The emerging role of genomic tools in mulberry (Morus) genetic improvement

Mulberry (Morus L) is one of the economically important trees that have a long history of extensive cultivation in Asia. Mulberry leaf is the sole food for the silkworm Bombyx mori; hence, the sustainability of the sericulture industry is dependent on the continuous supply of nutritious mulberry leaf. Genetic improvement of mulberry for leaf yield, leaf nutritional contents, and adaptability has great socioeconomical importance because the sericulture is the backbone of rutal economy in several Asian countries. Much effort has been made on germplasm collection, characterization, and varietal development through conventional methods. However, the complexity of important agronomic traits, the substantial lag time between germination and sexual maturity, the absence of inbred lines, and the outbreeding nature of mulberry delay the genetic improvement via conventional breeding techniques. In this postgenomic era, having the next generation sequencing facilities in its fold, it is possible to integrate modern genomic tools with conventional breeding techniques to dissect the complex traits into their individual components to gain better control over them. In mulberry, such efforts are lacking. This paper, therefore, summarizes the current position of genetic and genomics research in mulberry and discusses the directions for future research, utilizing the emerging technologies in molecular markers, association genetics, quantitative trait locus mapping, transcriptomics, metabolomics, marker-assisted selection breeding, and transgenesis.