| Slow rusting mechanism for leaf rust operating in bread
wheat varieties (Triticum aestivum L.) against Puccinia recondita
f.sp. tritici Rob. Ex Desm. SHRISHAIL S. NAVI, SRIKANT KULKARNI and R.K. HEGDE Department of Plant Pathology, University of Agricultural Sciences, Dharwad-580005, India Leaf rust of wheat caused by puccinia recondita f.sp. tritici Rob. ex Desm. is one of the dangerous diseases in reducing the yield and quality of the wheat grains. This disease is known to occur in all the wheat growing tracts of the world. In India, the two successive epidemics of leaf rust have been reported during 1971-72 and 1972-73 from North-Western regions causing a loss of 0.8 to 1.0 million tonnes and 1.5 million tonnes respectively (JOSHI et al. 1975). The experiments conducted revealed that, the rapid loss of race specific resistance (vertical resistance) to cereal rusts has attracted the attention of plant breeders and plant pathologists to other form of resistance which may be more durable (SINGH 1985). The term slow rusting among others, has been applied to such resistance which allow some disease to develop, may result in reduced selection pressure for preferential development of previously undetected virulent rust strains and accordingly may remain effective longer such forms of resistance may have the effect of slowing down development of an epidemic (ROMING 1957, HOOKER 1967). WILCOXSON (1986) shown that slow rusting vary with environment as well as races of pathogen. Among the different control measures use of slow rusting varieties is also playing an important role against leaf rust of wheat. Hence, an attempt was made to study the slow rusting mechanism in T. aestivum (Bread wheat). Material and Methods An experiment on slow rusting mechanism was carried out at Agricultural College Farm, Dharwad, varieties included under the study were DWR-16, DWR-39, HD-2189, NI 5439, HD 2278, Kalyan Sona, Sonalika, Lal Bahadur and CC-464. These varieties were sown separately in each plot (2m x 2m) during rabi season of 1985 - 86 in a randomised block design with three replications. After one and half months of sowing, uredospore suspension was sprayed once in a week. Uresospore inoculum of leaf rust was collected from Regional Wheat Rust Research Station, Mahabaleshwar, IARI Regional Station, Flowerdale, Shimla and IARI Regional Station, Wellington (Tamil Nadu). Disease severity was recorded in each variety for every week (by following the scale given in Fig. 1 ) and average coefficient of infection was calculated by multiplying the percent infection (severity) by the response value, assigned to each infection type (LOEGERING 1959). So that both the intensity of infection and type of reaction may be combined to study the disease progress in each variety. Further 1000 grain weight and yield data were recorded. |
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