Most of the researchers nowadays use detached leaves of a certain plants to check the pathogenicity of a plant pathogenic fungi. Is there any current reference is available for that method.
I. J. Misaghi. 2012. Physiology and Biochemistry of Plant-Pathogen Interactions Springer Science & Business Media,Pp.304. ISBN 1468411497, 9781468411492
page 264 in: P. Narayanasamy. 2010 Microbial Plant Pathogens-Detection and Disease Diagnosis:: Fungal Pathogens, Springer Science & Business Media, Pp.291. ISBN904819735X, 9789048197354
Page 130 in: P. Narayanasamy. 2001. Plant Pathogen Detection and Disease Diagnosis, Second Edition, CRC Press,Pp.544. ISBN0824705912, 9780824705916
for the primary screening it is not bad considering your survey but for more study for gene expression during the special time it is not ok so first see your your job sensitivity and after that getting decision although according to fungus and host it is may be get the different decision for testing pathogenicity
But it will not give you accurate pathogenicity data. Data can be misleading. Because detached leaves from plants....cannot express plant response as in living plant.
Detached leaves can sometimes give a measure of pathogenicity, but do have to be used with great caution. Some proceedures, whilst not being reliable for pathogenicity (ie +/- infection/disease) in that infections may occur with non-pathogenic species or races, can still provide an excellent estimate for virulence (the degree/ intensity of disease) or the predisposition of tissues to disease. Other detached plant parts can be used in quick assays too, see e.g. here. BUT as stated already, results need to be treated in context and with a good deal of caution!