Effect of Thidiazuron, NAA and BAP on in vitro propagation of Alstroemeria aurantiaca CV. ‘Rosita’ from shoot tip explants

The objective of the study was to evaluate the potency of Thidiazuron (TDZ) as a plant growth regulator when compared to combined auxin (NAA) and cytokinin (BAP) in evoking morphogenic responses from Alstroemeria aurantiaca cv. ‘Rosita’ shoot tip explants. Shoot tips cultured on basal medium devoid of any plant growth regulators (PGRs) only increased slightly in length and formed only 1 leaf per shoot during the culture period. The addition of various PGRs to the induction or culture medium significantly influenced the number and length of shoots as well as the number of leaves formed. While low concentrations of TDZ (0.1 μM) had no significant effect and high concentrations (5.0 μM) were inhibitory, medium concentrations (0.4‐1.0 μM) significantly increased the number and length of shoots as well as the number of leaves formed from the explants. The longest shoots were formed from explants cultured in media supplemented with 1.0 μM TDZ. Slightly better but comparable responses were observed from explants cultured on media supplemented with 1.0 mg/L BAP and low concentrations (0.01 mg/L) of NAA. The explants cultured in 1.0 mg/L BAP + 0.01 mg/L NAA formed the greatest number of shoots while those cultured in 1.0 μM TDZ formed the greatest number of leaves/ ex‐plant. Increasing the NAA concentration to 0.1 mg/L and combining this with either 1.0 mg/L BAP or 1.0 μM TDZ depressed shoot formation and shoot length. In conclusion, TDZ at concentrations between 0.4 and 1.0 μM were just as effective as combined auxins (NAA) and cytokinin (BAP) in evoking morphogenic responses from Alstroemeria aurantiaca cv. ‘Rosita’ shoot tip explants.Key Words: Thidiazuron, Alstroemeria aurantiaca, explant

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

In vitro Propagation of Ornithogalum saundersiae: potential of Thidiazuronas a chemical of choice.

The objective of the study was to evaluate the efficacy of Thidiazuron (TDZ) as a plant growth regulator in evoking morphogenesis, whole plant regeneration and subsequent rooting and bulbing from shoot tip cultures of Ornithogalum saundersiae L. Shoot tip explants maintained on MSO (basal medium devoid of any plant growth regulators), formed only one shoot over the 10-week period of culture, which also failed to root or form bulbs. Inclusion of TDZ at various concentrations (0.1-5.0 &#956M) promoted direct adventitious shoot proliferation. Most of the shoots subsequently formed roots and bulbs when transferred to MSO. Addition of naphthalene acetic acid (NAA) to the culture medium inhibited shoot formation causing the shoot tip explants to brown and die after about 7 days of culture without further growth, development or callus formation. Benzylaminopurine (BAP), on the other hand, slightly improved shoot formation above the controls, although subsequent rooting and bulbing were low. Of significance was the synergistic effects of BAP and NAA which, in combination, improved shoot proliferation, as well as subsequent root and bulb formation from the shoot tip explants to levels comparable to those of explants cultured in TDZ at 0.1-0.4 &#956M concentration range. In summary, TDZ at 5 &#956M concentration was more effective, but at lower concentrations (0.1-1.0 &#956M) was just as effective as combined NAA + BAP in eliciting morphogenic responses from shoot tip explants of Ornithogalum saundersiae L.Keywords:Ornithogalum saundersiae; Thidiazuron (TDZ); propagationJAGST Vol 6(1) 2004: 60-6

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 (

Effect of Thidiazuron, NAA and BAP on in vitro propagation of Alstroemeria aurantiaca CV. ‘Rosita’ from shoot tip explants

The objective of the study was to evaluate the potency of Thidiazuron (TDZ) as a plant growth regulator when compared to combined auxin (NAA) and cytokinin (BAP) in evoking morphogenic responses from Alstroemeria aurantiaca cv. ‘Rosita’ shoot tip explants. Shoot tips cultured on basal medium devoid of any plant growth regulators (PGRs) only increased slightly in length and formed only 1 leaf per shoot during the culture period. The addition of various PGRs to the induction or culture medium significantly influenced the number and length of shoots as well as the number of leaves formed. While low concentrations of TDZ (0.1 μM) had no significant effect and high concentrations (5.0 μM) were inhibitory, medium concentrations (0.4‐1.0 μM) significantly increased the number and length of shoots as well as the number of leaves formed from the explants. The longest shoots were formed from explants cultured in media supplemented with 1.0 μM TDZ. Slightly better but comparable responses were observed from explants cultured on media supplemented with 1.0 mg/L BAP and low concentrations (0.01 mg/L) of NAA. The explants cultured in 1.0 mg/L BAP + 0.01 mg/L NAA formed the greatest number of shoots while those cultured in 1.0 μM TDZ formed the greatest number of leaves/ ex‐plant. Increasing the NAA concentration to 0.1 mg/L and combining this with either 1.0 mg/L BAP or 1.0 μM TDZ depressed shoot formation and shoot length. In conclusion, TDZ at concentrations between 0.4 and 1.0 μM were just as effective as combined auxins (NAA) and cytokinin (BAP) in evoking morphogenic responses from Alstroemeria aurantiaca cv. ‘Rosita’ shoot tip explants.Key Words: Thidiazuron, Alstroemeria aurantiaca, explant