Secondary metabolites are among the major contributors of host-plant resistance. Cowpea produces secondary metabolites that are known to enhance resistance to insect pests including flower bud thrips. However, environmental conditions tend to affect the production of secondary metabolites, thereby affecting the response of the host plants to insect pest. The objective of this study was to determine the effect of the genotype × environment interaction on the production of secondary metabolites and flower bud thrips resistance in cowpea. Six cowpea genotypes were evaluated for flower bud thrips damage and the contents of flavonoids, antioxidants, phenolics, proteins, lignin, tannins and reducing sugars in four environments with varying temperatures and rainfall patterns. The data collected were subjected to the analysis of variance and genotype and genotype × environment (GGE) analysis. Flower thrips damage, and the contents of flavonoids, antioxidants, lignin, tannins and reducing sugars varied significantly (p < 0.001) among genotypes. Genotype Sanzi produced high levels of antioxidants, while TVU-9820 led in phenolic concentrations respectively. Metabolite contents were significantly (p < 0.001) different among environments, with the long rain season of field experiments led to increased production of flavonoids, proteins, lignin and tannins. A resistant genotype, TVU-3804, produced relatively stable contents of flavonoids, antioxidants, phenolics, proteins and reducing sugars across environments. In this study, the environment influenced the concentration of the metabolites, which in turn affected the cowpea’s resistance to flower bud thrips.

Soybean is a high oil and protein-rich legume with several production constraints. Globally, several fungi, viruses, nematodes, and bacteria cause significant yield losses in soybean. Coniothyrium glycines (CG), the causal pathogen for red leaf blotch disease, is the least researched and causes severe damage to soybean. The identification of resistant soybean genotypes and mapping of genomic regions associated with resistance to CG is critical for developing improved cultivars for sustainable soybean production. This study used single nucleotide polymorphism (SNP) markers generated from a Diversity Arrays Technology (DArT) platform to conduct a genome-wide association (GWAS) analysis of resistance to CG using 279 soybean genotypes grown in three environments. A total of 6395 SNPs was used to perform the GWAS applying a multilocus model Fixed and random model Circulating Probability Unification (FarmCPU) with correction of the population structure and a statistical test p-value threshold of 5%. A total of 19 significant marker–trait associations for resistance to CG were identified on chromosomes 1, 5, 6, 9, 10, 12, 13, 15, 16, 17, 19, and 20. Approximately 113 putative genes associated with significant markers for resistance to red leaf blotch disease were identified across soybean genome. Positional candidate genes associated with significant SNP loci-encoding proteins involved in plant defense responses and that could be associated with soybean defenses against CG infection were identified. The results of this study provide valuable insight for further dissection of the genetic architecture of resistance to CG in soybean. They also highlight SNP variants and genes useful for genomics-informed selection decisions in the breeding process for improving resistance traits in soybean.

Stem rust (Puccinia graminis f. sp tritici) poses a major threat to wheat (Triticum aestivum L.) production worldwide. The interaction between wheat and pathogen in presence of favorable environment can cause a complete crop failure. This study was conducted with the objective to identify wheat genotypes with resistance to stem rust with high and stable yield under four environments in Kenya. Forty wheat genotypes were tested in two consecutive growing seasons, using an alpha lattice design with three replications. Host response to stem rust was recorded based on the modified Cobb scale. The disease severity was recorded on scale of 0 to 100%. The results of the coefficient of infection indicated that about 30% of genotypes were moderately resistant. Yield and disease data were subjected to statistical analyses to estimate the stability parameters. The top three genotypes in yield performance were G25, G18 and G29 with 2.07, 1.98 and 1.97 t ha-1 respectively. Considering both stem rust and yield stability G5, G16, G18, G24 and G36 were the best genotypes which could undergo further testing for future release. Key words: Wheat, stem rust, resistance, stability, genotype × environment interaction.

Plant secondary metabolites are part of defense mechanism that form host plant resistance. Understanding the inheritance of secondary metabolites is preliquisite for conducting an effective plant breeding program. The objective of this study was to determine the mode of inheritance of secondary metabolites associated with resistance of cowpea to flower bud thrips. Five cowpea genotypes with varying level of resistance to flower thrips were crossed in full diallel method 1. The F2 were evaluated for secondary metabolites and flower thrips damage in field and screen house. The results confirmed genotype TVU-3804 as resistant, and TVU-9820 and TVU-201 as susceptible to flower bud thrips. Flavonoids, antioxidants, proteins and reducing sugars had significant (p < 0.001) GCA and SCA effects indicating the importance of additive and dominance effect in controlling resistance of flower bud thrips. In addition, significant reciprocal observed for crosses such as Lori Niebe × Sanzi and Sanzi × TVU-3804 for flavonoids and antioxidants is an indication that maternal effect is key in governing resistance of cowpea to thrips. The broad sense heritability was low for secondary metabolites except flavonoid which had moderate value, an indication that delaying selection to a later generation would yield better results while breeding for resistance to flower thrips based on secondary metabolites. The results of this experiment showed that it is possible to use secondary metabolites to breed for improved cowpea resistance to flower bud thrips.