Root-knot nematodes, (Meloidogyne spp.) are main pathogens of tomato in India. A survey was undertaken to find out the effect of physico-chemical properties of soil on the incidence and infestation of two root-knot nematode species namely Meloidogyne javanica and Meloidogyne incognita on tomato growing fields in Aligarh. Maximum disease frequency (87.5%) was found in Shah Jamal and Mahraval and minimum (25%) was found in Chherat Sudhal. Population density of Meloidogyne spp. was found to be the highest (750 J2 100 cmG 3) in Mahraval while as the lowest (170 J2 100 cmG 3 in Chherat Sudhal. The highest nematode population observed in Mahraval having greater nitrogen, phosphorous and potassium with somewhat higher moisture content in the sandy loamy type of soil. Least nematode population was observed in Chherat Sudhal with least nitrogen, phosphorous and moisture content. Analysis of correlation coefficient showed that population of Meloidogyne spp. had significantly positive correlation with sand percentage, soil moisture, organic carbon, nitrogen, phosphorous and potassium while negative correlation with the silt, clay, soil temperature and soil pH at (p#0.01). A total of 59 (61.45%) samples out of 96 were found infested with root knot nematode Meloidogyne spp. showing 83 and 75% distribution of M. javanica and M. incognita.

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The present investigation was conducted to evaluate the silicon (Si) mediated responses in different cultivars of Indian mustard (Brassica juncea) and to evaluate if Si could be used as an essential, beneficial, or quasi-essential element for growth and development of these cultivars. Surface sterilized seeds were sown in pots and allowed to germinate under natural environmental conditions. At 10, 12, 14, 16, and 18 days after germination, a range of Si concentrations (0.0, 0.2, 0.4, 0.8 and 1.6 mM) was administered to the soil and at 30 days post germination the plants were sampled to assess growth and development, leaf gas exchange traits and plant biochemical parameters, including activities of carbonic anhydrase, catalase, peroxidase, superoxide dismutase, and protein and proline content. The results demonstrate a dual response to Si concentration: 0.8 mM of Si significantly increased plant growth and development (length of root and shoot, fresh and dry biomass, and leaf area) and photosynthetic efficiency, and enhanced the antioxidant response in T-59 over all the other cultivars tested, whereas, 1.6 mM of Si significantly reduced the above parameters. It is therefore concluded that low levels of Si could be used as a quasi-essential element for enhanced photosynthetic efficiency and antioxidant response ofBrassica junceaplants; however, the response is cultivar specific and concentration dependent.

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