A laboratory bioassay to distinguish isolates of Peronospora tabacina D.B. Adam was developed utilizing 7-mm acetone-dipped disks cut from tobacco leaf panels from several cultivars of Nicotiana tabacum, sporangiospores of P. tabacina, a germination indicator (Calcofluor), and fluorescence microscopy. Sporangiospore germination percentage of each isolate X cultivar pair was determined. Mean germination of sporangiospores differed between domestic and international collection locations (except between the two Mexican isolates). These results suggest the presence of different pathotypes of P. tabacina.

Crop ScienceVolume 30, Issue 1 cropsci1990.0011183X003000010071x p. 241-242 Registration of Germplasms Registration of NC-BMR 42 and NC-BMR 90 Germplasm Lines of Tobacco R. C. Rufty, Corresponding Author R. C. Rufty n/[email protected] Dep. of Crop ScienceCorresponding author.Search for more papers by this authorE. A. Wernsman, E. A. Wernsman Dep. of Crop ScienceSearch for more papers by this authorC. E. Main, C. E. Main Dep. of Crop ScienceSearch for more papers by this authorG. V. Gooding Jr., G. V. Gooding Jr. Dep. of Plant Pathology, North Carolina State University, Raleigh, NC, 27695Search for more papers by this author R. C. Rufty, Corresponding Author R. C. Rufty n/[email protected] Dep. of Crop ScienceCorresponding author.Search for more papers by this authorE. A. Wernsman, E. A. Wernsman Dep. of Crop ScienceSearch for more papers by this authorC. E. Main, C. E. Main Dep. of Crop ScienceSearch for more papers by this authorG. V. Gooding Jr., G. V. Gooding Jr. Dep. of Plant Pathology, North Carolina State University, Raleigh, NC, 27695Search for more papers by this author First published: 01 January 1990 https://doi.org/10.2135/cropsci1990.0011183X003000010071xCitations: 5AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article.Citing Literature Volume30, Issue1January–February 1990Pages 241-242 RelatedInformation

Rufty, R. C., and Main, C. E. 1989. Components of partial resistance to blue mold in six tobacco genotypes under controlled environmental conditions. Phytopathology 79:606-609. Two susceptible and four partially resistant tobacco genotypes were Mutant, NC-BMR 42, and NC-BMR 90 produced fewer and smaller evaluated for components of partial resistance to blue mold. Disease lesions, had lower sporulation capacity, and exhibited longer patent efficiency, incubation period, latent period, degree of colonization, and periods than susceptible genotypes. Breeding line NC-BMR 90 was sporulation capacity were measured under high and low inoculation superior to all other partially resistant genotypes in this study. The presence density in experiments conducted at the Southeastern Plant Environmental of multiple resistance components in NC-BMR 90 makes this line a Laboratory (North Carolina State University Phytotron), Raleigh, NC. desirable source of blue mold resistance. Results obtained in these Genotypes differed significantly for all components of resistance in all experiments corroborated field observations and indicate that deployment trials. Commercial cultivars Speight G-70 and McNair 944 were of tobacco germ plasm with partial resistance to blue mold should reduce consistently the most susceptible genotypes based on all components of onset and progress of blue mold epidemics. partial resistance measured. Partially resistant genotypes Chemical Additional keywords: Nicotiana tabacum, Peronospora tabacina. Tobacco blue mold, also known as downy mildew of tobacco derived from N. velutina) and Chemical Mutant (resistance (Nicotiana tabacum L.), is caused by the fungus Peronospora obtained after treating seeds of flue-cured tobacco cultivar tabacina Adam. Occurrence of blue mold is generally sporadic, but Virginia Gold with triethylene iminotriazine) (9); two resistant severe economic losses can occur when the disease reaches breeding lines, NC-BMR 42 (derived from the cross Ovens 62 X epidemic proportions. For example, an epidemic of blue mold in McNair 944) and NC-BMR 90 (derived from the cross Ovens 62 X 1979 resulted in an estimated $250 million loss to U.S. and KY 17) (12); and two susceptible commercial cultivars, Speight

Tobacco blue mold caused by Peronospora tabacina is a highly weather sensitive disease which occurred in the major tobacco production areas of North Carolina in 1980. Dates of first reported occurrence of blue mold by county units in eastern North Carolina progressed in a northeastward direction from the South Carolina border to the Virginia border between 1 May and 6 June. In the central piedmont region of the state, blue mold was first reported in mid-May while in the western mountains, blue mold was recorded in early June. Temperatures and total weekly rainfall data were analyzed for 18 weeks from late March to early August from 102 weather stations across North Carolina and from the bordering regions of surrounding states. An analysis of first occurrence dates and the temporal and spatial properties of temperature and precipitation indicated that the epidemic continued to spread despite temperatures outside the range previously considered favorable for the disease. Availability of moisture on the tobacco leaves for spore germination appeared to be the predominant factor in all parts of the state. Trajectory analysis was used to identify possible source regions for the spores which arrived over North Carolina tobacco fields. The analysis indicated that there were many days in April, May, and June 1980 when conditions were considered favorable for spore transport to North Carolina from the infected fields located to the south. Taking into account epidemiological latent periods, certain of these trajectory dates were selected as representing the most probable periods of spore transport.

Beneficial microbes in the microbiome of plant roots improve plant health. Induced systemic resistance (ISR) emerged as an important mechanism by which selected plant growth–promoting bacteria and fungi in the rhizosphere prime the whole plant body for ...Read More