Application of molecular approaches to characterize pathogens, disease diagnosis, host resistance and addressing emerging diseases in sugarcane

Abstract

The common fungal diseases affecting sugarcane such as red rot, wilt and smut were recorded nearly a century ago. Although research efforts were continued for many decades the disease severity remains a concern in many endemic regions. Varietal break down due to red rot affects longevity of many elite cultivars. Apart from these diseases, yellow leaf disease (YLD) caused by SCYLV and leaf fleck caused by SCBV are the recently reported disease from almost all parts of the country. Besides these, RSD, mosaic and sugarcane grassy shoot diseases are omnipresent and are associated with varietal degeneration along with YLD. Recently, the country witnessed sudden outbreak of minor diseases such as pokkah boeng, brown spot and rust in severe form threatening cane cultivation. Overall, these diseases affect cane yield and quality and decide cultivation of a specific variety in a region. Apart from identifying sources of resistance to major diseases, focused studies were made to manage the diseases through novel approaches, characterizing the associated pathogens, developing diagnostics and host resistance. Through detailed pathogenic and molecular studies, Fusarium sacchari was established as sugarcane wilt pathogen. Genomic and proteomic approaches have enhanced understanding of red rot resistance mechanism in sugarcane. Recently NGS platform has been utilized to further understand the resistance mechanism and many genes involved in red rot resistance have been identified from sugarcane. Genome and transcriptomes of red rot pathogen have been sequenced and characterized for the first time. It has been established that both SCMV and SCSMV cause mosaic in India either separately or together. SCSMV was characterized as a new genus “Susmovirus” in the family Potyviridae based on its distinct coat protein genome. Apart from genome characterization of different pathogens, sensitive molecular techniques were developed for the precise diagnosis of the pathogens. Elimination of different viruses and phytoplasma through meristem culture combined with molecular diagnosis has been successfully applied to produce healthy planting materials in sugarcane in the country. To manage the emerging diseases, efforts were made to identify resistant progenies and sources of resistance in the parents/germplasm by employing new screening techniques. Further, efficient fungicide delivery systems through sett treatment and in field have been developed to enhance fungicide efficacy against major fungal pathogens and their management in sugarcane.