Sorghum Root and Stalk Rots: Basic Disease Problems Summary and Synthesis

The eight background papers on basic disease problems provide an overall view of the biology of the causal agents and the epidemiology of root and stalk rot diseases. Since the effects of plant physiological and environmental factors and disease control are presented in later sessions, my coments will be confined to crop loss and some ects of the biology of the causal organisms

Sorghum Root and Stalk Rots A Critical Review

Despite several decades of research, diseases remain a major constraint to sorghum product ion throughout the world. That was the reason ICRISAT and Texas A &M University cosponsored the first international workshop on sorghum diseases, hosted by ICRISAT at Hyderabad, India, in December 1978. It was also the reason for a second major international effort exact ly 5 years later, by INTSORMIL and ICRISAT, to gain more understand ing for better control of these diseases. This took the form of a highly specialized consul tants' group meeting to make recommendat ions on the research needs and strategies for control of sorghum root and stalk rots. Root and stalk rots are a group of diseases that reduce crop stands in the emergence and seedling stages, or most commonly cause stalk lodging in the postf lowering and grain-filling stages of plant development. The improved high-yieldpotential varieties and hybrids under good management tend to be particularly suscept ible to Iodging i nduced by root and stalk rot. Al though good progress has been made against other diseases of sorghum, research for control of root and stalk rots has been painfully slow. This is due to the complexi ty of the diseases themselves and the pauci ty of intensive interdisciplinary research on them. ICRISAT and INTSORMIL are commi t ted to supporting and conduct ing research that will provide the technology necessary for farmers to improve sorghum yields and help meet world food needs. Their joint ponsorship of the Consultative Group Discussion on Research Needs and Strategies for Control of Sorghum Root and Stalk Rot Diseases and the publication of these proceedings are important steps toward this objective. The contents of the background papers, the discussions, and the recommendat ions contained in this book represent the combined exper ience and knowledge of 27 scientists in the disciplines of breeding, physiology, and pathology. We feel certain that if national, international, and other sorghum improvement programs follow the various strategies and recommendat ions, significant progress will be made in this field. ICRISAT expresses special appreciat ion to the scientists who participated in this meet ing, to INTSORMIL for its help in funding the conference, and to the Rockefeller Foundation for hosting the meeting at its Study and Conference Center at Bellagio, Italy

Strategies for Sorghum Disease Control

Most sorghum diseases are amenable to some degree of control through the application of one or more appropriate control measures. These measures fall under the general disease control methods of host resistance, chemical control. cultural control and integrated control. The decision as to whfch method to apply in any disease situation would depend upon whether the method met the criteria of agronomic effectiveness, environmental effectlveness, economic feasibility. social acceptability, and implementabillty (Bailey and Waddel 1980)

Charcoal Rot of Sorghum

Charcoal rot of sorghum causedby the fungus ~acrophorfdnap haseolina is a root andstalk rot disease of great destructive potential in most sorghum-growing regions. Improved, highyielding cultivars under good management tend to be very susceptible to the disease. M. phaseolina is a common soilborne, nonaggressive, and plurivorous pathogen that attacks plants whose vigor has been reduced by unfavorable growing conditions. Drought stress is the primary factor that predisposes sorghum to charcoal rot. In diseased roots and stalks, M. phaseolina is often associated with other fungi, suggesting that the disease is of complex etiology. Control by fungicides, cultural practices, and host resistance are briefly discussed, and priority areas for future research are listed

Evaluation of greenhouse inoculation techniques to screen sorghum for resistance to downy mildew

Six inoculation techniques were compared for the artificial promotion of downy mildew (Peronosclerospora sorghi) in sorghum. These were (1) sprouted seeds incubated between sporulating infected leaves, (2) sprouted seeds dipped in conidial suspension, (3) sprouted seeds sprayed with conidial suspension, (4) seedlings at plumule stage inoculated with drops of a conidial suspension, (5) seedlings at plumule stage sprayed with a conidial suspension, and (6) seedling showered with conidia falling from infected leaves. Seedlings at the one-leaf stage sprayed with a conidial suspension (6 × 105 ml-1) showed the highest systemic infection (100%) in the susceptible lines IS 643 and IS 18433. This technique is effective, repeatable, and allows the deposition of a conidial suspension as a fine mist on the entire seedling surface. In the greenhouse, the technique was used to test the downy mildew reaction of genotypes previously reported as resistant (< 5% incidence) in 3-4 years of field screenings. Of the 61 genotypes tested, 21 were free from downy mildew, 14 had less than 5% incidence, and the rest showed variable susceptible reactions. Therefore, the technique can be reliably and effectively used in the greenhouse to detect disease escapes and to indentify resistance

Prospects for successful integrated control of biotic yield -reducing agents of sorghum and pearl millet in the tropics

Sorghum and pearl millet, staple cereals in the semi-arid tropics, are attacked by many pests of several kinds, from the seedling stage up to and after crop maturity. Some of the more important pests of these two crops are described, and possibilities for their control are discussed. Management practices, host-plant resistance, and pesticides are available, in various combinations, to control the pests of these crops, and more options will become available in the future. The combinations of pest control methods that farmers are able and willing to use, however, depend upon the interaction of several biological, social, economic, commercial, and political factors, and due attention must be given to all of these if effective pest control and sustained increased production of these crops is to become a reality

Sorghum in the Eighties Proceedings of the International Symposium on Sorghum Volume 1

In October 1971 in Hyderabad. India an international symposium on sorghum was held which examined and reviewed the then scientific, production, and nutritional knowledge of sorghum as a crop and as a human food. Almost exactly 10 years later, ICRISAT hosted Sorghum in the Eighties—an international symposium sponsored by USAID Title XII Collaborative Research Support Program on Sorghum and Pearl Millet (INTSORMIL); the Indian Council of Agricultural Research (ICAR); and the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT). It was felt by the organizers that because so much knowledge and information had been attained in the intervening 10 years, scientists should meet again. Consequently, 245 scientists from 37 countries attended the Symposium from 2 to 7 November 1981 at ICRISAT Center near Hyderabad. They examined and evaluated the achievements made in the last decade, discussed the current problems, and made recommendations for future research and other activities. The participants showed a critical awareness of sorghum's role as an important cereal for food, feed, construction material, and fuel in the developed and the developing countries. On a world production and utilization basis, sorghum ranks fifth after wheat, rice, maize and barley. About 90% of the total production and 90% of the harvested area are located in 12 countries in Asia, the Americas, Africa, and Oceania. Sorghum is one of the main staple food grains of the world's poorest people, particularly in the semi-arid tropics (SAT). Over 55% of world sorghum production is in the SAT. Of the total SAT production, Asia and Africa contribute about 65%, of which 34% is harvested in India. Matters of considerable concern are that sorghum production is growing more slowly than population and that the food situation in parts of Africa is rapidly deteriorating. Situations such as these clearly indicate that more socioeconomic factors will need to be taken into account to guide and influence the direction of future scientific research on sorghum. The deliberations and discussions during the Symposium on factors related to sorghum and its environment, including climate, insects, fungi, and birds; the genetic resources; breeding for improvement; production technology; food quality and utilization; and the socioeconomic issues showed that many studies will still have to be made to further unravel the potentialities of this cereal. Sharp notice has been taken of research fields where there has been little progress in the last 10 years. A main value of the Symposium has been to determine work priorities for ICRISAT and the national programs in the SAT, and to emphasize the need for continued cooperation with other institutions. Sorghum in the Eighties has been a rewarding Symposium which has not lost sight of the basic objective to increase the yield and production of better sorghum to feed people

Systemic Infection of Sorghum by Acremonium strictum and Its Transmission Through Seed

The fungus Acremonium strictum was isolated from stems of wilted sorghum plants collected from Pantnagar, Uttar Pradesh, India, and its pathogenicity was established in the greenhouse. Of the several inoculation methods examined, drenching soil in pots containing 10-day-old plants of the susceptible cultivar IS 18442 with a conidial suspension of the pathogen resulted in more than 70% disease incidence. Disease symptoms in the greenhouse were similar to those in the field. Grains from diseased plants were small and shrunken with reduced weight, germination, and seedling vigor. A. strictum was isolated from all parts of infected plants, from roots to grains, indicating the systemic colonization of the host. Infected seeds produced diseased plants when sown in autoclaved soil

Etiology of stalk rot and lodging in grain sorghum

The effects of fungi alone, dmught-stres* alone, and in combination on the development of stalk rot (%lodging)Sorghum were studied in field experiments at ICRISAT Asia Center, Patancheru and at University of Agricultural Sciences, Dharwad in india. Stalk rot and lodging occurred In drought-stressed................