Document Type : Research Paper
Authors
1
ResearchAssistant Professor, Plant Protection, Rice Research Institute, Rasht, Iran
2
Senior Scientist PBGB, IRRI, Philipines
3
ResearchInstructors, Plant Protection, Rice Research Institute, Rasht, Iran
4
Experts of Plant Protection, Rice Research Institute, Rasht, Iran
Abstract
Rice sheath blight disease caused by Rhizoctonia solani AG1- IA is the second
economically important disease of the crop in most rice- growing regions of the world,
including Northern of Iran. The disease is mainly controlled through application of fungicides.
The present study was performed to identify the candidate cultivar (cultivars) as source of
resistance to the pathogen in rice field conditions in Northern Iran. Thirty seven vs twenty
three rice cultivars respectively from Iranian Local (IL) and IranianImproved (II) cultivars
along with ten Foreign Resistant (FR) cultivars were field grownat the Rice Research Institute
of Iran. They were inoculated with the mycelial mass of a virulent isolate (G309) of pathogen,
45 days after being transplanted. To supply favorable humidity for disease development, the
plants were kept wet until the evaluation time through 2-5 times of daily water spraying, while
applying a overhead water sprayer system available on the field. Assessment of cultivars,
reaction was done by recording the Sheath Blight Severity as appeared on the sheath (SSS),
number of Lesions on the Sheath (LS), Relative Lesion Height (RLH), percentage of Infected
Tiller (IT), number of Dead and Green Leaves(DL and GL), Number of tillers (Nt), Tiller
Angle (TA), Stem Width (SW), and Plant Height (PH). Results indicated that, the group of FR
cultivars significantly differed from groups (IL) and (II) cultivars by exhibiting less SSS, LS,
DL vs more GL. Cluster analysis of the cultivars as based on RLH, SSS and DL, using
UPGMA method revealed 4 groups. One of the grpups comprised of: Jasmine 85, Teqing,
Pecos and Tetep was observed as resistant, whereas, another one containing Swarna (Foreign
susceptible), Moosatarom, Hassansaraei, Jamshidjo, Khazar, Shiroodi, D4 (IL and II), and
Fujiminori was recorded as susceptible. Analysis of the relationship between plant traits and
disease response indicated that RLH and SSS were not significantly correlated with the
assessed morphological characteristics as regarded FR cultivars, whereas a positive significant
correlation was observed between SSS and TA (r = 0.20, P. value= 0.033), and a negative one
between RLH and PH (r = -0.29, P. value= 0.002) as detected on local cultivars.
Keywords
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