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Molecular basis of systemic acquired resistance against diseases and allelopathic interactions in horticultural crops(Ongoing)

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  • To assess the efficacy of simple inorganic molecules exhibiting SAR characteristics
  • To understand the biochemical mode of action of simple inorganic molecules exhibiting SAR characteristics
  • To study the effects of a few SAR chemicals on the incidence of Alternaria infection on tomato
  • To develop a method for the management of Alternaria in tomato by application of SAR agents
  • To determine the effects of cropping sequence on weed population dynamics, resource competition between crop and weed and allelopathic impact of crop residues.
  • To work out specific components of cropping sequences that may be important for weed control/management and crop yield.
  • To understand the benefits of allelopathic cover crop, Mucuna utilis, when taken in rotation with vegetable crops
  • To study the benefits of allelopathic cover crop on soil physical, chemical and biological properties
  • To develop suitable non-chemical strategies for weed management for horticulture cropping systems.


Date of start of this programme: July 2007




S Shivashankar




V. Ravindra

V.K. Rao

A. Ganesha Murthy

Paneer Selvam




  • Application of the elicitor  to tomato leaves before infection by the pathogen resulted in a rapid increase of the activities of antioxidative enzymes like, peroxidase, polyphenol oxidase  and superoxide dismutase  as against little or no change in pathogen infected samples.
  • Plants treated with the elicitor followed by the pathogen also showed a marked increase in the activities of both Peroxidase and SOD up to 7 days indicating that the chemically induced enzyme activity using elicitor was positively responding to host-pathogen interaction.
  •  Results revealed that the elicitor application before pathogen helps to induce positive defense reaction in tomato for at least 7 days and remained active for up to 12 days as shown by the activity of SOD.
  • The levels of the three ROS namely, superoxide, hydroxyl and hydrogen peroxide showed a marked increase in elicitor treated plants as compared to control plants. The results indicate that the disease controlling effect of phosphate was mediated by the host response.
  • The tomato plants treated with the elicitors were found to be protected against the pathogen by as much as 60%.
  • The weed species including the noxious weed, Cyperus were checked to an extent of >95% by   Mucuna.
  • Weed species like Mollugo, Urena, Portulaca, Bacopa, Euphorbia, Digitaria, Eclipta Sonchus etc have been completely eradicated.
  • Mucuna has left about 20t/ha biomass at harvest.
  • The analysis of soil samples revealed substantial increase in the contents of phenolic acids like p-hydroxy benzoic acid, vanilic acid, p-coumaric acid and syrengic acid.
  • The total phenolic acids were more than twice as compared to the samples drawn from non-Mucuna area.
  • The fungi counts (X 105) were more than twice in the area where Mucuna was grown as compared to non-Mucuna area. The Bacteria and Actinomycetes population was also substantially higher in the Mucuna grown area.
  • Glomalin”, a polysaccharide, involved in soil aggregate stability was found to increase by three fold in Mucuna plot over non-Mucuna plot.  This is a confirmation test to say that soil quality improves following Mucuna cultivation.
  •  Mucuna residues had no deleterious effects but benefited these vegetable crops by increasing their yields by 10 to 15% through improvement in soil physical, chemical and biological properties besides providing excellent weed control by more than 98%.
  • The studies revealed that the allelopathic activity of the crop wastes is two dimensional in nature. Firstly, allelopathy has a physical dimension in the form of shade to prevent the germination and growth of certain weed seeds of the soil seed bank. Secondly, the chemical dimension of allelopathy is caused by release of allelochemicals in to the soil from the organic mulches due to their bio-degradation in course of time.
  • Most significant achievement: It is possible to control / eradicate the highly noxious weed Cyperus allelopathically through continuous use of allelopathic crop wastes as mulches, which otherwise cannot be controlled with any of the pre-emergent weedicides available in our country.
  • Growing crops in mango orchards with minimum tillage can control weeds, enhance biodiversity, alter pest and disease dynamics, improve soil health, and enhance carbon sequestration in addition to additional income to the farmers.
  •  French bean, sweet potato and potato as sole crops and Mucuna as cover crop under mango orchard can be recommended for cultivation in bearing mango orchards in peninsular India.