Morphological evaluation of Asparagus azerbaijanensis accessions and effect of drought stress on Iranian asparagus seedlings growth

Drought stress is one of the most common environmental stresses in agriculture crops production process worldwide. Asparagus officinalis is the most economically important species of asparagus which is susceptible to some of the most common biotic and abiotic stresses. According to reports, Iranian species of asparagus can well tolerate some of unsuitable soil conditions. The purposes of current study were identification and morphological evaluation of different accessions of A. azerbaijanensis Iranian species, evaluation of seed germination indices and seedling growth of Iranian asparagus under drought stress condition, comparing of Iranian accessions tolerance rate with Mary Washington commercial cultivar and introducing of superior accessions for using in asparagus breeding programs with aim of producing drought resistant hybrids.

The current study was carried out in two different sections at university of Zanjan, during 2020-2021, which the first experiment was related to collection and morphological evaluation of two wild accessions of A. azerbaijanensis species and the second experiment was related to evaluation of drought stress (in four levels: 0 (control), 5, 10 and 15 % of polyethylene glycol) on seed germination indices (germination speed and percentage) and seedling growth (length of radicle and plumule, radicle length to plumule length ratio and fresh and dry weights of radicle and plumule) of Iranian asparagus in laboratory condition.

The average of spear length and diameter in Ahar and Makou accessions were 48.94 cm and 4.70 mm. The mean numbers of seed per fruit and fruit per plant were 2.37 and 159.40 numbers in evaluated accessions and average of 10.28 cladode number was evaluated in accessions of A. azerbaijanensis species. The highest seed germination speed and percentage and also length of radicle and plumule were recorded in Gazanak accession under stress conditions. The percentage and speed of seed germination in Gazanak accession were averagely 56.73 and 70.52% higher than those of Mary Washington commercial cultivar under drought stress conditions. The mean comparing results for fresh and dry weights of radicle and plumule traits showed that fresh and dry weights of radicle and plumule decreased by increasing of stress level in all of evaluated accessions.

Wild accessions of A. azerbaijanensis species, due to their suitable morphological variation and producing of spears with desired taste and size, are suitable candidates to employ in asparagus breeding programs with the aim of producing asparagus with superior vegetative growth. Also, the superiority of Iranian asparagus different accessions over the commercial cultivar used in this study in tolerating of water deficit conditions and stress, promises the possibility of further evaluation of Iranian asparagus in asparagus breeding projects and studies with aim of producing dry resistant cultivars. Keywords: Drought stress, Germination percentage, Iranian asparagus, Polyethylene glycol.