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

Co-limitation towards lower latitudes shapes global forest diversity gradients

The latitudinal diversity gradient (LDG) is one of the most recognized global patterns of species richness exhibited across a wide range of taxa. Numerous hypotheses have been proposed in the past two centuries to explain LDG, but rigorous tests of the drivers of LDGs have been limited by a lack of high-quality global species richness data. Here we produce a high-resolution (0.025° × 0.025°) map of local tree species richness using a global forest inventory database with individual tree information and local biophysical characteristics from ~1.3 million sample plots. We then quantify drivers of local tree species richness patterns across latitudes. Generally, annual mean temperature was a dominant predictor of tree species richness, which is most consistent with the metabolic theory of biodiversity (MTB). However, MTB underestimated LDG in the tropics, where high species richness was also moderated by topographic, soil and anthropogenic factors operating at local scales. Given that local landscape variables operate synergistically with bioclimatic factors in shaping the global LDG pattern, we suggest that MTB be extended to account for co-limitation by subordinate drivers

Maternal and neonatal outcomes after caesarean delivery in the African Surgical Outcomes Study: a 7-day prospective observational cohort study.

BACKGROUND: Maternal and neonatal mortality is high in Africa, but few large, prospective studies have been done to investigate the risk factors associated with these poor maternal and neonatal outcomes. METHODS: A 7-day, international, prospective, observational cohort study was done in patients having caesarean delivery in 183 hospitals across 22 countries in Africa. The inclusion criteria were all consecutive patients (aged ≥18 years) admitted to participating centres having elective and non-elective caesarean delivery during the 7-day study cohort period. To ensure a representative sample, each hospital had to provide data for 90% of the eligible patients during the recruitment week. The primary outcome was in-hospital maternal mortality and complications, which were assessed by local investigators. The study was registered on the South African National Health Research Database, number KZ_2015RP7_22, and on ClinicalTrials.gov, number NCT03044899. FINDINGS: Between February, 2016, and May, 2016, 3792 patients were recruited from hospitals across Africa. 3685 were included in the postoperative complications analysis (107 missing data) and 3684 were included in the maternal mortality analysis (108 missing data). These hospitals had a combined number of specialist surgeons, obstetricians, and anaesthetists totalling 0·7 per 100 000 population (IQR 0·2-2·0). Maternal mortality was 20 (0·5%) of 3684 patients (95% CI 0·3-0·8). Complications occurred in 633 (17·4%) of 3636 mothers (16·2-18·6), which were predominantly severe intraoperative and postoperative bleeding (136 [3·8%] of 3612 mothers). Maternal mortality was independently associated with a preoperative presentation of placenta praevia, placental abruption, ruptured uterus, antepartum haemorrhage (odds ratio 4·47 [95% CI 1·46-13·65]), and perioperative severe obstetric haemorrhage (5·87 [1·99-17·34]) or anaesthesia complications (11·47 (1·20-109·20]). Neonatal mortality was 153 (4·4%) of 3506 infants (95% CI 3·7-5·0). INTERPRETATION: Maternal mortality after caesarean delivery in Africa is 50 times higher than that of high-income countries and is driven by peripartum haemorrhage and anaesthesia complications. Neonatal mortality is double the global average. Early identification and appropriate management of mothers at risk of peripartum haemorrhage might improve maternal and neonatal outcomes in Africa. FUNDING: Medical Research Council of South Africa.Medical Research Council of South Africa