E. O. Monda

Inoculation of tomato seedlings with Trichoderma Harzianum and Arbuscular Mycorrhizal Fungi and their effect on growth and control of wilt in tomato seedlings

A green house study was conducted to investigate the ability of an isolate of Trichoderma harzianum (P52) and arbuscular mycorrhizal fungi (AMF) in enhancing growth and control of a wilt pathogen caused by Fusarium oxysporum f. sp. lycopersici in tomato seedlings. The plants were grown in plastic pots filled with sterilized soils. There were four treatments applied as follows; P52, AMF, AMF + P52 and a control. A completely randomized design was used and growth measurements and disease assessment taken after 3, 6 and 9 weeks. Treatments that significantly (P < 0.05) enhanced heights and root dry weights were P52, AMF and a treatment with a combination of both P52 and AMF when compared the control. The treatment with both P52 and AMF significantly (P < 0.05) enhanced all growth parameters (heights; shoot and root dry weight) investigated compared to the control. Disease severity was generally lower in tomato plants grown with isolate P52 and AMF fungi either individually or when combined together, though the effect was not statistically significant (P0.05). A treatment combination of P52 + AMF had less trend of severity as compared to each individual fungus. T. harzianum and AMF can be used to enhance growth in tomato seedlings.

Downregulation of transcription factor aflR in Aspergillus flavus confers reduction to aflatoxin accumulation in transgenic maize with alteration of host plant architecture

Key messageWe report success of host-induced gene silencing in downregulation of aflatoxin biosynthesis inAspergillus flavusinfecting maize transformed with a hairpin construct targeting transcription factoraflR.AbstractInfestation of crops by aflatoxin-producing fungi results in economic losses as well as negative human and animal health effects. Currently, the control strategies against aflatoxin accumulation are not effective to the small holder farming systems in Africa and this has led to widespread aflatoxin exposure especially in rural populations of sub-Saharan Africa that rely on maize as a staple food crop. A recent strategy called host-induced gene silencing holds great potential for developing aflatoxin-resistant plant germplasm for the African context where farmers are unable to make further investments other than access to the germplasm. We transformed maize with a hairpin construct targeting the aflatoxin biosynthesis transcription factor aflR. The developed transgenic maize were challenged with an aflatoxigenic Aspergillus flavus strain from Eastern Kenya, a region endemic to aflatoxin outbreaks. Our results indicated that aflR was downregulated in A. flavus colonizing transgenic maize. Further, maize kernels from transgenic plants accumulated significantly lower levels of aflatoxins (14-fold) than those from wild type plants. Interestingly, we observed that our silencing cassette caused stunting and reduced kernel placement in the transgenic maize. This could have been due to “off-target” silencing of unintended genes in transformed plants by aflR siRNAs. Overall, this work indicates that host-induced gene silencing has potential in developing aflatoxin-resistant germplasm.

Efficacy of onion (Allium cepa l.) and garlic (Allium sativum l.) juice against common pathogens associated with meat

Meat contains high nutrients that make it get spoilt readily and currently used preservatives like soluble nitrites are carcinogenic. The aim of this study was to evaluate the efficacy of Onion ( Allium cepa L.) and Garlic ( Allium sativum L.) juice as alternative preservatives. Efficacy of the single preservatives an d their combinations was determined by the disk diffusion method against the following four meat pathogens; Bacillus subtili s (ATCC 6633), Salmonella typhi (ATCC 2202), Staphylococcus aureus (ATCC 20591) and Escherichia coli (ATCC 25922) at 0.2 g of meat. Accelerated shelf life of meat was established by determining the number of microorganisms at an interval of 1 - 2 h. The results indicated that garlic was significantly, more effective (P ≤ 0.05) in inhibition of meat pathogens than all the other test treatments. Garlic juice reduced Gram positive pathogen, Staphylococcus aureus and Bacillus subtilis to 0 by the 12th h. These results are an important reference that confirms the use of Garlic to control common pathogens associated with meat. Keywords: Garlic ( Allium sativum L); Onion ( Allium cepa L); Inhibition zones, Efficacy; Meat.