RA 00110.pdf - OAR@ICRISAT

above 15 ppm. Nitrogenase activity of millet and sorghum plants in the greenhouse was stimulated by the
addition of 20 kg ha" 1 N over the control without applied N, but higher doses of N than 20 kg ha -1 reduced the
activity. In tube culture studies of millet plants grown in unsterilized Alfisol and sand.FYM (93:3 w/w)
mixture, nitrogenase activity was higher in tubes inoculated with a culture of some nitrogen-fixing bacteria
than in noninoculated tubes.
Mycorrhiza in Cereals
(Mycorhizes chez les cereales)
D.J. Bagyaraj
Microbiologist, Department of Agricultural Microbiology, University of Agricultural Sciences, GKVK
Campus, Bangalore, Karnataka 560 065, India
The most common mycorrhizal association in crop plants is the vesicular-arbuscular mycorrhizal ( V A M )
type, which produces vesicles and arbuscules in the cortex region of the root. These associations are
geographically ubiquitous and occur over a broad ecological range, from aquatic to desert environments.
They are formed by nonseptate phycomycetous fungi belonging to the genera Glomus, Gigaspora, Acaulospora,
and Scekrocystis in the family Endogonaceae. These fungi are obligate symbionts and have not been
cultured on nutrient media. It is now well established that V A M improve plant growth, mainly through
improved phosphorus nutrition. Other beneficial effects are a role in the biological control of root pathogens,
enhancement of biological nitrogen fixation, hormone production, and greater ability of the host plant to
withstand drought stress. In the last few years there has been a rapid increase in the number of scientists
working and publishing on the biology of V A M . Reviewing the progress at this point one could visualize
research in two main directions. First there is continued emphasis on the measurement and prediction of plant
growth responses, inoculum production, and field inoculation. Second there has been great progress in our
basic understanding of the V A M symbiosis, especially in the areas of anatomy, taxonomy, physiology,
ecology, axenic culture, and biological interactions. The current status of V A M research with special emphasis
on cereals is discussed.
Vesicular-Arbuscular Mycorrhizal Symbiosis in Relation to Pearl Millet Phosphorus
Nutrition
(Symbiose vesiculaire-arbusculaire des mycorhizes liee a la nutrition en phosphore du mil)
K.R. Krishna
Microbiologist, Pearl Millet Group, ICRISAT, Patancheru, Andhra Pradesh 502 324, India
and
K.K. Lee
Principal Cereals Microbiologist, ICRISAT, Patancheru, Andhra Pradesh 502 324, India
Vesicular-arbuscular mycorrhizal ( V A M ) association with pearl millet is ubiquitous in the SAT regions of
both India and West Africa. The extent of root colonization, the fungal species involved, and their densities
differ with location. Glomus spp. predominate in Indian soils, but pearl millet in West Africa is predominantly
colonized by Gigaspora spp.
A series of experiments in pots conducted in India and West Africa has shown that V A M inoculation
increased growth and phosphorus uptake. The extent of increased phosphorus uptake varied with the
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