® The European Journal of Plant Science and Biotechnology ©2012 Global Science Books Sorghum Pathology and Biotechnology - A Fungal Disease Perspective: Part II. Anthracnose, Stalk Rot, and Downy Mildew Tesfaye Tesso1 • Ramasamy Perumal2 • Christopher R. Little3 • Adedayo Adeyanju1 • Ghada L. Radwan4 • Louis K. Prom5 • Clint W. Magill4* 1 Department of Agronomy, Kansas State University, Manhattan, Kansas 66506, USA 2 Western Agricultural Research Center - Hays, Hays, Kansas 67601, USA 3 Department of Plant Pathology, Kansas State University, Manhattan, Kansas 66506, USA 4 Department of Plant Pathology and Microbiology, Texas A&M University, College Station, Texas 77845, USA 5 Southern Plains Agricultural Research Center, USDA-ARS, College Station, Texas 77845, USA Corresponding author : * [email protected] ABSTRACT Foliar diseases and stalk rots are among the most damaging diseases of sorghum in terms of lost production potential, thus commanding considerable research time and expenditure. This review will focus on anthracnose, a fungal disease that causes both foliar symptoms and stalk rots along with the stalk rots caused by Fusarium spp. and Macrophomina phaseolina. Although the downy mildews are caused by oomycetes rather than true fungi, recent outbreaks have revealed resistance to previously effective chemical seed treatments and the evolution of new pathogenic races, once again pointing out the need for continuous vigilance. Sorghum diseases are described with respect to the causal organism or organisms, infection process, global distribution, pathogen variability and effects on grain production. In addition, screening methods for identifying resistant cultivars and the genetic basis for host resistance including molecular tags for resistance genes are described where possible along with prospects for future advances in more stable disease control. _____________________________________________________________________________________________________________ Keywords: Colletotrichum sublineolum, Colletotrichum graminicola, Fusarium, Macrophomina phaseolina, Peronosclerospora sorghi CONTENTS ANTHRACNOSE........................................................................................................................................................................................ 31 Introduction ............................................................................................................................................................................................. 31 Biology of Colletotrichum sublineolum................................................................................................................................................... 32 Disease symptoms and losses .................................................................................................................................................................. 32 Pathogenic races ...................................................................................................................................................................................... 32 Disease screening techniques .................................................................................................................................................................. 32 Host resistance......................................................................................................................................................................................... 34 DNA-based diversity and molecular tags ................................................................................................................................................ 34 Future prospects....................................................................................................................................................................................... 35 STALK ROT ................................................................................................................................................................................................ 35 Introduction ............................................................................................................................................................................................. 35 Biology of stalk rot.................................................................................................................................................................................. 36 Disease symptoms and losses .................................................................................................................................................................. 36 Factors associated with stalk rot incidence in grain sorghum.................................................................................................................. 37 Pathogen races......................................................................................................................................................................................... 38 Disease screening techniques .................................................................................................................................................................. 38 Host resistance......................................................................................................................................................................................... 38 DNA-based diversity tags........................................................................................................................................................................ 39 DOWNY MILDEW ..................................................................................................................................................................................... 39 Introduction ............................................................................................................................................................................................. 39 Biology of Peronosclerospora sorghi...................................................................................................................................................... 39 Disease symptoms and losses .................................................................................................................................................................. 39 Pathogen races......................................................................................................................................................................................... 40 Disease screening techniques .................................................................................................................................................................. 40 Disease control and host resistance.......................................................................................................................................................... 40 DNA-based diversity and molecular tags ................................................................................................................................................ 41 Future directions...................................................................................................................................................................................... 41 ACKNOWLEDGEMENTS ......................................................................................................................................................................... 41 REFERENCES............................................................................................................................................................................................. 41 _____________________________________________________________________________________________________________ ANTHRACNOSE of taxa in the genus Colletotrichum. During the past decade there have been important changes in our knowledge of Introduction how the grass-associated Colletotrichum spp. have evolved, and an increased understanding of the mechanisms by Anthracnose, a disease that impacts the health of cereals which these fungi engage in hemibiotrophic interactions and grasses worldwide is caused by a monophyletic group with their host plants (Crouch and Beirn 2009). Anthrac- Received: 25 August, 2011. Accepted: 12 November, 2011. Invited Review The European Journal of Plant Science and Biotechnology 6 (Special Issue 1), 31-44 ©2012 Global Science Books nose of sorghum (Sorghum bicolor (L.) Moench) is caused study was 77%. by the fungus Colletotrichum sublineolum Henn. (syn. C. Although cultural strategies such as rotation may reduce graminicola (Ces.) G. W. Wilson [Sutton 1980; Sheriff et al. the impact of the disease, the use of resistant genotypes is 1995]. It is widely prevalent and economically significant in the best means for anthracnose control. However, the vari- warm and humid regions of Asia, Africa and the Americas able nature of the pathogen offers challenges in breeding for (Pastor-Corrales 1980; Ali and Warren 1992; Leslie 2002; durable resistance (Pande et al. 1991; Valèrio et al. 2005). Mathur et al. 2002; Marley et al. 2004; Figueiredo et al. Three phases of the disease are recognized: foliar anthrac- 2006; Thakur et al. 2007b; Chala et al. 2007). The pathogen nose (Figs. 1, 2), anthracnose stalk rot (Fig. 2), and panicle is capable of infecting the stalk, foliage, panicle, and grain, and grain