Aflatoxin contamination of maize, groundnut, and sorghum grown in Burkina Faso, Mali, and Niger and aflatoxin exposure assessment

Open Access Journal; Published online: 12 Oct 2022Aflatoxin contamination of staple crops by Aspergillus flavus and closely related fungi is common across the Sahel region of Africa. Aflatoxins in maize, groundnut, and sorghum collected at harvest or from farmers’ stores within two weeks of harvest from Burkina Faso, Mali, and Niger were quantified. Thereafter, aflatoxin exposure values were assessed using per capita consumption rates of those crops. Mean aflatoxin concentrations in maize were high, 128, 517, and 659 µg/kg in Mali, Burkina Faso, and Niger, respectively. The estimated probable daily intake (PDI) of aflatoxins from maize ranged from 6 to 69, 29 to 432, and 310 to 2100 ng/kg bw/day in Mali, Burkina Faso, and Niger, respectively. Similarly, mean aflatoxin concentrations in sorghum were high, 76 and 259 µg/kg in Mali and Niger, respectively, with an estimated PDI of 2–133 and 706–2221. For groundnut, mean aflatoxin concentrations were 115, 277, and 628 µg/kg in Mali, Burkina Faso, and Niger, respectively. Aflatoxin exposure values were high with an estimated 9, 28, and 126 liver cancer cases/100,000 persons/year in Mali, Burkina Faso, and Niger, respectively. Several samples were extremely unsafe, exceeding manyfold regulatory levels of diverse countries (up to 2000 times more). Urgent attention is needed across the Sahel for integrated aflatoxin management for public health protection, food and nutrition security, and access to trade opportunities

Present status of the development of mycoherbicides against water hyacinth: successes and challenges. A review

Recent trends in the implementation of bioherbicide use in the control of water hyacinth (Eichhornia crassipes [Martius] Solms Laubach) have depended primarily on several strategies. The use of bioherbicides has been stimulated as part of the search for alternatives to chemical control, as the use of these more environmentally-friendly formulations minimizes hazards resulting from herbicide residue to both human and animal health, and to the ecology. In addition, one of the major strategies in the concept of biological control is the attempt to incorporate biological weed control methods as a component of integrated weed management, in order to achieve satisfactory results while reducing herbicide application to a minimum. Several fungal pathogens with mycoherbicide potential (Sclerotinia sclerotiorum in Hyakillä and Cercospora rodmanii, named ABG-5003) have been discovered on diseased water hyacinth plants, but none has become commercially available in the market. Biological, technological, and commercial constraints have hindered progress in this area. Many of these constraints are being addressed, but there is a critical need to better understand the biochemical and physiological data regarding the pathogenesis of these new bioherbicides. Oil emulsions are recognized as a way to increase both efficiency of application and efficacy of biocontrol agents

Synthèse bibliographique : problématique de la jacinthe d'eau, Eichhornia crassipes, dans les régions tropicales et subtropicales du monde, notamment son éradication par la lutte biologique au moyen des phytopathogènes

eview: problems of the water hyacinth, Eichhornia crassipes, in the tropical and subtropical areas of the world, in particular its eradication using biological control method by means of plant pathogens. Water hyacinth, probably originating from South America, grows between 35th North and South parallels of the planet. It was introduced into several regions of the world as ornamental plant, where it became later one of the most dangerous world water weed. Its infestation can be controlled by physical and chemical treatments. However, these methods are expensive and dangerous for human health and environment. Moreover, following Western legislations example, those of developing countries are highly restrictive against authorised chemical molecules. Consequently, a growing interest was given to alternative solutions, such as biological control. That control using insects, fishes and mammiferes against water hyacinth could be strengthened with the application of mycoherbicides. These mycoherbicides are more respectful for environment and public health and seem to constitute an additional realistic alternative for water hyacinth durable management

Characterization of new races of Xanthomonas oryzae pv. oryzae in Mali informs resistance gene deployment

Bacterial leaf blight caused by Xanthomonas oryzae pv. oryzae represents a severe threat to rice cultivation in Mali. Characterizing the pathotypic diversity of bacterial populations is key to the management of pathogen-resistant varieties. Forty-one X. oryzae pv. oryzae isolates were collected between 2010 and 2013 in the major rice growing regions in Mali. All isolates were virulent on the susceptible rice variety Azucena; evaluation of the isolates on 12 near isogenic rice lines, each carrying a single resistance gene, identified six new races (A4 to A9) and confirmed race A3 that was previously reported in Mali. Races A5 and A6, isolated in Office du Niger and Selingue, were the most prevalent races in Mali. Race A9 was the most virulent, circumventing all of the resistance genes tested. Xa3 controlled six of seven races (i.e., 89% of the isolates tested). The expansion of race A9 represents a major risk to rice cultivation and highlights the urgent need to identify a local source of resistance. We selected 14 isolates of X. oryzae pv. oryzae representative of the most prevalent races to evaluate 29 rice varieties grown by farmers in Mali. Six isolates showed a high level of resistance to X. oryzae pv. oryzae and were then screened with a larger collection of isolates. Based on the interactions among the six varieties and the X. oryzae pv. oryzae isolates, we characterized eight different pathotypes (P1 to P8). Two rice varieties, SK20-28 and Gigante, effectively controlled all of the isolates tested. The low association observed among races and pathotypes of X. oryzae pv. oryzae suggests that the resistance observed in the local rice varieties does not simply rely on single known Xa genes. X. oryzae pv. oryzae is pathogenically and geographically diverse. Both the races of X. oryzae pv. oryzae characterized in this study and the identification of sources of resistance in local rice varieties provide useful information to inform the design of effective breeding programs for resistance to bacterial leaf blight in Mali

Broad-spectrum resistance and susceptibility to bacterial blight and bacterial leaf streak of rice

Quantitative trait loci (QTL) that confer broad-spectrum resistance (BSR) have been elusive targets of crop breeding programs. Bacterial leaf streak (BLS) and bacterial blight (BB), caused by Xanthomonas oryzae pv. oryzicola (Xoc) and Xanthomonas oryzae pv. oryzae (Xoo), respectively, are responsible for major losses in rice production in Asia and Africa. Controlling these two diseases is particularly important in Sub-Saharan Africa, where no sources of BSR are available in currently deployed varieties. Our goal is to identify novel, broad-spectrum resistance sources to control BLS and BB in rice, using a Multi-parent Advanced Generation Inter-Cross (MAGIC) population, derived from eight elite indica cultivars. MAGIC populations have an increased level of recombination and provide higher precision and resolution to detect QTL. The MAGIC parents and lines were genotyped and phenotyped in both greenhouse and field conditions by screening with diverse strains of Xoc and Xoo. Using genome-wide association and interval mapping analysis, we identified 37 strain-specific QTL, and 14 QTL effective against multiple X. oryzae strains. From these, three QTL are pathovar-specific and 11 confer resistance to both pathovars. By detecting phenotypic effects of causal alleles, we have identified resources that will facilitate a better understanding of how the involved genes contribute to resistance or susceptibility. Because the MAGIC founders are elite varieties, the BSR QTL identified can be rapidly incorporated into breeding programs to achieve more durable resistance to BLS and BB

Allelic variation for broad-spectrum resistance and susceptibility to bacterial pathogens identified in a rice MAGIC population

Quantitative trait loci (QTL) that confer broad-spectrum resistance (BSR), or resistance that is effective against multiple and diverse plant pathogens, have been elusive targets of crop breeding programmes. Multiparent advanced generation intercross (MAGIC) populations, with their diverse genetic composition and high levels of recombination, are potential resources for the identification of QTL for BSR. In this study, a rice MAGIC population was used to map QTL conferring BSR to two major rice diseases, bacterial leaf streak (BLS) and bacterial blight (BB), caused by Xanthomonas oryzae pathovars (pv.) oryzicola (Xoc) and oryzae (Xoo), respectively. Controlling these diseases is particularly important in sub-Saharan Africa, where no sources of BSR are currently available in deployed varieties. The MAGIC founders and lines were genotyped by sequencing and phenotyped in the greenhouse and field by inoculation with multiple strains of Xoc and Xoo. A combination of genomewide association studies (GWAS) and interval mapping analyses revealed 11 BSR QTL, effective against both diseases, and three pathovar-specific QTL. The most promising BSR QTL (qXO-2-1, qXO-4-1 and qXO-11-2) conferred resistance to more than nine Xoc and Xoo strains. GWAS detected 369 significant SNP markers with distinguishable phenotypic effects, allowing the identification of alleles conferring disease resistance and susceptibility. The BSR and susceptibility QTL will improve our understanding of the mechanisms of both resistance and susceptibility in the long term and will be immediately useful resources for rice breeding programmes