Estimating the potential of sugarcane families to produce elite genotypes using univariate cross prediction methods

A quick, accurate method to determine the potential of a sugarcane (Saccharum spp.) cross to produce elite progeny is needed for maximizing genetic gain. Development of a practical cross appraisal method was initiated by evaluating 1,800 progeny from 15 crosses among 23 parents at two intrarow plant spacings (41 cm and 82 cm). Plant spacing was examined for its affect on stool weight variability. The goals were to identify the most reliable and/or easily obtained cross appraisal statistic and to determine the earliest breeding program stage and crop to collect these statistics. Three tests, on plant cane (PC) and first ratoon (FR) single stool seedlings and clonal plant cane plots, were conducted. Four statistics, the family mean, the estimated elite proportion (PROB), the observed elite proportion, and the best linear unbiased predictor (BLUP) were estimated and examined for each cross. These statistics were strongly correlated within each test (0.69≤r≤1.00). Family worth estimates based on single stool data were moderately correlated (ca. range 0.5≤r≤0.7) to the family worth estimates based on clonal plots.The research suggested that the potential of a cross to produce elite progeny for a trait could be accurately predicted by the cross mean of that trait. Data for the mean were the most easily obtained and, hence, would be the most practical family appraisal statistic to use in a breeding program. Correlations of statistics among the PC and FR seedlings and the clonal plots showed that the PC estimates of Brix, stalk weight, and its components, stalk length and stalk diameter, could be used for cross appraisal. Genotypic selection by the Louisiana Sugarcane Variety Development Program (LSVDP) occurs among the FR seedlings. FR stalk number and PC Brix and stalk weight data could be used to perform family selection prior to the currently practiced individual plant selection. The benefits of family selection to the LSVDP were demonstrated by the expected genetic gains for two selection scenarios. The gains were consistently larger for an initial 50% family selection and subsequent 20% individual selection than they were for simple individual selection at a 10% selection intensity. Our research also suggests that the use of a wider intrarow spacing may improve the ability to discern among seedlings due to its enhancement of stool weight variability.