Analysis of varietal response to bakanae infection Fusarium fujikuroi and gibrellic acid through morphological, anatomical and hormonal changes in three rice varieties
Fusarium fujikuroi, the causal organism of bakanae disease, is mainly seed borne pathogen on rice. The response of different rice varieties have more concern to understand pathogenesis process and host pathogen interaction complex. Therefore, the present study had some objectives: to determine response of some rice genotypes to bakanae infection and Gibberellic acid (GA3) treatment through morphological, anatomical and plant hormones changes. The highly virulent isolate no. 10 of F. Fujikuroi was used in evaluation of three rice cultivars; Sakha 101, Giza 179 and promising line GZ 10101-5-1-1-1. Changes in all morphological, anatomical traits and plant hormones activities Gibberellic acid (GA3), Indol Acetic acid (IAA) and Abscisic Acid (ABA) with bakanae infection and GA3 treatment were assessed from 15-60 days after inoculation and GA3 treatment during season 2018. Results indicated that bakanae infection caused severe morphological changes as abnormal elongation, degradation of chlorophyll and seedling death. Morphological changes were associated with wide anatomical changes of leaf as deformation of motor cell, mesophyll layer. For stem, infection and GA3 induced significant increase in the No. of aerenchyma and their diameter and increase pith diameter, and stem elongation. As well as, anatomical changes in roots were significant increase in diameter of epidermis, cortex layers, vascular cylinder, and reduction in diameter of xylem vessels. Out of anatomical results, Fusarium fujikuroi prefer to grow in aerenchyma, pith, cortex, vascular bundle of both sheath and stem. There is a significant increase in plant hormones Gibberellic acid (GA3), Indol Acetic acid (IAA) and Abscisic Acid (ABA) with bakanae infection and GA3 treatment combined with bakanae infection and GA3 treatment. GZ 10101-5-1-1-1 was recorded the lowest response to GA3 treatment with the lowest infection % and stem elongation%. While Sakha 101 and Giza 179 were the highly susceptible cultivars to bakanae with the highest infection %, stem elongation% and response to GA3. The fast and highest stem elongation %, No. of nodes and internode length was considered as remarkable phenotypic markers it can be used as valuable and early selection marker of susceptibility in breeding program to bakanae disease. GZ 10101-5-1-1-1 as new promising line and high tolerant to bakanae and low response to GA3 could be used as a good source in bakanae resistance breeding program.
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