Early Stage Sugarcane Selection Using Different Plot Sizes
2007
Milligan, Scott B. | Balzarini, Monica | Gravois, Kenneth A. | Bischoff, Keith P.
Most sugarcane (Saccharum spp.) cultivar development programs use single-row plots in their first clonal trials. We hypothesized that a larger plot size would increase the accuracy of selection and compared selection efficiencies of 1.82-, 3.35-, and 4.88-m single-row plots. The 1.82-m plots generated larger genetic and residual variances than the larger plot sizes for sugar and cane yields and stalk number and weight but not for sugar concentration. Broad-sense heritabilities for yield components for the examined plot sizes differed little. Genetic correlations for the same trait among the plot sizes were high for most traits except stalk number. Consequently, the correlated response in larger plots to selection for the same trait selected in small plots was not affected by plot size. The proportion needed to confidently retain the top 1% of the genotypes was also not affected by plot size but was very high (>80%) for sugar and cane yields. It was substantially lower for sugar concentration and stalk weight (<43%), whereas it was higher (43–55%) for stalk number. The estimated probability of retaining the top genotypes by selecting the top 33% of the population was 59 to 66% for sugar and cane yields, but it ranged from 77 to 90% for the other yield components. Thus, increasing the plot size would not improve the selection efficiency of the program, but the study highlighted that there was still room for improvement in the initial stage of selection.
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