Genetic Basis of Maize Resistance to Multiple Insect Pests: Integrated Genome-Wide Comparative Mapping and Candidate Gene Prioritization.

Several species of herbivores feed on maize in field and storage setups, making the development of multiple insect resistance a critical breeding target. In this study, an association mapping panel of 341 tropical maize lines was evaluated in three field environments for resistance to fall armyworm (FAW), whilst bulked grains were subjected to a maize weevil (MW) bioassay and genotyped with Diversity Array Technology's single nucleotide polymorphisms (SNPs) markers. A multi-locus genome-wide association study (GWAS) revealed 62 quantitative trait nucleotides (QTNs) associated with FAW and MW resistance traits on all 10 maize chromosomes, of which, 47 and 31 were discovered at stringent Bonferroni genome-wide significance levels of 0.05 and 0.01, respectively, and located within or close to multiple insect resistance genomic regions (MIRGRs) concerning FAW, SB, and MW. Sixteen QTNs influenced multiple traits, of which, six were associated with resistance to both FAW and MW, suggesting a pleiotropic genetic control. Functional prioritization of candidate genes (CGs) located within 10-30 kb of the QTNs revealed 64 putative GWAS-based CGs (GbCGs) showing evidence of involvement in plant defense mechanisms. Only one GbCG was associated with each of the five of the six combined resistance QTNs, thus reinforcing the pleiotropy hypothesis. In addition, through in silico co-functional network inferences, an additional 107 network-based CGs (NbCGs), biologically connected to the 64 GbCGs, and differentially expressed under biotic or abiotic stress, were revealed within MIRGRs. The provided multiple insect resistance physical map should contribute to the development of combined insect resistance in maize.

Microbial Assessment of Tomatoes (Lycopersicon esculentum) Sold at Some Central Markets in Ghana.

BACKGROUND: Tomato (Lycopersicon esculentum) has a high water content which predisposes it to spoilage by pathogenic bacteria that can pose significant health threats to consumers. AIM: The study aimed to determine the various pathogenic bacteria associated with tomatoes sold in some central markets in the Accra Metropolis. METHOD: A total of 120 tomatoes were sampled, out of which 60 fresh, firm, undamaged tomatoes and 60 spoilt tomatoes were analysed. Cut portions of the fresh and spoilt tomatoes were swabbed with sterile swabs and cultured on Blood agar, Nutrient agar, and MacConkey agar. The antibiogram of bacterial isolates was determined by Kirby-Bauer disc-diffusion method. RESULTS: Out of the 120 tomatoes analysed, a total of 66 bacterial isolates were recovered, 68.2% were associated with spoilt tomatoes, and 31.8% were from fresh tomatoes. Klebsiella sp. (34.8%), Enterobacter sp. (24.2%), and Citrobacter sp. (7.6%) were the predominant bacteria isolated. Agbogbloshie market (36.4%) had both fresh (18.2%) and spoilt (18.2%) tomatoes contaminated, whilst Makola market (31.8%) had a higher spoilt (30.3%) tomatoes contaminated. Although none of the isolates expressed resistance to ciprofloxacin, resistance was found for ampicillin (63.1%), tetracycline (60.1%), and cefuroxime (59.1%). CONCLUSION: Varying levels of antibiotic resistance bacteria amongst tomatoes sold at various markets were found. Contamination might have been caused by poor sanitation, improper handling or transportation from the farms to the markets. The presence of antibiotic resistance bacteria amongst tomatoes raises concern on public health risks associated with the consumption of fresh tomatoes.