Efficacy of Oryza sativa husk and Quercus phillyraeoides extracts for the in vitro and in vivo control of fungal rot disease of white yam (Dioscorea rotundata Poir)

Abstract

Tuber rot disease is a major constraint to white yam (Dioscorea rotundata) production, accounting for 50-60% of annual yield losses in Nigeria. The main method of control using synthetic fungicides is being discouraged due to human and environmental health hazards. The potential of Oryza sativa husk (OSH) and Quercus phillyraeoides (QP) extracts for the in vitro and in vivo control of six virulent rot-causing fungal pathogens, Lasiodiplodia theobromae, Aspergillus niger, Rhizoctonia solani, Penicillium oxalicum, Sclerotium rolfsii, and Fusarium oxysporum was evaluated, using five different extract concentrations of 0.5%, 1.0%, 1.5%, 2.5%, and 3.5% w/v. These fungi were isolated from rotted tubers of D. rotundata, across three agroecological zones in Nigeria―the Humid rainforest, Derived savanna, and southern Guinea savanna. All treatments were subjected to three methods of inoculation 48 hours before the application of both extracts and stored at 28 ± 2°C for 6 months. Radial mycelial growth of the test pathogens was effectively inhibited at concentrations ≤ 3.5% w/v in vitro for both OSH and QP extracts. Rotting was significantly reduced (P ≤ 0.05) to between 0 to 18.8% and 0% to 20.9% for OSH and QP extracts respectively. The extracts significantly (P ≤ 0.05) inhibited percent rot of the test pathogens at 3.5% concentration w/v in vivo. Rot incidence was, however, lower in replicate tubers that were inoculated, treated with extracts and exposed than treatments that were covered. Phytochemical analysis of OSH and QP extracts revealed the presence of secondary metabolites such as alkaloids, flavonoids, saponins, tannins, ferulic acid, phlobatanins, Terpenoids, phenols, anthraquinone and pyroligneous acid. The efficacy of both extracts in reducing rot in this study recommends their development as prospective biopesticide formulation and use in the management of post-harvest rot of yam tubers.

Holm Oak (Quercus ilex subsp. ballota (Desf.) Samp.) Bark Aqueous Ammonia Extract for the Control of Invasive Forest Pathogens

“…Robin) Berkhout , Penicillum feniculosum Thom, and P. ochrochloron Biourge has also been observed for methanolic extracts of Q. acutissima Carruth ., Q. macrocarpa Michx., and Q. robur L. bark, with MIC values ranging from 160 to 2000 µg·mL −1 [ 29 ]. Dania et al [ 30 ] found that Q. phillyreoides A. Gray bark aqueous extract, at a concentration of 3%, resulted in strong inhibition of mycelial growth (>77%) in in vitro tests against Rhizoctonia solani J.G.…”

Pathogenicity of Sclerotium rolfsii Isolates Causing Stem and Root Rot Disease of Cowpea Vigna unguiculata (L.) Walp and Management Using Trichoderma Species

“…Preparation of inoculum was done as previously described in the pathogenicity experiment. Trichoderma species were applied as soil drench at 4 ml per planting hole at a concentration adjusted to 2.5 × 10 8 using an hemocytometer (Dania et al, 2014) before sowing. Seven and half grammes of isolate SR 06-ramified wheat seeds were used to inoculate the soil around the base of healthy cowpea plants at two weeks after sowing while control plants were not inoculated with the pathogen.…”

Bioefficacy of Trichoderma species against important fungal pathogens causing post-harvest rot in sweet potato (Ipomoea batatas (L.) Lam)

“…Detailed structural features of each isolate were observed using a compound microscope and identification was done following standard manual of fungi (Barnett and Hunter, 1998). Inoculum concentration was quantified and adjusted to 2 x 10 4 using the method of Dania et al (2014).…”

“…Inoculated treatments were incubated in aerated crates at 28±2 0 C for four months. Percent rot inhibition was calculated according to Dania et al (2014).…”