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 Exherohilum turcicum, 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 E. turcicum 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 E. turcicum 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 E. turcicum 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.

A large‐scale survey reveals agro‐ecological factors influence spatio‐temporal distribution and epidemics of maize leaf blight: Implications for prioritizing sustainable management options

“…Similarly, the NLB is favoured by mild temperatures (15–25°C), high relative humidity (90%–100%), extended periods of leaf wetness, and frequent light showers as noticed by Ogliari et al (2007). It had also been reported that the distribution and development of NLB is favoured by long dew periods, and cool to moderate temperatures with high relative humidity across maize‐growing areas of the world (Ahangar et al, 2022; Badu‐Apraku et al, 2021). Hence, extreme impact of leaf blight on maize in the mid‐ and high‐land agro‐ecologies of Uganda, Kenya, Ethiopia, Zambia and South Africa have been reported (Ramathani et al, 2011).…”

“…Such environmental conditions may support sporulation and conidia germination, infection, establishment and development of NLB in maize. Other studies also reported that epidemic of NLB is influenced by weather variables, among other factors (Ahangar et al, 2022;Badu-Apraku et al, 2021;Camera et al, 2019;Wathaneeyawech et al, 2015).…”

“…The practices could play a role in the accumulation and dissemination of crop residues that are potential sources of reservoir inocula for infection and NLB development. Ahangar et al (2022) also indicated that the fungus has saprophytic survival which overwinters as dormant mycelia, conidia and chlamydospores on maize residues, and could serve as the primary inoculum for the next crop (De Rossi et al, 2015).…”

“…Moreover, maximum and minimum turcicum leaf blight severity were recorded at grain filling and vegetative growth stages in that order in northern Karnataka of India (Kalappanavar, 2017). That is, the damage becomes more pertinent at late silking to dough or maturity growth stages (Ahangar et al, 2022;Jackson-Ziems, 2016;Meghana et al, 2022).…”

“…Moreover, earlier survey in different areas also documented that both local and released varieties had different susceptibility performance to NLB or turcicum leaf blight (Aliyi et al, 2018;Ramathani 2011). Thus, the development of genotypes with resistance to E. turcicum is the most efficient and inexpensive way for NLB management (Ahangar et al, 2022), as genotype resistance could reduce NLB by limiting lesion formation, prolonging the incubation period and/or production of fungal spores (Jackson-Ziems, 2016).…”