Selection of open pollination progenies in some pear species in order to achieve dwarf and drought tolerant rootstocks
One of the important products in Iran and Isfahan province is the pear that its cultivation has been limited by drought stress and global warming in recent years. The use of drought-tolerant rootstocks is one of the available solutions for pear orchards in semi-arid regions. In addition, the lack of dwarf or semi-dwarf rootstocks, which are appropriate and compatible with Iran climatic conditions, limited high density pear orchards. In order to obtain drought tolerant rootstocks, in this research fruit of Pyrus glabra, Pyrus syriaca, and Pyrus salicifolia, along with P. communis cv. Spadona, Dargazi, as well as Khoj n. 1 and n. 2 species were collected from different regions of Iran in August and September of 2016. The seeds were separated from the flesh and dried at room temperature. The seeds were cultivated in uniform and light texture of soil in November in the field condition to break the seed dormancy. Seedlings were irrigated regularly for three months in order to establish in the soil; drought stress began in July. In order to apply drought stress, irrigation time was considered based on 80% of allowed water depletion. Morphological traits of seedlings were recorded before stress and at the end of the stress period (late September). The viability percentage of seedlings after drought stress was between 14.28% (P. communis cv. Dargazi progenies) to 82.55% for P. salicifolia. Comparison of the means and cluster analysis, among populations showed that the three populations of P. salicifola, P. glabra and P. communis cv. Khoj n. 2 had the lowest height and were placed in the same group. After studying single genotypes in these three populations, genotypes no. 31, 32, 41, 57 and 12 from P. salicifolia, genotypes 10, 11, 7, 3 and 9 of P. glabra and genotype 4 of P. communis cv. Khoj n. 2 populations were selected as drought tolerant and dwarf genotypes and were taken to the propagation phase for future evaluation.
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