Morphological, histochemical and biochemical indices of downy mildew resistant cultivar of opium poppy.

摘要

Histopathological and biochemical parameters during infection were studied in opium poppy (Papaver somniferum) cultivars resistant (RC) and susceptible (SC) cultivars (Gazipur Local and Jawhar Aphim, respectively) to downy mildew (Peronospora arborescens). The number of stomata was higher in RC, but because SC had a greater leaf area, the total number of stomata was higher in the latter by 36.51%. The length and width of stomata were also greater in SC. Starch granules were more abundant and smaller, and mostly arranged just below the epidermal cells in RC. In SC, the starch granules remained scattered throughout the leaves. In SC, the polyphenol oxidase (PPO) [catechol oxidase] activity increased markedly at 6 h after pathogen inoculation (API) and remained very high up to 18 h API. The phenol content decreased after 18 h API. After 24 h API, PPO activity declined and the phenol content increased. The reduction in carbohydrate was greatest at 6-12 h API. At 18 h API, the carbohydrate content marginally increased. In RC, the phenol content increased following pathogen inoculation, whereas the PPO activity remained low. The conidia of the pathogen germinated within 6 h after inoculation, but the growth of the germ tube remained slow up to 12 h API. At 12-18 h API, the PPO activity increased, the phenol content decreased by 50%, germ tube growth increased, and the carbohydrate content decreased. At 24 h API, the phenol content was further reduced to normal levels with the increase in PPO activity. At this stage, further growth of the germ tube and an increase in peroxidase activity were observed.