Vegetos

Abstract

Rice false smut [Ustilaginoidea virens (Cooke) Takahashi] is an upcoming major disease in India. The chlamydospores of test pathogen associated with paddy seeds as concomitant contamination drastically reduce seed quality parameters. Physical methods of seed health testing are not successful to identify inoculums with seeds and hence the rapid and reliable techniques are essentially required for detection of U. virens in paddy seeds to formulate better management strategies. Presently, the light microscopy demonstrated distortion of lemma and seed coat but results were inconsistent with different samples. Therefore, we standardized an advanced microscopy (SEM) and simple PCR techniques. These two methods could detect the U. virens associated with apparently healthy seeds having very few chlamydospores. Further analysis with seeds of susceptible variety (Pusa 44) confirmed reliability of SEM, displaying proliferation and penetration of infective hyphae from single spore into seed coat/glumes. The low level of pathogen inoculums (100 spores-seed) was detected (109 bp) by amplifying two μl of total genomic (16srDNA) of this pathogen by using ITS and specific (Uvr1497F and Uvr1586R) primers. We confirmed by using pure inoculums as positive control and with healthy seed coat from susceptible variety as negative control during amplification of 16srDNA of the pathogen. The partial genome sequencing of U. virens was positive for apparently healthy seeds with U. virens. Sequences of two representative isolates (U.v-H and U.v-K) were deposited (KJ195461 and KJ195462) in GenBank database. Therefore, both advanced methods could be useful for rapid and reliable detection of rice false smut pathogen (U. virens).