Quality and Yield stability of Orange Fleshed Sweet Potato( Ipomoea batatas(L.)lam.) Varieties in Different Agro-Ecologies.
Date
2011-02-18
Authors
Mbwaga, Zabron
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Abstract
Orange fleshed sweet potatoes Ipomoea batatas (L.)Lam) has high B-carotene content which is useful in preventing vitamin A deficiency. Unfortunately suitable varieties of orange fleshed absent. The results from Participatory Rural Appraisal (PRA) conducted in three villages of southern highlands of Tanzania revealed that, most varieties grown are white and cream fleshed. Yields mentioned to be very low ranging from 4.5 to 7.0 t ha-1. A gap difference of 15.5t ha-1 from potential yield mean were estimated. Based on the above findings a study was conducted to determine the adaptability of orange fleshed sweet potato varieties in different agro-ecologies , so as to identify varieties which can suit to the wider environments. Specifically determining beta-carotene and yield stability across different environments. Multilocational field trials involving 12 yellow/orange –fleshed sweet potato varieties were conducted at six different locations (altitude range from 495 and 1798 meters above sea level) in the southern highlands of Tanzania. A randomized complete block design was employed. Tuber yield and B-carotene content of the roots were determined at maturity. B-carotene concentration of the roots was analysed by high performance liquid chromatograph method. Results showed that genotype and environment influence d B-carotene concentration of sweet potato roots. Varieties 199024.1, SPK004, 101055 and Resisto produced high concentrations of B-carotene. These were 28.74, 28.30, 27.8 and 27.7ug/100g respectively. Out of these, varieties 199004.2 (b=0.89) and 101055(b=0.78) considered to have stable performance in terms of B-carotene and stable performance suggested wider adaptation. The B-carotene content in sweet potato roots showed no clear trends with increasing or decreasing altitude for most of the varieties tested. Yields were significantly different (P<0.05) among varieties and across sites. Varieties, Resisto 440443, SPNO, 102020.2, 199024.1 and Carot-Dar displaced near the center of AMMI biplot. These were considered stable in terms of yield performance, according to addictive Main effect and Multiplicative Interaction (AMMI) biplot. Out of the varieties, varieties 440443 and 199024.1 had high yield and stability. These varieties were considered to have wider adaptation .Storage root yield and B-carotene showed low significant negative correlation ( r=-0.1092, P<0.05), while, yield and dry matter, B-carotene and dry matter content were none significantly correlated. This effect signified possibly of getting varieties that can combine these traits at high levels through conventional breeding. Further study was recommended to explore the nature of sweet potato B- carotene content variation with environments.
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Keywords
Oranged Fleshed Sweet Potato-Varieties , Quality and Yield of Orange Fleshed Sweet Potato