Browsing by Author "Kizito, Elizabeth B."

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Evaluation of Ugandan cassava germplasm for drought tolerance
    (2013) Turyagyenda, F. Laban; Kizito, Elizabeth B.; Baguma, Yona; Osiru, David
    Increased pressure on prime arable land for agriculture to meet food demand for global population has resulted in shifting agriculture to marginal areas where drought is frequent. Focusing research towards development of drought tolerant varieties is thus necessary. Replicated field trials for farmer preferred cassava genotypes were established to evaluate their morphological and yield trait responses and adaptability to moisture stress. Results showed significant (P<0.05) differences among genotypes for all the parameters evaluated. Moisture stress resulted in a decline in Harvest Index by 22.34%, Fresh Root Yield by 37.04%, Number of Roots by 19.43%, Dry matter content by 16.58%, Root starch content of 20.81%, Leaf Retention by 25.72% and Plant height by 16.62%. Results therefore, evidently showed that water stress has significant devastating effects on vegetative and yield parameters of cassava. Breeding strategies to develop drought tolerant cassava varieties to cope up with increased water scarcity and semi-arid conditions are thus paramount. Varietal variability in response to water stress reported is a cornerstone in the breeding process. Besides genetic effects were dominant indicating breeding objectives would be easily achieved. Genotypes MH96/0686, Magana, Yellow, TME 204, Nyamutukura, MH97/2961, NASE 1, NASE 2 and NASE 12 were least affected by drought and may provide gene sources for cassava improvement. Genotype x Location was significant (P<0.05) suggesting that rational distribution of genotypes to agro-ecological zones with different levels of drought stress is possible. Some genotypes had stable yield and its components suggesting that cassava can easily adapt to dry environments.
  • Thumbnail Image
    Item
    Physiological and molecular characterization of drought responses and identification of candidate tolerance genes in cassava
    (AoB plants, 2013) Turyagyenda, Laban F.; Kizito, Elizabeth B.; Ferguson, Morag; Baguma, Yona; Agaba, Morris; Harvey, Jagger J. W.; Osiru, David S. O.
    Cassava is an important root crop to resource-poor farmers in marginal areas, where its production faces drought stress constraints. Given the difficulties associated with cassava breeding, a molecular understanding of drought tolerance in cassava will help in the identification of markers for use in marker-assisted selection and genes for transgenic improvement of drought tolerance. This study was carried out to identify candidate drought-tolerance genes and expression-based markers of drought stress in cassava. One drought-tolerant (improved variety) and one drought-susceptible (farmer-preferred) cassava landrace were grown in the glasshouse under well-watered and water-stressed conditions. Their morphological, physiological and molecular responses to drought were characterized. Morphological and physiological measurements indicate that the tolerance of the improved variety is based on drought avoidance, through reduction of water loss via partial stomatal closure. Ten genes that have previously been biologically validated as conferring or being associated with drought tolerance in other plant species were confirmed as being drought responsive in cassava. Four genes (MeALDH, MeZFP, MeMSD and MeRD28) were identified as candidate cassava drought-tolerance genes, as they were exclusively up-regulated in the drought-tolerant genotype to comparable levels known to confer drought tolerance in other species. Based on these genes, we hypothesize that the basis of the tolerance at the cellular level is probably through mitigation of the oxidative burst and osmotic adjustment. This study provides an initial characterization of the molecular response of cassava to drought stress resembling field conditions. The drought-responsive genes can now be used as expression-based markers of drought stress tolerance in cassava, and the candidate tolerance genes tested in the context of breeding (as possible quantitative trait loci) and engineering drought tolerance in transgenics.
  • Thumbnail Image
    Item
    Stalk-eyed fly, Diopsis sp. population dynamics under varying temperature and Relative Humidity in rice ecosystems
    (2018) Kayongo, Charles; Mbogga, Michael S.; Goncalves de Abreu, Aluana; Masika, Fred; Masanza, Michael; Freitas Barrigossi, Jose Alexandre; Kizito, Elizabeth B.
    Although the stalk-eyed fly (Diopsis sp.) has been observed in Ugandan rice fields, there is limited information on the fly’s population and its potential threat to rice production. This study assessed the stalk-eyed fly (Diopsis longicornis and Diopsis apicalis) population dynamics under varying temperature and relative humidity in rice ecosystems of Uganda. It was conducted in purposively selected small scale rice farming sub-counties in low land rain fed and irrigated rice agro-ecologies (Lake Victoria Crescent, Kasese transition zone and Northern moist farmlands). Diopsis sp. populations were monitored by sampling rice fields every 40 days for a period of 17 months. Weather parameters including air temperature and humidity were recorded by use of data loggers throughout the study period. R-statistical tool and MS Excel were used to assess the population dynamics and interactions of the diopsids. D. longicornis fly was dominantly abundant in rice fields of Lake Victoria Crescent and Northern Moist zones while D. apicalis was dominant in Kasese transition zone. There was significant mean count variations per survey for both species in all the agro-ecological zones with P-values of 0.000958 (D. longicornis) and 1.12e-12 (D. apicalis) in Lake Victoria crescent, 0.000473 (D. apicalis) and 0.0173 (D. longicornis) in Northern moist farmlands, 0.0188 (D. apicalis) and 0.0353 (D. longicornis) in Kasese transition zone. Temperature and relative humidity had a direct effect on the population of both species in Northern moist zone and only on D. apicalis in Kasese transition zone. The optimum/favorable temperatures for abundance were between 27oC and 29oC. Interpretation of the results? Integrated pest management strategies and introduction of improved Diopsis pest resistant rice varieties are some of the recommendations for managing the stalk-eyed fly populations in these rice ecosystems.