Abstract
Cassava productivity is hampered by pests and diseases including cassava mosaic disease (CMD) and cassava brown streak disease (CBSD). The main objective of this study was to identify stable superior genotypes that combine disease resistance and high yield. Sixteen cassava genotypes were planted in a randomized complete block design with three replications for six planting seasons (years) at five sites in Tanzania. The genotypes were assessed using the additive main effect and multiplicative interaction (AMMI) analysis, and highly significant (P by-environment (G*E) interactions were observed for all traits studied. Percent sum of squares (SS) due to environment (12.66% - 85.23%) was the highest followed by G*E (14.12% - 39.56%) for CMD foliar symptoms, root weight and dry matter. On the other hand, % SS due to genotype (52.14% - 69.14%) was highest followed by G*E (26.14% - 35.91%) for CBSD foliar and root symptoms indicating that the environment and G*E greatly influenced trait expression. The most stable genotypes which combined disease resistance and high yield were NDL 2003/31 and NDL 2003/111. The findings of this study will give impetus for the release of new cassava varieties that are not only high yielding but are also dually resistant to both CMD and CBSD in different locations and sites.
Highlights
Cassava (Manihot esculenta Crantz) is a vital food staple in sub-Saharan Africa (SSA), ranked as the number one root crop, followed by sweet potato and yam [1]
G*E interaction SS was partitioned into four significant Interactive Principal Components Axes (IPCAs) for cassava mosaic disease (CMD) 3 MAP while CMD 6 and 9 MAP had three significant IPCAs
This justified the use of AMMI2 (IPCA2 vs IPCA1) biplot model for CMD foliar symptoms
Summary
Cassava (Manihot esculenta Crantz) is a vital food staple in sub-Saharan Africa (SSA), ranked as the number one root crop, followed by sweet potato and yam [1]. Tanzania has the largest area (885,091 ha) under cassava production in East Africa, its average yield is low at 5.7 t/ha [1], which is far below the estimated yield potential of cassava (50 - 60 t/ha) [8]. This is due to many biotic and abiotic factors including the two viral diseases: cassava mosaic disease (CMD), and cassava brown streak disease (CBSD) [9] [10] [11]. Dual infections of CMD and CBSD are common and a serious threat to cassava production and food security as losses more than 80% have been reported in susceptible varieties [13]
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