Mapping of QTLs associated with recovery resistance to streak virus disease in maize

Open Access Article; Published online: 10 June 2018Maize streak virus (MSV, genus Mastrevirus, family Geminiviridae), vectored by the leafhoppers (Cicadulina sp.), is the most economically important viral disease of maize endemic to Sub-Saharan Africa and its offshore islands. Yield losses due to MSV are mainly controlled through use of resistant varieties. ‘Recovery’ (ability of plants to reduce symptom severity), is one of the types of resistance being used to develop MSV resistant cultivars through breeding. This study was conducted to map Quantitative Trait Loci (QTLs) associated with recovery resistance to MSV in a mapping population comprising 250 S1 lines derived from a cross between two MSV resistant lines. The population was genotyped using single nucleotide polymorphism (SNP) markers at 269 loci. A genetic map of 11 linkage groups was constructed comprising 230 SNP markers. Four QTLs, two putative QTLs with significant effect on chromosome 3 and two other QTLs with reduced effect on chromosomes 7 and 9, were identified from the population. The two QTLs on chromosome 3 together accounted for 47 to 51% of the total phenotypic variance while the other two QTLs accounted for 28 to 32% of the total variation. These QTLs originated from the two parents of the mapping population had both additive and dominance effects but interaction among the four loci was not significant. Further validation of these QTLs associated with recovery resistance in other diverse populations will lead to the development of new genomic resources to enhance breeding for MSV resistant maize

Management of Giant Cell Tumour: A Nigerian Experience

Giant cell tumours (GCT) are the commonest bone tumours worldwide. It is rarely malignant but when it does it progresses to fibrosarcoma with high mortality. Otherwise it causes poor cosmesis, disability and pathological fractures. A total of 19 cases of histologically established Giant cell tumour of the bone were reviewed prospectively in a 5 year study. 14 cases were benign, 4 malignant and one was a malignant transformation. Lesions around the knee accounted for 42.2% of the cases, but the radius was the commonest single bone affected with 26.3%. Eleven patients had curettage, five of them had autogenous bone grafting while the remaining six had bone grafting and plate augmentation. One patient had fore-quarter amputation while seven had tumour resection. There was no recurrence recorded among those that had currretage and autogenous bone grafting. 33% of those that had curettage and bone cementing as well as 16.6% of those that had resection presented with recurrence. One patient died within 3 months of surgery due to metastasis to the lungs, liver and spleen. Mean follow up was 9.2 months (range of 2 to 60 months). With early presentation, curretage and bone grafting is often effective; late presentation however has an increased risk of recurrence due to soft tissue involvement, dearth of investigative tools and financial constraints. Nigerian Journal of Surgical Sciences Vol. 17 (2) 2007: pp. 91-9

Challenges in the diagnosis and management of musculoskeletal tumours in Nigeria

The management of musculoskeletal tumours is important because of the high mortality rates associated with the available treatment modalities. A 5-year prospective study of bone and soft-tissue tumours is presented, along with the difficulties encountered in diagnosis and treatment. There were 71 patients (male:female ratio of 1.7:1, age range 5–85 years, mean age 32 years) with an average duration of 24.7 weeks (range 1 day to 34 years) before presentation. No patient had computed tomography (CT) scanning or magnetic resonance imaging (MRI) due to financial constraints, 95% had biopsies and X-rays, 15% could afford chemotherapy/ror chemotherapy is a sad consequence. 50% agreed to amputation. In the soft-tissue sarcoma group, only one of three patients could pay for limb-sparing surgery. In the benign group, 65% had limb-sparing surgeries and 15% had amputation. Fifty percent (50%) of patients were lost to follow up within 3 months and 39% of the malignant group died within the same period. Musculoskeletal tumours are a reality in our environment and a significant portion of our population have financial limitations. Ignorance and cultural beliefs promote late presentation to our hospitals, which are poorly equipped to give optimal care, despite the presence of trained personnel

Multi-parent populations in crops: a toolbox integrating genomics and genetic mapping with breeding

Crop populations derived from experimental crosses enable the genetic dissection of complex traits and support modern plant breeding. Among these, multi-parent populations now play a central role. By mixing and recombining the genomes of multiple founders, multi-parent populations combine many commonly sought beneficial properties of genetic mapping populations. For example, they have high power and resolution for mapping quantitative trait loci, high genetic diversity and minimal population structure. Many multi-parent populations have been constructed in crop species, and their inbred germplasm and associated phenotypic and genotypic data serve as enduring resources. Their utility has grown from being a tool for mapping quantitative trait loci to a means of providing germplasm for breeding programmes. Genomics approaches, including de novo genome assemblies and gene annotations for the population founders, have allowed the imputation of rich sequence information into the descendent population, expanding the breadth of research and breeding applications of multi-parent populations. Here, we report recent successes from crop multi-parent populations in crops. We also propose an ideal genotypic, phenotypic and germplasm 'package' that multi-parent populations should feature to optimise their use as powerful community resources for crop research, development and breeding