First comprehensive study on distribution frequency and incidence of seed-borne pathogens from cereal and legume crops in Sri Lanka

Abstract

Sri Lanka as an agricultural country requires seed health testing to manage crop diseases. So far no comprehensive research has been carried out for the proper identification of seed mycoflora affecting the seed quality in Sri Lanka. The present study strives to address this issue by identifying seed-borne fungal pathogens from stored seeds using morpho-molecular characterization. Fungal pathogens were isolated from surface-sterilized and non-surface sterilized seeds of Arachis hypogea, Oryza sativa, Vigna radiata, and Vigna sinensis. PCR amplification and DNA sequencing of the internal transcribed spacer (ITS) region was carried out for molecular identification of pathogens. The germination quality of each seed variety was calculated by pot experiments. Distribution frequencies, percentage of germination, and seedling vigor were calculated and analyzed for each seed variety tested. In total eighteen isolates were recovered from the four seed varieties. Molecular characterization revealed that the fungal isolates recovered from all the four seed varieties belong to seven genera: Aspergillus, Bipolaris, Daldinia, Macrophomina, Orbilia, Rhizopus, and Talaromyces. Rhizopus spp. showed the highest distribution frequency (75%). Arachis hypogea showed the lowest germination percentage (20%) and lowest seedling vigor index (585). The seeds of Oryza sativa showed no germination probably due to their high incidence of fungal pathogens (four out of seven genera). This study is the first comprehensive study analyzing the seed-borne pathogens of the four most commonly consumed Sri Lankan cereal and legume crops. Results reported in this study helps to identify and implement optimum storage facilities and control such fungal pathogens in future agricultural practices.