburn University, 2006. / Abstract. Vita. Includes bibliographic references (p.93-105).

No description available.

The object of this research was follow up the cumulation of nitrates in individual kinds of vegetables. Analysed was 240 samples of root crops, cole crops and potatoes distributed in the trade network in Humpolec in the years 2008 - 2010. The measurement results show that all the vegetables went beyond the nitrate permitted limit, according to a law n. 53/2002. The most frequently it was in potatoe samples (50 % samples). The next was a carrot (27 %), kohlrabi (25 %), broccoli (24 %) and celery (17 %). From aspect cumulation of nitrates is parsley unchallenged kind of vegetable. Permitted limit was transcendent in 10 % about less than 1 %. The origin of the vegetables was detected as well. Czech republic had the worst results (52,5 %) because of the high nitrate concentration in potatoes. It is grown by a domestic growers. Spain had 20 % in broccoli and kohlrabi. It is imported to our market. Although the high nitrate concentration in some vegetable samples the vegetable influence the human health in a positive way and it doesn?t make health hazard.

Downy mildew has been a potentially devastating constraint to crop production within the Brassicaceae family worldwide (CABI, 2022) and on the Central Coast of California (Smukler, et al, 2008; Koike, et al. 2007). Downy mildew is a foliar disease, caused by the pathogens in the Hyaloperonospora genus on plants within the Brassicaceae family (Goker, et al, 2009). Downy mildew is a disease that is common in region of the world with Coastal climates that provide humidity and moderate temperatures (Sarahan, et al, 2017). Crops within the Brassicaceae family maintain a predominant role in agricultural systems worldwide (Cartea, et al, 2011) and on the Central Coast of California, in Monterey, San Luis Obispo, Santa Cruz, San Benito, and Ventura Counties (Hidalgo, et al, 2022; Settevendemie, et al, 2022; Sanford, et al, 2022; Griffin, et al, 2022; Chang, et al, 2022; Williams, et al, 2022). The crop production within the Brassicaceae family includes broccoli, cabbage, and cauliflower, and the spring mix production of wild arugula, cultivated arugula, and baby kale. In the first study, an in-lab screening of wild arugula (Diplotaxis tenuifolia) for downy mildew resistance was conducted to identify accessions that contain potential resources of resistance to Hyaloperonospora diplotaxidis. The germplasm of 199 wild arugula accessions was grown out under greenhouse conditions and inoculated with a v single isolate of H. diplotaxidis. A subset of 40 accessions of wild arugula were further inoculated with an additional three isolates of H. diplotaxidis and the ten most resistant accessions were selected for further inoculations. The inoculations of the final subset of ten accessions with the same three isolates were replicated an additional two times. When a factorial ANOVA was conducted to test the interaction between the isolate and accession used, it was found that the impact of the accession on disease incidence was independent from the isolate (P=0.993). Three accessions, 185, 79, and 17 were identified as a potential source of resistance to the isolates utilized in this study, for maintaining a disease incidence below 1%. To compare the results found in the in-lab resistance screening, a field trial was conducted with a subset of wild arugula accessions with diverse reactions to downy mildew. When a regression was conducted comparing the disease incidence under field and lab conditions, the R2 value was found to be 0.37. A second study was conducted to characterize the genetic, morphological, and host range diversity of downy mildew causing pathogens in the Hyaloperonospora genus of hosts in the Brassicaceae family. An isolate collection of approximately 40 isolates of Hyaloperonospora spp. was established and the phylogenetic relationships of these isolates were analyzed by creating two phylogenetic trees using their cox2 mtDNA and ITS rDNA sequences. The H. brassicae and H. diplotaxidis isolates from this study formed separate monophyletic groups in both the cox2 mtDNA and ITS rDNA phylogenetic analyses. When the host range of H. brassicae and H. diplotaxidis were characterized by inoculating a genetically and morphologically diverse set of four host plant species, the H. brassicae and H. diplotaxidis were found to have distinct host ranges. The H. brassicae isolate was found to be parasitic of all B. oleracea morphotypes including broccoli, cabbage, kale, kohlrabi, and ornamental cabbage. The H. diplotaxidis isolate was found to only be parasitic on wild arugula, not cultivated arugula, wild mustard, or any of the B. oleracea morphotypes. The difference between sporangia of H. brassicae and H. diplotaxidis were found to be statistically significant, where the sporangia of H. brassicae were nearly circular and the sporangia of H. diplotaxidis were closer to an oval.

No description available.

In Quebec, the swede midge (Contarinia nasturtii), a newly invasive pest, was found for the first time in 2003. During a two year study (2004-2005) I studied the seasonal development of the swede midge, the presence of natural enemies and tested entomopathogenic nematodes for its control. Results showed that the overwintering generation of the swede midge emerged during the second half of June. Based on adult captures and abundance of larvae in the field, there were three to four overlapping generations. Late transplants were more heavily attacked by the swede midge and broccoli and cauliflower were the most susceptible crops. No parasitoids were found in the experimental sites during either year of the study and two polyphagous coccinellid predators (Harmonia axyridis and Coccinella septempunctata) were field-collected for further evaluation under laboratory conditions. Although these two coccinellid species fed on swede midge larvae in plastic containers, further experiments demonstrated that H. axyridis was not able to prey on swede midge larvae on infested broccoli plants. The susceptibility of swede midge larvae to three species of entomopathogenic nematodes (Steinernema feltiae, S. carpocapsae, and Heterorhabditis bacteriophora) was also evaluated in laboratory assays. Heterorhabditis bacteriophora was the only species that caused significant mortality to swede midge larvae and, at a concentration of 1000 IJs/larva, caused 90-100% mortality in loam, sandy loam, clay and muck soil. This is the first study describing the seasonal development of the swede midge in Quebec. In addition, the potential use of entomopathogenic nematodes as biological control agents against the swede midge is demonstrated.