Sorghum Fungal Diseases

Abstract

Sorghum is a vital life-sustaining food crop for humans and livestock. Sorghum is also a biofuel crop of growing importance. Moreover sorghum is drought and heat tolerant, and is an important crop in arid and semi-arid regions where major cereals fail to grow successfully. Sorghum thus constitutes a major staple foods for the world's poorest people. Sorghum is an important food crop within traditional low input, cereal-based farming systems in Africa, where 41 % of the world-wide area of this crop's production is located. However, the crop suffers from low yields due to a number of biotic stresses. Sorghum is distinguished among other cereals by its unusually broad range of diseases which is one of the most important constraints to its production. The most destructive sorghum diseases reported are fungal diseases which are widespread globally and result in huge losses in yields both in terms of the quantity and quality of the grains. Anthracnose, turcicum leaf blight, charcoal root rot and other fungal diseases are epidemics in many parts of the world. They cause severe crop losses depending upon the crop stage, susceptibility of cultivar and the prevailing environmental conditions. Food security issues have prompted many of the national as well as international programmes such as International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), India, African programmes which actively encourage farmers to grow sorghum. Whilst traditional landrace materials showed some tolerance to many of these problems, often by escaping disease through late maturity associated with photoperiodicity, or a tall growth habit, the improved materials are frequently of short to intermediate height and early maturation and therefore more susceptible to disease problems, particularly fungal diseases. Knowledge on disease epidemics and characterization of pathosystems is particularly important for long term disease management to achieve significant impact in reducing aspects of poverty and food and security in sorghum based semi arid cropping systems. This chapter reviews the current status of information on the most common fungal diseases of sorghum and discusses various aspects including disease significance and symptoms, genetics of resistance and host pathogen interaction and, management of disease. Besides the new approaches in disease control such as Quantitative Trait Loci mapping and transgenic approaches have also been discussed. Molecular markers and quantitative trait loci (QTL) analysis have been useful for locating the resistance gene(s) on the genome of sorghum and to carry out marker-assisted selection for some of the fungal diseases. It has provided foundation for fine-mapping and advancing the molecular breeding for others. Furthermore, the markers tagged to QTL regions can be used to enhance the sorghum breeding program for fungal resistance through marker-assisted selection and map-based cloning. As we have the whole genome sequence available of sorghum, it will be helpful to advance the molecular breeding by facilitating the positional cloning as well as marker-assisted selection. This will also be instrumental in determining the function of disease resistance genes available in the sorghum genome.