[Cellular responses of rice to Magnaporthe grisea at the early stages of disease development].

This paper presents a detailed investigation of the cytological and cytochemical events in rice cells infected by Magnaporthe grisea during the early stages of disease development. It was demonstrated that the spatial and temporal development of cytoplasmic aggregation, host cell autofluorescence, callose deposition and phospholipase D (PLD) accumulation were some of the earliest responses of host cells to M. grisea attacking and showed different patterns between the compatible and incompatible interaction. In the cv. IR64 and strain BN111 interaction (resistant), the earliest cellular response observed in the inner epidermis of rice leaf sheath was aggregation of the cytoplasm. Then, the attacked host cells turned brown and the cell cytoplasm collapsed (HR). In the moderately resistant reactions of cv. IR64 to strain PO66, the granule formation was delayed, and no apposition was observed in host cells. In the compatible reactions of cv. IR64 to strain Ca89, no visible cellular response was detected until 40 h after inoculation. As to auto-fluorescence of host cells, some penetration sites showed faint fluorescence under blue light as early as 12 h after inoculation in the cv. IR64-strain BN111 interaction. As the disease developed, the percentage of attacked epidermal cells showing autofluorescence increased quickly from 20 to 24 h after inoculation and the penetrated host cells showed strong autofluorescence. In the moderately resistant interaction, autofluorescence had been detected until 24 h after inoculation. In the compatible interaction, little autofluorescent cell was detected during the disease development. Patterns of callose deposition and phospholipase Dgamma (PLDgamma) showed the similar dynamic characteristics as did the phenolic compounds.