Diversity and path coefficient analysis of Southern African maize hybrids

Detailed knowledge on genetic diversity among germplasm is important for hybrid maize ( Zea mays L.) breeding. The objective of the study was to determine genetic diversity in widely grown hybrids in Southern Africa, and compare effectiveness of phenotypic analysis models for determining genetic distances between hybrids. Fifty hybrids were evaluated at one site with two replicates. The experiment was a randomized complete block design. Phenotypic and genotypic data were analyzed using SAS and Power Marker respectively. There was significant (p < 0.01) variation and diversity among hybrid brands but small within brand clusters. Polymorphic Information Content (PIC) ranged from 0.07 to 0.38 with an average of 0.34 and genetic distance ranged from 0.08 to 0.50 with an average of 0.43. SAH23 and SAH21 (0.48) and SAH33 and SAH3 (0.47) were the most distantly related hybrids. Both single nucleotide polymorphism (SNP) markers and phenotypic data models were effective for discriminating genotypes according to genetic distance. SNP markers revealed nine clusters of hybrids. The 12-trait phenotypic analysis model, revealed eight clusters at 85%, while the five-trait model revealed six clusters. Path analysis revealed significant direct and indirect effects of secondary traits on yield. Plant height and ear height were negatively correlated with grain yield meaning shorter hybrids gave high yield. Ear weight, days to anthesis, and number of ears had highest positive direct effects on yield. These traits can provide good selection index for high yielding maize hybrids. Results confirmed that diversity of hybrids is small within brands and also confirm that phenotypic trait models are effective for discriminating hybrids.

A comparison of risky sexual behaviours between circumcised and uncircumcised men aged 30-44 years in Botswana.

Background: The principal mode of HIV transmission in Southern Africa is through sexual intercourse, and this has prompted uptake of safe male circumcision. Engaging in risky sexual behaviour by circumcised men increases the risks of acquiring HIV, though male circumcision coupled with preventive behaviour reduces this risk. Objective: To compare the factors associated with risky sexual behaviour among circumcised and uncircumcised men in Botswana. Methods: Nationally representative data from the Botswana AIDS Impact Survey III were used. A sample of 313 sexually active men was used. The data was analysed by cross-tabulation and logistic regression. Results: The study revealed that uncircumcised men (odds ratio, 5.711) were more likely to have sex while intoxicated with alcohol compared to circumcised men. Low levels of education (odds ratio, 8.736), urban residency (city/town: odds ratio, 1.238 and urban village: odds ratio, 1.098) were more likely to influence risky behaviour (more than one sexual partner) for circumcised men. The results also show that marital status (never married) (odds ratio, 1.947) influences risky behaviour (having sex while intoxicated with alcohol) among uncircumcised men. Conclusion: Low level of education, place of residence and alcohol consumption influences risky sexual behaviour for both circumcised and uncircumcised men. Policies and programmes should thus focus on the attitudes underlying sexual behaviour.