Competition among three species of bees (Apis mellifera, Bombus sonorus, and Xylocopa arizonensis) visiting Agave schottii was studied. Honeybees were found to predominate in the most productive habitats, Xylocopa in the least; Bombus as most abundant in patches of intermediate quality. It is suggested that these observations are consistent with a simple graphical model relating the standing crop of available nectar to foraging energetics and the additional costs of colonial life (cost of sociality). Temporal variations in foraging behavior were also observed, with Apis again preferring to forage at those times of day (early morning and late afernoon) when resources were most abundant. Bombus was less crepuscular than Apis, and carpenter bees foraged without obvious regard to variation in standing crop. Several factors which may account for this pattern are discussed.

Sugarcane (Saccharum spp.) and other members of Saccharum spp. are attractive biofuel feedstocks. One of the two World Collections of Sugarcane and Related Grasses (WCSRG) is in Miami, FL. This WCSRG has 1002 accessions, presumably with valuable alleles for biomass, other important agronomic traits, and stress resistance. However, the WCSRG has not been fully exploited by breeders due to its lack of characterization and unmanageable population. In order to optimize the use of this genetic resource, we aim to 1) genotypically evaluate all the 1002 accessions to understand its genetic diversity and population structure and 2) form a core collection, which captures most of the genetic diversity in the WCSRG. We screened 36 microsatellite markers on 1002 genotypes and recorded 209 alleles. Genetic diversity of the WCSRG ranged from 0 to 0.5 with an average of 0.304. The population structure analysis and principal coordinate analysis revealed three clusters with all S. spontaneum in one cluster, S. officinarum and S. hybrids in the second cluster and mostly non-Saccharum spp. in the third cluster. A core collection of 300 accessions was identified which captured the maximum genetic diversity of the entire WCSRG which can be further exploited for sugarcane and energy cane breeding. Sugarcane and energy cane breeders can effectively utilize this core collection for cultivar improvement. Further, the core collection can provide resources for forming an association panel to evaluate the traits of agronomic and commercial importance.

Sugarcane (Saccharum spp.) supplies globally ∼80% of table sugar and 60% of bioethanol. Sugarcane orange rust and Sugarcane yellow leaf virus (SCYLV) are major sugarcane diseases, causing up to 50 and 40% yield losses, respectively. Sugarcane cultivars resistant to these diseases are needed to sustain sugarcane production in several regions. Dissecting DNA sequence variants controlling disease resistance provides a valuable tool for fulfilling a breeding strategy to develop resistant cultivars. In this study, we evaluated disease reactions to orange rust and SCYLV of a sugarcane diversity panel in repeated trials. We conducted a genome-wide association study between high-density markers and disease resistance reactions. We identified 91 putative DNA markers and 82 candidate genes significantly associated with resistance to one of the two diseases. These provide an important genetic resource for finding genes and molecular markers for disease resistance. Our results emphasized the importance of utilizing a wide germplasm collection for breeding resistant sugarcane cultivars.

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Sugarcane (Saccharum spp.) is a highly energy-efficient crop primarily for sugar and bio-ethanol production. Sugarcane genetics and cultivar improvement have been extremely challenging largely due to its complex genomes with high polyploidy levels. In this study, we deeply sequenced the coding regions of 307 sugarcane germplasm accessions. Nearly five million sequence variations were catalogued. The average of 98× sequence depth enabled different allele dosages of sequence variation to be differentiated in this polyploid collection. With selected high-quality genome-wide SNPs, we performed population genomic studies and environmental association analysis. Results illustrated that the ancient sugarcane hybrids, S. barberi and S. sinense, and modern sugarcane hybrids are significantly different in terms of genomic compositions, hybridization processes and their potential ancestry contributors. Linkage disequilibrium (LD) analysis showed a large extent of LD in sugarcane, with 962.4 Kbp, 2739.2 Kbp and 3573.6 Kbp for S. spontaneum, S. officinarum and modern S. hybrids respectively. Candidate selective sweep regions and genes were identified during domestication and historical selection processes of sugarcane in addition to genes associated with environmental variables at the original locations of the collection. This research provided an extensive amount of genomic resources for sugarcane community and the in-depth population genomic analyses shed light on the breeding and evolution history of sugarcane, a highly polyploid species.

Sugarcane (Saccharum spp.) is an important sugar and biofuel crop with high polyploid and complex genomes. The Saccharum complex, comprised of Saccharum genus and a few related genera, are important genetic resources for sugarcane breeding. A large amount of natural variation exists within the Saccharum complex. Though understanding their allelic variation has been challenging, it is critical to dissect allelic structure and to identify the alleles controlling important traits in sugarcane. To characterize natural variations in Saccharum complex, a target enrichment sequencing approach was used to assay 12 representative germplasm accessions. In total, 55,946 highly efficient probes were designed based on the sorghum genome and sugarcane unigene set targeting a total of 6 Mb of the sugarcane genome. A pipeline specifically tailored for polyploid sequence variants and genotype calling was established. BWA-mem and sorghum genome approved to be an acceptable aligner and reference for sugarcane target enrichment sequence analysis, respectively. Genetic variations including 1,166,066 non-redundant SNPs, 150,421 InDels, 919 gene copy number variations, and 1,257 gene presence/absence variations were detected. SNPs from three different callers (Samtools, Freebayes, and GATK) were compared and the validation rates were nearly 90%. Based on the SNP loci of each accession and their ploidy levels, 999,258 single dosage SNPs were identified and most loci were estimated as largely homozygotes. An average of 34,397 haplotype blocks for each accession was inferred. The highest divergence time among the Saccharum spp. was estimated as 1.2 million years ago (MYA). Saccharum spp. diverged from Erianthus and Sorghum approximately 5 and 6 MYA, respectively. The target enrichment sequencing approach provided an effective way to discover and catalog natural allelic variation in highly polyploid or heterozygous genomes.

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PI 699125) sugarcane (an interspecific hybrid of Saccharum spp.) was released on 10 Apr. 2019 for commercial production in the Louisiana sugar industry. L 12-201 was derived from a cross between the female parent 'L 97-128' and the male parent 'HoCP 96-540'. Early-stage selection through the seedling and two unreplicated clonal stages by researchers at the Louisiana State University Agricultural Center culminated in the assignment of a permanent varietal designation in 2012. Thereafter, the experimental variety was further evaluated cooperatively with personnel from the USDA-ARS at Houma and the American Sugar Cane League, Inc., at Thibodaux, LA, through several stages at multiple locations. In the final testing stage, data were collected from 60 replicated, combine-harvested trials at 12 representative light-and heavy-textured soil locations. Averaged across the plant-cane crop, the sucrose content, cane yield, and sugar yield were significantly (P < .05) higher in L 12-201 than in 'L 01-299', the most widely grown cultivar in the Louisiana sugar industry. In the first-and second-ratoon crops, L 12-201 had significantly (P < .05) less cane yield and sugar yield than L 01-299, but sucrose content was not significantly different between L 12-201 and L 01-299. When averaged across the light-textured versus heavy-textured soil locations, no significant differences in performance were found for L 12-201 in any of the traits measured. The new cultivar had a lower stalk population and greater stalk weight compared with L 01-299, especially in the ratoon crops. L 12-201 is a mid-maturing cultivar. Whenever possible, L 12-201 should be harvested before the arrival of subfreezing temperatures because it is among the least cold tolerant cultivars in the industry. L 12-201 is resistant to sorghum mosaic, smut, leaf scald, and ratoon stunt; moderately resistant to brown rust; and susceptible to yellow leaf and the sugarcane borer.