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

Can the understory affect the Hymenoptera parasitoids in a Eucalyptus plantation?

The understory in forest plantations can increase richness and diversity of natural enemies due to greater plant species richness. The objective of this study was to test the hypothesis that the presence of the understory and climatic season in the region (wet or dry) can increase the richness and abundance of Hymenoptera parasitoids in Eucalyptus plantations, in the municipality of Belo Oriente, Minas Gerais State, Brazil. In each eucalyptus cultivation (five areas of cultivation) ten Malaise traps were installed, five with the understory and five without it. A total of 9,639 individuals from 30 families of the Hymenoptera parasitoids were collected, with Mymaridae, Scelionidae, Encyrtidae and Braconidae being the most collected ones with 4,934, 1,212, 619 and 612 individuals, respectively. The eucalyptus stands with and without the understory showed percentage of individuals 45.65% and 54.35% collected, respectively. The understory did not represent a positive effect on the overall abundance of the individuals Hymenoptera in the E. grandis stands, but rather exerted a positive effect on the specific families of the parasitoids of this order

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

Intra-plant spatial distribution of Thaumastocoris peregrinus Carpintero & Dellapé (Hemiptera: Thaumastocoridae) on Eucalyptus grandis plants

The bronze bug Thaumastocoris peregrinus (Hemiptera: Thaumastocoridae), which is native to Australia, damages eucalyptus plantations. In Brazil, this insect was recently introduced, but its distribution on eucalyptus plants remains to be studied. The best sample collection points of T. peregrinus are important to determine infestations of adults, nymphs and eggs on eucalyptus canopy. This study was conducted with Eucalyptus grandis (Myrtaceae). Ten leaves per branch of the prospected trees were collected and the number of T. peregrinus adults, nymphs and eggs on each was counted. Leaves sampled in the middle one-third of the canopy of E. grandis yielded representative data for the T. peregrinus biological cycle. This insect showed vertical intra-plant distribution of 58.28, 46.66 and 49.19 % of adults, nymphs and eggs, respectively, in this stratum. The horizontal distribution of T. peregrinus was 35, 46 and 41 % of adults, nymphs, and eggs in the east, west, and south quadrants, respectively. Thus, Thaumastocoris peregrinus should be sampled on leaves of the middle one-third part of E. grandis