Disease resistant maize variety to be a reality soon

By Shikha T. Malik

New Delhi: We all relish maize – be it as popcorn, sweet corn or corn flakes. It is the world’s leading cereal grain. Its global production surpasses both wheat and rice. India is one of the eight major maize growing countries in Asia. However, its production is affected due to various diseases. Scientists are now a step closer to developing a disease-resistant maize variety.

Sorghum Downy Mildew (SDM), which is an important foliar disease caused by a fungus called Peronosclerosporasorghi, has been an issue of major concern for maize famers. A chemical compound, Metalaxyl, is used to kill the fungus but its effectiveness has been declining as the fungus developed resistance due to extensive use.

Scientists at International Maize and Wheat Improvement Centre (CIMMYT) at Hyderabad have, in collaboration with their counterparts in Nairobi, Kenya, recently come up with new findings that promise to help out.

The scientists conducted a genomic study for SDM resistance in a panel of 368 inbred lines adapted to the Asian tropics. Along with previously reported regions conferring resistance to SDM, they have identified novel SNPs in the genome that are shown to be important. SNPs or Single Nucleotide Polymorphism is a variation in a single nucleotide – the basic unit of DNA- that occurs at a specific location in the genetic code. Each change or variation is present to some degree within a population.

“Downy mildew being a devastating problem for the entire Asian maize cultivation, understanding the genetics of the trait, and using that information in breeding resistant varieties is an ecologically efficient way of managing the disease,” explained Dr Sudha K Nair, senior molecular geneticist at CIMMYT who led the team.

The group has used a panel of 400 maize inbred lines and genome-wide SNP markers for identifying genomic regions responsible for quantitative resistance towards downy mildew in maize.

“We are in the process of validating the resistance-associated SNP markers in our maize breeding program, which could then be shared with all our partners, both public and private, for routine use in maize breeding programs in the region,” Dr Nair added.

“This study has identified eight novel genomic regions associated with SDM resistance, which is significant. This, along with ten marker-phenotypic trait associations identified, could provide critical information for future studies for improvement of breeding programs in maize”, commented Dr. Vishal Acharya, scientist at the CSIR-Institute of Himalayan Bioresource Technology, Palampur, who was not part of the study.

The International Maize and Wheat Improvement Center, known by its Spanish acronym, CIMMYT, is one of the 15 agricultural research organizations that make up the Consultative group on International Agricultural Research.

The research team included Zerka Rashid, Pradeep Kumar Singh, Hindu Vemuri, Pervez Haider Zaidi, and Sudha Krishnan Nair (all from CIMMYT, Hyderabad); and Boddupalli Maruthi Prasanna (CIMMYT, Nairobi). The study results have been published in journal Scientific Reports.

(India Science Wire)