Exogenously applied putrescine improves the physiological responses of tomato plant during nematode pathogenesis

Polyamines are ubiquitous organic polyvalent compounds involved in regulating the plant growth and development. The present study deals with the investigation of their role in plant physiology during nematode pathogenesis. Tomato seeds var. Pusa Ruby (susceptible to nematodes) were treated with different concentrations (0.5, 0.7 and 0.9 mM) of putrescine and allowed to germinate in earthen pots. Seedlings were inoculated with second stage juveniles (J2s) of Meloidogyne incognita with 130 J2s per seedling. After 45 days of nematode inoculation, various growth parameters, stress indices, photosynthetic pigments, enzymatic and non enzymatic biochemical parameters were studied in control (C), nematode inoculated (NI) and nematode inoculated plus treated plants (NI + 0.5, NI + 0.7 and 0.9 mM). Percentage germination, number of leaves, shoot/root length, fresh shoot/root weight, and dry shoot/root weight enhanced with putrescine application whereas the number of galls, average gall index, number of egg masses and root knot nematode severity level decreased. Stress indices like H2O2 and MDA content decreased whereas proline content increased with putrescine treatment. Further, reduced specific activities of enzymes in putrescine treated infected plants and enhanced levels of non-enzymatic antioxidants depicted improved response of tomato plant during nematode stress. Thus, the polyamines were found to improve the physiological responses of tomato plant even during nematode pathogenesis.