Evaluation of orange -fleshed sweet potato (ipomoea batatas (l) lam) clones for yield, disease and pest resistance and consumer acceptability

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Fifteen orange-fleshed sweet potato clones selected from a preliminary yield trial of thirty (38) sweet potato clones, (thirty - six (36) from International Centre for Potato-Kenya and two locally improved varieties from Crops Research Institute Fumesua) were evaluated in Advanced Yield Trials (AYT) at two agroecological zones (forest and transition) of Ghana in 2006 major season using Randomised Complete Block Design (RCBD) and harvested at 4 month^^er planting.The clones were morphologically characterized using CIP/AVRDC/IBPGR Descriptors for Sweet Potato. Evaluation for yield, insect pests resistance and food quality was done after harvest whilst that for disease was done at 90 days after planting. Results showed that both fresh vine and fresh tuber yields significantly differed between the clones. The results also showed that yields and yield components for all the clones were higher at the forest ecozone (3.55-29.25t/ha) than at the transition (1.5-17.5t/ha). The yield of locally improved variety Apomuden was not significantly different from 75% of the introduced clones. Significant (P<0.05) environment (E), genotype (G) and GxE interaction were observed for percent establishment, percent ground cover, total fresh vine yield, dry matter content and other yield components such as number of tubers per plant and tuber weight. The clones exhibited different levels of susceptibility to sweet potato virus diseases (SPVD) ranging from no apparent damage to considerable damage caused with the disease incidence higher in the forest ecozone. The local variety Jukwa Orange was the most tolerant among the clones. Crop damage by Cylas sp and millipedes was more serious in the forest ecozone than in the transition. The clones showed varying degree of susceptibility to the pests. Jukwa orange, Nemanete, NCI560, Excel and CN 1448-29 showed resistance/tolerance to Cylas sp. Sensory evaluation results indicated that 92.3% of the introduced clones had acceptable cooking characteristics (dry mealy flesh, low fibre content and moderately sweet) due to high percent dry matter. In conclusion the clones showed adaptability to the environmental conditions pertaining in the forest and transition ecozones. Beauregard, Excel, Tainung No.65 and TIS2534 which produced yields above 20t/ha and were resistant to Cylas sp should be considered for further testing to be released to farmers.
A Thesis submitted to the School of Graduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfillment of the requirement for the award of MSc Agronomy degree, 2008.