Study of Tobacco (Nicotiana tabacum L.) Genotypes Reaction to Broomrape (Orobanche cernua L.) Weed Using Stress Tolerance Indices

In order to study the resistance of tobacco genotypes to Broomrape (Orobanche cernua L.), two experiments based on the randomized complete block design with three replications were conducted at non-stress and broomrape stress conditions at the tobacco research center of Urmia for two sucsessive years (2007-2009). The results showed that the broomrape infestation reduced the mean of all studied traits. The maximum reduction was recorded in aerial part dried weight (31%) and root dried weight (30%), respectively. So that, these traits were known as susceptible traits. The traits such as number of leaves, aerial part dried weight and root dried weight showed highly positive and significant correlation with tobacco yield at non-stress and stress conditions, respectively. So, one can use these traits for selecting tobacco genotypes with high yield performence. It was also found that there is a high correlation between the tobacco yield in non-stress and stress conditions with harmonic and geometric mean indices and stress tolerance index, so these indices can be used to assess tolerance to Broomrape stress in tobacco. Cluster analysis grouped the studied genotypes into three clusters containing susceptible genotypes (42 genotypes), moderately resistant (13 genotypes) and resistance (9 genotypes). In overall, the genotypes C.H.T.209.12e, C.H.T.209.12e×F.K.40-1 and genotypes SPT413, SPT432 and SPT412 are introduced as the most resistance and the highest susceptible genotypes to Broomram, respectively.