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- Author or Editor: Christine D. Smart x
Cucurbit downy mildew, a disease caused by the oomycete pathogen Pseudoperonospora cubensis (Berk. & Curt.) Rostov., is a serious threat to cucumber (Cucumis sativus L.) production worldwide and can result in 100% yield losses in affected environments. In the last decade, strains of the pathogen have overcome the resistance of commercial cultivars in the United States, and currently no cultivar has robust resistance to the disease. This lack of resistance has been especially problematic for cucumber growers seeking to capture the late-season market, when downy mildew is ubiquitous throughout Eastern and Great Lakes production environments. Our objectives were to identify sources of resistance genes and to introgress these genes into high-quality, high-yielding breeding material. Using the moderately resistant cucumber cultivars Marketmore 97 and Ivory Queen as well as the Cornell-developed cultivars Platinum and Salt & Pepper, we have developed lines with excellent disease resistance. In a trial of 27 lines that included Cornell breeding material and the most resistant cultivars and U.S. Department of Agriculture (USDA) accessions identified in previous studies, the Cornell breeding line DMR-NY264 had the highest level of downy mildew resistance and the highest yields under disease pressure. In New York, plants of DMR-NY 264 produced fruit until frost without fungicide application.
In 2011, total marketable yield, fruit size, and number of lobes; fruit discoloration due to silvering; and plant structure were compared among eight commercial green bell pepper (Capsicum annuum) varieties and four breeding lines at three field sites in central New York. Tolerance to phytophthora blight (Phytophthora capsici) was also assessed at one of these sites. No wilting or plant death due to phytophthora blight was observed on the four breeding lines. ‘Paladin’, ‘Intruder’, and ‘Aristotle’ had the highest levels of tolerance to phytophthora blight, among the commercial varieties and maintained their yields in the presence of disease. In the absence of phytophthora blight, yields from these three varieties were comparable to susceptible varieties, but fruit tended to be smaller, and incidence of silvering was high in ‘Paladin’ and ‘Intruder’. Less silvering was observed on ‘Aristotle’ fruit. Total marketable yields from the breeding lines and percent of fruit with four lobes was comparable to the commercial varieties, and some breeding lines also had a low incidence of silvering, but fruit were smaller and set later in the season. Overall, this study suggests that ‘Paladin’, ‘Intruder’, and ‘Aristotle’ will yield well in fields with a history of severe phytophthora blight, but new large-fruited varieties with low incidence of silvering and good tolerance to phytophthora blight are needed.
Twelve commercial cauliflower (Brassica oleracea var. botrytis) varieties were evaluated for horticultural traits and susceptibility to alternaria leaf spot (Alternaria brassicicola) at the New York State Agricultural Experiment Station in Geneva, NY, in 2014 and 2015. Data including total yield, curd weight, curd width, plant height, days to maturity, and length of harvest were collected for each variety. A duplicate trial was planted in each year and inoculated with A. brassicicola, the causal agent of alternaria leaf spot, and the percentage of disease was assessed for each commercial cauliflower variety. Most of the commercial varieties were similar in susceptibility to disease and yield. ‘Artica’ and ‘Apex’ were ranked among the highest yielding varieties each year of the trial. The varieties ‘Graffiti’ and ‘Violet Queen’, both of which produce purple curds, had significantly less alternaria leaf spot compared with other varieties. Differences were seen between the 2 years of the trial in performance of individual varieties as influenced by temperatures during the growing season. This study demonstrates that some cauliflower varieties perform better than others under New York State growing conditions.
Phytophthora crown and root rot, caused by the oomycete pathogen Phytophthora capsici, is a devastating disease of squash and pumpkin (Cucurbita pepo). No currently available cultivars provide complete resistance to this disease. Three newly developed squash lines and four hybrids were evaluated in greenhouse and field experiments for their resistance to phytophthora crown and root rot as well as for their horticultural performance. The three newly developed lines ranked among the most resistant entries included in 2 years of field trials. In addition, in a separate greenhouse experiment, one of the lines was shown to display the least severe disease symptoms among a group of accessions previously reported to possess partial resistance to phytophthora crown and root. Furthermore, the resistance was observed to be robust to several isolates of P. capsici. However, the phytophthora-resistant lines had reduced yield relative to standard squash cultivars. These lines are useful for continued breeding efforts toward a phytophthora crown and root rot-resistant cultivar.
Phytophthora capsici is an oomycete pathogen that causes disease on bell pepper (Capsicum annuum) and many other vegetable crops globally. Newly developed bell pepper inbred lines have been shown to be resistant to P. capsici and have been previously evaluated for green harvest yield. Nine P. capsici-resistant inbred lines and three commercial cultivars were evaluated for red harvest yield and fruit characteristics at three sites and disease resistance was evaluated through field inoculation studies. Three of the P. capsici-resistant lines were further evaluated as hybrid parents by measuring hybrid yield and disease resistance. P. capsici-resistant lines had excellent disease resistance and provided high levels of resistance to F1 hybrids. Inbred lines had comparable yields to the commercial cultivars, but fruit were smaller in size and weight. These lines are suitable for use as inbred lines for markets where small fruit size is acceptable and have potential for use as hybrid parents.