Maize (Zea mays L) is one of main nutrients sources for humans and animals worldwide. In Africa, storage of maize ensures food resources availability throughout the year. However, it often suffers losses exceeding 20% due to insects such as the larger grain borer, Prostephanus truncatus (Horn) (Coleoptera; Bostrichidae), major pest of stored maize in the tropical countries. This study aims to select resistant varieties to reduce maize storage losses and explain the physicochemical parameters role in grains susceptibility. In the first study, maize grains were artificially infested under no-choice method with insects. Susceptibility parameters such as weight loss, grain damage, number of emerged insects, median development time and susceptibility index varied significantly through maize varieties. Dobie susceptibility index (SI) was assessed as a major indicator of resistance. The most resistant varieties were Early-Thaï, DMR-ES and Tzee-Yellow. Conversely, Synth-9243, Obatampa and Synth-C varieties were susceptible. SWAN, Across-Pool and Tzee-White were classified as moderately resistant varieties. The insect reproductive potential was significantly different in the nine maize varieties and Early-Thaï, DMR-ES and Tzee-Yellow varieties were the least favourable host. To assess the relationship between grains physicochemical characteristics and varietal susceptibility, moisture, total phenolics, palmitic acid, proteins, amylose, density and grain hardness were evaluated according to standardized methods. Palmitic acid, SI, insects emerged and grain damage were significantly and positively correlated with each other, and negatively correlated with grains hardness, phenolics and amylose contents. Maize susceptibility index was significantly and negatively correlated to amylose, and phenolics contents and positively correlated to palmitic acid content. This
In Burkina Faso, the seeds of sorrel, Hibiscus sabdariffa L. are attacked by a pest identified morphologically as Spermophagus niger which is maintained all year on seeds and causing considerable damages. In the current study, for the first time, genetic characterization for S. niger was performed to determine its genetic identity and place it in its phyletic group. Mitochondrial gene, the Cytochrome oxidase I (COI) of the pest was partially sequenced after extraction and amplification by Polymerase Chain Reaction (PCR). Then the variability of genetic parameters namely the number of polymorphic and monomorphic sites, the frequencies of the different nucleotides and amino acid composition were determined. The nucleotide sequence of S. niger ob-tained was submitted in Genbank and the accession number is KU710716. Nucleotide sequences of S. niger obtained and those of different species of Spermophagus and Z. subfasciatus available in the GenBank database, we determined the percentage of similarity on the one hand and kinship through Phylogenetics reconstructions on the other hand. The results showed the absence of polymorphic sites for 406 sites obtained with 36.5% of thymine, 17.5% of cytosine, adenine 31% and 15% of guanine. Leucine was the majority amino acid (14.50%); the lysine was minority amino acid (0.76%) and cysteine was absent. The percentage of similarity obtained and phylogenetics reconstructions showed that S. niger is very close to the different species of Spermophagus particularly S. drak and different from Z. sub-fasciatus.
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