Indian Phytopath. 57 (1) : 24-29 (2004) Towards an ideal method of inoculation for screening sugarcane genotypes against red rot caused by Colletotrichum falcatum S.K. DUTTAMAJUMDER and S.C. MISRA Division of Plant Pathology, Indian Institute of Sugarcane Research, Lucknow 226 002 ABSTRACT: Assessment of relative performance of plug method, nodal method, and the proposed Parafilm method of red rot inoculation was made. Inoculations were carried out in both plug and nodal methods as suggested by the AICRP on Sugarcane. In the proposed Parafilm method, nodal maturity of cane stalk was taken as the guiding factor for inoculation. Thus, 5 th or 6 th node (the node up to which leaf sheath can be removed from the node without breaking/injuring the top) of the cane stalk from the 1 st open leaf was taken for this purpose. After careful removal of the leaves, a sterile absorbent cotton swab (just sufficient to cover the node and easily holds 1 ml fluid) soaked in red rot inoculum (10 6 conidia/ml) was placed around the node and was sealed by wrapping Parafilm strip to prevent moisture loss. Immature nodes of the top catch more infection than the mature nodes at the bottom. The success of infection increased substantially, from the maximum 18 per cent in the nodal inoculations to the minimum 83 per cent in the Parafilm method. The Parafilm method excelled the standard plug method of inoculation with a consistent higher success rate of disease development. This method has the advantage of both nodal and plug method (placement of inoculum on the immature exposed node and advantage of superficial injury due to removal of leaf) and provides much more stable disease reaction for a longer period from July to November in comparison to both the prevalent methods. Key words: Red rot, resistance, inoculation technique, Parafilm, Colletotrichum falcatum, sugarcane Red rot, caused by Colletotrichum falcatum Went is the most important disease of sugarcane in India inflicting substantial loss to both cane industry and cane growers besides causing enormous expenditure to the exchequer for the identification and development of disease resistant/ moderately resistant genotypes. This disease has several epidemics to its credit and virtually during 1938-40, it wiped out sugarcane cultivation in eastern U.P. and northern Bihar. Once the disease appears in the field, there is no satisfactory chemical or physical control measure(s) that can effectively put a check on this disease (Duttamajumder, 2002). Therefore, to sustain the productivity of both cane crop and sugar it is imperative to breed and grow red rot resistant/ moderately resistant cane genotypes. The primary prerequisite for any successful breeding programme for disease resistance is an efficient method of screening of the segregating population of progenies to identify the desired resistant genotype(s). From the very beginning of systematic red rot research in India plug method was tried for the artificial production of red rot disease (Butler and Khan, 1913) and later this method became the main method of testing disease resistance against red rot pathogen (Duttamajumder, 1997). Over the years, plug method of screening has faced and still facing stiff opposition from the sugarcane breeders, as most of the promising cane genotypes fail miserably against red rot by this method. Since the popularisation of standard plug method by Chona (1954) objections were often raised as it is “too harsh a technique” and it does not take into account the physical barrier naturally offered by the rind and the nodal tissues to the germination of conidia, subsequent penetration and establishment