Screening of national and exotic new promising lines and endemic rice cultivars for their resistansce to the rice striped stem borer, Chilo suppressalis Walker, and the effect of resistant and susceptible genotypes on Trichogramma brassicae Bezdenko

Amooghli-Tabari, Mehrdad and Fathi, Ali Asgar and Razmjou, Jebraeil and Moumeni, Ali and Nouri Ganbalani, Gadir (2017) Screening of national and exotic new promising lines and endemic rice cultivars for their resistansce to the rice striped stem borer, Chilo suppressalis Walker, and the effect of resistant and susceptible genotypes on Trichogramma brassicae Bezdenko. Doctoral thesis, University of Mohaghegh Ardabili.

Text (غربال‏گری جرم‏پلاسم‏های ملی، خارجی، امید بخش جدید و ارقام متداول برنج در کشور از نظر مقاومت به کرم ساقه‏خوار نواری، Chilo suppressalis Walker، و تاثیر جرم‏پلاسم‏های مقاوم و حساس روی زنبور تریکوگراما، Trichogramma brassicae Bezdenko) Mehrdad Amooghli-Tabari.pdf Download (1MB)

Abstract

Striped stem borer (Chilo suppressalis (Walker) (Lepidoptera: Crambidae) is one of the most important insect pest of rice (Oryza sativa L.) throughout the world as well as in Iran. In this research, we have focused on various aspects of reaction of rice genotypes against striped stem borer, including mass screening in field condition, characterizing of resistance mechanisms to this insect pest, effect of silicon fertilizer application on the silica content in rice genotypes as well as their resistance reaction, and finally the interaction between rice genotypes and Trichogramma brassicae Bezdenko. This study was carried out in Rice Research Institute of Iran, Mazandaran Branch during 2013-2015. Initially, a total of 98 rice genotypes was screened for their resistance performance to this pest in field conditions. The results of different analysis of this trial indicated that a) there was a positive significant correlation between the percentage of whiteheads and the number of larvae/plant among all traits of interest, b) according to to the cluster analysis, all rice genotypes were classified into five main groups: 19 resistant, 24 moderately resistant, 23 moderately susceptible, 18 and 14 susceptible and highly susceptible genotypes, respectively. Therefore, we have selected eight resistant genotypes for further study. The results of the second trial on resistance mechanisms of selected genotypes showed that the genotype Novator had the highest antixenosis resistance. Other rice genotypes such as Novator, AN74, Nemat and AB1 indicated the least attractiveness for oviposition preference compared to Tarom, as susceptible check genotype. As for the antibiosis resistance mechanism, several genotypes i.e. IR-825, AN-74, AN-74 and AB1 performed a moderate resistance reaction with lower the survival rate of larvae, larval tunnel length, larval weight, and pupal weight. We found that two components such as larval weight and larval tunnel length could be considered as an important index for antibiosis resistance. As for tolerance mechanism, rice genotype AN-74 showed lower whiteheads and grain yield, therefore could be considered as a high tolerance genotype. At third trial, we have determined silica content and resistance reaction of eight selected rice genotypes with and without application of silicon fertilizer. Results indicated that there was a significant difference among rice genotypes in silica content. We found that the rice genotype AN-74 indicated the high silica content, the lowest percentage of whiteheads and larval survival rate, while two rice genotypes including Nemat and AN-74 showed lower larval weight. There was also a significant negative correlation between silica content with several traits such as larval weight, the percentage of whiteheads and the percentage of larval survival. Therefore the application of silicon fertilizer resulted in a positive effect in reducing the infestation rate, as an important component of antibiosis resistance. At fourth trial, which was carried out to identify interaction in a plant-pest-parasitoid system. We found that there was a significant difference between rice genotypes and parasitism behavior of Trichogramma such as the parasitism rate and the percentage of emerging rate in both field and laboratory conditions, with a clear predominance in laboratory condition. We also observed that rice genotypes with a high density of leaf trichomes had a negative effect on the parasitism behavior of Trichogramma. In conclusion, two rice genotypes including Novator and AN-74 indicated better performance than the other rice genotypes as they showed lower percentage of whiteheads, larval weight and yield losses and could be used as resistant rice genotypes in IPM strategy for rice stem borer.

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