PCR-based identification of Fusarium spp. and impact of wound healing time on dry rot infection

Abstract: Dry rot is an important fungal storage and field rot found on potatoes world wide, which is caused by various Fusarium spp. Out of the thirteen Fusarium species reported, F. sambucinum Gibberella pulicaris) and F. coeruleum (F. solani var. coeruleum) are more frequently associated with dry rot of tubers. Quick and reliable identification of dry rot pathogens is important in the diagnosis, phylogenetics and suggesting the right management practices and storage possibilities for processors and growers. Modern molecular-based techniques play a major role in quick, reliable and accurate identification of pathogens. In this study, the process of amplifying the ITS and LSU region of the rDNA from F. sambucinum and F. coeruleum using the universal primers was laborious and time consuming. The universal primer pairs ITS1 x ITS2, ITS1-F x ITS 2, ITS 1 x LR 1, ITS 1-F x LR 1 were able to amplify F. sambucinum DNA samples but failed to get a product using primer pair ITS 1 x ITS 4. The F. sambucinum primer pair S3F x S3R has failed to discriminate the DNA samples from F.coeruleum and T. viride. Therefore, these regions of rDNA were not reliable for effective diagnosis of Fusarium strains that cause dry rot. However, it helped to investigate the polymorphism between Fusarium spp. used to identify a specific ITS region. The impact of wound healing on dry rot infection was also investigated by this work. A decline in relative mean rot volume of laboratory infected tubers with F. avenaceum and F. coeruleum spores was observed after 4-6 days of wound healing time. The highest mean rot recorded for both F. coeruleum and F. avenaceum infected tubers was at 0 and 2 days wound healing time, which might be due to the combined effect of bacteria and fungal infection. Furthermore, the F. avenaceum strain used in this study was more aggressive with the highest rot symptoms compared to the F. coeruleum strain.