Peter Wasswa

Viral diseases significantly constrain sweetpotato production. While laboratory-based virus cleaning techniques can generate clean planting material, they are often costly and inaccessible to smallholder farmers. This study evaluated a low-cost, farmer-led approach for virus detection and production of virus-free vines using Ipomoea setosa as an indicator plant. Farmers’ groups in Iganga, Bukedea and Mpigi districts were trained on field-based virus detection and macropropagation of virus-free sweetpotato vines in the screenhouses. The training included practical sessions on vine sampling, grafting onto I. setosa, symptom observation, and propagation of clean material. Ten farmers from each of the three districts (Iganga, Bukedea and Mpigi) were trained as future trainers of trainees. After training, farmers’ results on virus indexing and macropropagation were similar to those of experts, indicating that the empowerment was successful. Symptoms of viral infections were studied on I. setosa grafted with apparently healthy sweetpotato vines. Sweet potato feathery mottle virus (SPFMV) was the most prevalent across all sites, followed by Sweet potato chlorotic stunt virus (SPCSV). Sweet potato leaf curl virus (SPLCV) was less common and detected only in Iganga and Bukedea. Mpigi had the highest virus incidence (54% SPFMV, 13% SPCSV and 4% Sweet Potato Virus Disease [SPVD]), followed by Iganga (35% SPFMV, 2% SPCSV and 4% SPLCV) and Bukedea (5% SPFMV, 2% SPCSV and 1% SPLCV). Within three months, trained farmers produced 103,610 vines in Iganga, 107,798 in Mpigi and 97,237 in Bukedea. These results demonstrate the feasibility of a decentralized clean seed production system. Scaling up this approach nationally can enhance sweetpotato productivity, household incomes, and food security. Key words: Clean seed systems, Ipomoea setosa, macropropagation, smallholder farmers

Controlling banana aphid (Pentalonia nigronervosa) vectors of banana bunchy-top disease is crucial for integrated disease management. Synthetic insecticides, though effective in aphid control, pose health and environmental risks. Biorational pesticides (including botanicals and soaps) are safer alternatives. This study screened four fresh and fermented aqueous plant extracts (chili pepper, garlic, neem, and peppermint) and three soaps (bathing, laundry bar, and liquid soap) singly or in mixtures against banana aphids through in vitro and in vivo experiments. Aphid-inoculated banana leaf-blade disks were used for the in vitro studies over 96 h. Potted plantlets were used for the in vivo studies over eight weeks. Applying these preparations resulted in significant (p ≤ 0.05) aphid mortality (28.6 to 100%) compared to the water control (3.3%) at 96 h post-spray (hps). In vitro, a single application of nimbecidine^® (Azadirachtin 0.03%), garlic, chili-pepper botanicals, insecticidal, and bathing soap caused >50% mortality at 96 hps. Mixed applications of chili pepper, garlic-based, and neem botanicals with soap caused >70% mortality at 96 hps in vitro. Binary mixtures of neem oil, garlic, fermented garlic, or fermented peppermint with insecticidal soap, and neem oil with bar soap, were promising in vivo, reducing the aphid populations to 200 aphids after week 8. However, these potential preparations incurred a higher cost (USD 1.30/banana mat) compared to the synthetic pesticide (USD 0.022/mat). Thus, biorational mixtures have a potential to effectively control banana aphids.

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.