Browsing by Author "Rwegasira, Gration M."
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Item Mapping of quantitative trait loci (QTL) related to yield, nut quality and plant size of cashew (anacardium occidentalel)(2017) Mzena, Geradina P.; Kusolwa, Paul M.; Rwegasira, Gration M.; Yao, Nasser K.Improvement of yield, nut quality and plant size in cashew is a complex process through conventional technique. It takes at least 9-12 years to develop new varieties, this causes inadequate supply of improved planting materials to farmers. To overcome this limitation, we need to use marker-assisted selection. However, to date, MAS in cashew breeding has been hampered by the absence of markers linked to yield, nut quality and plant size. This study aimed at identifying quantitative trait loci associated with yield, nut quality and plant size. To map QTL a genetic linkage map with 761 single nucleotide polymorphism markers was developed using F2 population of cashew derived from ATA19/250 × Cook05. The linkage map consisted of 21 linkage groups covering 2230cM with an average marker distance of 3.3cM. The F2 progenies were evaluated for yield, number of nuts, nut weight, number of kernels, kernel weight, plant size, canopy diameter and percentage outturn in three seasons namely 2013, 2014 and 2015. A total of 13 QTLs were mapped on 8 linkage groups which explained 25.6 - 56% of the total phenotypic variation. The identified QTLs will speed up the development of high-yielding varieties with good nut quality through marker assisted selectionItem Relationship between symptoms expression and virus detection in cassava brown virus streak-infected plants(Canadian Center of Science and Education, 2012) Rwegasira, Gration M.; Rey, Chrissie M. E.Diagnosis of Cassava brown streak disease (CBSD) has for long been based on foliar and root symptoms expression on infected plants. Variability in patterns of symptoms expression between varieties and seasons however, has meant that symptom-based diagnostics are unreliable. The current study established the relationship between symptom expression on cassava plants and the infection with Cassava brown streak virus (CBSV) using RT-PCR diagnostic tool. It was established that manifestation of CBSD-like symptoms (particularly the foliar chloroses and necrotic blotches) may not be an absolute indication of CBSV-infection. Only 67% of tested samples were both foliarly symptomatic and infected by the virus. About 22% of samples were free from CBSV despite being foliarly symptomatic and 7% were CBSV-infected but foliarly symptom less. Some CBSV-infected plants did not exhibit any foliar symptoms although had root necroses. A few CBSV-free plants were regenerated from infected cuttings in one of the four tested cultivars, Albert. Five out of fifteen (33%) plants cv. Albert were symptom less and two out of the five (40%) were CBSV-free. The findings from this study suggest that symptoms-based diagnosing for CBSV infections is unreliable. As some of CBSV-infected plants tend to be considered CBSV-free due to lack of the disease symptoms, the scenario might have contributed to unlimited spread of CBSD through latently-infected planting materials.