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Selection in Six Crops of Sugarcane. II. Efficiency and Optimum Selection Intensities

Selection was applied for stalk number, stalk diameter, and Brix in six crops of a population of 376 sugarcane (Saccharum sp.) clones with intensities from 2 to 100%. In both cost and land use, efficiency of selection for stalk number was somewhat greater in the plant crop of seedlings and 1.2-m clonal plots than in the first ratoon crops. For stalk diameter, efficiency was equal in the plant and ratoon seedling crops and greater in the plant crop than in the ratoon crop of 1.2-m clonal plots. Selection efficiency for Brix was somewhat greater in the ratoon crop than in the plant crop of seedlings and about equal in both crops of 1.2-m clonal plots.

The optimum intensity for independent selection of stalk number and stalk diameter was 40% in both plant and first ratoon crops of seedlings. The optimum selection intensity for Brix in the plant crop of seedlings ranged from 30 to 50% and in the first ratoon crop of seedlings was 40%. In the plant crop of 1.2-m clonal plots, the optimum selection intensity was 50% for the three characters. In the first ratoon crop, optimum selection intensities were 60, 40, and 40% for stalk number, stalk diameter, and Brix, respectively.

The optimum simultaneous selection intensity for the three characters in the plant crop of seedlings ranged from 4.8 to 8% and was 6.4% in the first ratoon crop of seedlings. Optimum selection intensities in the 1.2-m clonal plots were 12.5% and 9.6% in the plant and first ratoon crops, respectively.

At the optimum selection intensities, gains from selection were 8 to 10% for stalk number and diameter and 4 to 5% for Brix.

Key Words: Land-use efficiency • Cost efficiency • Gain from selection • Stalk number • Stalk diameter • Brix

Received for publication May 6, 1974.