Study on genetic diversity of some oriental and water pipe’s tobacco genotypes (Nicotiana tabacum L.) under Orobanche stress conditions by using multivariate statistical methods

In this research, the genetic diversity of some oriental and water pipe’s tobacco genotypes was investigated under normal (without Orobanche) and Orobanche stress conditions during 2007-2008 and 2008-2009 at Urmia Tobacco Research Centre with randomized complete block design with three replications. Combined analysis of variance revealed extent genetic variability among the genotypes for most of the studied traits. This suggests that there is high genetic variability among tobacco genotypes for resistance to Orobanche which can be effectively used in biotic resistance breeding programs. A high genotypic coefficient of variation was seen for studied traits especially for FWL and DLYP in normal and Orobanche stress conditions. The highest broad-sense heritability was estimated for FD, NL and PH in both normal and Orobanche stress conditions. The results of the genetic advance calculation showed that the highest genetic advance was related to LAI, APFW, PH and FWL traits. Based on the results of genetic correlation coefficients of traits, positive and significant genetic correlations were observed between DLYP with all studied traits in both normal and Orobanche stress conditions. Cluster analysis classified all tobacco genotypes into four clusters under normal and stress conditions. In Orobanche stress condition, ratings the clusters in view of traits average showed that the second and fourth clusters contain genotypes that are resistant and sensitive to Orobanche stress, respectively. Therefore, by selecting suitable parents from these groups and crossing them, it will be possible to produce segregated populations in Orobanche resistance breeding programs and to make desirable changes in tobacco yield. Results of cluster analysis were confirmed by results of canonical discriminant function results. The principal component analysis identified two components in each condition which explained more than 75 and 73 percent of the total variation in normal and stress conditions, respectively. Genotypes classified in the second cluster can be potentially used in the Orobanche infested areas.