No abstract

Current knowledge of yield potential and best agronomic management practices for perennial bioenergy grasses is primarily derived from small-scale and short-term studies, yet these studies inform policy at the national scale. In an effort to learn more about how bioenergy grasses perform across multiple locations and years, the U.S. Department of Energy (US DOE)/Sun Grant Initiative Regional Feedstock Partnership was initiated in 2008. The objectives of the Feedstock Partnership were to (1) provide a wide range of information for feedstock selection (species choice) and management practice options for a variety of regions and (2) develop national maps of potential feedstock yield for each of the herbaceous species evaluated. The Feedstock Partnership expands our previous understanding of the bioenergy potential of switchgrass, Miscanthus, sorghum, energycane, and prairie mixtures on Conservation Reserve Program land by conducting long-term, replicated trials of each species at diverse environments in the U.S. Trials were initiated between 2008 and 2010 and completed between 2012 and 2015 depending on species. Field-scale plots were utilized for switchgrass and Conservation Reserve Program trials to use traditional agricultural machinery. This is important as we know that the smaller scale studies often overestimated yield potential of some of these species. Insufficient vegetative propagules of energycane and Miscanthus prohibited farm-scale trials of these species. The Feedstock Partnership studies also confirmed that environmental differences across years and across sites had a large impact on biomass production. Nitrogen application had variable effects across feedstocks, but some nitrogen fertilizer generally had a positive effect. National yield potential maps were developed using PRISM-ELM for each species in the Feedstock Partnership. This manuscript, with the accompanying supplemental data, will be useful in making decisions about feedstock selection as well as agronomic practices across a wide region of the country.

‘L 79‐1002’ (Reg. No. CV‐132, PI 651501) sugarcane (a complex hybrid of Saccharum officinarum L., S. spontaneum L., S. barberi Jeswiet, and S. sinense Roxb. amend. Jeswiet) was released on 26 Apr. 2007 by the Louisiana State University Agricultural Center in cooperation with the USDA‐ARS and the American Sugarcane League, Inc. The cross for L 79‐1002, a F1 hybrid, was made in 1974 using ‘CP 52‐68’ as the female parent and Tainan, a S. spontaneum clone, as the male parent. Initial clonal selection was done in single stools. Testing was done from 1976 through 1983 in yield trials conducted in the traditional sugarcane growing area in south Louisiana and in the colder, non‐sugarcane growing regions of north Louisiana. Yield testing was resumed in 2002 through 2005 as interest in biofuels research renewed. L 79‐1002 was released for an emerging biofuels industry because of its high fiber content and biomass (cane yield) potential. Average fiber content for L 79‐1002 is approximately 257 g kg−1 The new cultivar also has excellent vigor and ratooning ability. Experiments conducted at Bossier City, Louisiana (32.1° N lat) indicated a broader range of adaptability than sugarcane cultivars grown for the production of sucrose.

Estimates of genetic variances and derived statistics of pertinent traits are essential for efficient plant breeding programs. For clonal sugarcane (Saccharum spp.) populations in Louisiana, such estimates (and unconfoanded estimates of genotype by environment [GE] and genotype by crop [GC] variances) were lacking. The objectives of this study were to estimate broad‐sense genetic and GE variance components for a clonal sugarcane population representative of initial stages of replicated testing and to determine the relative importance of years, locations, and crops. Thirty‐seven genotypes were planted in 1983 and replanted in 1984 in replicated tests at five locations. Data from two 3‐yr. crop cycles were used. Genetic advance (GA) indicated considerable improvement potential in sucrose yield, cane yield, and stalk number and weight. Genotypic variance was generally secondary to error variance in determining phenotypic variance; GE variances were tertiary to genotypic and error variances. Within a crop, genotype by location (GL) variances tended to be larger than genotype by year (GY). Estimates of potential of plant cane sucrose yields over years and locations implied testing across locations could substitute for years, effectively reducing the time to identify elite clones. Analysis across crops showed GC, GL and GYL interaction variances were usually larger than GY. Estimates of GA showed no difference in potential gain from replicating across years vs. crops. For several traits, the most potential for improvement is in older crop performance, and selection is best practiced with regard to crop.

The inheritance of ratooning ability and the relationship of traits among crops in sugarcane (Saccharum spp. hyb.) has not been well examined. Ratooning ability (RA) was defined as the second ratoon (SR) crop yield percent of the plant cane yield. A replicated 4-yr test at four locations of 37 genotypes was studied for two three-crop cycles. Broad-sense single-plot heritabilities for RA were low (H _< 17%), while the genetic coefficient of variation of RA was largest for sucrose yield and cane yield (GCV = 14.5%), and smallest for stalk diameter (GCV = 1.5%). Cane and sucrose yield RA demonstrated the largest potential for gain, while stalk weight, stalk diameter, and stalk length showed the least. Except for sucrose and cane yield and stalk number, other traits were highly correlated between plant cane and SR crops (r >_ 0.78). Stalk number in the younger crop was the only trait significantly correlated to ratoon crop cane yield (r = 0.56), suggesting that selection for stalk number in the younger crops would enhance older crop yields. The results indicate that SR crop yields could be predicted by first ratoon crop yields. However, the best improvement of SR yields would be realized by selection in the SR. p~ LANTING OPERATIONS and seed (stalks for vegetative propagation) costs constitute the largest input of sugarcane production (Salassi and Giesler, 1995). Inadequate ratoon crop yields limit the economic production of sugarcane in semi-tropical regions such as Louisiana, where ratoon crop yields typically decrease with age (Johnson et al., 1993; Ricaud and Arceneaux, 1986; Shrivastava et al., 1992). The reasons for this decline are complex, but primarily relate to diseases, insects, weed competition, management practices, and winter kill (Shrivastava et al., 1992). Additionally, genotypes can vary substantially in their ratoon crop yields (Chapman, 1988; Chapman et al., 1992; Ricaud and Arceneaux, 1986; Tripathi et al., 1982). Ratooning ability can be enhanced by indirect selection for disease or insect resistance, or by direct selection of genotypes with high ratoon crop yields. Traits such as high stalk number, bud viability, vigorous root formation, high biomass accumulation, and high light use efficiency have been suggested as being indicative of better ratooning cultivars (Sundara, 1989; Ferraris et al., 1993). The importance of maintaining stalk weight in older crops has also been noted (Chapman, 1988; Chapman et al., 1992). Ratooning ability can be defined in either absolute or relative terms. In absolute terms, a good ratooning cultivar is one that produces high ratoon crop yields or several profitable ratoon crops. Relative to other cultivars, a