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Colletotrichum is a fungal genus comprising several pathogenic species that cause anthracnose in an array of key cash and food crops in the world's tropical, subtropical, and temperate regions. Considerable losses in various crops due to anthracnose in the African tropics have been reported despite the efforts to curb the disease. Several options are used to manage the disease in the region with little success. The challenges in managing Colletotrichum species include toxicity, high cost, inadequate farmers' knowledge of applying synthetic fungicides, variable and cross-infection nature of pathogenic species, physiological variability of pathogens, and unavailability of biological control agents to farmers in rural areas in tropical Africa. Several species of Colletotrichum are also known to develop mechanisms that allow them to counter immunity factors of the host plants. Consolidated information on the species prevalent, losses, and evaluation of the current control methods for anthracnose in the African tropics are essential for developing and adopting sustainable management strategies for anthracnose. This review discusses the key pathogenic Colletotrichum species in Africa, infection mechanisms, colonisation in several hosts, and the plant-pathogen interaction and losses due to the disease. Pathogen identification methods, disease management options, challenges, and prospects for the management of anthracnose in tropical Africa are also discussed. [ABSTRACT FROM AUTHOR]

Weevils (Sitophilus spp) are serious pests that can damage sorghum grains in stores if not controlled. The infestation of sorghum by the pest can cause huge economic loss ranging from 15% to 75% depending on levels of susceptibility. While the weevil uses several infection mechanisms such as avoidance, adaptation and sequestration to arrest its host, the host plant has developed certain chemical mechanisms for defence. The weevil must overcome the hosts’ defensive layers of chemical compounds such as protein resistant molecules, tannin, phenolics and flavonoids that confer antixenosis and or antibiosis functions in sorghum. Besides, the biochemical molecules present in sorghum are also responsible for modulating grain hardness and strength, which are important phenotypic parameters for grain resistance to weevil in sorghum. This paper reviews traits and or their associated produced chemical compounds in sorghum and reveals the gaps or need for incorporating appropriate desirable traits in sorghum through plant breeding techniques as a strategy towards management of grain weevils in sorghums. [ABSTRACT FROM AUTHOR]

Late blight disease caused by Phytophthora infestans (Mont.) de Bary is a serious challenge in tomato (Solatium fycopersicum L or Lycopersicon esculentum L) production worldwide. In tropical Africa, the disease is increasing always due to its biology and different complex infection mechanism(s) used by its causative pathogen to survive, spread, and invade the tomato host plant and environment. Management options of the disease, such as integrated disease management (IPM), use of resistant tomato varieties, use of plant extracts and synthetic chemical pesticides have been recommended but are either poorly practised or limited in tropical Africa. Thus, this review discusses the status and commonly recommended management options against late blight disease-causing pathogen(s) including the pathogen strain complexes so that tomato growers and other stakeholders can understand specific strains and how they can design appropriate managerial approaches to halt challenges of the disease in tomato production in the tropical Africa. [ABSTRACT FROM AUTHOR]

Bacterial leaf spot (BLS) caused by Xanthomonas spp. is a serious and a major constraint to tomato production worldwide. The seed-borne nature of BLS, the complex nature of the disease, which is caused by different bacterial species and the current ineffective control measures have made the evaluation of alternative control compounds for seed treatment necessary. Therefore, the efficacy of 11 essential oils applied as seed treatments to control Xanthomonas perforans in tomato and the effect on seed germination and seedling growth was evaluated. Seed treatment with oils of eucalyptus (Eucalyptus globules Labill.), rosemary (Rosmarinus officinalis L.) and niaouli (Melaleuca viridiflora Sol. ex Gaertn.) at 2% concentration inhibited the growth of X. perforans in the in vitro assays and consistently reduced the incidence and severity of BLS in planta tests. Negative effects on seed germination and seedling growth were not observed when tomato seeds were treated with the essential oils of eucalyptus and rosemary. Therefore, eucalyptus and rosemary oils can be used for seed treatment to control BLS in tomato. Further investigation is required on the shelf life of these oils, mode of action and their effects on other seed-borne pathogens of tomato and in other crop systems in Tanzania. [ABSTRACT FROM AUTHOR]

Conventional agricultural practices often rely on synthetic fertilizers and pesticides which have immense and adverse effects on humans, animals and environments. To minimize these effects, scientists world over are now deeply engaged in finding alternative approached for crop production which are less dependent on chemical inputs. One such approach is the use of rhizospheric bacteria as vital components of soil fertility and plant growth promotion (PGP) through their direct and indirect processes in plant rhizospheres. Among the most studied rhizobacteria are the Bacilli, particularly for production of antibiotics, enzymes and siderophores all of which are important aspects of PGP. Despite this, little information is available especially on their potentiality in crop production and their direct application only involves a few species, leaving a majority of these important rhizobacteria unexploited. This paper gives an overview of the unique properties of Bacilli rhizobacteria as well as their different PGP mechanisms that if mined can lead to their successful application and agricultural sustainability. It further points out the missing aspects with regards to these important rhizobacteria that should be considered for future research. This information will be useful in analyzing the PGP abilities of Bacilli rhizobacteria with an aim of fully mining their potential for crop production and environmental sustainability., (Copyright © 2018 Elsevier GmbH. All rights reserved.)