Bridging conventional and molecular genetics of sorghum insect resistance

Sustainable production of sorghum, Sorghum bicolor (L.) Moench, depends on effective control of insect pests as they continue to compete with humans for the sorghum crop. Insect pests are a major constraint in sorghum production, and nearly 150 insect species are serious pests of this crop worldwide and cause more than 9% loss annually. Annual losses due to insect pests in sorghum have been estimated to be $1,089 million in the semiarid tropics (ICRISAT Annual report 1991. International Crop Research Institute for Semi-arid Tropics. Patancheru, Andhra Pradesh, India, 1992), but differing in magnitude on a regional basis. Key insect pests in the USA include the greenbug, Schizaphis graminum (Rondani); sorghum midge, Stenodiplosis sorghicola (Coquillett); and various caterpillars in the Southern areas. For example, damage by greenbug to sorghum is estimated to cost US producers$248 million annually. The major insect pests of sorghum on a global basis are the greenbug, sorghum midge, sorghum shoot fly (Atherigona soccata Rond.), stem borers (Chilo partellus Swin. and Busseola fusca Fuller), and armyworms (Mythimna separata Walk and Spodoptera frugiperda J.E. Smith). Recent advances in sorghum genetics, genomics, and breeding have led to development of some cutting-edge molecular technologies that are complementary to genetic improvement of this crop for insect pest management. Genome sequencing and genome mapping have accelerated the pace of gene discovery in sorghum..

Seasonal incidence of Stenodiplosis sorghicola (Coquillett) (Diptera : Cecidomyiidae) and its parasitoids on Sorghum halepense (L.) Pers. in south-eastern Queensland, Australia

To quantify the role of Johnson grass, Sorghum halepense, in the population dynamics of the sorghum midge, Stenodiplosis sorghicola, patterns of flowering of Johnson grass and infestation by sorghum midge were studied in two different climatic environments in the Lockyer Valley and on the Darling Downs in south-eastern Queensland for 3 years. Parasitism levels of S. sorghicola were also recorded. In the Lockyer Valley, Johnson grass panicles were produced throughout the year but on the Darling Downs none were produced between June and September. In both areas, most panicle production occurred between November and March and infestation by S. sorghicola was the greatest during this period. The parasitism levels were between 20% and 50%. After emergence from winter diapause, one to two generations of S. sorghicola developed on S. halepense before commercial grain sorghum crops were available for infestation. Parasitoids recorded were: Aprostocetus diplosidis, Eupelmus australiensis and two species of Tetrastichus. Relationships between sorghum midge population growth rate and various environmental and population variables were investigated. Population size had a significant negative effect (P < 0.0001) on population growth rate. Mortality due to parasitism showed a significant positive density response (P < 0.0001). Temperature, rainfall, open pan evaporation, degree-days and host availability showed no significant effect on population growth rate. Given the phenology of sorghum production in south-eastern Queensland, Johnson grass provides an important bridging host, sustaining one to two generations of sorghum midge. Critical studies relating population change and build-up in sorghum to sorghum midge populations in Johnson grass are yet to be performed

Preliminary studies on two Diaspididae (Hemiptera) species feeding on Johnsongrass (Sorghum halepense) in Turkey

The scale insects Acanthomytilus sacchari (Hall) and Duplachionaspis erianthi Borchsenius (Hemiptera, Diaspididae) are newly recorded as indigenous insects from Turkey. Both A. sacchari and D. erianthi were found to feed only on rhizomes of Johnsongrass. A field study was conducted to determine host ranges and feeding effects of these scale insects on Johnsongrass, Sorghum halepense (L.) Pers. No feeding of these species was observed on Zea mays L. (maize), Sorghum sudanense Staph. (sorghum), Aegilops triuncialis L. (barbed goatgrass), Avena fatua L. (wild oat), A. sterilis (sterile oat), Bromus tectorum L. (downy brome), Cynodon dactylon (L.) Pers. (bermudagrass), Phragmites australis (Cav.) Trin. ex Steudel (common reed), Poa bulbosa L. (bulbous bluegrass), or Secale montanum Guss. (wild rye). The mean infestation rates of the scale insects on Johnsongrass in southeastern Anatolia were 11.47% and 1.64% for A. sacchari and D. erianthi, respectively. Further investigations are required to clarify their biology and damage to Johnsongrass under field conditions.The scale insects Acanthomytilus sacchari (Hall) and Duplachionaspis erianthi Borchsenius (Hemiptera, Diaspididae) are newly recorded as indigenous insects from Turkey. Both A. sacchari and D. erianthi were found to feed only on rhizomes of Johnsongrass. A field study was conducted to determine host ranges and feeding effects of these scale insects on Johnsongrass, Sorghum halepense (L.) Pers. No feeding of these species was observed on Zea mays L. (maize), Sorghum sudanense Staph. (sorghum), Aegilops triuncialis L. (barbed goatgrass), Avena fatua L. (wild oat), A. sterilis (sterile oat), Bromus tectorum L. (downy brome), Cynodon dactylon (L.) Pers. (bermudagrass), Phragmites australis (Cav.) Trin. ex Steudel (common reed), Poa bulbosa L. (bulbous bluegrass), or Secale montanum Guss. (wild rye). The mean infestation rates of the scale insects on Johnsongrass in southeastern Anatolia were 11.47% and 1.64% for A. sacchari and D. erianthi, respectively. Further investigations are required to clarify their biology and damage to Johnsongrass under field conditions.</p