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The Canal Point (CP) sugarcane (Saccharum spp.) breeding program has developed high-yielding cultivars for the organic soils of South Florida, but cultivar development has not been as successful for sand soils in this region. Our objectives were to improve final-stage (Stage 4) selection efficiency of this program by assessing interactions among genotypes, soils, and locations and other sources of variation and by comparing the relationship between repeatability and number of replications as a measure of precision for testing sugarcane genotypes on sand and muck soils. Sources of variation were partitioned for plant-cane, first-ratoon, and second-ratoon data, from 7 yr and five CP series in Stage 4 tested at eight locations on muck soils and two locations on sand soils. Variation related to genotype x location (soil) was highly significant for cane and sugar yields for all series and crops, but most genotype x soil interactions were nonsignificant. This suggested that planting more Stage-4 tests on sand may improve genotype selection for these soils. The six replications used routinely in Stage 4 provided elevated levels of precision for both soil types. All locations with muck and sand soils in Stage 4 have ample testing resources for discriminating among genotypes. Our results indicate that, to improve sugarcane genotype selection for sand soils, increasing the number of sand locations would be a more successful strategy than increasing replications within locations. doi: 10.2135/cropsci2009.09.0539

Selection for productive sugarcane (Saccharum spp.) cultivars in Florida has been more successful for organic than for sand soils. The objectives of this study were to assess the contributions of a sand-soil location to the final stage of multienvironment testing of sugarcane genotypes in Florida, and to identify locations with organic soils that, if replaced with a sand-soil location, would be least likely to compromise superior cultivar selection for organic soils in Florida. Sixteen genotypes were harvested in two or three crop cycles from 2002 to 2005 at nine locations. Traits analyzed were cane and sucrose yields (Mg [ha.sup.-1]) and theoretical recoverable sucrose (TRS) (g [kg.sup.-1]). The sand-soil location, Lykes, was generally neither highly representative of locations nor highly discriminating of genotypes. Results revealed the desirability of replacing an organic-soil location with a sand-soil location in the final testing stage of this sugarcane breeding and selection program. Caution must be exercised, however, to ensure that such action would not compromise genotype discrimination for TRS and sucrose yield. Ability to identify productive cultivars on organic soils by the Florida sugarcane selection program would be least compromised by replacing either Osceola or Knight with a sand-soil location.

Sugarcane (Saccharum spp.) is a successful crop in the Florida Everglades Agricultural Area (EAA) that is characterized by high-N organic and low-fertility sandy soils, periodic freeze, and flood events. After 50 yr of breeding, the possibility of a yield plateau was investigated in the cooperative Florida sugarcane breeding program via an assessment of yield gains in the industry and an evaluation of the contribution attributed to breeding efforts. Long-term commercial and selection trial data, covering a 33-yr period (1968-2000), were used in single-degree-of-freedom regression analyses to determine rates of improvement in sucrose content (SC; kg [Mg.sup.-1]), cane yield (CY; Mg [ha.sup.-1]), and sugar yield (SY; Mg [ha.sup.-1]). Analyses of commercial data reflected yearly increases of 0.80 ± 0.08 kg Mg t of cane for SC, 0.31 ± 0.10 Mg [ha.sup.-1] for CY, and 0.10 ± 0.01 Mg [ha.sup.-1] for SY. Corresponding gains from selection trial data were 0.74 ± 0.15 kg [Mg.sup.-1] 1.06 ± 0.40 Mg [ha.sup.-1] and 0.16 ± 0.05 Mg [ha.sup.-1] respectively. Improvements were significant for all three traits across plant-cane, and first- and second-ratoon crops grown on organic soils but not on sandy soils. About 69% of the total gain in SY was attributed to the cooperative Canal Point public breeding program, via a greater allocation of assimilates toward sucrose accumulation, resulting in a contribution of $99 to 203 million as additional profits to the Florida economy across the 33 yr. The genetic potential of the working germplasm has not been exhausted (no evidence of a yield plateau for SC) in this sugarcane breeding program. These gains and future advances are possible because of the use of a diverse gene pool and a breeding strategy that integrates growers' participation into the program., COMMERCIAL SUGARCANE CULTIVARS are hybrids that originated from progeny of crosses between 'noble' cane (S. officinarum L.) and its wild relatives (S. spontaneum L., S. sitzense Roxb., or S. barberi [...]

Sugarcane (Saccharum spp.) is the primary crop on the Histosols of the Everglades Agricultural Area (EAA), where periodic floods and undesirably high water tables are increasing in occurrence and duration. Improved understanding of the physiologic responses of sugarcane to these conditions could help develop strategies to sustain high yields. The purpose of this study was to evaluate the effects of periodic flooding followed by drainage to different depths on single-leaf net photosynthetic rate (Ps), transpiration (Ts), and stomatal conductance (SC) of sugarcane. In 2000 and 2001, two sugarcane genotypes were planted as split plots in 12 lysimeters filled with Pahokee muck soil. Responses of Ps, Ts, and SC to four water-table treatments were measured for four 21-d cycles each year. Three treatments consisted of 7-d flooding followed by 14-d drainage to depths of 16, 33, or 50 cm. The fourth treatment was a continuous 50-cm water table. Analyses of individual cycles and analyses repeated over cycles generally identified neutral or positive responses of Ps, Ts, or SC to flood. Drained water-table depth did not consistently affect Ps, Ts, or SC, but when differences occurred, 16 cm was often a favorable drainage depth. These neutral and sometimes positive responses to short-duration flood or long-duration high water tables support previous reports of acceptable and sometimes enhanced yields from sugarcane exposed to high water tables. Previous findings were supported that time of formation of stalk aerenchyma in sugarcane may be a key factor for sustaining high yields after exposure to flood., THE EAA is a 280 000-ha basin of Histosols that lie on limestone bedrock in the northern region of the historic Everglades in Florida. Sugarcane is grown on about 148 [...]

The purposes of this article are, first, to present agricultural, ecological, and hydrological evidence that controlling soil subsidence in the Everglades Agricultural Area (EAA) while growing conventional crops may be [...]

Superior genotypes of sugarcane (interspecific hybrids of Saccharum spp.) must continue to be developed with current resources as selection criteria evolve and expand. Developing future cultivars of sugarcane for the Everglades Agricultural Area (EAA) of South Florida with high water table tolerance and increased P-uptake efficiency could be an integral part of Everglades restoration. The objective of this study was to assess the current allocation of resources in the final selection phase of cultivar (clonal) development of the Canal Point, FL, sugarcane breeding program. Variance component analyses were conducted on elite genotypes from 7 yr of trials. Variance components were used to compare relative magnitudes of sources of variation and to explore more efficient use of resources. Variation attributable to crop x location interaction was nearly always the largest relative source of variation next to the residual term. The contributions to variance due to genotype x crop and genotype x location interactions were low, though these interactions cannot be discounted in cultivar release decisions. Variance due to replications was extremely low. Four statistics were used as metrics of experimental precision when reducing the number of replications. Reducing replications from eight to four did not compromise experimental precision. Removing the second-year planting sequence compromised little, if any, useful information for effective cultivar release decisions. Better allocation of resources could be achieved by alternative experimental design scenarios. Testing for high water table tolerance or P-uptake efficiency could also be included, improving ecological compatibility of agriculture in the EAA., THE SUGARCANE CULTIVAR development program of he USDA/ARS, Florida Sugar Cane League, Inc., and University of Florida consists of four clonally propagated selection stages beyond the initial planting of seedlings [...]