Field Assessment and Inheritance of Cassava Resistance to Superelongation Disease
1983
Kawano, Kazuo | Umemura, Yoshiki | Kanō, Yoshiaki
Effects of superelongation disease, caused by the fungus Elsinoe Brasiliensis Zeigler and Lozano, on cassava (Manihot esculenta Crantz) clones (different genotypes) were studied in fields under high natural disease infection to assess value of genetic resistance and efficiency of field selection. The disease caused 20 to 70% yield reduction on susceptible clones relative to resistant clones depending on planting time and presence of cassava bacterial blight. Susceptible clones could not produce good planting stakes for next plantings. On resistant clones, the disease spread slowly while on susceptible ones it spread rapidly causing abnormal stem elongation and leaf death. Resistance was a quantitative trait controlled largely by additive genetic factors and not negatively correlated with yielding ability per se. Cultivar order of resistance was stable over 8 years of observation. Use of resistant parents in hybridizations combined with simple phenotypic field selection under high natural disease pressure should effectively improve resistance of cassava cultivars.
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