An Analysis on Somaclonal Variation: a Tool For Crop Improvement and Tissue Culture: Exploring the impact of microRNAs on somaclonal variation in plant tissue culture

Abstract

Somaclonal variation is an important phenomenon that canbe observed at high levels in plant tissue culture. Although known to sciencesince plant cell culture techniques were first developed, its origins remainmysterious. Here, we propose that misregulation of microRNAs and small RNApathways can make a significant contribution to the phenomenon. For manyreasons, micro-RNAs and related small RNAs appear ideal candidates. Their mode of action gives them disproportionateinfluence over the transcriptome, proteome and epigenome. They regulateimportant developmental and physiological events such as meristem formation,phase changes and hormone responses. However, the genomic locations of microRNAgenes and their unique biogenesis might make them unusually susceptible toaberrant regulation in vitro. Fifteen somaclonalvariants developed from adventitious shootderived callus from the cotyledonaryexplants of pigeonpea [Cajanus cajan (L.)Millsp.] var. ‘ICPL 87’ were assessed across two seasons for some agronomic andcooking quality characters. The mutant inbreds showed significant variation fordays to maturity, plant height, seed size, seed colour and grain yield. Some ofthe somaclonal variants such as ‘ICPL 99073’, ‘ICPL 99072’ and ‘ICPL 99070’were found promising and displayed significant positive changes for someimportant agronomic traits. Those include a change from small seed size andbrown seed coat colour to more preferred large white seeds endowed with moreseed yield. For grain yield, ‘ICPL 99073’ showed 25.3% yield advantage over theparent variety. The studies demonstrated the scope of genetic improvement inpigeonpea through deployment of somatic culture and exploitation of somaclonalvariation.