The population structure of wild sorghum species in agro-ecological zones of Western Kenya

There is need to understand the genetic structure of wild sorghums that grow alongside cultivated traditional sorghum varieties in order to assess the potential effect of crop genes in wild populations. In this study, 175 wild sorghum samples were collected from 13 agroecological zones (AEZs) from three counties in Western Kenya and genotyped using microsattelite markers. Crop alleles were observed in wild sorghum populations. The range of allelic frequencies varied from low (˂0.4), to moderate (0.4-0.7) and to high (0.7) in the AEZs. Wild sorghum populations had moderate to high expected heterozygosity (HE) values of between 0.453 in LM1 to 0.715 in LM2. Differences in the magnitude of diversity was significant in the counties (Busia HE = 0.59 – 0.71; Homabay HE = 0.58-0.68 and Siaya HE = 0.45-0.59) but not distinct among the AEZs. Whole population FIS, FST and FIT values were low at 0.15, 0.16 and 0.29, respectively indicating low level of inbreeding, low genetic differentiation of the population and low to moderate deviation from Hardy–Weinberg (HW) equilibrium respectively. The deviation from HW equilibrium was significant in some wild populations from Siaya and Busia. Intra-population diversity (HS) was larger than inter-population diversity (DST) in 13 populations from the sampled AEZs, indicating the importance of gene flow between populations of wild sorghums. Heterozygosity values under mutation drift equilibrium (HEQ) varied under infinite allele model (IAM), two–phase model (TPM) and the step wise mutation model (SMM). However, significant population bottlenecks were absent in the wild sorghums. Presence of significant geographic county clusters and lack of significance on AEZ clusters indicate that human activities have had more influence on the distribution and diversity of wild sorghums than the prevailing climatic conditions. Efforts towards physical and genetic containment of crops genes need to be enhanced for successful ecologically sensitive confined field trials and future adoption of transgenics in cropping systems.Keywords: Diversity, Sorghum bicolor, Sorghum halepense, Sorghum sudanense, microsatellite loci.Abbreviation: AEZ, Agro-ecological zone; DST, inter-population gene diversity; FIS, fixation index; FIT, index of deviation from HW equilibrium; FST, degree of population differentiation; GST, proportion of inter-population gene diversity; HE, expected heterozygosity; HEQ, heterozygosity values under mutation drift equilibrium; HO, observed heterozygosity; HT, total gene diversity; IAM, infinite allele model; SMM, stepwise mutation model; TPM, two-phase model; LM, lower Midlands; UM, upper midlands; HB, Homabay; SY, Siaya; BU, Busia counties; SSR, simple sequence repeats

Real time PCR mediated determination of the spontaneous occurrence of Sorghum bicolor alleles in wild sorghum populations

The study evaluates the utility of Real Time PCR (RT-PCR) in quantitative and qualitative analysis of alleles in sorghum populations and the spontaneous occurrence of Sorghum bicolor alleles in wild populations of sorghum. Leaf and seed material from wild sorghum accesions were sampled in Homabay, Siaya and Busia counties to represent Western Kenya sorghum producing regions. A second sampling was done on S2 populations of S. bicolor, Sorghum halepense and Sorghum sudanense maintained in the greenhouse. Crop loci were evaluated in all materials using a LightCycler® 2.0 system. Real Time PCR was effective in qualitative and quantitative determination of crop alleles in both crop and weedy backgrounds of S. sudanense, S. halepense and S. verticilliflorum. Crossing point values ranged between 19.7 from 30 ng template to 35.9 from 0.015 pg of template on locus SB1764. Melting peaks analysis ranged between 83.29 to 88°C on locus SB1764 and between 86.01 to 80.88°C on locus SB3420 effectively differentiating the 4 species. RealTime-PCR was successful in quantitative and qualitative analysis of specific crop alleles from loci SB1764 and SB3420 from seed and leaf DNA. Spontaneous occurrence of crop and rare alleles in wild sorghum populations growing in sympatry with crop cultivars showed the presence of crop and rare alleles in wild sorghum populations. Means of wild populations from lower midland1 (LM1), LM2, LM3 and LM4 AEZs were not significantly different. It is therefore vital to test S. bicolor seeds and other plant materials in transit, at entry points and populations of growing plants for foreign genes including transgenes using RT-PCR. Keywords: Real time polymerase chain reaction (PCR), Sorghum bicolor, Sorghum halepense, Sorghum sudanense

Effects of nitrogen and phosphorus fertiliser on growth and yield of ironweed (Vernonia galamesis)

No Abstract Available E. Afr. Agric. For. J. 2003 69(2), 109-11

Effect of levels and timing of application of gibberellic acid on growth and yield components of common beans

This study was conducted to determine the effect of levels and timing of application of gibberellic acid (GA3) on growth and yield components of common beans (Phaseolus vulgaris L.). Experiments were conducted at the Field Station Farm at the Faculty of Agriculture, University of Nairobi, Kenya during 1997 and 1998. "Mwezi moja" bean cultivar was used in study. Gibberellic acid (GA3) was sprayed at 0, 2.5, 5.0 and 7.5 mg l-1 to whole bean plants at 7, 14 or 28 days after emergence (DAE). The effect of GA3 and timing of application on growth, yield and yield components was significant (

Effects of Ethephon on the Growth, Yield and Yield Components of Beans (Phaseolus vulgaris L.)

Two experiments to determine the effects of timing and levels of application of ethephon on the growth and yield of common bean (Phaseolus vulgaris L). were conducted. Bean cultivar \'Mwezi moja\' was used. Four levels of ethephon (0, 100, 200 and 300 mg/l) were sprayed to the plants at 7, 14 or at 28 days after emergence (DAE). Application of ethephon at all the three timings led to reduced plant height. Application of ethephon at 28 DAE reduced the leaf area index (LAI), fractional solar radiation interception, shoot dry mass and total dry mass. Root dry mass was not affected by ethephon application. Application of ethephon particularly at 28 DAE reduced yield and number of pods per plant. Application at 7 and 14 DAE in experiment 1 and 28 DAE in both experiments increased the number of seeds per pod. Ethephon application at 14 DAE increased the 100-seed mass in experiment 1 but reduced it in experiment 2. Most reduction in 100-seed mass occurred with application at 28 DAE. The harvest indices were reduced by application of ethephon at 28 DAE in both experiments and 14 DAE in experiment 1. It was concluded that ethephon (ethylene) application did not have any beneficial effects in bean production. KEY WORDS: Beans; ethephon; growth; yield and yield components. J. agric. Sci. technol. Vol.5(1) 2003: 22-3

Effect of packaging materials on weight loss and nutrient quality changes of rechanded sweet potatoes (Ipomoea batatas Poir) during short-term storage

The effects of packaging materials on weight loss and nutrient quality changes of recharged submerged in clean tap water) sweet potatoes (Ipomoea batatas Poir) roots during storage were determined. Sweet potatoes from two genotypes, ‘KEMB 10\' and ‘Yanshu\' were recharged for 14 hours and packaged in perforated polyethylene bags (0.02 mm), Kraft paper bags (0.025 mm) and nylon gunnysacks, with roots placed on open plate as control. The packages were then stored at prevailing ambient conditions (23 &#177 2 oC, 77.5 &#177 5.5 % relative humidity (RH)) for 21 days. During storage the sweet potatoes\' change in weight was determined every 3 days. Change in reduced ascorbic acid, &#223-carotene, total sugars and total soluble solids contents were determined every 7 days. There was a significant (p &#8804 0.05) weight loss as well as reduced ascorbic acid loss, but total sugars and &#223-carotene contents increased during storage. Although total sugars showed an apparent gradual increase in all packages and genotypes during storage, the increase was not significant (p &#8804 0.05). Perforated polyethylene bags significantly (p &#8804 0.05) prevented weight loss (up to 1.8 %) as well as allowed for the most retention in reduced ascorbic acid (13.45 g/100 g fresh weight), and increase in &#223-carotene (4.9 mg/100 g fresh weight) and total sugar (6.4 g/100 g dry weight) contents than Kraft paper bags and nylon gunnysacks. Roots packaged in Kraft paper bags were not different in weight and nutrient quality changes from those packaged in nylon gunnysacks. The control sweet potatoes always showed the highest losses in weight (up to 27.8 %) and nutrient quality. Packaging materials did not affect total soluble solids content during storage. The results show that packaging in perforated polyethylene bags can improve shelf life of recharged sweet potatoes by 14 days.Keywords: Ipomoea batatas; packaging; weight lossJAGST Vol 6(1) 2004: 29-4

Genomic interventions to improve resilience of pigeonpea in changing climate

Pigeonpea is an important food legume crop for rainfed agriculture in developing countries, particularly in India. Productivity gains in pigeonpea have remained static, and the challenge of improving pigeonpea yield is further aggravated by increasingly uncertain climatic conditions. Improved pigeonpea cultivars with favourable traits, allowing them to cope with climatic adversities, are urgently required. Modern genomic technologies have the potential to rapidly improve breeding traits that confer resistance to biotic and abiotic stresses. Recent advances in pigeonpea genomics have led to the development of large-scale genomic tools to accelerate breeding programs. Availability of high-density genotyping assays and high-throughput phenotyping platforms motivate researchers to adopt new breeding techniques like genomic selection (GS) for improving complex traits. Accurate GS predictions inferred from multilocation and multiyear data sets also open new avenues for ‘remote breeding’ which is very much required to achieve genotype selection for future climates. Speed breeding pigeonpea with deployment of rapid generation advancement (RGA) technologies will improve our capacity to breed cultivars endowed with resilient traits. Once such climate-resilient cultivars are in place, their rapid dissemination to farmer’s fields will be required to witness the real impact. Equally important will be the acceleration of varietal turnover to keep pace with the unpredictably changing climatic conditions so that cultivars are constantly optimized for the climatic conditions at any given time