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Incidence and severity of cavity spot of carrot as affected by pigmentation, temperature, and rainfall : an international journal of applied plant pathology

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Field trials to determine the effect of carrot pigmentation and weather parameters on cavity spot of carrot (CS) were conducted in the Holland/Bradford Marsh region of Ontario between 2002 and 2009. Twenty three colored carrots from the USDA-ARS breeding program at the University of Wisconsin (5) and commercial seed companies (18) were seeded in organic soil (pH 6.4 – 7.2, 39- 60% organic matter) in late May to early June and harvested in late October or early November. Carrots were assessed for CS severity mid-season and post harvest. Evaluations post harvest indicated that the purple pigmented carrot from breeding line ‘USDA 106-3’ and cultivars Purple Rain and Purple Haze consistently had low CS severity. The orange pigmented ‘USDA 101-23’, ‘Cellobunch’, ‘YaYa’ and ‘Envy’ had moderate CS and the red pigmented carrot breeding line ‘USDA 104-3’ and cultivars Atomic Red, Proline Red, Dragon and an unnamed line from India had high CS. Differences in CS severity in carrot cultivars between evaluations at mid-season and post harvest suggest that some carrots are more susceptible to Pythium spp. inoculum in soil (alloinfection) and others to secondary infection (autoinfection) that can be attributed to the Pythium sp. involved in CS. Cavity spot severity was positively correlated with total rainfall two and three months after seeding, and was negatively correlated with number of days with air temperature = 30ºC three and four months after seeding. Soil temperature and total rainfall were the best predictors of CS incidence and severity. These results could allow a forecast of disease incidence and severity at harvest.
C. Saude , P. W. Simon , M. R. McDonald
USDA Scientist Submission
Plant disease 2014 v.98
Journal Articles, USDA Authors, Peer-Reviewed
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