Selection in Two Seedling Crops of Four Sugarcane Progenies

Abstract

Phenotypic correlations were obtained among stalk number, stalk diameter, and Brix, within and among the plant‐cane seedling crop, first‐ratoon seedling crop, and the plant‐cane clonal crop, in progenies of four sugarcane (Saccharum spp.) crosses. Associations among characters within crops were low.The correlation coefficients for stalk number were .378** and .363** between the plant‐cane clonal crop and the plant‐cane and first‐ratoon seedling crops, respectively. Stalk diameter was more closely associated than stalk number between the plant‐cane clonal crop and the plant‐cane seedling crop (r : .618"*). Correlation coefficients for stalk diameter between the clonal crop and first‐ratoon seedling crop were heterogeneous among progenies and ranged from .406** to .673**. Stalk diametera ppearedto be a morer eliable selection criterion than stalk number, particularly in plant‐cane seedlings. Correlation coefficients for Brix among the crops were about equal to those for stalk number, indicating that the two characters were less reliable than stalk diameter, as sdection criteria.Various culling levels imposed on the plant‐cane and first‐ratoon seedling crops indicated that effectiveness of selection was equal when the same selection pressure was applied in both crops. Results were similar with independent and simultaneous selection for the three characters. These data indicated that the most reliable selection criterion was stalk diameter. Stalk numberw as less reliable than either stalk diameter or Brix.Selected populations could be obtained with high frequencies of segregates acceptable for stalk diameter. The trequency of segregates acceptable for stalk numbera nd Brix could be increased by selection, but populations with high frequencies of acceptable segregates could be obtained only when levels of acceptability were low.