Distribution, Etiology, Molecular Genetics and Management Perspectives of Northern Corn Leaf Blight of Maize (Zea mays L.)

Abstract

Maize is cultivated extensively throughout the world and has the highest production among cereals. However, Northern corn leaf blight (NCLB) disease caused by <i>Exherohilum turcicum</i>, is the most devastating limiting factor of maize production. The disease causes immense losses to corn yield if it develops prior or during the tasseling and silking stages of crop development. It has a worldwide distribution and its development is favoured by cool to moderate temperatures with high relative humidity. The prevalence of the disease has increased in recent years and new races of the pathogen have been reported worldwide. The fungus <i>E. turcicum</i> is highly variable in nature. Though different management strategies have proved effective to reduce economic losses from NCLB, the development of varieties with resistance to <i>E. turcicum</i> is the most efficient and inexpensive way for disease management. Qualitative resistance for NCLB governed by Ht genes is a race-specific resistance which leads to a higher level of resistance. However, some Ht genes can easily become ineffective under the high pressure of virulent strains of the pathogen. Hence, it is imperative to understand and examine the consistency of the genomic locations of quantitative trait loci for resistance to NCLB in diverse maize populations. The breeding approaches for pyramiding resistant genes against <i>E. turcicum</i> in maize can impart NCLB resistance under high disease pressure environments. Furthermore, the genome editing approaches like CRISPR-cas9 and RNAi can also prove vital for developing NCLB resistant maize cultivars. As such this review delivers emphasis on the importance and current status of the disease, racial spectrum of the pathogen, genetic nature and breeding approaches for resistance and management strategies of the disease in a sustainable manner.