QTL mapping: a conceptual approach to improving cold tolerance at seedling stage in rice (Oryza sativa. L)

Much of what is known about the process of technological innovation in agriculture has yet to be captured in the discussions of abiotic stress plant tolerance as well as rice cold tolerance. The development of research and technological solutions to minimize risks of current abiotic stresses to the plant can lead to two possible outcomes: increase in agricultural productivity and assist the future of plant breeding work. Research efforts about the role of technological development, driven by abiotic stress constraints, are pivotal in making any assertion about the likely tolerance of plant to abiotic stress. Drawing upon the hypothesis of QTL mapping, this research investigates on detection of QTLs for cold tolerance at the seedling stage in rice (Oryza sativa. L), QTLs identified from a BC1F2 breeding population derived from the cross between Chomrongdhan, a donor parent tolerant with Vary botry a susceptible parent, that lead to increase rice productivity in Madagascar. Using a controlled environment and molecular work, out of total 500 BC1F2 segregating plants, 144 plants were used for genotyping based on of visual seedling stage cold tolerance symptom. A total of 4606 SNP markers evenly spread throughout the whole 12 rice genome was used for parental polymorphism survey. The 34% polymorphic markers were used for QTL mapping for cold tolerance at seedling stage. QTL analysis using inclusive composite interval mapping detected four QTLs on chromosome 2 and 10 with phenotypic variances (R2) of 11.11, 7.55, 12.8 and 8.8%, respectively. The position of QTL on chromosome 2 was flanked by 2262412 and 2237404, three other QTLs were detected on chromosome 10 conferred cold tolerances for seedling growth and leaf growth at 14day after recovery and appear to be a novel QTLs. Selected tolerant plant in this research should be useful for the farmers and the markers flanking those identified QTLs should be useful for molecular marker assisted breeding for cold tolerance for the breeder. Keywords: QTL mapping, cold tolerance, seedling, rice

Estimating Rice Yield under Changing Weather Conditions in Kenya Using CERES Rice Model

Effects of change in weather conditions on the yields of Basmati 370 and IR 2793-80-1 cultivated under System of Rice Intensification (SRI) in Mwea and Western Kenya irrigation schemes were assessed through sensitivity analysis using the Ceres rice model v 4.5 of the DSSAT modeling system. Genetic coefficients were determined using 2010 experimental data. The model was validated using rice growth and development data during the 2011 cropping season. Two SRI farmers were selected randomly from each irrigation scheme and their farms were used as research fields. Daily maximum and minimum temperatures and precipitation were collected from the weather station in each of the irrigation schemes while daily solar radiation was generated using weatherman in the DSSAT shell. The study revealed that increase in both maximum and minimum temperatures affects Basmati 370 and IR 2793-80-1 grain yield under SRI. Increase in atmospheric CO2 concentration led to an increase in grain yield for both Basmati and IR 2793-80-1 under SRI and increase in solar radiation also had an increasing impact on both Basmati 370 and IR 2793-80-1 grain yield. The results of the study therefore show that weather conditions in Kenya affect rice yield under SRI and should be taken into consideration to improve food security

Assessment of phenotypic and genetic variation against pod borer among a subset of elite pigeonpea (Cajanus cajan) genotypes in Kenya

Molecular marker information supported by quality morphological data facilitates the choice of suitable parents for applied breeding. The main aim of this study was to assess genetic diversity among 55 cultivated yield elite pigeonpea lines using 21 simple sequence repeat (SSR) markers that are well distributed across the genome. Among the 55 pigeonpea genotypes, 16 medium duration were selected and evaluated in the field for response to pod borer resistance in varied agro-ecological zones of Kenya during long rains of April-October cropping season Twenty one primer pairs detected 80 alleles with a mean of 3.9 alleles per locus and polymorphism information content (PIC) ranging from 0.09 to 0.75 averaging to 0.39 suggesting a low genetic diversity. However, marker CcM1820 revealed the highest number of alleles (9) with a PIC value of 0.75. The genotype response to pod borer attack was significant (P≤0.05) with three genotypes (ICEAPs 01541, 01154-2 and 00902) revealing tolerance to pod borer. The markers based on Neighbor Joining, grouped the 55 genotypes into three main clusters based on parentage selection. Most genotypes developed from ICEAP 00068 as the maternal parent were grouped in Cluster I while cluster II comprised of improved genotypes and cluster III comprised genotypes developed from ICPL 87091 as maternal parent. The resistant genotypes identified in the field experiment were grouped in cluster I except ICEAP 00902 which grouped in cluster II. Future studies should focus on broadening genetic base by including more landraces and wild relatives to maximize selection and improve breeding work

Evaluation of Genotype x Environment Interaction and Stability of Grain Yield and Related Yield Components in Pearl Millet (Pennisetum glaucum (L.) R.Br.)

Thirty six pearl millet genotypes were evaluated in randomized complete block design with two replications during 2011/2012 at two locations to study the magnitude of genotype by environment interaction for yield and yield related traits and identify the most stable high yielding genotypes. ANOVA of data at individual locations revealed significant differences among genotypes at Marigat and Koibatek for all yield components. Combined mean analysis of variance showed that the Genotype and location main effects and the genotype by environment interaction were highly significant (P≤0.01) for grain yield and other traits, indicating differential response of genotypes across testing locations and the need for stability analysis. Marigat was the most suitable environment and gave highest mean grain yield of 3620 kg/ha. The lowest yield 870 Kg/ha was recorded at Koibatek. Genotypes EUP 32, EUP 35, EUP 19 and EUP 10 produced high mean yield of 3530, 3080, 2690 and 2590 kg/ha respectively. The lowest grain 1290 kg/ha was obtained from genotype EUP 4.Based on the parameters of stability, three stable (widely adapted) and high yielding genotypes (EUP 34, EUP 18, and EUP 9) were identified. They also out-yield the standard open pollinated variety (OPV) check, Kat PM2. Genotypes EUP 32 was the highest yielding across all sites followed by EUP 35 and could be recommended for further multi-location evaluation in warmer environment and possible release for commercial production. The findings of this study showed that pearl millet hybrids have high potential for commercial production in Kenya than the OPVs. The ANOVA results showed that the effects of environments, genotypes and genotype x environment interaction (GE) were important in trait expression and performance of genotypes. In addition, it was observed that amount of rainfall received at both vegetative and post-anthesis phases and temperature had an effect on grain yield. The GGE biplot analysis characterised the environments in terms of stability and productivity, where Marigat was the best for grain yield; implying that environment-specific selection should be adopted. Genotypes EUP 34, EUP 18, and EUP 9 were the best performing since they out yielded the standard OPV check. These stable high yielding genotypes can be evaluated further in varied agro-ecologies and recommended for release as commercial hybrid varieties in ASALs of Kenya

Evaluation of Selected Pigeonpea (Cajanus cajan (L.) Millsp.) Genotypes for Resistance to Insect Pest Complex in Dry Areas of North Rift Valley, Kenya

Pigeonpea is an important pulse crop that has gained importance in semi-arid tropics, although its yield potential has not been fully realized due to biotic and abiotic stresses that limit its production. Insect pest complex of pod borer (Helicoverpa armigera), sucking bug (Clavigralla tomentosicollis) and pod fly (Melanagromyza cholcosoma) are the major limiting factors to its production causing up to 100% yield loss. The objective of this study was to evaluate resistant genotypes to insect pest complex in dry parts of North Rift Valley Kenya. The study was carried out in three sites (Kenya Agricultural Livestock Research Organization- Marigat, Agricultural Training Centre-Koibatek and Fluorspar-Chepsirei) for one season during long rain of April-November 2014 growing season. Sixteen ICRISAT elite genotypes were evaluated in randomized complete block design (RCBD) with 75cm inter and 25 cm intra spacing. Significant (P≤0.05) differences in grain yield performance, incidence and severity of the insect pests were revealed in all sites. The damage was more severe in Marigat (Pod borer-37.2%, Sucking bug-39.3% and pod fly-5.9%) than ATC- Koibatek (Pod borer-1.9%, Sucking bug-8.4% and pod fly-5.9%) and Fluorspar (Pod borer-3.6%, Sucking bug-6.8% and pod fly-2.9%). Genotypes ICEAPs 00850R, 00902, 01541 and 1154-2 showed potential levels of resistance to the insect pest complex and high yields. Grain yield associated negatively (P≤0.05) with pod borer and sucking bug damage correlated non-significantly with pod fly damage. The potential genotypes identified in this study need to be further evaluated in two seasons and in other multi-locations to validate these findings to be used in breeding

Discovery of the vector of visceral leishmaniasis, Phlebotomus (Artemievus) alexandri Sinton, 1928, in Kenya suggests complex transmission dynamics

Visceral and cutaneous leishmaniasis are endemic to specific regions due to the ecological preferences of phlebotomine sand flies and Leishmania spp. transmission. Sand fly entomological data in northern Kenya are scarce due to limited studies and neglect of leishmaniasis. The aim of this study was to investigate: (i) sand fly diversity and distribution; (ii) occurrence of Leishmania DNA within sand flies; and (iii) blood-meal sources of sand flies in Laisamis, northern Kenya. We conducted an entomological survey during February and March of 2021 in five areas of Laisamis sub-county using standard CDC light traps. A total of 1009 sand flies (394 male and 615 female) were morphologically identified, and representative samples verified by PCR amplification and sequencing of the cytochrome c oxidase subunit 1 (cox1) gene. Similarly, we identified blood-meal sources and Leishmania DNA in female sand flies by PCR amplicon sequencing of the vertebrate cytochrome b (cyt b) gene and internal transcribed spacer 1 (ITS1) of the 28S rRNA gene, respectively. Sergentomyia clydei (59.8%) was the most abundant sand fly species. Though collected mainly from one locality (Tirgamo), 14.8% of samples belonged to Phlebotomus (Artemievus) alexandri Sinton, 1928. We detected DNA of Leishmania major in 5.19% of Ph. alexandri, whereas Leishmania adleri DNA was detected in S. clydei (7.51%), Sergentomyia squamipleuris (8.00%), and Sergentomyia africanus (8.33%). Nine of 13 blood-fed sand flies had obtained blood from humans, of which 33.3% had L. major DNA. Both Ph. alexandri and S. clydei primarily fed on humans and could potentially be involved in the transmission of cutaneous leishmaniasis. The findings of this study contribute to the understanding of sand fly vector populations and their potential to transmit leishmaniasis in the area