ISHS Acta Horticulturae 380: Symposium on Tropical Root Crops in a Developping Economy
CASSAVA BREEDING AT CIAT: HERITABILITY ESTIMATES AND GENETIC PROGRESS IN THE 1980S |
| Authors: | Carlos A. Iglesias, Clair H. Hershey |
| DOI: | 10.17660/ActaHortic.1994.380.23 |
| Abstract:
Broad-sense heritability (H) estimates were obtained from regression analysis of data sets of cassava clones evaluated in 8 consecutive years. Estimates were obtained for the two main edapho-climatic zones (seasonally dry and acid soil savannas), two semesters (A and B), and two stages of selection: single row observational trials (OT); and preliminary or advanced yield trials, (PYT/AYT). Pooled estimates had high values of H (0.4–0.6) for traits such as harvest index, reaction to super-elongation disease, and root dry matter, and HCN content; HI values were intermediate (0.2–0.4) for root yield, and visual evaluation of foliage; and HI were low (0–0.2) for visual evaluation of roots, and reaction to bacterial blight. HI estimates based on PYT/AYT were higher for those traits with low and intermediate pooled estimates as compared to those from OT. The realized genetic progress was not consistent with the expected genetic improvement. Improvement for individual traits is expected to be small when selecting for many traits simultaneously. Progress was obtained for root yield, the main selection criterion. For traits with high H such as harvest index or HCN content, there was no progress. Good progress was obtained for resistance to super-elongation disease and dry matter (%) in the last 5 yr. Overall, foliage and root evaluation were complex and highly subjective traits but progress was most evident for foliage evaluation. | |
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