Determination Of Effective Characteristics Of Rice Varpietieson The Resistance To Striped Stem Borer, Chilo Suppressalis Wlk.

The effectiveness of 9 morphological characteristics of rice plant including tillers number, stem length and hill height, internal and external diameter of the stem, length and width of flag leaf as an effective genetic diveristy on enhancing resistance of 10 varieties in Gilan ( Binam, Khazar, Sepeed-roud, Hassani, Dasht, Neamat, Hassan-saraii, Dom-zard, Shah-pasand and Bejar) and 7 varrieties in Mazandaran( Tarom, Dashet, Khazar, Nemat, Sahel, Fajer and Onda) to the striped stem borer (S.S.B.), Chilo suppressalis Wlk. during vegetative and reproductive phase, were investigated in RRIIandrsquos rice fields during 1999-2001. The trials showed clearly that the whole rice varieties tested have significant differences (P=0.01) about above mentioned characteristics. Variance analysis of the rice varieties tested to first and second generation infestion showed that there are significant differences at the 5 and 1% level respectively, and these varieties to white heads infestation showed differences at the 1% level during the harvesting season. Besides, these varieties due to number and weight of S.S.B. larvae had heavily differences together (P=0.01) and most number and heaviest larvae among varieties of Gillan were in Shah-pasand variety, and least number and lightest larvae were in Neamat and among varieties of Mazandaran most number larvae were in Nemat and Khazar varieties( P= 0.007) and heaviest larvae were in Onda variety(P= 0.0001). There were significnant correlation between the number of white heads with the tillers number only in the study of 2000 (r = 0.474** ). Also there was a correlation between first generation infestation with the stem height of rice tested in the early and late cultivation in experiment of 2001 (r = 0.534** and 0.492 ** , respectively), whereas this correlation in reproductive phase was only in the late cultivation condition (r =0.540**). There was a less correlation between stem length and second generation infestation at the reproductive phase in the early and late cultivation of 2002 experiment (r=0.419** and 0.423** , respectively), this correlation with hill length was more and heaviest (r = 0.517** and 0.511**, respectively). There was no correlation between hill length with white heads numbers during 2000 and 2001 experiment. Also there was correlation between during growing of plant with number (r = 0.551**) and heavy of larvea(r = -0.644**). There was negative correlation between number of tillering with heavy of larvea(r = 0.469*). Our study showed that resistance principle of the rice plant to S.S.B. are complex and many factors interfer in this matter. There was a significant correlation between infestation of rice varieties and stem diameter (r = 0.498**) in 2000. A correlation observed between length of flag leaf and infestation of rice varieties in the harvesting phase of 2000 (r = 498**) and between width of flag leaf and white heads number of late cultivation (r= 0.533**) in 2001. The present study showed that Neamat and Khazar varieties has agronomical characteristics and probably desirable chemical one which can use it in the integrated pest management (IPM) program of S.S.B.