Abstract
The cereal cyst nematode Heterodera avenae is one of the important soil-borne pathogens of cereal crops and causes high yield losses worldwide. Trichoderma spp. formulations are applied as commercial bio-control agents against soil-borne plant pathogens such as H. avenae. However, the relationship between Trichoderma longibrachiatum fermentation parameters and its bio-control potential against H. avenae has not been exclusively established. In the present study, the effect of 10 different fermentation media and conditions on the nematicidal activity of T. longibrachiatum T6 (T6) was evaluated with a single-factor method and a Plackett–Burman design, and the interaction between different fermentation parameters was investigated by a Box–Behnken design. The variables for enhancing the nematicidal activity of T6 culture filtrates were explored and optimized using response surface methodology (RSM). The Minor Medium (MM) plus wheat bran-2 medium was found to be the most effective fermentation medium for T6 culture filtrates against the second stage juveniles (J2s) of H. avenae. The maximum mortality of the J2s was obtained using the T6 culture filtrates under the following fermentation conditions: initial pH 6, 28°C culture temperature, 180 rpm rotating speed, 60 ml of fermentation media, 7 days of incubation time, and 1 ml of inoculation volumes. Among these parameters, the initial pH, inoculation volume, and incubation day were identified as the most significant parameters and critical independent variables for enhancing the nematicidal activity of the T6 culture filtrates. After further optimizations based on statistical predictions, the highest nematicidal activity (92.42%) was obtained with the T6 culture filtrates fermented under an initial pH of 6.06, an inoculation volume of 1.62 ml, and an incubation time of 7.15 days. The nematicidal activity was increased approximately by as high as 1.07% compared with that before optimization. Bio-control efficacy of T6 culture filtrates was 83.88% at the 70th day after wheat seeds sowing in greenhouse experiments. The results from the validation experiments agreed with the model predictions. Our study has improved the bio-control potential of Trichoderma spp. against the plant-parasitic nematodes H. avenae and provided a cost-efficient bio-resource in the future development of novel bio-control agents.
Highlights
The cereal cyst nematode (CCN, Heterodera avenae) is a plant pathogen found in cereal crops in more than 30 countries (Nicol et al, 2003; Jones et al, 2013; Baklawa et al, 2017)
We found that the strain of T. longibrachiatum Trichoderma longibrachiatum T6 (T6) (T6) had a significant parasitic and lethal effect on the nematodes of H. avenae and M. incognita with a great potential to be used as a bio-control agent
Sharma et al (2014) found that the mortality of M. incognita second stages juveniles (J2s) was increased to 100% if the nematode pathogenic strain P. lilacinus 6029 was fermented on the medium of Karanja cake than the Czapeck–Dox filtrate under the fermentation parameters of a lower pH and 15 days’ incubation time
Summary
The cereal cyst nematode (CCN, Heterodera avenae) is a plant pathogen found in cereal crops in more than 30 countries (Nicol et al, 2003; Jones et al, 2013; Baklawa et al, 2017). The pathogen causes significant crop yield losses (Long et al, 2012), of rainfed cereals (Nicol and Rivoal, 2008). Strategies to manage plant parasitic nematodes in cropping systems have been mainly relied on chemical nematicides (Huang et al, 2014); such a method often causes concerns to environmental sustainability because of chemical pollution. The development of bio-control agents for plant diseases in agriculture has attracted more attention to minimize the use of chemical nematicides (Sergio, 2011). Some beneficial microorganisms, such as nematophagous bacterial and fungal species, are considered as ecologically friendly bio-control agents for the control of nematodes (Jatala, 1986). The entomopathogenic fungi of Paecilomyces and Pochonia genus in nematode-suppressive soils have been reported to have potential to combat plant parasitic nematodes (Nitao et al, 2002; Sharon et al, 2007; Mukhtar et al, 2013)
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