| Changes in ribonucleases and protein content after
powdery mildew inoculation on different genotypes of wheat U.S. KANUGO and H.S. CHAWLA Plant Breeding Dept., G.B. Pant University Pantnagar, U.P. 263145, India Wheat, which is one of the most important cereals, is affected by various fungal diseases. Powdery mildew (Erysiphe graminis f.sp. tritici) is an obligate fungal pathogen. Infection on higher plants by the pathogen is accompanied by major changes in the metabolism of the host. Changes in soluble protein content takes place during pathogenesis (De WITT et al., 1980) and new proteins are also synthesized (GIANINAZZI et al., 1980). Role of ribonucleases in disease resistance has been reported by ROHRINGER et al. 1961, RANDLES 1968, and SUTTON & SHAW 1982. In vew of this, role of proteins and ribonucleases were studied during pathogenesis in different lines of wheat carrying powdery mildew resistant genes and susceptible cultivars. Materials and Methods Material consisted of 14 gonotypes with different powdery mildew (Pm) resistant genes in donor parents (P) and crossed with Chancellor variety in hybrid combination (H) along-with susceptible cvs Chancellor, Lal bahadur, Agra local and Kharchia local. Plants were raised in glass house under controlled conditions. After 100 days of germination one set of pots were inoculated with Pm pathogen with the procedure given by ARYA (1962) with little modifications. One set of pots were kept free from disease i.e., healthy uninoculated. Protein estimation and enzymatic studies were conducted on inoculated and healthy genotypes after 10th, 15th and 20th day of inoculation on 100 day old plants. The extract was prepared by homogenising 2g of sample material in prechilled mortar and pestle. The homogenate was centrifuged at 12,000g for 20 min at 0C. Soluble proteins were estimated by dye binding method of BRADFORD (1976) and ribonuclease I (RNase I) and combined ribonuclease II and nuclease I (RNase II + Nu I) activities were determined by the procedure of SODEK & WRIGHT (1969) with some minor modifications. The spectrophotometric readings were converted to standard units as described by WILSON (1975) and the specific activity was calculated from these units. Results and Discussion Total soluble protein content in resistant and susceptible genotypes and in both inoculated and healthy plants showed no marked difference at the 10th day stage. At 15th day stage, protein content was generally less in the inoculated and healthy genotypes of resistant plants in relation to susceptible genotypes. There was little increase or decrease at the 20th day stage. However, the soluble protein in resistant genotypes was lower as compared to susceptible genotypes (Fig. 1a). JOHNSON et al. (1968) also did not observe any variation between healthy and inoculated leaves infected with Erysiphe graminis f.sp. hordei and in wheat leaves infected with Puccinia recondita. |
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