Abstract
Despite the significance of cassava as food, feed and industrial root crop, little is known regarding the gene action determining root dry matter content (RDMC), fresh root yield, and tolerance to cassava mosaic disease (CMD), cassava green mite (CGM), and cassava mealy bug (CMB). Thus, a study was conducted to determine the general and specific combining abilities for disease, pest, RDMC, root yield and related traits by crossing 10 parents in a 6 × 4 line by tester design. The F1 progenies and their parents were assessed in-field in a randomized complete block design (RCBD) with three replicates. Findings implied sufficient genetic variability for all traits studied. Family TMEB419×IBA030305 had the highest RDMC of 35.47%, whilst family TMEB7×IBA0000203 had the least RDMC (23.87%). Genotypes IBA020588, IBA916132 and TMEB419 were the best parents for improvement of harvest index (HI) and RDMC due to its high positive and significant GCA effects. Genotype IBA000203 contributed the highest to increased plant height, whereas TMEB1, TMEB47 and ZAR010116 had significant negative GCA effects. ZAR010116 was the best tester for HI. Families TMEB778×ZAR010116 (34.23) and IBA020588×ZAR010116 (32.78) were the best performing families for mean RDMC, with parent ZAR010116, exhibiting the highest GCA effect for RDMC. Families TMEB419×ZAR000156, IBA916132×ZAR000156 and IBA020588×IBA000156 had low mean CMD scores of 1.1, 1.2 and 1.2, respectively. The preponderance of non-additive gene actions indicated that selection of superior plants should be postponed to later generation. Key words: Cassava, genetic improvement, agronomic traits, combining ability, heritability, progeny performance.
Highlights
Analysis of variance showed that mean squares due to crosses were significant for traits such as plant height (PHT), number of storage root (NSR), cassava bacterial blight (CBB), fresh storage root weight (FSRW) and harvest index (HI) and highly significant for cassava green mite (CGM) (Table 1)
Mean squares values for line were highly significant for CGM and significant for PHT, NSR, CBB, FSRW, HI and root dry matter content (RDMC)
The mean squares values for testers were significant for PHT, cassava mosaic disease (CMD), CBB and HI
Summary
Cassava (Manihot esculenta Crantz) is an important staple food crop consumed by over 800 million people. Cassava has varying food, feed and industrial applications that support many livelihoods around the world. In Sierra Leone, cassava is the most consumed root crop. Cassava fresh storage roots are enrich in starch and possess small amounts of calcium (16 mg/100 g), phosphorus (27 mg/100 g), vitamin C (20.6 mg/100 g), minute quantities of protein and other nutrients (USDA, 2016). The leaves of cassava are consumed in the country as vegetables since they contain protein such as lysine, but lack the amino acid methionine and possibly tryptophan (FAO, 2010). Other cassava products utilized in the country include cassava pellets for animal feed, cassava starch for sweeteners, thickeners and textile paper industry (Chipeta et al, 2013)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
