Evaluation of growth and yield of black poplar (Populus nigra L.) clones under drought stress period in comparative populetum of Sanandaj

Regarding the effects of climate change and the recent drought in Iran, it is necessary to assess the growth and producion of poplar varieties under drought stress. In this research, 14 clones of black poplar (Populus nigra L.) were studied during 2001-2008 in Sanandaj, Kurdistan province. Cuttings were planted in early March of 2000, and the samplings were transplanted in early April of 2001 in 3m × 3m spacing and a Randomized Complete Block Design (RCBD) with 3 replications. The yearly field works included uniformly-applied irrigation, weeding and pruning. However, they were subjected to drought stress in 2007 due to the impossibility of providing water by the tenth of July (103 days). The results showed that drought caused leaf yellowing and fall, as well as mildew (Melanophylla picta) outbreak and finally drying of a number of trees. Moreover, simultaneous drought and increase the range of traits changes limited the growth of poplar clones, so that the trees could not show their potential growth rate. Responses to drought stress among poplar clones showed a significant variation, so that P.n.M and P. n. 42/53 showed zero percentage, while P. n. 63/135 showed about 50% damage caused by drought. The average loss of drought in the clones was 20.49%. In addition, the P. n. 56/52and P. n. 56/75cloneswith 25.61 and 24.80 m3/ha per year wood yield and moderate (25-30%) damage caused by drought were defined as high-yield and relatively tolerant clones. The results of multivariate statistical analysis (correlation coefficients, cluster analysis, and principal component analysis- PCA) showed a negative effect of drought stress on the wood yield and its components. They also showed that smaller clones with fewer leaf sizes have higher drought tolerance by more water maintaining potential and lower evaporation levels. Finally, the presence of genetic diversity in terms of stress tolerance among poplar clones as well as their segregation pattern in cluster analysis and PCA biplot indicated the interference of genetic factors in its control and the availability of stable clones that can be compatible with dry conditions of the country via their hybridization