Ergot: A New Disease Threat to Sorghum in the Americas and Australia

Sorghum, Sorghum bicolor (L.) Moench, is the world’s fifth most important cereal crop, cultivated on about 45 million hectares for food, feed, beverage, and fodder. The most significant technological change since the 1960s has been the development and use of F1 hybrid seed (14), which has lead to a dramatic improvement in the crop’s productivity. Sorghum cultivation in intensive, commercialized systems where yields average 3 to 5 t ha-1 relies almost totally on hybrid seed. In contrast, yields vary widely and average less than 1 t ha-1 in low-input production systems

Evaluation of sorghum germplasm used in US breeding programmes for sources of sugary disease resistance

Ergot or sugary disease of sorghum has become an important constraint in North and South American countries that rely on F1 hybrid seeds for high productivity. The objective of this research was to determine the vulnerability of various germplasm sources and publicly bred sorghum lines to sugary disease (Claviceps africana) in the United States. Flower characteristics associated with sugary disease resistance were also studied. A-/B-line pairs, R-lines, putative sources of resistance and their hybrid combinations with an A3 cytoplasmic male-sterile source were evaluated using a disease incidence, severity, and dual-ranking system. Trials were planted in a randomized complete block design with three replications and repeated in at least two planting dates. Planting dates and pedigrees had significant effects on overall ranking for resistance. A-lines were most susceptible to sugary disease. R-lines were more susceptible than B-lines with respect to incidence and severity of the disease. Newer releases of A- and B-lines were more susceptible to sugary disease than older releases. Sugary disease reaction of A-lines was a good indicator of disease reaction of B-lines. Tx2737, a popular R-line, was highly susceptible to sugary disease in spite of being a good pollen shedder because the stigma emerged from glumes 2±3 days before anthesis. The combination of flower characteristics associated with resistance were least exposure time of stigma to inoculum before pollination, rapid stigma drying after pollination, and small stigma. An Ethiopian male-fertile germplasm accession, IS 8525, had good levels of resistance. Its A3 male-sterile hybrid had the highest level of resistance in the male-sterile background. IS 8525 should be exploited in host-plant resistance strategies

A new species complex including Claviceps fusiformis and Claviceps hirtella

Isolates of Claviceps species with lunate to fusiform macroconidia were collected from panicoid grasses in Texas and Zimbabwe and described as new species based on anamorphs since no teleomorphs were available. Characterization was based upon morphology and partial sequences of rDNA and β-tubulin. The isolates grouped into two stronglysupported clades. The first clade contained ancestral C. hirtella and C. fusiformis from pearl millet (Pennisetum glaucum) in clade terminal position with Texas isolates from native cup grass (Eriochloa sericea) and pearl millet grouped between them. The second clade consisted of African isolates from Urochloa and Eragrostis. The isolates from Texas from pearl millet and buffel grass (Cenchrus ciliaris) and isolates from E. sericea were described as new species, Sphacelia texensis and Sphacelia eriochloae, respectively. Both species had morphology, DNA markers, and alkaloid production that was intermediate between those features exhibited in C. fusiformis and C. hirtella. The African isolates from Urochloa and Eragrostis were also described as a new species, Sphacelia lovelessii. In shaken cultures, C. hirtella readily produced a whole range of clavines with agroclavine and festuclavine predominating, but ergometrine was also detected. Claviceps fusiformis produced mainly agroclavine and elymoclavine, S. eriochloae produced mainly agroclavine, elymoclavin and festuclavine and the cultures of S. texensis contained small amounts of agroclavine and festuclavine. Only traces of clavines were found in cultures of S. lovelessii of the second clade. The alkaloid content of infected florets in the sphacelial (honeydew) developmental stage was also measured. Only C. fusiformis and S. eriochloae produced alkaloids in planta at this early stage

New Claviceps species from warm-season grasses

Eight undescribed species of Claviceps were recognized from the combinations of molecular and morphological characters. The teleomorph was observed only for Claviceps setariicola. Phylogenetic affinities of the new species inside the genus were revealed by a 5.8S-ITS-28S nrDNA analysis. Claviceps chloridicola, C. tenuispora, C. setariicola and C. setariiphila are related to C. maximensis; C. truncatispora is a sister species to C. pusilla. Claviceps clavispora and C. langdonii cluster with species colonizing maize and sorghum. The position of C. loudetiae is unclear. Comparisons with herbarium specimens showed C. setariicola as a well-established species on Setaria spp. in the southern USA. C. tenuispora was recorded on Cenchrus and Pennisetum in Brazil, USA, and Zimbabwe. C. setariiphila was found on S. geniculata in Brazil. C. chloridicola, C. loudetiae and C. truncatispora occurred in African savannas on Chloris, Loudetia, and Hyparrhenia spp., respectively. C. clavispora was found on Paspalum sp. and Urochloa sp. in Mexico and C. langdonii colonized Dichanthium spp. in the southern USA and probably in Mexico. The occurrence of C. pusilla on pearl millet in the USA (Texas) is reported and the record of C. sulcata on Urochloa brizantha in Brazil is confirmed by nrDNA sequence comparison with an African herbarium specimen. No alkaloids were detected in sclerotia and/or sphacelia of the new species

Biomass production of herbaceous energy crops in the United States: field trial results and yield potential maps from the multiyear regional feedstock partnership

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