Preventing Losses from Botrytis

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The Problem:Botrytis is one of the most serious post-harvest problems facing the floral industry. Botrytis, also known as gray mold, causes brown spots on petals and leaves and results in soft, mushy flowers that are not marketable. In less severe cases, Botrytis-infected flowers have reduced vase life. Interestingly, Botrytis damage has been shown to result in ethylene production within flowers. For the flower industry, Botrytis causes significant losses and reduced profits.

Background:Botrytis is extremely difficult to control! The spores germinate at a wide range of temperatures, including temperatures typically used for shipping and storage and at humidity levels of 93% or higher. Spores will germinate in 4 – 8 hours if water is present. In other words, the conditions used for production, shipping and storage are good for Botrytis growth.

Additionally, the spores survive on living or decayed plant material for up to one year and may be spread by water, wind or on the hands and clothes of workers. Then, when moisture is present, the spores germinate and invade the petals and leaves. The germinated spores inject a toxin in the petal and leaf cells that leads to the damage we see on Botrytis-infected petals and leaves. The worst cases of Botrytis damage occur when production areas experience rain and high humidity conditions, water is present on leaves and stems in the shipping boxes, and temperature fluctuations cause condensation on the flowers and on the sleeves.

Current Research:Research supported by AFE provides an integrated and comprehensive program to tackling Botrytis. Progress has been made through the following research projects AFE is currently funding:

  1. Finding Solutions to Pre-Harvest Botrytis Infection of Cut Roses (Lead researcher: Dr. James Faust, Clemson University. Other researchers: Guido Schnabel, Dr. Uttara Samarakoon)
  2. Objective: Developing and understanding the relationships between the greenhouse environment, such as temperature, humidity, leaf wetness and cultural practices on Botrytis spore populations in cut roses.
  3. Postharvest Management of Botrytis During Shipping and Storage (Lead researcher:Dr. John Dole, North Carolina State University. Other researchers: Mike Benson, Alicain Carlson)
  4. Objective: Identifying the relationship between ethylene sensitivity and Botrytissusceptibility of cut roses and whether use of anti-ethylene agents reduce Botrytisdevelopment. Also, the relationship of temperature and relative humidity conditions inside shipping boxes will be related to incidence of Botrytisrelative to packing materials and pre-cooling methods.

Future Research:There are multiple approaches to the control of Botrytis – cultural, environmental control, pre- and post-harvest treatments, and modification of shipping and handling practices. Interestingly, very little research has been conducted on Botrytis control practices on cut flowers, potted plants and bedding plants.

The elements of the research will include the following:

  1. To measure the environmental conditions in commercial rose greenhouses in Colombia and assess Botrytisinfection risk using the Strawberry Advisory System model (SAS).
  2. To quantify Botrytissporulation in two greenhouses in Colombia over time using Burkhard spore traps and correlate these data with environmental conditions and/or cultural practices.
  3. a) To assess the current calcium nutrition program and determine if there are opportunities to conduct experiments to improve petal tissue calcium levels. b) To determine the calcium levels required in petals to reduce the incidence of Botrytis. c) To determine if there is a different calcium level in petals of varieties sensitive and tolerant to Botrytis.
  4. Develop a quick, easy and practical method to detect susceptibility on new varieties in the breeding process to help to stay away from coming varieties on an early stage.
  5. Determine strategies to avoid sporulation of Botrytis in the lower part of the plant and the floor in dead leaves, desirable with biological agents. This place is normally the inoculum pool of the greenhouse.
  6. Develop defense response activators with interference RNA (RNAi) using CRISPR, if possible.

Industry Education:As new research results demonstrate effective ways to control Botrytis, AFE will publish trade magazine articles and encourage industry educational programs to include research supported by AFE.

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American Floral Endowment

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