J. A. Dahlberg

Toward Sequencing the Sorghum Genome: A U.S. National Science Foundation-Sponsored Workshop Report

Members of the worldwide sorghum (Sorghum spp.) community, including private sector and international scientists as well as community representatives from closely related crops such as sugarcane (Saccharum spp.) and maize (Zea mays), met in St. Louis, Missouri, on November 9, 2004, to lay the groundwork for future advances in sorghum genomics and, in particular, to coordinate plans for sequencing of the sorghum genome. Key developments that made this workshop timely included advances in knowledge of the sorghum genome that provide for the development of a genetically anchored physical map to guide sequence assembly and annotation, the growing role of the sorghum genome as a nucleation point for comparative genomics of diverse tropical grasses including many leading crops, and the need for dramatically increased sorghum production to sustain human populations in many regions where its inherent abiotic stress tolerance makes it an essential staple. This report reviews current knowledge of the sorghum genome, a community-endorsed schema for integrating this knowledge into a finished sequence, and early plans for translating the sequence into sustained advances to benefit a worldwide group of stakeholders.

Sorghums of the sudan: analysis of regional diversity and distribution

Sorghum [Sorghumbicolor (L.) Moench] is a very important crop in the Sudan serving as a primary source of food, beverage, and total livelihood for millions of people in the country. The crop originated in the Northeast quadrant of Africa, and the Sudan is widely recognized as a major center of diversity. Although Sudanese sorghum germplasm has been assembled and stored over the last 50 years, careful analysis of this valuable germplasm has not been made. The objectives of this study were to assess phenotypic diversity and compare pattern of distribution among Sudanese sorghum landraces collected from different geographical regions. Phenotypic diversity among landraces was high, as expressed by the large range of variation for mean quantitative traits and the high (0.81) Shannon-Weaver diversity index. Landraces from Gezira-Gedarif tended to be shorter in stature, earlier in maturity and less sensitive to changes in photoperiod. They also had long, narrow and compact panicles that may result from adaptation to low rainfall and early adoption of mechanized farming practices. In contrast, taller and later maturing plant types characterized sorghums from Equatoria, most of which delayed their flowering in response to increased day-length. These sorghums included many genotypes with small and light kernels. Collections from Kassala showed a higher frequency of landraces with kernels that were more difficult to thresh. Landraces from Blue Nile tended to have greater agronomic eliteness with higher proportion of landraces with white kernels, poorly covered and that were easy to thresh. Sorghums from the Upper Nile tended to have loose panicles with poorly covered kernels that may result from adaptation to high rainfall of the Southern region. Although distinct distributions of types were represented by geographical origin, a high level of within-region diversity was present among all Sudanese sorghums.

Development of a Sorghum Core Collection: Refinement and Evaluation of a Subset from Sudan

The U.S. National Plant Germplasm System (NPGS) maintains over 40 000 sorghum accessions, which is too large to adequately screen at one time. The objectives of this research were to establish an initial core collection and use clustering techniques to refine one sub-set of that core. Because much of the total sorghum collection lacks complete descriptor or other usable data, the collection was broken out into its respective country of origin and random selection of 10% of the accessions from each country was used to develop the core. Based on these criteria, a core collection of 3011 accessions representing 77 different countries was developed. A more complete phenotypic dataset representing the Sudan allowed for the development of a refined subset of the core collection from this country. The core from Sudan is made up of 352 accessions that represent 13.8% of the total Sudan collection. This core was then evaluated for imbibitional high temperature sensitivity, leaf high temperature sensitivity, and acquired thermotolerance. The results show that these assay systems evaluate distinct aspects of the sorghums ’ metabolism and that each assay provides unique information about the relative heat tolerance of the sorghum. The impact of the sorghum core collection at this time is unknown. Theoretically, the core should provide a road map from which scientists can map genetic diversity of sorghum and further enhance the capabilities to isolate and clone genes of importance in the future.

Image and statistical analyses of early sorghum remains (8000 B.P.) from the Nabta Playa archaeological site in the Western Desert, southern Egypt

Carbonized grains of sorghum, with consistent radiocarbon dates of ca. 8000 B.P., have been excavated at an early Holocene archaeological site (E-75-6) in Nabta Playa near the Egyptian-Sudanese border. The objective of the investigations reported here was to classify these early sorghum grains within the known wild or domesticated races or working groups of sorghum through the use of image-analysis procedures. Image-analysis is a non-destructive analytical method that can provide rapid, repeatable, and accurate measurements of ancient cereal grains. Measurements were taken on samples representing the five major domesticated sorghum races, eight wild relatives, and samples from the Nabta Playa and Jebel et Tomat excavation sites. Statistical and clustering techniques indicated significant differences existed among the sorghums with respect to the various measurements made. Sorghum from Nabta Playa was significantly smaller, with respect to most measurements, than either the wild relatives or the five cultivated sorghums. Smaller grain size and the lack of any spikelets containing attached branchlets of the inflorescence or rachis fragments suggest that the material harvested and eaten at the Nabta Playa site were of a wild type.

Multivariate Calibration Models for Sorghum Composition using Near-Infrared Spectroscopy

NREL developed calibration models based on near-infrared (NIR) spectroscopy coupled with multivariate statistics to predict compositional properties relevant to cellulosic biofuels production for a variety of sorghum cultivars. A robust calibration population was developed in an iterative fashion. The quality of models developed using the same sample geometry on two different types of NIR spectrometers and two different sample geometries on the same spectrometer did not vary greatly.

Inhibition of germination and sporulation of Claviceps africana from honeydew encrusted sorghum with seed treatment fungicides.

The inhibitory e!ects of six fungicides on macrospore germination and production of secondary conidia of Claviceps africana were studied. E!ects of these fungicides on germination of sorghum seed also were determined. Panicles from male-sterile sorghums with honeydew exudate were harvested from the USDA-ARS Research Farm, Isabela, Puerto Rico in the Spring of 1997. Honeydew exudate-infested panicles were used as inoculum to infest ergot-free sorghum seed. Seeds were placed on 1 and 2% water agar containing 100 mg/l each of streptomycin sulfate and ampicillin and were also plated on soil. They were incubated at 21}223C, 16 h of light. At 24 and 48 h, samples were examined under a microscope, equipped with 50] and 100] objectives, for germination of macroconidia and the formation of conidiophores and secondary conidia on both seed, soil, and agar surfaces. Samples also were evaluated for seed germination. Abundant conidiophores with conidia were observed over the entire seed surface of (control) honeydew-infested seed while none were observed on untreated control seed. Fungicidal e!ects and seed germination results showed that captan (Captan 400 ’ ) and thiram (42-S Thiram ’ )e !ectively inhibited conidiophore production and secondary conidia formation without severely reducing viability of the sorghum seed. ( 1999 Elsevier Science Ltd. All rights reserved.