Assessing Genetic Diversity and Heritability in Growth Traits of Quercus Brantii from Different Provenances of Zagros Forests in Field Trials

Extended Abstract Background: Quercus brantii Lindl., as the dominant species of Zagros forests, has a high ecological and social value. The study of genetic and phenotypic diversity is critical and necessary for understanding the adaptation of forest species to environmental stresses, such as climate change, and it can cause the preservation of genetic resources, restoration, and breeding of forest trees. A provenance trial, in which the seeds of mother trees from populations of different geographical regions are planted in the same experimental environment, is one of the ways to study intraspecific adaptive genetic diversity. Methods: Three provinces from northwest to southwest of Zagros, Baneh (north), Khorramabad (Middle), and Yasuj (South) were selected for research. The mother trees from Khorramabad province were selected from three different altitudes (lower, middle, and upper), and Yasuj provenance from two forest stands (Sapidar and Dehbaraftab). A total of 60 mother trees from all provenances were selected and their seeds were randomly planted in the same conditions in the Yasuj region in November. After the germination of the seeds in the spring of the next year, quantitative and qualitative growth traits, such as height, diameter, volume, the number of leaves, diameter, and height growth during summer, vitality, bending, the number of branches, and survival of Q. brantii seedlings, were measured and calculated in two times, June (before the dry season) and late October (the end of the growing season). Then, quantitative genetic parameters, such as the coefficient of additive genetic variation (CVg), individual narrow-sense heritability (h2), and the coefficient of quantitative genetic differentiation (Qst) of different traits, were calculated and compared in the total provenance and each provenance separately. Results: The variance components between the mother trees in different traits were from 4.7% in the number of branches and bending to 25% for the volume, vitality, and survival of the seedlings. The variance components percentage of traits in different provenances was less than mother trees. It was observed less than 5% in traits, such as bending, diameter, and height growth during the dry season, the number of branches, survival, and the leaf number of seedlings, respectively. However, the height and volume of seedlings, especially in October, had a higher variance in the provenance level (about 20%). The heritability ranged from 0.15 to 0.74 for different trains. The lowest and highest values of CVg were observed in the number of branches and survival percentage, respectively. However, the lowest (less than 0.05) of Qst was observed in qualitative traits, growth during the dry season, vitality, and survival, and the highest value was observed in the height of seedlings in October (0.6). The comparison between different provenances for genetic parameters also showed large differences in heritability, the genetic diversity coefficient, and yield in all the traits measured in the seedlings, except for the height in June. The heritability of vegetative traits increased from June to October in the low-altitude of Khorramabad and Sepidar-Yasuj, but it was the opposite in the rest of the provenances. Seedlings of Baneh showed the highest values of quantitative growth traits, such as height, diameter, and volume, among the studied provenances, while the performance, CVg, and heritability of this provenance for growth during the dry season, vitality, and survival were lowest compared to the other provenances, especially the low-altitude of Khorramabad. Among the studied provenances, the middle and upper altitudes of Khorramabad showed the lowest yield, genetic diversity, and heritability in most of the measured traits. Despite the low performance and survival rate of Dehbaraftab-Yasuj, it had high genetic diversity and heritability, while the Sepidar population of Yasoj showed higher adaptation due to a high survival percentage, but its genetic diversity was low. Conclusion: The results of this research revealed highly significant differences in the phenotypic and genetic variability of traits among provenances. Quantitative growth traits, such as the height, diameter, and volume of Q. brantii seedlings, can be used for the initial selection of seedlings due to their medium and high heritability values (more than 0.4) despite qualitative traits such as bending and the number of branches. Moreover, the low altitude of Khorramabad has higher adaptability to climate change due to the highest survival rate, heritability, and CVg of this provenance in the drier planting site (Yasuj). Therefore, it seems that this provenance has a higher adaptability to climate change, and collecting seeds of suitable mothers in this provenance can increase the adaptability of seedlings and reforestation in the face of global climate changes in the future. On the other hand, based on the results of this research, it can be concluded that the local population does not always have more chances to establish and grow, and factors other than geographical factors, such as climatic factors and rainfall, can be effective. Therefore, it is suggested to study the seeds of different provenances to determine the best provenance for reforestation in each region. Furthermore, since the results showed that the genetic difference between the mother trees is more than the provenance, and due to the high genetic diversity and adaptation of Dehbaraftab-Yasuj seedlings to the climate of Yasuj, the seeds of suitable mother trees in this provenance can be used for the restoration program of Yasuj.