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Obtaining greater genetic gains, particularly for biomass yield, requires a good understanding of the gene action governing the inheritance of traits with economic importance in switchgrass (Panicum virgatum L.). Individual genotypes from three different accessions were crossed in single-pair matings with reciprocals to assess the relative importance of additive to nonadditive genetic variation and the potential of using inter-ecotypic crosses to improve dry matter yield (DMY), in vitro dry matter digestibility (IVDMD), lignin content (ADL and KL), and ethanol yield (ETOH). Crosses and four reference populations were planted in a randomized complete block design with eight replications of single family-rows plots, with five-plants each and 1 m spacings. A linear mixed model was applied as per the restricted maximum likelihood method, integrated with a pedigree tracing back to the original founders of these parental populations, and augmented with the designation of four genetic groups. Variation due to SCA (specific combining ability) was predominant for all traits, contributing from 20% to 57% of the total phenotypic variation and with Baker’s ratios (GCA/SCA) varying from 0.003 to 0.67. Heritability values calculated at the fullsib-family mean level were moderate to very high. Variation due to GCA (general combining ability) was detected with a lesser significance for DMY and ETOH. A reciprocal GCA effect was present in the form of maternal inheritance for DMY, suggesting the use of the highest biomass-yielding parent as female in inter-ecotypic breeding. Selecting and deploying fullsib families, deploying clonal hybrids, and adopting an introgression breeding approach are all possibilities available to switchgrass breeders to exploit the complementary genes from this germplasm and capitalize on the non-additive genetic variation present in these crosses.

Switchgrass (Panicum virgatum L.) has been subject to breeding to improve its yield and composition for bioenergy. Increased tolerance of environmental stress is another factor that can improve yields over the life span of a field plot. Natural ploidy series act as somewhat distinct gene pools in switchgrass that maintain differences with respect to tolerance of environmental stress and which can only be bridged through whole genome reduction or duplication events. In order to document potential wide-ranging effects of whole genome duplication, we examined the effects of water stress on growth, physiology, and gene expression in individual tetraploid clones of the switchgrass cultivar “Liberty” as well as neo-octoploid lines derived from it. The neo-octoploids behaved similarly to Liberty under water stress and recovery conditions: Water-stressed plants had approximately 50% or greater reduction of biomass, plant height, and node numbers. Tiller number and photosynthesis rates of stressed plants were reduced by up to 50%, while proline levels were significantly higher in stressed plants than well-watered plants. A total of 6134 differentially expressed genes (8% of the annotated genes with detectable expression in crown tissue) were detected under water-deficit stress, while 3310 differentially expressed genes were detected in crown tissue after 1 week of recovery from water-deficit stress relative to well-watered treatments. Only 187 genes were identified as being differentially expressed between 4x Liberty and its 8x derivatives. This study indicates neo-octoploids could be viable 8x-equivalent Liberty stand-ins for future breeding assays.

Panicum mosaic virus (PMV) (genus Panicovirus, family Tombusviridae) and its molecular parasite, Satellite panicum mosaic virus (SPMV), synergistically interact in coinfected proso and pearl millet (Panicum miliaceum L.) plants resulting in a severe symptom phenotype. In this study, we examined synergistic interactions between the isolates of PMV and SPMV by using PMV-NE, PMV85, SPMV-KS, and SPMV-Type as interacting partner viruses in different combinations. Coinfection of proso millet plants by PMV-NE and SPMV-KS elicited severe mosaic, chlorosis, stunting, and eventual plant death compared with moderate mosaic, chlorotic streaks, and stunting by PMV85 and SPMV-Type. In reciprocal combinations, coinfection of proso millet by either isolate of PMV with SPMV-KS but not with SPMV-Type elicited severe disease synergism, suggesting that SPMV-KS was the main contributor for efficient synergistic interaction with PMV isolates. Coinfection of proso millet plants by either isolate of PMV and SPMV-KS or SPMV-Type caused increased accumulation of coat protein (CP) and genomic RNA copies of PMV, compared with infections by individual PMV isolates. Additionally, CP and genomic RNA copies of SPMV-KS accumulated at substantially higher levels, compared with SMPV-Type in coinfected proso millet plants with either isolate of PMV. Hybrid viruses between SPMV-KS and SPMV-Type revealed that SPMV isolates harboring a CP fragment with four differing amino acids at positions 18, 35, 59, and 98 were responsible for differential synergistic interactions with PMV in proso millet plants. Mutation of amino acid residues at these positions in different combinations in SPMV-KS, similar to those as in SPMV-Type or vice-versa, revealed that A35 and R98 in SPMV-KS CP play critical roles in enhanced synergistic interactions with PMV isolates. Taken together, these data suggest that the two distinct amino acids at positions 35 and 98 in the CP of SPMV-KS and SPMV-Type are involved in the differential synergistic interactions with the helper viruses.

Estimating genetic parameters is an essential step in breeding by recurrent selection to maximize genetic gains over time. This study evaluated the effects of selection on genetic variation across two successive cycles (C1 and C2) of a ‘Summer’x‘Kanlow’ switchgrass (L.) population. Two progeny tests were planted in 2007 and 2011 near Mead, NE and respectively analyzed for 2 and 4 yr. Each test was a randomized complete block design, with four replicates of 34 halfsib families in single-row plots of 10 seedlings in C1 and with three replicates of 111 halfsib families in single-row plots of five seedlings in C2. The C2 test included C0, C1, and parental populations for comparison. Multivariate mixed linear models revealed ample additive genetic variation for dry matter yield (DMY), Klason lignin (KL), and predicted ethanol yield (ETOH) in both cycles, with heritability ranging from 0.40±0.18 to 0.5±0.14 at the family level, from 0.22±0.17 to 0.36±0.22 at the individual level, and from 0.25 to 0.31 within family in C1. Matching values in C2 were: from 0.42±0.09 to 0.63±0.07, from 0.10±0.07 to 0.34±0.13, and from 0.12 to 0.48. More opportunity exists to improve DMY, with a coefficient of additive genetic variation of 11 to 32%, than KL (3–5%) or ETOH (3–6%). The traits were properly aligned for joint improvement for high DMY and reduced KL in C1, owing to favorable genetic correlations (=−0.33±0.11) and each having respective of 0.600.05 and −0.620.07 with ETOH. In C2, the between DMY and KL (−0.19±0.10) or ETOH (0.04±0.04) decreased towards zero, and that between KL and ETOH was moderately less negative (−0.35±0.15). These results suggest a strong genetic basis for improvement of the traits and monitoring of their patterns every cycle to find the proper weights that maximize the breeding goal of designing the ideal bioenergy switchgrass.

The genetics and responses to biotic stressors of tetraploid switchgrass (Panicum virgatum L.) lowland cultivar 'Kanlow' and upland cultivar Summer are distinct and can be exploited for trait improvement. In general, there is a paucity of data on the basal differences in transcription across tissue developmental times for switchgrass cultivars. Here, the changes in basal and temporal expression of genes related to leaf functions were evaluated for greenhouse grown 'Kanlow', and 'Summer' plants. Three biological replicates of the 4th leaf pooled from 15 plants per replicate were harvested at regular intervals beginning from leaf emergence through senescence. Increases and decreases in leaf chlorophyll and N content were similar for both cultivars. Likewise, multidimensional scaling (MDS) analysis indicated both cultivar-independent and cultivar-specific gene expression. Cultivar-independent genes and gene-networks included those associated with leaf function, such as growth/senescence, carbon/nitrogen assimilation, photosynthesis, chlorophyll biosynthesis, and chlorophyll degradation. However, many genes encoding nucleotide-binding leucine rich repeat (NB-LRRs) proteins and wall-bound kinases associated with detecting and responding to environmental signals were differentially expressed. Several of these belonged to unique cultivar-specific gene co-expression networks. Analysis of genomic resequencing data provided several examples of NB-LRRs genes that were not expressed and/or apparently absent in the genomes of Summer plants. It is plausible that cultivar (ecotype)-specific genes and gene-networks could be one of the drivers for the documented differences in responses to leaf-borne pathogens between these two cultivars. Incorporating broad resistance to plant pathogens in elite switchgrass germplasm could improve sustainability of biomass production under low-input conditions.

Switchgrass (Panicum virgatum L.) exists as multiple cytotypes with octaploid (8x) and tetraploid (4x) populations occupying distinct, overlapping ranges. These cytotypes tend to show differences in adaptation, yield potential, and other characters, but the specific result of whole-genome duplication is not clear and 8x and 4x switchgrass populations are reproductively isolated with limited genetic exchange. To create new opportunities for population improvement and to study the effects of whole genome duplication on switchgrass, seedling treatment of the tetraploid cultivar Liberty with microtubule inhibitors was used to generate an octaploid population. Resulting octaploids, tetraploids, and cytochimeras were resolved by intercrossing octaploid sectors to produce a population of 19 octaploid families. Fertility of octaploid sectors was significantly reduced relative to tetraploid sectors and caryopsis size significantly increased. Cell size was significantly increased which resulted in quantitative changes to leaf anatomy. During seedling and early vegetative growth stages, no differences in vigor or tillering ability were seen. This technique resulted in efficient genome doubling and was simple to perform. However, aneuploids were also identified with both larger and smaller than expected genome sizes.

Biofuels and bio-based products can be produced from a wide variety of herbaceous feedstocks. To supply enough biomass to meet the needs of a new bio-based economy, a suite of dedicated biomass species must be developed to accommodate a range of growing environments throughout the USA. Researchers from the US Department of Agriculture’s Agricultural Research Service (USDA-ARS) and collaborators associated with the USDA Regional Biomass Research Centers have made major progress in understanding the genetics of switchgrass, sorghum, and other grass species and have begun to use this knowledge to develop new cultivars with high yields and appropriate traits for efficient conversion to bio-based products. Plant geneticists and breeders have discovered genes that reduce recalcitrance for biochemical conversion to ethanol and drop-in fuels. Progress has also been made in finding genes that improve production under biotic and abiotic stress from diseases, pests, and climatic variations.

Switchgrass (Panicum virgatum), a perennial, polyploid, C4 warm-season grass is among the foremost herbaceous species being advanced as a source of biomass for biofuel end uses. At the end of every growing season, the aerial tissues senesce, and the below-ground rhizomes become dormant. Future growth is dependent on the successful over-wintering of the rhizomes. Although the importance of rhizome health to overall year-upon-year plant productivity has been long recognized, there is limited information on seasonal changes occurring during dormancy at both the transcriptome and metabolite levels. Here, global changes in transcriptomes and metabolites were investigated over two growing seasons in rhizomes harvested from field-grown plants. The objectives were: (a) synthesize information on cellular processes that lead to dormancy; and (b) provide models that could account for major metabolic pathways present in dormant switchgrass rhizomes. Overall, metabolism during dormancy appeared to involve discrete but interrelated events. One was a response to abscisic acid that resulted in dehydration, increases in osmolytes and upregulation of autophagic processes, likely through the target of rapamycin complex and sucrose non-fermentative-related kinase-based signaling cascades. Another was a recalibration of energy transduction through apparent reductions in mitochondrial oxidative phosphorylation, increases in substrate level generation of ATP and reducing equivalents, and recycling of N and possibly CO2 through refixation. Lastly, transcript abundances indicated that cold-related signaling was also occurring. Altogether, these data provide a detailed overview of rhizome metabolism, especially during dormancy, which can be exploited in the future to improve winter survival in switchgrass.

‘CPCL 05-1102’ (Reg. No. CV-157, PI 667556) sugarcane (a complex hybrid of spp.) is the product of research initiated by the United States Sugar Corporation (USSC) and completed cooperatively by the USDA-ARS, the University of Florida, and the Florida Sugar Cane League, Inc. CPCL 05-1102 was released to growers in Florida on 16 Oct. 2012. CPCL 05-1102 was selected from a cross between the USSC proprietary cultivars CL 89-5189 (female) and CL 88-4730 (male) made at Clewiston, FL on 18 Dec. 2000. CL 89-5189 was adapted to muck soils, where it was used only briefly in commercial plantings of USSC due to yield losses to ratoon stunt (caused by subsp.). CL 88-4730 is widely used on commercial plantings of USSC, particularly on sand soils. CPCL 05-1102 has acceptable resistance to leaf scald (caused by Ashby, Dowson), strain E (mosaic), smut (caused by Sydow & P. Sydow), orange rust (caused by E.J. Butler), and brown rust (caused by H. & P. Sydow). 1, a major gene for resistance to brown rust, was not detected in the DNA of CPCL 05-1102. CPCL 05-1102 has high cane and sucrose yields and excellent freeze tolerance and is expected to be used on muck soils in Florida.

A better understanding of sugarcane (Saccharum spp.) genetic variability in agronomic performance will help optimize breeding and selection strategies. Vigor ratings and Brix data were collected from the 2009 and 2010 clones in the first clonal selection stage (stage I) of the Canal Point (CP) sugarcane cultivar development program. Stage I individual selection was based on disease resistance and on the product of vigor and Brix. Vigor ratings (from 1 to 9) from all clones and Brix of any clones with a vigor rating ≥6 were collected in the stage I fields and analyzed for relationships between vigor and Brix, for selection rate in each family (i.e., cross), and for their coefficients of variation (CV) within and among families. There was no correlation between vigor and Brix, suggesting that it would be feasible in stage I to select sugarcane clones with both high vigor and high Brix. Variability was high (CV = 59%) for both the number of planted clones and selection rates among families, and vigor (7.2%) ...

CPCL 00-4111' (Reg. No. CV-144, PI 660673) sugarcane (a complex hybrid of Saccharum spp.) is the latest in a series of commercial sugarcane cultivar releases developed by the United States Sugar Corporation (USSC) and completed by the cooperative Canal Point sugarcane breeding and selection program, which included the USDA-ARS, the University of Florida, and the Florida Sugar Cane League, Inc. CPCL 00-4111, which was released in Florida on 18 Feb. 2011, was selected from a cross of genotype CL 83-3431 × CL 89-5189 made at Clewiston, FL on 4 Dec. 1998. The female and male parents, CL 83-3431 and CL 89-5189, respectively, are proprietary genotypes of USSC. CPCL 00-4111 was released because of its high cane yield and commercial recoverable sucrose on organic (muck) soils and because of its resistance to brown rust (caused by Puccinia melanocephala H. & P. Sydow), orange rust (caused by Puccinia kuehnii E.J. Butler), smut (caused by Ustilago scitaminea H. & P. Sydow), and Sugarcane mosaic virus strain E (the causal agent of mosaic), as well as its moderate resistance to leaf scald (caused by Xanthomonas albilineans (Ashby) Dowson). All of these diseases are of economic importance to sugarcane production in Florida.

Background The definition of prosthesis-patient mismatch (PPM) remains to be refined to enhance its prognosis insight after SAVR, especially in obese patients. Purpose To test the prognostic impact of effective and predicted prosthetic orifice area (OA) according to body weight status after surgical aortic valve replacement (SAVR) for severe aortic stenosis (AS). Methods Between 2009 and 2016, we prospectively explored all consecutive patients referred to our Heart Valve Clinic for a first SAVR for severe AS. Indexed OA predicted from reference normal value (iPOA) and calculated by transthoracic echocardiography (iEOA) were assessed at discharge. Patients were followed for major events (ME), i.e. cardiovascular death, cardiac hospitalization for acute heart failure and stroke. Results 762 patients were included with a mean follow-up of 4 ± 2.5 years. Severe PPM was more frequently observed with iEOA than iPOA (20.5% vs. 7%, P Conclusion iEOA with the unique cut-off of 0.85 cm2/m2 showed the best accuracy to predict ME after SAVR in lean and overweight but not in obese patients. Further studies are needed to explore the lack of prognostic insight of PPM in obese patients.

Research to develop ‘CPCL 99–4455’ (Reg. No. CV-142; PI 659802) sugarcane (a complex hybrid of Saccharum spp.) was initiated by the United States Sugar Corporation (USSC) and completed cooperatively by the USDA-ARS, the University of Florida, and the Florida Sugarcane League, Inc. CPCL 99–4455 was released to growers in Florida on 15 Dec. 2009. CPCL 99–4455 was selected from a cross of the USSC proprietary genotype CL 90–4643 × ‘CP 84–1198’ made at Clewiston, FL on 22 Dec. 1998. The female parent, CL 90–4643, has high yields of cane and sucrose but it is not used commercially by the USSC because of susceptibility to Sugarcane mosaic virus strain E. The male parent, cultivar CP 84–1198, has moderately high commercial recoverable sucrose (CRS) and cane yields and has been grown commercially on about 1–5% of Florida’s sugarcane acreage since 1996. CPCL 99–4455 is moderately resistant to smut (caused by Ustilago scitaminea Sydow & P. Sydow), brown rust (caused by Puccinia melanocephala H. & P. Sydow), orange rust (caused by Puccinia kuehnii E.J. Butler), leaf scald (caused by Xanthomonas albilineans Ashby, Dowson), and Sugarcane mosaic virus strain E. CPCL 99–4455 is expected to be used mostly on organic (muck) soils in Florida, where it had high CRS and acceptable yields of cane in our tests.

The Canal Point (CP) sugarcane (Saccharum spp.) breeding program has developed highyielding 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 fi nal-stage (Stage 4) selection effi ciency 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, fi rst-ratoon, and second-ratoon data, from 7 yr and fi ve CP series in Stage 4 tested at eight locations on muck soils and two locations on sand soils. Variation related to genotype × location (soil) was highly signifi cant for cane and sugar yields for all series and crops, but most genotype × soil interactions were nonsignifi cant. 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. USDA-ARS, Sugarcane Field Station, 12990 US Hwy. 441 N., Canal Point, FL 33438. Received 23 Sept. 2009. *Corresponding author (ali

Research to develop ‘CPCL 97-2730’ (Reg. No. CV-137, PI 655943) sugarcane (a complex hybrid of Saccharum spp.) was initiated by the United States Sugar Corporation (USSC) and completed cooperatively by the USDA–ARS, the University of Florida, and the Florida Sugar Cane League, Inc. CPCL 97-2730 was released to growers in Florida in December 2008. CPCL 97-2730 was selected from a cross of USSC proprietary genotypes CL 75-0853 × CL 88-4730 made at Clewiston, FL, in December 1996. The female parent, CL 75-0853, had high commercial recoverable sucrose (CRS) but because of low cane yields was not used extensively by USSC. The male parent, CL 88-4730, is a high-yielding genotype that USSC is evaluating in commercial fi elds with sand and muck soils for possible extended use. CPCL 97-2730 was released because of its acceptable yields of cane and CRS on sand soils and its resistance to smut (caused by Ustilago scitaminea Syd. & P. Syd.), brown rust (caused by Puccinia melanocephala Syd. & P. Syd.), orange rust [caused by P. kuehnii (Kruger) E. Butler], leaf scald [caused by Xanthomonas albilineans (Ashby) Dowson], and sugarcane mosaic virus strain E.

'CP 01-1372' (Reg. No. CV-136, PI 655942) sugarcane (a complex hybrid of Saccharum spp.) was developed through cooperative research conducted by the USDA―ARS, the University of Florida, and the Florida Sugar Cane League, Inc., and was released to growers in Florida in December 2008. CP 01-1372 was selected from a cross of genotype CP 94-1200 x 'CP 89-2143' made at Canal Point, FL, in December 1998. The female parent, CP 94-1200, was advanced to the final selection stage (Stage 4) of the Canal Point sugarcane cultivar breeding and selection program. The male parent, CP 89-2143, is a major sugarcane cultivar in Florida. CP 01-1372 was released because of its high cane yield and commercial recoverable sucrose on both organic and sand soils, and its acceptable levels of resistance to brown rust (caused by Puccinia melanocephala Syd. & P. Syd.), orange rust [caused by P. kuehnii (Kruger) E. Butler], leaf scald [caused by Xanthomonas albilineans (Ashby) Dowson], Sugarcane mosaic virus strain E (mosaic), and ratoon stunt (caused by Clavibacterxyli subsp. xyli Davis et al.) in Florida.

CP 00-1446' (Reg. No CV-133, PI 654092) sugarcane (a complex hybrid of Saccharum spp.) was developed through cooperative research conducted by the USDA-ARS, the University of Florida, and the Florida Sugar Cane League, Inc., and was released to growers in Florida in September 2007. CP 00-1446 was selected from a cross of genotypes CP 93-1607 × CP 91-1150 made at Canal Point, FL, in January 1998. The female and male parents were advanced to the penultimate selection stage (Stage 3) and the fi nal stage (Stage 4), respectively, of the Canal Point sugarcane cultivar breeding and selection program. CP 00-1446 was released and recommended for sand soils in Florida because of its high plant cane and acceptable ratoon per hectare yields of cane and sucrose and commercial recoverable sucrose on sand soils, and its acceptable disease reactions to smut (caused by Ustilago scitaminea (Sydow & P. Sydow)) (moderately susceptible), brown rust (caused by Puccinia melanocephala H. & P. Sydow) (moderately resistant), orange rust (caused by Puccinia kuehnii E.J. Butler) (moderately resistant), leaf scald (caused by Xanthomonas albilineans Ashby, Dowson) (resistant), Sugarcane mosaic virus strain E (mosaic) (moderately susceptible), and ratoon stunting disease (caused by Clavibacter xyli subsp. xyli Davis) (resistant) in Florida.

'CP 00-2180' (Reg. No. CV-134, PI 654093) sugarcane (a complex hybrid of Saccharum spp.) was developed through cooperative research conducted by the USDA-ARS, the University of Florida, and the Florida Sugar Cane League, Inc., and was released to growers in Florida in September 2007. CP 00-2180 was selected from a self-cross of cultivar HoCP 91-552 made at Canal Point, FL, in January 1998. Based on its high cane yields and fiber content (16%), HoCP 91-552 was released as a cultivar for bioenergy in Louisiana. CP 00-2180 was released and recommended for sand soils in Florida because of its high plant cane and acceptable ratoon per hectare yields of cane and sucrose and commercial recoverable sucrose on sand soils, and its resistance to smut [caused by Ustilago scitaminea (Sydow & P. Sydow)], brown rust (caused by Puccinia melanocephala H. & P. Sydow), orange rust (caused by Puccinia kuehnii E.J. Butler), leaf scald [caused by Xanthomonas albilineans (Ashby) Dowson], Sugarcane mosaic virus strain E, and ratoon stunting disease (caused by Clavibacter xyli subsp. xyli Davis) in Florida.

Characterization of wild germplasm provides essential information on genetic diversity that breeders utilize for crop improvement. The potential of the sequence-related amplified polymorphism (SRAP) technique, which preferentially amplifies gene-rich regions, was evaluated to assess the genetic relationships among members of theSaccharumspecies. A panel of 31 SRAP primer combinations were used to score 30 genotypes ofSaccharum officinarum,Saccharum spontaneum,Saccharum robustum,Saccharum sinense,Saccharum barberiand sugarcane hybrids, withMiscanthusandErianthusincluded as outgroups. The amplifications produced 1364 DNA fragments for an average of 44 per primer combination, with 83% (1135) being polymorphic and 8.7% (119) being species specific. Based on the Dice index, all 30 genotypes were differentiated from each other with genetic similarity (GS) estimates ranging from 0.60 to 0.96 (mean = 0.79). Both the dendrogram [obtained by the unweighted pairgroup method with arithmetic mean or (UPGMA)] and the non-metric multidimensional scaling method grouped the genotypes according to their phylogenetic relationships.ErianthusandMiscanthuswere separated as two outgroups (at GS levels of 0.56 and 0.72, respectively) into two major clusters: cluster I separated theS. robustum,S. sinense,S. barberiand hybrids as different subgroups with each one including someS. officinarumclones, while cluster II included theS. spontaneumclones, exclusively. AS. officinarum–S. spontaneumsequence comparison of some of the monomorphic and polymorphic bands revealed 65–90% homology with rice, corn or sugarcane sequences deposited in databases. The high discriminatory power coupled with the possibility that most of the amplicons may be amplifying gene-rich regions of the genome makes SRAP a potentially robust tool for genetic mapping aimed at marker-assisted introgression in sugarcane.

'CP 88-1165' (Reg. No. CV-131, PI 651884) sugarcane (a complex hybrid of Saccharum spp.) was developed through cooperative research conducted by the USDA-ARS, the Centro Guatemalteco de Investigacion y Capacitacion de la Cana de Azucar, and the University of Florida. It was released to growers in Guatemala in September 2004. CP 88-1165 was selected from the cross 'CL 61-620' x CP 81-1302 made at Canal Point, FL, in January 1986. The female parent, CL 61-620, formerly a major commercial cultivar in Florida, was developed by a private breeding program in Clewiston, FL, conducted by the United States Sugar Corp. The male parent, CP 81-1302, was advanced to the final testing stage (Stage 4) of the Canal Point (CP) cultivar development program but was not released due to susceptibility to brown rust (caused by Puccinia melanocephala Syd. & P. Syd.). CP 88-1165 was not released in Florida because of its susceptibility to brown rust and low yield of commercial recoverable sucrose. However, after testing in Guatemala, CP 88-1165 was released there because of its high plant cane and ratoon per hectare yields of cane and sucrose and its acceptable resistance or tolerance to smut [caused by Ustilago scitaminea (Sydow & P. Sydow], brown rust, Sugarcane mosaic virus strain E (mosaic), Sugarcane yellow leaf virus, and red stripe (Acidovorax avenae subsp. avenae) in Guatemala.

Genetic mapping techniques can be used to study the interaction between two different genomes after hybridization. This study investigated a Saccharum officinarum (Green German or GG, 2n approximately 11x approximately 110) x S. spontaneum (IND 81-146 or IND, 2n approximately 7x approximately 56) interspecific cross. Segregation of 193 microsatellite (SSR) loci was evaluated in the F(1) progeny of 169 full-sibs of the cross. Following the two-way pseudo-testcross strategy and 'cross pollination' population type, linkage groups (LG) and phases were established for each parent map, using the criteria of LOD scoreor = 3.0 and a maximum recombination frequency of 0.35. Of the 193 markers analyzed, 61 were IND-specific, 106 were GG-specific, and 26 were heterozygous in both parents. About 78% of the markers segregated in a Mendelian fashion and 22% were distorted (as evaluated by chi(2)-tests, Por = 0.01). The GG map included 91 marker loci arranged into 25 LG covering 1180 cM of the officinarum genome. The IND map consisted of 46 marker loci assembled into 10 LG, which spanned 614 cM of the spontaneum genome. A specific chromosome associated with segregation distortion was detected in the female (GG) genome only, probably as a result of double reduction. The segregation patterns of the marker loci indicated a centromere-driven distortion process with the shared allelic markers (as putative centromeres) regulating the placement and association of markers with opposite phase (coupling vs repulsion) and dosage on either side. Although incomplete, the framework maps were informative with respect to segregation distortion, chromosome fusion, rearrangements, and translocations, observed in both parental genomes as a result of their merger.

Sugarcane (interspecific hybrids of Saccharum spp.) in the Everglades Agricultural Area (EAA) in Florida is frequently subjected to periods of higher-than-desired water levels. This study was conducted to evaluate yields of nine sugarcane cultivars subjected to two higher-than-conventional water tables in the EAA during the summer rainy season from the plant cane through the second-ratoon annual crop cydes. Field experiments were planted in February 1997 and January 1998. During the summers from 1997 through 1999, we sought to maintain water

This document is SS-AGR-270, part of the Florida Sugarcane Handbook, published by the UF Agronomy Department, June - October 2007. SS-AGR-270/SC084: Performance of Foreign Sugarcane Germplasm on Florida Sandlands (ufl.edu)

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 -1 ), cane yield (CY; Mg ha -1 ), and sugar yield (SY; Mg ha -1 ). Analyses of commercial data reflected yearly increases of 0.80 ± 0.08 kg Mg -1 of cane for SC, 0.31 ± 0.10 Mg ha -1 for CY, and 0.10 ± 0.01 Mg ha -1 for SY. Corresponding gains from selection trial data were 0.74 ± 0.15 kg Mg -1 , 1.06 ± 0.40 Mg ha -1 , and 0.16 ± 0.05 Mg ha -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.