Saturday, 15 July 2006

Zinc Efficient Rice Genotypes Resistant to Nematode Infection?.

Ramasamy Krishnasamy1, Chinnappan Sudhalakshmi1, U. Surendran1, and A. RajaRajan2. (1) Tamil Nadu Agricultural Univ, Lawley Road, Coimbatore, India, (2) Regional Research Station, Tamil Nadu Agricultural Univ, Vridhachalam, India

Today, than ever before, the importance of zinc (Zn) in crop production is being felt. It is estimated that about 50 % of the soils used for cereal production in the world have low levels of plant available Zn. Correction of Zn deficiency via fertilization always dose not become a successful strategy due to agronomic and economic factors. A more efficient and sustainable solution to Zn deficiency limitation is the development and use of Zn efficient rice genotypes with the root system capable of greater mobilization that can more efficiently function under low soil Zn conditions. Zinc also variously decreased, increased and imparted no effect on plant's susceptibility to disease, although reports of decreases dominate. Though the present investigation was not intentional to bring out the influence of zinc efficiency on relative/ susceptibility to pest and disease infection, incidentally, the interaction of Zn with nematode infection could be established. About 10 kg soil was filled in ceramic pots and two rice genotypes viz., Norungan (Zn efficient) and PMK 3(Zn inefficient) were grown. Graded levels of zinc sulphate (labeled with 65Zn) were employed which include T1 control; T2 ZnSO4 @ 12.5 kg ha-1; T3 ZnSO4 @ 25 kg ha-1; T4 ZnSO4 @ 37.5 kg ha-1 and T5 ZnSO4 @ 50.0 kg ha-1. The experiment was laid out in factorial completely randomized design with each treatment replicated thrice. It was observed that the Zn efficient Norungan did not witness any nematode infestation whilst it was more conspicuous in PMK 3. The intensity of infestation reduced conspicuously with increased dose of applied zinc. The structural and functional integrity of cellular membrane is greatly affected by the lack of Zn, which plays both structural and protective roles in membrane integrity. There are reports indicating that due to the exudation of several organic compounds, carbohydrates or aminoacids, Zn deficient plants may be susceptible to root diseases such as Fusarium graminearum and Rhizoctonia solani (Sparrow and Graham, 1988). Graham (1983) has reported the suppressive effect of Zn on the infection of soil borne pathogens. Zinc deficient roots might leak more carbohydrates and attract zoospores by chemotaxis. The case witnessed here was that the Zn inefficient Norungan did not show any symptom of nematode infection, though grown under the same environmental condition. Further investigation is needed to unravel the unexplored aspect of the interaction of zinc nematode complex. Keywords : genotypes, nematode, zinc efficiency. References: (1) Graham, R.D. 1983. Effects of nutrient stress on susceptibility of plants to disease with particular reference to the trace elements. Adv. Bot. Res. 10: 221 276. (2) Sparrow, D.H. and R.D. Graham. 1988. Susceptibility of zinc-deficient wheat plants to colonization by Fusarium graminearum Schw. Group 1. Plant Soil 112: 261 266.

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