There are some databases of miRNA.
Identification and Characterization of MicroRNAs from Barley (Hordeum vulgare L.) by High-Throughput Sequencing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3317698/
Identification and characterization of microRNAs from barley (Hordeum vulgare L.) by high-throughput sequencing.
http://www.ncbi.nlm.nih.gov/pubmed/22489137
A computational-based update on microRNAs and their targets in barley (Hordeum vulgare L.)
http://bmcgenomics.biomedcentral.com/articles/10.1186/1471-2164-11-595
A Database:
"Identification and Characterization of MicroRNAs from Barley (Hordeum vulgare L.) by High-Throughput Sequencing"
http://www.mirbase.org/cgi-bin/reference.pl?medline=22489137
Database tool:
PmiRExAt: plant miRNA expression atlas database and web applications
http://database.oxfordjournals.org/content/2016/baw060.full.pdf
Concerning known and conserved microRNAs:
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572014000500010
"Although some miRNAs are known to be conserved throughout the plant kingdom,
the advent of massively parallel DNA sequencing methods allowed the identification of a vast number of non-conserved
genes, even in closely related plants (Rajagopalan et al., 2006; Fahlgren et al., 2007; Ma et al., 2010). To date, there are
about ten thousand mature miRNA sequences of green plants (Viridiplantae) deposited in the miRBase database
(miRBase) (Griffiths-Jones, 2004). However, these sequences are not evenly distributed among the taxa. For example,
information from economically important plants is almost entirely lacking".
Discovery of barley miRNAs through deep sequencing of short reads
http://sci-hub.cc/10.1186/1471-2164-12-129
Boron Stress Responsive MicroRNAs and Their Targets in Barley
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3608689/
You would like to have some soft. See this list:
MiRNA and pre-miRNA tools
http://wwwmgs.bionet.nsc.ru/mgs/programs/rnaanalys/mirna_premirna_prediction_tools.html
thank you for your help, but I am studying the hordeum vulgare. the company predicted lots of novel microRNAs which I don't think very reliable, so I plan to predict novel microRNAs by myself, can you recommend a software? and now I am very confused about the known and conserved microRNAs, can you explain a little bit ?