Bean scab caused by Elsinoe phaseoli is a major challenge to common bean cultivation in Kenya. However, knowledge about its epidemiology and management is limited. This study conducted three experiments in Kakamega, Kenya, evaluating scab inoculum sources and control options. The first experiment evaluated three different inoculum sources over two seasons; bean crop residue caused the highest scab incidence in both the 2021 (62.1%) and 2022 (81.1%) seasons. The second experiment assessed the effect of rotation history on scab over three seasons. Scab incidence consistently surpassed 90% within the first 30 days after planting in half-yearly rotated fields across all seasons, while the disease was absent after planting in fields with no recent history of legumes. Fields rotated out of legumes consistently had the highest grain yield, averaging 1.5 t ha(-1) over the seasons. Additionally, the rotation land treatment displayed significantly more pods per plant during the 2021 (9.7), 2022a (9.8), and 2022b (12.5) seasons. In the third experiment, the impact of five fungicides and four cropping systems on bean scab was investigated over two seasons. Neither fungicide treatments nor cropping systems had an effect on bean scab incidence even when only severe symptoms were considered. Carbendazim had the highest yield (1.9 t ha(-1)) outperforming the unsprayed control only in the 2022 season while none of the other fungicides outperformed the control treatment in yield parameters in either season. This study emphasizes the challenge of managing bean scab without proper crop rotation and underscores the role of crop residue as a critical inoculum source.

Fruit development has been central in the evolution and domestication of flowering plants. In common bean (Phaseolus vulgaris), the principal global grain legume staple, two main production categories are distinguished by fibre deposition in pods: dry beans, with fibrous, stringy pods; and stringless snap/green beans, with reduced fibre deposition, which frequently revert to the ancestral stringy state. Here, we identify genetic and developmental patterns associated with pod fibre deposition. Transcriptional, anatomical, epigenetic and genetic regulation of pod strings were explored through RNA-seq, RT-qPCR, fluorescence microscopy, bisulfite sequencing and whole-genome sequencing. Overexpression of the INDEHISCENT ('PvIND') orthologue was observed in stringless types compared with isogenic stringy lines, associated with overspecification of weak dehiscence-zone cells throughout the pod vascular sheath. No differences in DNA methylation were correlated with this phenotype. Nonstringy varieties showed a tandemly direct duplicated PvIND and a Ty1-copia retrotransposon inserted between the two repeats. These sequence features are lost during pod reversion and are predictive of pod phenotype in diverse materials, supporting their role in PvIND overexpression and reversible string phenotype. Our results give insight into reversible gain-of-function mutations and possible genetic solutions to the reversion problem, of considerable economic value for green bean production.

Crotalaria brevidens and C. ochroleuca commonly grown as vegetables have been extensively studied. However, information on breeding techniques is scanty. This study aimed to develop an artificial interspecific pollination protocol for two genotypes of Crotalaria with contrasting leaf and pod morphological features. The two are landraces that were previously collected from two counties in Kenya. The experimental design was a completely randomized design (CRD) in a greenhouse with C. ochroleuca as the female parent and C. brevidens as the male parent. Six-day-old flower buds of the female parent were emasculated. Pollen from a freshly opened flower was rubbed over the stigma of the emasculated flower. The pollinated stigma was inserted back into the keel petal and covered by the wing and standard petal. Data on success rate, pod, and seed production were subjected to analysis of variance. The developed artificial pollination method showed 75% success rate in the interspecies cross of C. ochroleuca and C. brevidens. Time of crossing did not significantly influence the success rate, pod, and seed production. The study demonstrated artificial interspecific pollination of Crotalaria by keel petal incision rubbing method. This protocol lays the foundation for genetic studies and improvement of Crotalaria spp.

Combination of pest management strategies that minimize pesticide use and conserve natural enemies is important for a sustainable environment. Overreliance on synthetic insecticides in the management of Tuta absoluta has led to pesticide resistance leading to difficulties in managing the pest. In this regard, alternative measures need to be put in place to reduce the effects of this pest. The objective of this study was, therefore, to assess the effectiveness of host plant resistance, biological control, and selective insecticides when used in combination, in the management of T. absoluta in tomato production. The study was set up in a greenhouse in a completely randomized design involving two tomato varieties, an insecticide (chlorantraniliprole), and a biological control agent(Macrolophus pygmaeus), applied singly or in combination. Data were collected on T. absoluta damage from the lower, intermediate, and upper leaves. The results from this study show that a combination of insecticide with a moderately resistant variety had a significantly lower T. absoluta damage as compared with a susceptible variety combined with an insecticide. However, the moderately resistant variety when combined with insecticide showed no effect when the biological control agent was added. The susceptible variety significantly reduced T. absoluta damage when combined with the biological control agent. These results indicate that treatment combinations in insect pest management can be utilized. The present study results indicate that using a moderately resistant variety (Riogrande VF) in combination with the insecticide chlorantraniliprole (Coragen®) and a susceptible variety (Pesa F1) in combination with the biological control agent (M. pygmaeus) can improve T. absoluta management. Under good habitat management, the susceptible variety will perform equally as the moderately resistant variety due to suppression of the T. absoluta populations by natural enemies. These findings show the importance of environmental conservation both by enhancing natural enemy abundance and use of selective insecticide in the management of T. absoluta in tomato production. Combinations in this present study are likely to reduce insecticide doses, thereby reducing the cost of production and enhancing environmental compatibility with natural enemies.

Aims: The objective of the study was to evaluate the cost-effectiveness of using different fertilizer combinations to improve Napier grass production within the smallholder farms. Study Design: The experimental design was a Randomised Complete Block Design (RCBD) with three replicates per treatment. The treatments were: Di-Ammonium Phosphate (DAP); rabbit (Oryctolagus cuniculus) manure; rabbit manure plus rabbit urine; DAP plus Calcium Ammonium Nitrate (CAN); DAP plus rabbit urine; Control; and Conventional method. Place and Duration of Study: The study was done in Embu County, Kenya from March 2015 to January 2016. Methodology: The economic analysis to determine the most cost-effective fertilizer was done using gross margins and cost-benefit ratios approach. Results: Rabbit manure plus urine had the highest cost of production averages at US$.154 8.13 per year at p<0.05 while the conventional method was US$ 494.59 at p<0.05. The study revealed that the most cost-effective fertilizer in Embu County was DAP plus rabbit urine treatment under ‘‘Tumbukiza’’ pits. Conclusion: The projections are that by the end of the second cropping year, the treatment top-dressed with either rabbit urine or CAN would be having higher gross margins since the initial cost would have been recovered. Farmers in Embu County are encouraged to integrate the use of both organic and inorganic fertilizers to achieve high production in a cost-effective way.

Pest invasion is one of the limiting factors affecting food production. Tomato leaf miner (Tuta absoluta) (Meyrick 1917) (Lepidoptera: Gelechiidae), is an invasive insect pest of tomato. However, In Kenya, there is limited information on the level of invasion of the pest in tomato producing areas in the country. We assessed the level of invasion of T. absoluta and farmer management practices in Kirinyaga County. Tomato farmers were interviewed using questionnaires aimed at identifying the management practices used by farmers to control T. absoluta and their awareness on the insect pest. Two hundred and eight tomato farmers were interviewed, 90% of the respondents rated T. absoluta as a major pest of tomato. Results show that 94% of the respondents use synthetic chemicals in the control of T. absoluta with an average frequency of 12 times per growing season of three months with the highest frequency being 16 times. Increased use of synthetic insecticides was associated with a negative impact on the natural enemies. Among the interviewed farmers, 52 and 46% of respondents stated that after chemical spraying natural enemies disappear and are killed respectively, while 2% did not know what happened to them. It is therefore imperative to design an integrated pest management program that integrates biological control and environmentally friendly chemicals for sustainable control of T. absoluta populations. Key words: Synthetic insecticides, management practices, natural enemies, abundance, severity.

A rapid and reliable detached-leaf technique was developed for screening common bean (Phaseolus vulgaris) genotypes against angular leaf spot (ALS) disease caused by Pseudocercospora griseola. It is helpful to differentiate between susceptible and resistance common bean genotypes. Detached leaves of common bean tested genotypes were inoculated by immersing them into a spore suspension followed by placing into petri dishes at room temperature on cotton moistened with tap water. After 10-day incubation, the leaves were monitored for symptom development. This screening method was effective to determine the pathotype of P. griseola isolates on a set of ALS differential common bean genotypes. With this specific screening technique, all known sources of ALS resistance genes, including MEX-54, BAT332, and AND277 exhibited resistant reactions to ALS and showed no reaction and symptom development following inoculation with P. griseola isolates collected from Ethiopia. However, all other common bean genotypes tested together with genotypes known for their susceptibility with reaction scores 4 to 9 developed lesions in the interveinal regions of the leaves. Hence, the proposed simple and rapid screening technique was efficient, low-cost, and able to differentiate between resistant and susceptible common bean genotypes. It can be used for screening in marker-assisted gene pyramiding and backcrossing programs to facilitate early selection of seedlings in segregating progenies. Key words: Detached leaf, Pseudocercospora griseola, genotype screening.

Common bean (Phaseolus vulgaris) is a rich source of protein, vitamins, and micronutrients and is an important crop for food security throughout Latin America, Asia, and Africa. Among tropical and subtropical regions of the world, where the majority of beans are grown, yield losses due to the pathogenic fungus Pseudocercospora griseola, causing angular leaf spot (ALS), can be as high as 80%. The strategic use of marker-assisted selection (MAS) to pyramid multiple resistance genes into a single genetic background with preferred morphological and cooking characteristics is being implemented by six research groups throughout East Africa that make up the African Bean Consortium (ABC). Identifying unique markers that are polymorphic among multiple parents is a major source of marker attrition. In this study, an illustration of how 22 DNA sequences physically linked to the Phg-2 ALS resistance locus were identified using the PhaseolusGenes marker database and checked for amplification and polymorphism among 16 ABC breeding parents are given. Only three polymorphic markers could be identified following this procedure; one (g796), showed a polymorphism present only in the ALS resistance donor, Mexico 54. The PCR protocol developed to identify the g796 polymorphism was validated among five laboratories. Furthermore, co-segregation analysis of the marker and ALS resistance phenotype in a population of 100 F2 individuals from the cross between French bean (that is, green bean) genotype Amy and ALS resistance donor Mexico 54 showed the marker is genetically linked (3 cM) to the Phg-2 locus, in addition to being physically linked. This study suggests that in the near future, genetic resequencing data of diverse common bean accessions, compiled within an easily accessible database, will facilitate identification of markers for MAS, marker/trait association, and candidate gene identification. Key words: Angular leaf spot resistance, Phaseolus vulgaris, marker-assisted selection.

Bean rust (Uromyces appendiculatus (Pers.:Pers.) Unger var. appendiculatus) is one of the most devastating and variable pathogens of common bean (Phaseolus vulgaris L.) worldwide that can cause total crop loss. Characterization of bean rust races can help in screening resistant materials during gene pyramiding. The aims of the present research were first, to characterize bean rust isolates collected from snap bean growing areas in Kenya. Secondly, to identify which of the available rust resistance genes in common bean differentials are most effective to control rust in those areas. Snap bean leaf tissues with rust pustules were collected from different farms in eight locations in central and western Kenya during the years 2010 and 2011. Forty seven single pustule isolates were obtained and inoculated on 12 bean rust differential cultivars. For consistent results, the inoculation was repeated twice. The new international classification system and the binary nomenclature grouped the 47 single pustule isolates of U. appendiculatus into 9 different races, most of this affected the Andean gene pool. Hierarchical cluster analysis grouped the races into two major clusters depending on the virulence of the races on the host differential cultivars. The most resistant genes for pyramiding in Kenya were identified as Ur-5, Ur-11 and Ur-CNC. An important output of this study was the identification of races with potential use during gene pyramiding process. Key words: Uromyces appendiculatus, snap bean, races, genes, characterization.