Tanweer Azam

Effect of different inoculum levels of Meloidogyne incognita on growth and yield of Lycopersicon esculentum, and internal structure of infected root

Lycopersicon esculentum (tomato) plants, grown in sterilised clay pots, were inoculated with 50, 500, 1000, and 3000 second-stage juveniles (J2) of the root-knot nematode (Meloidogyne incognita) and were kept in a greenhouse. A non-significant reduction in plant growth and yield was noticed in T1 plants. Significant reductions in plant growth and yield were found in T2, T3, and T4 plants. Highest reductions, in growth and yield, were observed in T5 plants. Transverse and longitudinal sections revealed that M. incognita traversed through the cortical tissues of the root, caused infection in the differentiating vascular tissues and successfully established in the infected roots. The post-infection changes in the affected parts were hypertrophy and hyperplasia, around the head of the nematodes. Five to 10, among the hypertrophied cells, developed into very large, multinucleate, prominent, and highly specialised giant cells. The nuclei in each giant cell enclosed one or more nucleoli. Xylem and the phloem strands were found to be disoriented. Abnormal xylem and phloem comprised a substantial portion near the giant cells. The metabolic changes in the affected part led to the formation of galls, characteristic of the root-knot infection.

Effects of PGPR and antagonistic fungi on the growth, enzyme activity and Fusarium root-rot of pea

The effects of plant growth-promoting rhizobacteria (PGPR) (Bacillus pumilus and Pseudomonas putida) and antagonistic fungi (Aspergillus awamori, Aspergillus niger and Trichoderma harzianum) were studied alone and in combination in glasshouse experiments on the growth, chlorophyll catalase and peroxidase activity and on the Fusarium root-rot of pea caused by Fusarium solani f. sp. pisi. Application of PGPR and antagonistic fungi caused a significant increase in growth, chlorophyll, catalase and peroxidase activities of both root-rot fungus inoculated and un-inoculated pea plants. Use of P. putida was more effective in reducing disease severity and improving the growth of root-rot fungus-inoculated plants than A. niger and T. harzianum. The greatest increase in growth, chlorophyll, catalase and peroxidase activities of root-rot fungus-inoculated plants and reduction in disease severity was achieved when A. awamori or B. pumilus was used with P. putida compared to other tested combinations.

Histopathology of roots of Glycine max (L.) Merrill induced by root-knot nematode (Meloidogyne incognita)

In Glycine max, the second-stage juveniles of Meloidogyne incognita entered the roots through the apical meristem or elongation zone. The juveniles induced giant cells in the zone of vascular strands. Near the head of the nematode and adjacent to the giant cells, the vascular strands exhibited abnormalities in their shapes and structures; both xylem and phloem were found to be affected. The giant cells had dense and granular cytoplasm, and large nuclei with large nucleoli. Some parenchyma cells exhibited hypertrophy, while others exhibited hyperplasia. The distinctive feature of the study is reporting the occurrence of abnormal xylem, abnormal phloem and abnormal parenchyma.

Pathogenicity of root-knot nematode, Meloidogyne incognita on Lens culinaris (Medik.)

Effects of the root-knot nematode (Meloidogyne incognita) on lentil (Lens culinaris) were studied under greenhouse conditions. The plants were inoculated with 250, 500, 1000, 2000 and 4000 J2 per plant. Plant growth, yield, nodulation, seed weight, chlorophyll, nitrogen, phosphorus and potassium, (NPK) contents, as compared to control, were found decreased in all the nematode infected plants. The extent of reduction increased with an increase in inoculum levels. The reductions were significant at 500 J2 and at higher inoculum levels, i.e. 1000, 2000 and 4000 J2 per pot over the control. An increase in inoculum level caused enhancement in galling, egg mass production and nematode population. At higher inoculum levels, the population of the nematode in the root as well as in the soil increased to a greater magnitude than at lower inoculum levels. On the contrary, reproduction factor (RF) and rate of population increase (RPI) decreased with increasing inoculum levels.