Studying Trichoderma is crucial if you want to avoid it. I talk, therefore, about a research paper that tries to find the most suitable organic substrates for the biomass production, viability, and efficacy of the biocontrol strain Trichoderma harzianum AS12-2.
Chemical pesticides are the most common way to protect plants against pests and diseases in agriculture. However, the use of synthetic compounds adversely affects the environment and human health. In addition, the high cost of investigating, developing, and registering new synthetic pesticides, and the rapid emergence of pathogen resistance, have also contributed to an increased interest in finding alternate disease control methods such as Trichoderma.
Trichoderma species are versatile, ubiquitous, and abundant fungi found in many soil types in diverse ecosystems. They have been known as biocontrol agents for plant pathogens for decades. They collectively are effective against various diseases of many crops in the greenhouse, nursery, field, and orchards. Considerable amounts of studies have focused on the mass production of Trichoderma in the hope of developing effective and safe bioproducts as substitutes for chemicals for the control of plant diseases.
Therefore, the objective of today’s research paper is to find, amongst 13 inexpensive and locally available substrates, the most suitable organic substrate for the colonization, conidiation, viability, and bioefficacy of a biocontrol strain of Trichoderma harzianum. The authors used strain AS12-2, a highly effective strain against Rhizoctonia solani, in vitro. The rice sheath blight disease by this pathogen under greenhouse and field conditions was used in this study.
The authors used rice husk, crushed (powdered) rice husk, rice straw, rice bran, wheat bran, broom sorghum grain, sawdust, cow dung, sugar beet pulp, soybean meal, peanut pod, used barley grain, and water fern as low-cost substrates.
300g of each substrate was filled in 1 L conical flasks and sterilized 3x at 121°C (250°F] for 30 minutes. After the cool down, the substrates were inoculated under aseptic conditions and kept at ambient temperature for 30 days while periodically shaken by hand.
[Colonization and Sporulation]
Trichoderma harzianum AS12-2 colonized all substrates to different intensities ranging from low to high. The lowest colonization was found on sawdust and soybean meal. The highest colonization of Trichoderma was found on rice husk, crushed rice husk, rice straw, broom sorghum grain, sugar beet pulp, cow dung, and water fern.
While the mycelium was white in the beginning, the color gradually changed, and various shades of green were observed among the substrates. The highest population could be found on broom sorghum grain and rice straw with 6.4E10 and 5.3E10 CFUs g-1, respectively. The lowest population could be found on water fern, sawdust, and waste barely grain.
After one month of incubation at room temperature, the population of the substrates remained almost stable or decreased very slowly. To test the storage time and the storage temperature, the 13 samples were stored either for 12 months at 25°C (77°F) or 4°C (39°F). The authors found that in both cases, the population of Trichoderma decreased, but the decrease was lower at 4°C (39°F).
To measure the efficacy of Trichoderma, the sheath blight severity was calculated as relative lesion length four weeks after the artificial inoculation of the pathogen. The infected control had a disease severity of 68.1%. The chemical control reduced the disease severity to 16.9%, while Trichoderma showed a decrease in disease severity of 50%.
Knowing which substrates Trichoderma grows the best and how long it can survive is important to know. As today’s research paper used no supplementation, I recommend that you check out the video on the right. In this video, I present a research paper in which the authors studied the effect of different carbon and nitrogen sources as well as inorganic salts on the growth of Trichoderma.
Talk to you there.
📝Naeimi, S.; Khosravi, V.; Varga, A.; Vágvölgyi, C.; Kredics, L. Screening of Organic Substrates for Solid-State Fermentation, Viability and Bioefficacy of Trichoderma harzianum AS12-2, a Biocontrol Strain Against Rice Sheath Blight Disease. Agronomy 2020, 10, 1258. https://doi.org/10.3390/agronomy10091258, https://creativecommons.org/licenses/by/4.0/