Vermicompost in combination with Trichoderma asperellum isolate T13 as bioagent to control sclerotium rot disease on vegetable soybean seedlings

Abstract

Importance of the work:Vermicompost is utilized as biofertilizer, especially in organic farming systems. It has potential for soilborne plant disease control but empirical studies are scarce. Objectives: To test the effect of vermicompost from African nightcrawler in combination with Trichoderma asperellum isolate T13 on the mycelial growth of Athelia rolfsii in vitro and the incidence of sclerotium rot disease on vegetable soybean seedlings under greenhouse conditions. Materials & Methods: Fungal confrontation assay using either vermicompost filtrate or in combinations with varied spore concentrations of T. asperellum isolate T13 was conducted to observe antagonistic activity against the mycelial growth of A. rolfsii in vitro. Vegetable soybean seeds were sown in the greenhouse in soil mixed with vermicompost and pathogen inoculum (mycelia or sclerotia) to observe the disease incidence on the seedlings. Results: For the in vitro bioassay, adding half the proportion of T. asperellum isolate T13 spores (1 × 10 8 spores/mL) relative to the total volume resulted in 80.4% inhibition of A. rolfsii diameter growth, producing the best antagonistic activity. Under greenhouse conditions, the soil amended with mycelial inoculum and pure vermicompost led to significantly lower disease incidence (19.7%) than for the pathogen-inoculated control (40.7%) and the mixture of vermicompost and T. asperellum isolate T13 (34.7%). However, no disease incidence was observed with soil amendment using vermicompost, T. asperellum isolate T13 and sclerotia. Main finding: Vermicompost can be used as a bioagent for soilborne disease control, especially when combined with T. asperellum isolate T13, suggesting a strategy to prevent sclerotium disease incidence rather than trying to control actively growing mycelia.

Dual-Purpose Vermicompost for the Growth Promotion and Suppression of Damping-Off Disease on Potted Vegetable Soybean

“…Vermicompost from AF exhibited significantly higher antagonistic activity against A. rolfsii in vitro than vermicompost from TG, with a 50% and 16% inhibition of diameter growth, respectively ( Figure 1 and Figure 2 ). This finding corresponded with a previous study by Nonthapa et al [ 21 ], who observed the inhibition activity of AF vermicompost filtrate against the mycelial growth of A. rolfsii in vitro. The suppressive effect of vermicompost from TG on the mycelial growth of Fusarium oxysporum f. sp.…”

“…The results indicated that AF vermicompost as a soil amendment led to the lowest damping-off disease incidence on vegetable soybean seedlings among all inoculated treatments under this experimental condition. The efficacious suppression of damping-off caused by A. rolfsii on vegetable soybean seedlings using the AF vermicompost amendment was shown by Nonthapa et al [ 21 ]. In this study, soil amendment with Tiger worm did not significantly reduce the incidence of damping-off disease.…”

“…It was collected from an agricultural field located in Ban Had District, Khon Kaen Province, Thailand. The basic physico-chemical properties of the soil were analyzed as described by Nonthapa et al [ 21 ] and presented in Table 2 .…”

“…On the other hand, vermicompost as a soil amendment exhibits the potential to control soil-borne fungal plant diseases [ 19 , 20 ]. For example, soil amendment with vermicompost from the African nightcrawler at 20% ( w / w ) demonstrated suppression of damping-off disease caused by A. rolfsii , with a lower percentage of disease incidence (19.7%) than for non-amended soil (40.7%) in vegetable soybean seedlings [ 21 ]. Soil amended with 10%, 25%, and 50% ( v / v ) Tiger worm vermicompost exhibited reduced chickpea seedling mortality following the infection of Sclerotium rolfsii [ 13 ].…”

“…(Anamorph: Sclerotium rolfsii Sacc.) is an important soil-borne pathogen that causes damping-off and sclerotium rot disease in Thai vegetable soybeans [ 21 ]. It produces sclerotia that encourage survival in the soil [ 27 ] and resistance to harsh environmental conditions [ 28 ].…”