Sorghum Diseases in India

Message from ICRISAT
This book is important for three reasons:
1. The widening food gap in the third world, especially in sub-Saharan Africa, is of great concern to
humanity. The only hope of narrowing this gap is by the use of improved production technology.
Disease-resisting high-yielding genotypes are the kingpins of this technology.
2. This book reflects 10 years of intense activity in sorghum research and we should pause and take
stock of the world situation and plan new strategies for research and development in the war
against diseases and pests.
3. ICRISAT wishes to benefit from the matters discussed in this book to evolve its strategic plan.
Increasing severity of diseases of sorghum and millet, particularly of pearl millet in Africa, is a
matter of great concern. Moreover, a second generation of problems accompanied the introduction of
new technologies based on shorter duration and higher-yielding genotypes; these problems call for
new strategies for removing the stress of diseases and pests. The new problems call for more intensive
and interdisciplinary efforts of research for achieving a breakthrough in the control of diseases for
increasing productivity.
We critically review, in this book, the advances in knowledge and the progress which we have
made in understanding, managing, and reducing the incidence of the diseases and developing genotypes
resistant to them.
In 1978, grain mold and stalk rots were identified as major disease problems of improved sorghum.
Ten years later, these diseases continue to be at the top of our list. ICRISAT scientists claim that they
have developed sound techniques for identification of resistant material and selected stable sources of
resistance, but this information is only of academic interest unless sorghum breeders make effective
use of this material, incorporating its resistance into agronomically superior sorghums.
Five years ago, an international workshop on stalk rot of sorghum critically reviewed the stalk rot
situation and made specific recommendations. I understand suitable techniques for screening for
disease resistance have been developed, but we have to go a long way to transfer this resistance to
sorghums with agronomically desirable backgrounds.
Sorghum leaf diseases are thought to be more serious in Africa. Some are endemic to certain
regions; in some cases, we do not know if they reduce yields significantly. Without understanding the
mechanisms of disease resistance or the processes and benefits of national and international cooperation,
success in building up disease resistance is difficult.
Certain diseases, such as ergot and viruses, are affecting the hybrids more than the varieties, and
steps need to be taken to develop resistance against them.
Some pathologists claim that downy mildew of sorghum is no problem. Sources of resistance are
available, as is the knowledge for controlling this disease in sorghum. Judging from the incidence of
this disease in sorghum fields at the Bulawayo facility, I believe we have a long way to go to achieve
success. In pearl millet, downy mildew still remains the severest enemy of the crop. We need to know
more about the mechanism of resistance of this disease. We cannot ignore the fact that there are more
virulent pathotypes in Africa than in India, and that resistance to disease is short-lived and breaks
down quickly. While the breeders are developing newer and newer genotypes resistant to the disease,
the pathogen is evolving more-virulent types. Surprisingly, the wild relatives of pearl millet show no
evidence of resistance to the new pathotypes. There is perhaps a silver lining in the dark cloud,
however, ICRISAT pathologists have found that, even in the susceptible hybrids and cultivars of pearl
millet, an odd plant will show recovery resistance to the pathogen. In the initial stages, these plants
may develop disease under severe disease pressure but later on will outgrow the disease and produce
a normal yield. Some varieties show greater percentages of recovery than others. S.B. King and
J. Craig explain it more authoritatively. This is an important mechanism of survival in cultivars, and
needs to be exploited. I suggest that a team of geneticists and pathologists study this phenomenon
critically, as it seems to hold the key to success in dealing with this disease.
vii