School of Agricultural Sciences (SAS)
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Browsing School of Agricultural Sciences (SAS) by Author "Adriko, J."
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ItemResponse of improved cassava varieties in Uganda to cassava mosaic disease (CMD) and their inherent resistance mechanisms(Academic Journals, 2011) Adriko, J. ; Sserubombwe, W.S. ; Adipala, E. ; Bua, A. ; Thresh, J.M. ; Edema, R.Field based trials were setup to evaluate response and inherent resistance mechanisms to cassava mosaic disease (CMD) of four improved varieties; Nase 9, Nase 11, 00036 and 00057 together with Nase 4 and Bao as resistant and susceptible standards, respectively. These were grown in a CMD epidemic hotspot at Namulonge in Central Uganda. There were differences in sensitivity to CMD and whitefly populations among tested varieties. The improved varieties were less affected by CMD than the susceptible standard Bao. Three resistance mechanisms were exhibited by the varieties tested, namely; low infectibility (00036), recovery (Nase 9 and Nase 11) and reversion. Two of the varieties, that is, Nase 4 and 00057 showed all three resistance mechanisms. High whitefly populations characterized Bao, Nase 4 and 00057. Most of the varieties had a higher infestation of whiteflies on healthy than diseased plants. Results also showed that growth and yield parameters depended on the variety, growth stage at infection and health status of the cuttings used with improved varieties recording lower yield losses than the susceptible Bao. Also, plants infected earlier in the growth period suffered higher yield losses. Furthermore, plots planted from diseased cuttings recorded higher yield losses compared to those planted from healthy cuttings.
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ItemResponse of local cassava varieties in Uganda to cassava mosaic virus disease(SCIENCEDOMAIN International, 2012) Adriko, J. ; Sserubombwe, W.S. ; Adipala, E. ; Bua, A. ; Edema, R.Cassava mosaic disease (CMD) resistant varieties have been used to manage CMD in Uganda. In spite the availability of a number of CMD resistant cultivars, several local landraces are continually grown in Uganda because they possess certain desirable traits, which may not have been fully met by the resistant varieties. Field based trials were setup to evaluate the response to CMD of some landraces that became prominent after the 1990s CMD pandemic. Experiments were located in areas where CMD is reported to have subsided namely, Mukono (Central Uganda) and Bulindi (Western Uganda). Three landraces were evaluated per site along with resistant (Nase 4) and susceptible (Bao) standards. Plots were planted with materials obtained from either diseased or healthy fields. The results showed differences in sensitivity to CMD among varieties tested, with landraces consistently having higher CMD incidences than Nase 4. The landraces tested in Mukono were more susceptible to CMD than even the Bao, while at Bulindi on the other hand, only Sibampale proved to be more resistant than Bao. There were differences in the whitefly populations among the cassava varieties and locations. High whitefly populations characterized all landraces and Nase 4. In most tested varieties, there was a higher infestation of whiteflies on healthy than diseased plants. Low spread of CMD among local landraces was observed in Bulindi as would be expected in areas where CMD has almost subsided (low pressure areas). However, in Mukono, disease spread among landraces was very rapid and high CMD incidences reaching 100% were recorded regardless of whether plots were planted with healthy or diseased cuttings suggesting it to be a CMD hot-spot. Thus, the use of clean planting materials as an effective phytosanitary method can only be employed under low disease pressure while high disease pressure areas need use of resistant varieties.