در زمان برداشت SECAMIA SPP ارزيابي مقاومت ارقام نيشكر به ساقه خواران

Evaluation of resistance to stem borers Sesamia spp. in sugarcane varieties at harvest time

A study was conducted to determine resistance of 150 sugarcane varieties to a mixture of stem borers (Sesamia cretica and S. nonagrioides) at harvest time in year 2000. Screening for resistance has been carried out under natural infestation in the field condition at two prominent Agro-Industries located in Khuzestan, southern province of Iran. Percentage of bored intemodes was used at both stations. In order to unify the findings of two stations, a bored internode index (BII) was created. Since the distribution of the finding was in a normal pattern, an intervals of standard deviation from the mean (ISDM) was developed to classify the varieties. Following the classification, canonical discriminate analysis (CDA) was used to assess the contribution of variables to separation, and also investigate the effectiveness of the classification procedure. The result of CDA confirmed the accuracy of the classification procedure used, showing that 98% of the original data was correctly classified in the predicted group membership. Moreover, hierarchical cluster analysis was used to group varieties into resistance potential classes. There were no substantial differences between the results obtained by the method of ISDM and those of the cluster analysis. The finding showed a significant positive correlation of Percentage of bored internodes between the two stations. Consequently, in spite of the considerable differences in the levels of bored internodes between two stations, it is concluded that the resistant varieties might be durable. Throughout the research process, varieties of sugarcane have shown a wide spectrum of resistance to stem borers; therefore potential long-term breeding program should address this resistance problem.