Over-expression of Osmotin (OsmWS) gene of Withania somnifera in potato cultivar ‘Kufri Chipsona 1’ imparts resistance to Alternaria solani

Abstract

Osmotin, a pathogenesis related (PR) protein belonging to PR-5 protein family is induced in plants exposed to various biotic and abiotic stresses. To evaluate the potential involvement of Osmotin in improving resistance to early blight of potato, transgenic lines of an important processing grade potato cultivar ‘Kufri Chipsona 1’ were developed. The integration of T-DNA was confirmed by amplification of 900 bp DNA fragment of Osmotin (OsmWS) gene. The regenerated microshoots were subjected to GUS assay and eight independent putative transgenic lines showing uniform expression of reporter gene were selected for further assessment. The selected lines (L1–L8) were hardened and transferred to the containment facility. The transgenic plants inoculated with spore suspension of Alternaria solani over-expressed OsmWS gene by about 22 folds after three days. The disease severity also decreased in the transgenic lines as the lesion diameter was significantly reduced in comparison to control plants after 8 days of inoculation. Although, variation in disease severity among the transgenic lines was observed, yet, all the transgenic lines over-expressing OsmWS gene showed decreased disease severity and disease incidence. As a measure of plant health, total chlorophyll content and osmotic potential were also measured. Following infection, higher chlorophyll content (160.2 mg/g FW to 252.32 mg/g FW) was recorded in the transgenic lines in comparison with control plants (114.48 mg/g FW). However, an inverse variation was observed in terms of osmotic potential, where infection causes a significant decrease in osmotic potential in some of the transgenic lines. Thus it seems that over-expression of OsmWS gene in potato have potential to confer certain degree of resistance to early blight. Induced over-expression of Osmotin gene cloned from Withania somnifera increased resistance to early blight in Indian potato cultivar ‘Kufri Chipsona 1’.