Crop losses and value degradation caused by plant diseases are major constraints to food security globally. Fungicides are important tools in management of plant diseases caused by fungal and oomycete pathogens. At present, major crop losses are inevitable without the use of fungicides. However, reliance on fungicides is not sustainable since the fungal pathogens that cause powdery mildews and gray mold are high-risk pathogens capable of developing fungicide resistance.
A non-chemical, environmentally friendly option of optical based strategies was tested against gray mold at controlled environment conditions at Petri dish and plant levels. Experiments with Petri dishes having potato dextrose agar (PDA) showed that the UV dose that optimized for powdery mildew management is not sufficient for gray mold. While germination of Pseudoidium neolycopersici conidia was completely inhibited with 1 min of daily UV (peak at 254 nm) exposure (3.8 ± 0.2 W m-2), there was no significant effect on conidial germination of Botrytis cinerea with similar UV treatment. Increasing the duration of exposure by 4 min or more significantly reduced conidial germination of Botrytis cinerea.
Experiments conducted at plant level showed similar trend with powdery mildew in tomato. On the other hand, the efficacy against gray mold was less significant even at high doses of UV. This might be because of the pathogen that causes powdery mildew is external (ecto pathogen), while gray mold will become internal after penetration to plant tissues (endo pathogen). This might help protection from direct UV exposure.
Controlled environment chamber experiments were conducted at Petri dish level to examine the potential resistance of 15 commercial grown tomato varieties for powdery mildew and gray mold. Leaflets from the 3rd leaf (from top) were detached, surface sterilized and placed adaxial side up in Petri dishes having water agar and benzimidazole.
For powdery mildew resistance experiment, leaflets were inoculated with 10-14 days old powdery mildew inoculum, by touching the cleaned leaflet by diseased leaflet (one for one). Petri dishes were sealed immediately after inoculation and maintained in controlled environment chamber with 21±1 °C, 75% relative air humidity, and 18 h of daily lighting supplied with high pressure mercury lamps (100±10 µmol/m2/s. Severity was assessed 7 days after inoculation by visual assessment.
Similar experiment was conducted to examine the resistance potential against gray mold. Leaflets were inoculated by placing 5 mm diameter mycelial plug prepared from 5 days old colonies of Botrytis cinerea grown in Petri dishes having potato dextrose agar medium. Severity was assessed 7 days after inoculation by visual assessment.
Among the 17 tested commercial tomato varies, 14 of them showed powdery mildew severity more than 50%, and one showed less than 10% severity.
To examine the potential of host resistance, 12 accessions representing tomato wild relatives were tested. Petri dish experiment with detached leaflets were executed as described above. Six tested accessions showed severity more than 50% for powdery mildew.
All the commercial and wild relatives tested showed more than 50% severity for gray mold.
Among the 27commercial strawberry accessions tested at Petri dish level with leaflets, three of them showed gray mold severity more than 50% and five of them showed less than 25%.
A first version of the spore trapping and imaging system has been built. The system includes two different types of illumination, a 10x magnification optical setup, a 20 MP camera, a stepper motor for focus control and an Arduino for controlling the whole system. We have tested that the system is able to trap spores under laboratory conditions and that the images have sufficient magnification of the spores to allow for development of classification algorithms.
The END-IT project addresses environmentally friendly production of tomato and strawberries with improved shelf life and enhanced consumer value. The project will expand the knowledge related to i) crop tolerance with wavelengths and dose ranges of optical environment effective to control a wide range of fungal diseases, ii) genes involved in induced systemic resistance that are regulated by optical radiation, and iii) the interaction between optical environment and the genes involved in antioxidant biosynthesis. Automated system will be developed, with artificial intelligence and advanced sensor technology, for timely identification of pathogen inoculum and on-site quantification of inoculum level.
This will collectively constitute an optical crop treatment system that ensures sustainable, environmentally friendly crop production with improved crop yield of high quality, reduced waste, reduced use of fungicides and increased profitability to society. END-IT is a multi-actor project and comprises experts with complimentary competence in the plant-fungal biology, photobiology, molecular biology, sensor technology and automation, agriculture extension, economic analysis, and trade and industry partners. This ensures smooth transfer of the research outcomes to relevant industry. This will ensure responsible research and innovation with societal interests and will benefit the society.