بررسی چگونگی مکانیزم های مقاومت در رابطه با بیماری شانکر ریزوکتونیایی سیب زمینی

One of the important factors in reducing the yield of potato (Solanum tuberosum L.) is the presence of various diseases. Rhizoctonia solani anastomosis group 3, AG-3PT-stem canker, is one of the most devastating diseases leads to severe economic loss and reduction in the quantity and quality of potato, globally. The easiest and safest options to control potato Rhizoctonia canker disease are the use of resistant genotypes. In this study, which was done in the greenhouse of Isfahan Agricultural Research Center, we analyzed the quantitative gene expression changes of ten candidate gene markers (WRKY8, PR-1, LOX, Gro1, GST, Mi-1.2, NAC2, Osmotin, PAL and PINII) in potato roots and leaves at three points(1,2,3 weeks) after inoculation (wpi) with R. solani AG3-PT in 'Savalan', 'Agria', 'Sagita' and 'Pashandi' cultivars in various ranges of resistance through real-time polymerase chain reaction, and enzymatic activity, Peroxidase or Peroxide reductases (POX), Superoxide dismutase (SOD), Polyphenol oxidase (PPO), Catalase (CAT), Phenylalanine ammonia-lyase (PAL), β-1,3-glucanase and phenolic content involved in defense processes by measuring product formation using spectrophotometry and as well as biomass traits. The results showed although, these ten candidate defense genes were up-regulated ranging from 1.3 to 3.5 fold in potato roots and leaves infected with R. solani, but they were highly regulated in resistant 'Savalan'. WRKY8, resistant to late blight, P infestans regulated in 'Savalan', 'Agria' and 'Sagita' indicated WRKY8 can govern the simultaneous resistance of the related cultivars to both stem canker and late blight disease. Almost, similar results were obtained on Osmotin gene resistant to early blight, A.alternata. The activity of antioxidant enzymes indicated the highest level of increase for enzyme activity in POX (4.02-fold at 3 wpi) ,CAT (1.55-fold at 3 wpi), SOD (6.8-fold at 1wpi) and PAL (2.69-fold at 3wpi) in resistant genotype, 'Savalan'. The highest increase in the activity level of total phenol (2.1-fold at 1 wpi) and enzyme activity in PPO (3.12-fold at 3 wpi), and Glocanase (2.28-fold at 1 wpi) enzymes was observed in Agria. In terms of biomass traits, stem length, fresh and dry weight of roots and stems in plants infected with R. solani were significantly different at the level of one percent and increased compared to the control. However, there was a highly significant correlation between the resistance and gene expression and enzyme activity levels in related potato cultivars.