Kwasi Yobo

FRONTISPIECE Growth comparison between unfertilized control plant (left) and plant treated with combination of Trichoderma harzianum Eco-T + Bacillus B69 (right) 35 days after planting. Treated plant shows healthier, more vigorous growth than the control plant.

The combination of yeast antagonists and Acibenzolar-S-Methyl (ASM) was tested against Fusarium graminearum on a spring wheat cultivar PAN3471. Two strains of Papiliotrema flavescens (Strains WL3 and WL6) and a strain of Pseudozyma sp. (MGO1) were combined with full strength ASM at anthesis, half strength ASM at anthesis and quarter strength ASM at late boot stages. The yeast and ASM treatments were applied prior to F. graminearum inoculation and disease progress was assessed over time. The combination of yeast and ASM treatments effectively reduced Fusarium Head Blight (FHB) severity and deoxynivalenol (DON) concentration compared to when the treatments were used alone. A positive correlation was observed between the Area Under Disease Progress Curve (AUDPC) and Percentage Seed Infection (PSI) (r = 0.44) whereas a negative correlation was observed between AUDPC and Hundred Seed Weight (HSW) (r = -0.77) and PSI and HSW (r = -0.44). The best combination treatment providing the highes...

Possible endophytic colonisation of rice cultivar parts (leaves, stem and roots) by Beauveria bassiana isolates and their potential as biocontrol agents against Sesamia calamistis Hampson (African pink stem borer) were investigated. Five promising B. bassiana isolates were evaluated for their endophytic colonisation, the effectiveness of the inoculation methods and the efficacy of the isolates as biocontrol agents against S. calamistis. The plant part colonised is often dependent on the inoculation method. Colonisation of plant parts was assessed at 30 and 60 days after seed inoculation and foliar spray. For the pathogenicity activity, third instar larvae of S. calamistis were fed with rice stems that were previously inoculated with endophytic isolates of B. bassiana. Both inoculation methods led to the colonisation of the rice cultivar tissues, but were affected by the interactions of cultivars x isolates x inoculation methods. The colonisation of the cultivar plant parts varied ov...

Abstract Composting is nature’s way of recycling nutrients to sustain soil fertility. Human population growth and enhanced industrialization have resulted in the production of high quantities of degradable waste that need proper disposal. Inappropriate monitoring of waste biomass has contributed to the emission of greenhouse gases and contaminated water and soil. Composted wastes include agricultural residue, animal manure, cafeteria waste, and paper. Agents involved in composting are detritivores that break the substrate to speed up biological processes. Earthworms are great biodegraders and together with their microbial counterparts break renewable into ecologically safe vermicompost and vermileachate. In situ and ex situ recycling of waste can be practically undertaken in an environmentally acceptable and economically feasible manner to reduce the cost of waste disposal. This can improve the socioeconomic status of both small scale and commercial farmers. Earthworms hasten the mineralization of organic matter and breakdown of structural polysaccharides and increase humification rates and leachate production. The world’s best worm composter of biomass Eisenia fetida (red wriggler) offer favorable and commercially acceptable products. Soil amendment by worms improves soil health, plant growth, and suppresses pathogens. Vermicomposting provides a means of handling high volumes of accessible organic wastes from livestock for raising crop organically. Managing excess manure in a sustainable way that prevents ecosystem pollution. This chapter discusses efficient production and use of a complex living system—“black gold” (vermicompost)—as a renewable source of plant nutrients.

K. S. Yobo Discipline of Plant Pathology, University of KwaZulu-Natal, Private Bag X01, Scottsville, 3209 Pietermaritzburg, South Africa Abstract Hunger and malnutrition are flammable pertinent issues that hinder progress of a nation and become an increasing risk. Biotechnology and food security have very good relationship both in the present and the future, concurrently embracing technology that offer new opportunities with increase crop and animal production. Additionally, they offer capacity building, collaboration, research and ensure sustenance. There is the need to engage and address exploration of new techniques and encourage various scientific and community debates with the support of respective governments. The way forward is to review biotechnology tools including biosafety processes, policies and proper implementation to sustain biodiversity.

This study was carried out to investigate the incidence of the aflatoxin-producing fungus, Aspergillus flavus in commercially available roasted and raw groundnuts sold by various vendors. Secondly, the study evaluated the antagonistic activity of Bacillus isolates against A. flavus in vitro and in vivo. All the 42 groundnut samples collected from the various vendors were contaminated with A. flavus. There was no significant difference (p > 0.05) in the incidence of A. flavus contamination in roasted and raw groundnut samples. The results of the in vitro bioassay indicated that the Bacillus isolates inhibited the growth of A. flavus ranging from 61 to 76%. In the in vivo study using groundnut kernels, increase in incubation time and concentration of the Bacillus isolates enhanced control of A. flavus. We showed that Bacillus isolates from the phyllosphere of ryegrass has potential as biocontrol agent for the control of A. flavus in groundnuts.

Four ASM (acibenzolar-S-methyl) concentrations were applied on wheat plants at different growth stages prior to inoculation with 1x105 conidia/ml of Fusarium graminearum. Thereafter, disease severity was monitored and recorded over time. All ASM concentrations reduced disease severity compared to the control. The best treatment, providing the lowest Area Under the Disease Progress Curve (AUDPC) units, high average Hundred Seed Weight (HSW) and reduced average Percentage Seed Infection (PSI), was 0.075 g/L ASM applied at anthesis. A weak but significant positive correlation was observed between AUDPC and PSI (r = 0.33; p = 0.0001). However, a moderate and weak negative correlation was observed between AUDPC and HSW (r = - 0.41; p < 0.0001) and HSW and PSI (r = - 0.18; p = 0.04) respectively. Higher ASM concentrations were more effective when applied at anthesis and lower concentrations at late boot. Moreover, repeated applications (applied at both late boot and anthesis) did not i...

Published online: 07 Oct 2021Sorghum bicolor L. Moench (Poaceae) is a cereal crop grown worldwide and playing an important role in human nutrition as well as feed for livestock. Lepidopteran stem borers are the most economically important insect pests that affect sorghum production and their management relies on the use of insecticide chemicals that have adverse effects on humans and biodiversity. The objective of this study was to investigate the endophytytic and pathogenic properties of Beauveria bassiana (Balsamo) Vuillemin as environmentally friendly, ecologically sound and sustainable bioncontrol method against Chilo partellus Swinhoe, one of the key stemborer of Sorghum in South Africa. In this study, 20 strains of Beauveria bassiana (Balsamo) Vuillemin were tested on sorghum cultivars Sugargraze AS 18, AS 79, AS 71 and PAN 8816 initially infested with Chilo partellus Swinhoe at 3rd instar larval stage. For the purpose, various strains of B. bassiana were inoculated in sorghum cultivars as foliar spray or seed treatment inoculum. At 30 and 60 days after the inoculation, the roots, stems and leaves of the cultivars were sampled to evaluate the endophytic property of each B. bassiana strain. Moreover, the 3rd instar larvae of C. partellus were fed with harvested stems previously colonized by the five best strains of B. bassiana to test their pathogenicity. Some 3rd instar larvae were fed with untreated stems (check). On both treated and untreated plants, number of dead larva was counted and recorded every seven days for 28 days interval. Results showed good endophytic ability of five B. bassiana strains (Bb3, Bb4, Bb10, Bb21 and Bb35) in the sorghum plants with varying degree of colonization and persistence in plant tissues, regardless the inoculation methods. However, colonization resulted from seed treatments were higher than that from foliar spray. The untreated plants did not show any presence of B. bassiana strains. Significant main effects (mostly P<0.0001) and interaction effects were observed between the application methods, strains, cultivars and date after inoculation. The endophytic strains (B3, B10 and B35) were highly pathogenic, recording up to 80% of larval mortality at 28 days after treatment. Five strains of B. bassiana (Bb3, Bb4, Bb10, Bb21 and Bb35) showed both endophytic colonization in S. bicolor and entomopathogenic activity on C. partellus, and can be used as potential systemic biocontrol agents against the spotted stem borer

Fusarium head blight (FHB), also known as head scab, is a devastating fungal disease that affects small grain cereal crops such as wheat (Triticum aestivum L.). The predominant causal agent, Fusarium graminearum Schwabe (teleomorph: Gibberella zeae (Schwein.) Petch), is ranked the fourth most important fungal plant pathogen worldwide. Apart from yield and quality losses, mycotoxin production can occur from FHB infection, resulting in harmful effects on human and animal health. Some level of disease control may be achieved by using certain fungicides and agronomic practices plus host resistance. In South Africa, there are currently no registered fungicides or bio-fungicides, no resistant wheat cultivars and only limited control is achieved by cultural practices. Because effective disease reduction cannot be achieved by using a single strategy, the integration of multiple management strategies can enhance disease control. We review possible strategies for reducing the risk for FHB inf...

A study was conducted over two seasons in a marginal soil with an acid saturation of 54%. A plant growth promoting rhizobacterium, Bacillus megaterium, a commercial biocontrol agent, Trichoderma harzianum Strain kd (Eco-T®), and soluble potassium silicate were used in this study. The objective was to control maize yield reduction caused by Rhizoctonia solani AG2 root rot isolated from infected maize. R. solani reduced maize yields significantly by 34% in the first season. However, the losses decreased in the second season from 34% to 10%. In the first season, combination of T. harzianum, B. megaterium and potassium silicate increased maize yields by 130%. The highest yield in the presence of R. solani was treatments with T. harzianum (216%) followed by T. harzianum plus potassium silicate (214%) and lastly T. harzianum plus B. megaterium (178%). However, in the second season, T. harzianum plus potassium silicate treatment resulted in the highest yields.

Rural South African smallholder farmers are deprived of knowledge, relying on eroded indigenous  knowledge to support crop production. Modern technology can play a role in supporting production  decisions and packaging knowledge so it is easily accessible to all levels of users. Information  Communication Technologies, such as Decision Support Tools (DST) play an important role in systematic dissemination of information in agriculture, thus improving the quality of farmer  decisions, especially in  rural areas. These tools are constantly developed, improved and evaluated to assess their applicability  and efficacy. The article is based on the study that aimed at evaluating the effectiveness of a recently developed DST, with a disease management component, to enhance production decisions and  crop-disease management, among organic and small-scale farmers. Due to resource-limitations of most smallholder farmers in South Africa, production  practices, including disease control could be much improved, using indigenous-based, local knowledge about cultural methods of controlling crop diseases. A group of 15 extension officers and 12 researchers were purposively selected for the study because they play a major role in organising and disseminating information to the farmers. Participatory workshop sessions were conducted with groups, where tools were presented, explored and critiqued. The DST was found to have the potential to benefit both organic and smallholder farmers, the study recommends that government should support the development of agricultural DSTs, building on and improving eroded indigenous knowledge, to help farmers improve production and address problems with extension officers and within their resource means. Keywords : Organic farming, small-scale farming, Decision Support Tool (DST), disease management.

Biological control agents are possibly the best alternative to agrochemicals for the control of livestock nematodes. Strains of Bacillus thuringiensis (Bt) and Clonostachys rosea were isolated from grazing pastures collected from pens of livestock. A total of 25 isolates of B. thuringiensis and 10 of C. rosea were successfully isolated. In vitro studies were conducted to determine the efficacy of B. thuringiensis (Bt) and C. rosea isolates as biological control agents against sheep nematodes. All of Bt and C. rosea reduced nematode counts considerably. Isolates of Bt and C. rosea reduced nematodes counts by 28.5 to 62% and 44 to 69.9%, respectively, in the faeces bioassay. In the water bioassay nematode count reductions of 62 to 85% and 62.7 to 89.3% by Bt and C. rosea, respectively, were observed. Majority of the best nematode-killing isolates were from a goat grazing pasture. Both biocontrol agents showed capability to reduce nematode counts in this study.

Selected Trichoderma and Bacillus isolates were tested as seed treatments with reduced concentrations of tolclofos-methyl against Rhizoctonia solani damping-off using cucumber as test plants. In vitro bioassays using filter paper disc infused with six concentrations [active ingredient (ai)] of tolclofos-methyl (0.005, 0.05, 0.125, 0.25, 0.5 and 1.5 g ai/l) showed that growth of Trichoderma isolates on agar plates were less inhibited at 0.005 and 0.05 g ai/l than 0.125 ‐ 1.5 g ai/l tolclofos-methyl concentrations while Bacillus isolates were not affected by any of the six concentrations. In a greenhouse study with a 0.05 g ai/l tolclofos-methyl concentration, Trichoderma and Bacillus isolates applied alone or in combination to cucumber seeds resulted in a better disease control than the Trichoderma and Bacillus treatments used alone. As high as 86% disease control was achieved by combining 0.05 g ai/l tolclofos-methyl with T. harzianum Isolate SYN which was significantly better (P = ...