Aflatoxin itself is not usually a big issue in Barley. Mostly, detection is for food safety issues only

Well, on barley seedlings Aflatoxin has no effect. Detecting the presence of aflatoxin-producing fungi in seeds ( mustly Aspergillus spp.) is important in determining whether or not they can be used for animal or human consumption. In cases where the levels of this kind of fungi is very high (either because the seeds are very old or because of bad storage conditions) just in that case, the fungi can affects seed germination and may impede the development of the plant. 

I didn´t understand very well the second question. If you question was that if the barley have some diseases, answer is yes, many....here you can see some  (not all)  https://www.apsnet.org/publications/commonnames/Pages/Barley.aspx

Hi: There is phytotoxicity effect on plant tissue, here is useful paper for you:

https://link.springer.com/article/10.1023/A:1007164617175 

https://link.springer.com/article/10.1023/A:1007164617175

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1568821/pdf/envhper00467-0264.pdf

http://pubmedcentralcanada.ca/pmcc/articles/PMC379944/pdf/applmicro00035-0179.pdf

http://libcatalog.cimmyt.org/download/reprints/98218.pdf

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC379944/

https://link.springer.com/article/10.1007/BF01111268

https://link.springer.com/article/10.1007/BF01454591

http://onlinelibrary.wiley.com/doi/10.1111/j.1472-765X.1988.tb01241.x/pdf