Sweet basil (Ocimum basilicum) is the most economically important culinary herb in the United States. In 2007, a new disease, basil downy mildew (BDM), caused by the oomycete pathogen Peronospora belbahrii, was introduced into the United States and has since caused significant losses in commercial basil production.
Although no commercial sweet basils available are resistant to P. belbahrii, other species of Ocimum have exhibited potential tolerance, resistance, or both. The objectives of this work were to determine if leaf morphological characteristics including stomata density and leaf curvature correlated with infection of plants by P. belbahrii, and thus could be used as selected characters in plant breeding. In 2011, 20 Ocimum cultivars including sweet (O. basilicum), cinnamon (O. basilicum), clove (O. basilicum), citrus (Ocimum ×africanum syn. Ocimum citriodorum), spice (Ocimum americanum syn. Ocimum canum), and holy basils (Ocimum tenuiflorum syn.
Ocimum sanctum) were evaluated for susceptibility to downy mildew. Sweet basils were determined to be the most susceptible; cinnamon, clove, and Thai types were moderately susceptible; and citrus, spice, and holy types were least susceptible to downy mildew. Using those same 20 Ocimum species and cultivars, stomata length and density and leaf curvature were measured and correlated with downy mildew incidence and severity.
In general, basil species with higher stomatal densities had higher downy mildew incidence and severity. High stomatal densities were mainly found in the sweet, cinnamon, and clove basils. Citrus and spice species with longer stomatal lengths generally exhibited lower downy mildew incidence.
Holy basil, the least susceptible of all Ocimum sp. to P. belbahrii evaluated in this study, had the greatest stomatal density and shortest stomatal length. Some sweet basil cultivars with the highest downy mildew incidence also had the greatest downward leaf curvature, whereas other sweet basil cultivars with moderate downy mildew incidence had leaves that were nearly flat or curved upward. Holy, citrus, and spice basils with low downy mildew incidence had leaves that were nearly flat or curved upward.
This study suggests that leaf curvature and stomatal density and length affect downy mildew development and sporulation. Considerations of these leaf morphological characteristics may be useful phenotypic traits in breeding for downy mildew resistance in Ocimum.
Access the full study at HortScience.






Announcements
Job Offers
- Directors - New Zealand
- Nursery Production Manager Victoria Australia
- Technical Sales Consultant, Washington
- Export Sales Manager North America Exports
- Head Grower Hydroponic Greenhouse
- Account Manager – South-East Asia
- Vegetable Seed - EU Sales and Regional Manager
- Business Developer – High Tech Horticulture
- Operations Manager Organic Farm Barka Oman
- Bravo Sales and Administration Officer
"Tweeting Growers"
Top 5 -yesterday
Top 5 -last week
Top 5 -last month
- "Honduras greenhouse park to become the largest producer-exporter in the Central American region"
- Netherlands: Codema Systems Group declared bankrupt
- Shanghai: Young people who can't get vegetables start to "help themselves" through hydroponic vegetables
- Canada: Dutch holding company acquires Ontario Plants Propagation
- Google meets agriculture at Go Green Agriculture
Receive the daily newsletter in your email for free | Click here
Other news in this sector:
- 2017-11-10 Be prepared to clean the inner glass by the end of the season
- 2016-11-30 CleanStart: Sustainable soil pest management from Certis Europe
- 2016-11-29 Implementing BioSecurity in 9 steps
- 2016-11-28 Susceptibility of basil species and cultivars to Peronospora belbahrii
- 2016-11-25 Three new lettuce varieties resistant to Fusarium
- 2016-11-24 US (KY): New strawberry scouting guide available for Kentucky
- 2016-11-23 Steaming is gaining steam
- 2016-11-22 Source of Dutch Ralstonia infection remains unknown
- 2016-11-21 Penn State tests nanotube device for plant disease detection
- 2016-11-18 Video: What is happening with all that used rockwool?
- 2016-11-17 Can soil be too sterile?
- 2016-11-16 Do you have a press release for our Clean Start and Crop Change special!
- 2016-11-11 Gleaning at the greenhouse
- 2016-11-10 How herbivores manipulate plant defences
- 2016-11-09 "Double protection provides significantly more security"
- 2016-11-08 BioConsortia raises $12 million for development of multi-microbe products
- 2016-11-07 Russell IPM wins Innovation Award at Strawberry and Asparagus Fair
- 2016-11-04 Weterings Mechanisatie speeds up greenhouse crop change
- 2016-11-03 Ensure optimum hygiene during crop change
- 2016-11-02 Australia: Nursery waste management for reducing costs