The future of food security in Africa is being severely threatened due to an exponential
increase in population, which is almost three times the increase of food production. Maize
production is constrained by stem borers which cause significant yield losses. Yield losses
can be further compounded by higher temperatures due to climate changes, which are expected
to increase the population of maize stem borers. While several methods have been
employed in stem borer management, there is still significant damage caused by maize
stem borers. This necessitates better control methods including the adoption of recent biotechnological
advancement in RNA interference (RNAi) technology. This review highlights
evidence of an increase in the stem borer population as well as the foreseen decline in
maize production worldwide due to the effects of climatic changes. Furthermore, we have
drawn attention to improved methods that have been used to control stem borers in maize
production as well as a reluctant acceptance of traditional biotechnology in Africa. Finally,
we suggest the application of alternative RNA interference techniques to breed maize for
efficient pest control in order to achieve food security, improve nutrition and promote sustainable
maize production.
Wheat dwarf virus (WDV) has been one of the most common viruses on cereal crops in
Poland in the last years. This single stranded DNA virus is transmitted by the leafhopper
spec, Psammotettix alienus (Dahlb.) in a persistent manner. It induces yellowing and
streaking of leaves, dwarfing or even death of infected plants. The presence of barley- and
wheat-specific forms of WDV (WDV-B and WDV-W) and their vector were previously
reported in the country, however the literature data did not include any information
on the infectivity of the vector in Poland. A duplex polymerase chain reaction (PCR)
procedure was developed and optimized for simultaneous detection and differentiation
of both forms in the vector. Two sets of primers amplify 734 bp and 483 bp specific fragments
for WDV-W and WDV-B, respectively. The results were verified by a sequencing
method. The studies were carried out on insect samples collected in autumn from four
different locations in Greater Poland. The results confirmed the presence of WDV-W
in the tested samples. They also suggested the concomitant of both forms of the virus
in the vector. Additional studies to determine virus-vector relationships should be undertaken.
Many species of Trichoderma produce secondary metabolites such as volatile organic
compounds (VOCs) that reduce plant diseases and promote their growth. In this work
we evaluated the antagonistic effects of VOCs released by eight strains of two Trichoderma
species against Pyrenophora teres Drechsler, the causal agent of barley net blotch. Antagonism
was estimated based on the percentage of mycelial growth inhibition according
to the confronted cultures method. VOCs extraction and identification were performed
by gas chromatography and mass spectrometry, through different methodologies for
VOCs emitted by antagonists and pathogens alone or when confronted. VOCs produced
by all Trichoderma strains inhibited mycelial growth of the pathogen in a range of 3 to
32%, showing weak and unpigmented mycelia with vacuolization. In addition, P. teres
stimulated the release of VOCs by both Trichoderma species. The major groups of VOCs
detected were sesquiterpenes, followed by diterpenes, terpenoids and eight-carbon compounds.
This is the first report about characterization of volatiles emitted by Trichoderma
in the presence of P. teres.
Fluorescent Pseudomonas (FP) is a major group of plant growth promoting rhizobacteria
and a well-known synthesizer of siderophores, which imparts a selective advantage on
rhizosphere competence and their biocontrol traits. The present study was aimed at examining
the factors affecting the production of siderophores and their potential biocontrol
traits. Sixteen FP isolates were shortlisted based on their siderophore-producing ability in
chrome azural S medium. The isolates were checked for variations in siderophore production
under varying incubation times, temperatures, pH, iron (Fe3+) concentrations and
mutagens. In addition, the iron binding affinity of siderophores, mycelial inhibition assay
and plant growth promotion traits were assessed. Results showed that the siderophore
production was highly influenced by the time of incubation, changes in pH, temperature
and iron concentration. Chemical characterization showed that the produced siderophores
were hydroxamates. Maximum siderophore production was observed at pH 7 whereas UV
and EtBr exposure invariably suppressed siderophore production drastically in all isolates.
All FPs from maize rhizosphere showed excellent siderophore production which could be
due to the competence in strategy-II of the plant rhizosphere and significant growth inhibition
on Fusarium oxysporum. Our results suggest the inclination of siderophores to iron, in
terms of various criteria affecting production and the possible role of environmental mutations
that affect the natural iron harvesting mechanism.
The use of Bacillus thuringiensis (Bt) to control insect pests has already been established in
various agronomic and forest crops. It is a bacterium that does not pollute the environment,
is safe for mammals and vertebrates, lacks toxicity to plants and specifically targets insects.
To date in-depth studies have not been conducted about the use of Bt to control the main
pest of mahogany (Swietenia macrophylla King) and other Meliaceae species, the Hypsipyla
grandella Zeller (Lepidoptera: Pyralidae). Therefore, this study aimed to test the pathogenicity
of Bt strains on H. grandella caterpillars, as well to determine the lethal concentration
required to kill 50% of the population (LC50) of the most promising strains. Ten strains
of Bt toxic to lepidopteran proven in previous trials were used and these were incorporated
into a natural diet with mahogany seeds to check their mortality. The LC50 of the top
five strains was determined. The results indicate that H. grandella is highly susceptible to
Bt toxins and the S1905 strain is highly toxic. Therefore, the use of Bt strains may be a tool
to be incorporated into the integrated management of this important pest.
Arbuscular mycorrizal (AM) fungi may enhance plant growth and polyphenol production,
however, there have been limited studies on the relationships between root colonization of
different fungal species and polyphenol production on cultivated Allium porrum (garden
leek). The effects of inoculation of AM fungi spores from Rhizophagus intraradices, Giga
-spora margarita, Glomus geosporum, Paraglomus occultum, Claroideoglomus claroideum,
and Glomus species on colonization of garden leek roots and symbiotic changes in polyphenol
production and plant growth were evaluated in greenhouse experiments. There were
significant differences (p < 0.05) in colonization of leek roots by AM fungi species. The
greatest level of root colonization was recorded on plants inoculated with R. intraradices
(73%) and the lowest level on C. claroideum (3.2%). Significant differences (p < 0.05) in
plant height were recorded between AM inoculated plants and the controls. Polyphenol
levels differed significantly (p < 0.05) between garden leek plants inoculated with AM fungi
and the non-inoculated controls. The percentage increases in polyphenol (a derivative of
kaempferol) on garden leeks inoculated with G. geosporum relative to the untreated controls
ranged from 28 to 1123%. Due to symbiosis with different AM species, other polyphenols
decreased in some instances (negative values) and increased in others for values of up to
590%. Results showed that AM fungi species exhibited remarkable differences in polyphenol
levels in garden leeks. The high polyphenol production by garden leek plants inoculated
with G. geosporum, and Glomus species could be exploited for enhanced resistance of garden
leeks to insects and diseases. This research highlights an understudied area, notably the
relationships between AM fungal inoculations, root colonizations and polyphenol production
in garden leeks. The findings can be utilized to improve pest resistance and the quality
of garden leek plants.