Investigate the effect of drought stress on root and shoot characteristics of safflower genotypes (Carthamus tinctorius L.)

This research was carried out in order to investigate the effect of irrigation regimes on morphological traits of root and shoot of safflower genotypes.

A field experiment has been conducted via polyvinyl chloride (PVC) pipes at research field of Seed and Plant Improvement Institute in Karaj, during 2019-2020. A factorial experiment has been laid out in a randomized complete block design with three replications. This study deals with six genotypes of safflower (Varamin landrace, Hamand landrace, Kazakhstan genotype and Amir, Goldasht and Pernian cultivars) in two irrigation regimes, including full irrigation (control) and drought stress (Irrigation after depletion of 40% and 80% of soil available moisture respectively) treatments.

The results showed that under drought stress conditions, root length and root diameter have increased by 28.6% and 13.6%, respectively and root dry weight, leaf relative water content (RWC), number of bolls, number of seeds per plant and seed yield per plot and was decreased by 23.6%, 15.2%, 25.4%, 63.3%, and 74.9%, respectively. Under full irrigation conditions, Amir with suitable root system (root dry weight 7.7 g and root length 71 cm) and maximum number of seeds had the highest seed yield (5.03 g per plot). In addition, under drought stress conditions, Amir cultivar had early flowering, maximum root dry weight and length, highest activity of catalase and peroxidase enzymes, and the highest seed yield per plot (1.67 g).

Generally, Amir cultivar had more seed yield due to having a suitable root system and superior agronomic characteristics and was selected as the superior genotype.