D. J. Bagyaraj

Effect of crop rotation on native vesicular arbuscular mycorrhizal propagules in soil

The effect of crop rotation of native vesicular arbuscular mycorrhizal fungi was studied. Finger millet was grown as the first season crop in 15 plots. In the second season a mycorhizal host (cowpea) and a non-mycorrhizal host (mustard) were grown in 5 plots each, and the remaining 5 plots were left fallow. In the third season cowpea was grown in all the plots. Leaving the land fallow reduced the mycorrhizal propagules by 40% while growing a non-mycorrhizal host reduced it by 13%. Cowpea grown in the third season coincided with a slow build up of mycorrhizal propagules in soil. There was a slow build up of mycorrhizal propagules late in the season irrespective of the treatment in the preceding season.

Mycorrhizal colonization in cowpea is host dependent and heritable

Cowpea genotypes (101) of diverse origin were evaluated for their endomycorrhizal colonization under natural field conditions in an alfisol soil. There was considerable variation in colonization ranging from 0 to 28.6%. The genetic coefficient of variability was high (55.9), heritability moderate (46.2) with high genetic advance (78.3) revealing that mycorrhizal colonization is not only host dependent but heritable.

Use of pesticides for mass production of vesicular-arbuscular mycorrhizal inoculum

Nine fungicides, 3 nematicides and 5 insecticides/acaricides were incorporated into the pot cultures of the VAM fungusGlomus fasciculatum in order to study their effect on the mycorrhizal association and the contaminant organisms. All the pesticides were found to be deleterious to VAM at the recommended level. Captan and carbofuran, at half the recommended level (125 mg and 144.5 mg respectively/2.5 litre of the substrate mix), increased significantly the percentage root colonization, extra-matrical chlamydospore number and inoculum potential. Captan and carbofuran at this level also significantly suppressed the contaminant fungi and nematodes in the pot cultures ofG. fasciculatum. The insecticides/acaricides formothion and malathion at half the recommended level, had no deleterious effect onG. fasciculatum but suppressed mites and collumbola in pot cultures.

Growth and nutrient uptake of peanut inoculated with the mycorrhizal fungusGlomus fasciculatum compared with non-inoculated ones

SummaryIn a greenhouse study, inoculation with the mycorrhizal fungusGlomus fasciculatum enhanced peanut growth and increased its dry matter more than 2-fold compared with the non-inoculated control, in both sterilized and non-sterilized soil. It also significantly increased uptake of phosphorus and micronutrients such as zinc, copper, manganese and iron.

Interaction of vesicular arbuscular mycorrhiza with root knot nematodes in tomato

SummaryThe interaction between the VA mycorrhizal fungus,Glomus fasciculatus and the root-knot nematodes,Meloidogyne incognita andM. javanica, and their effects on the growth and phosphorus nutrition of tomato was studied in a red sandy loam soil of pH 6.0. Inoculation of tomato roots with root-knot nematodes enhanced infection and spore production byG. fasciculatus. Inoculation of tomato plants withG. fasciculatus significantly reduced the number and size of the root-knot galls produced byM. incognita andM. javanica. Inoculation withG. fasciculatus although improved plant growth and its total phosphorus content compared to the uninoculated plants, the difference were not statistically significant.

Preinoculation with VA mycorrhiza improves growth and yield of chilli transplanted in the field and saves phosphatic fertilizer

SummaryNursery beds were inoculated with four different VA mycorrhizal fungi,Glomus fasciculatus and three local isolates I4, I6 and I14, and mycorrhizal seedlings were transplanted to field plots with two levels of phosphatic fertilizer. Of the fungi studied, isolate I4 increased significantly growth, P and Zn nutrition, flowering, yield of chilli plants and also the ascorbic acid content of green chillies. Yield of I4 inoculated plants given half the recommended level of P was slightly more than the uninoculated plants given the full level of phosphatic fertilizer. This suggests the possibility of extending the simple technology of inoculating nursery beds with mycorrhiza to farmers in order to improve plant growth and save phosphatic fertilizer.

Effect of vesicular-arbuscular mycorrhiza on survival, penetration and development of root-knot nematode in tomato

SummaryEffect of mycorrhizal colonisation byGlomus fasciculatum on survival, penetration and development of the root knot nematodeMeloidogyne incognita in tomato was studied. The number of giant cells formed in mycorrhizal plants was significantly low. Mycorrhizal roots did not prevent the penetration by nematode larvae. Root extract from the mycorrhizal plants brought about 50% mortality of the nematode larvae in four days time.

Selection of a suitable host for mass production of VA mycorrhizal inoculum.

SummaryThis study was conducted to select a suitable host for maintenance and mass production of VA mycorrhiza since sudan grass does not grow well under Bangalore conditions. Of the eight grasses tested, guinea grass was found to be a better host since it is more susceptible to infection and also supported higher spore production by VA mycorrhizal fungus,Glomus fasciculatus.

Effect of four soil-applied insecticides on symbiosis of Rhizobium sp. with Arachis hypogaea Linn.

SummaryThe effect of four soil-applied insecticides viz. carbofuran, thimet, dasanite, and heptachlor at the recommended rate on the number, weight and leghaemoglobin content of root nodules and on the yield, dry weight, and nitrogen content of groundnut (Arachis hypogaea Linn.) inoculated with Rhizobium was studied. Application of thimet, heptachlor, and dasanite was found to reduce significantly the number of root nodules. But the size of the nodules was bigger and weighed significantly more compared to nodules in the control plants. Application of insecticides was found to have no significant effect on the leghaemoglobin content of the root nodules, yield, dry weight, and nitrogen content of the plants. It can be inferred that the application of these four insecticides to the soil at recommended rate has no harmful effect on nodulation and yield of groundnut inoculated with Rhizobium. re]19730529

Chloris gayana (Rhodes grass), a better host for the mas production ofGlomus fasciculatum inoculum

Seven different hosts,Panicum maximum, Chrysopogon fulvis, Themeda triandra, Chloris gayana, Brachiaria brizantha, Paspalum scrobiculatum andEleusine coracana were screened in order to select a better host for mass multiplication ofGlomus fasciculatum inoculum. Of these,Chloris gayana (Rhodes grass) was found to be the best host on the basis of root colonization and spore production and of the infective propagules of the potball.