STALK STRENGTH IMPROVEMENT IN CROP PLANTS: A PROGRESS REPORT

Stalk lodging is one of the serious problems in all cereal crops that can result in enormous yield loss. Severe stalk lodging interferes with mechanical harvest resulting in loss of grain. The genetics of stalk strength is complex and inmost crops the trait is controlled by multiple minor quantitative trait loci (QTLs). Screening for stalk strength is not only variable from crop to crop because of variable stalk structures but also time consuming and has reproducibility issues. A series of mutants including brittle culm in rice and brittle stalk in maize have been isolated. Similarly, potential candidate genes showing close association with genes involved in the biosynthesis of cell wall components like cellulose and lignin have been cloned in rice, maize, barley, and Arabidopsis. Several QTLs for stalk strength have been mapped in maize, rice, canola, and soybean using GWAS and genomic selection approaches. To our knowledge, candidate genes for only two QTLs have been cloned by map-based cloning approaches including stiff1 in maize and SCM2 in rice. So far, transgenic approaches such as overexpression of the candidate gene, gene silencing, and genome editing have been used only for candidate gene validation and not for any crop development. However, novel beneficial alleles identified by allele mining or generated by transgene/gene editing approaches may be combined through marker-assisted selection (MAS) to supplement the conventional breeding process for improving stalk strength and lodging resistance. In this article, we review the published information on stalk strength and update its status in crop plants.