Selection of Cow Cockle (Vaccaria hispanica) Ecotypes based on Agronomic Traits under Different Irrigation Regimes

The cow cockle has a great potential for producing medicinal products due to its triterpenoid saponins. This experiment was aimed to investigate different cow cockle ecotypes under drought stress conditions and select the tolerant ecotype(s) based on agronomic traits using selection indices under different irrigation regimes.

This experiment was carried out as a split-plot experiment based on a randomized complete block design with three replications in 2020-2021 at the Ghezel Moghan Seed Production Company in Parsabad. The main plots were assigned to three treatments of irrigation cycle of 7 days (no stress), 10 days (mild stress), and 14 days (severe stress), and sub-plots were allocated to eight cow cockle ecotypes native to the northwest of Iran.

The analysis of variance showed the effect of drought stress on all studied traits and the effect of ecotype on all traits except for seed weight per plant was significant. Also, their interaction effect was significant in most of the studied traits such as plant height, number of branches, seed weight per plant, number of filled and hollow capsules, straw weight, grain yield, biological yield, and harvest index and was nonsignificant for the percentage of full capsules, plant biomass, and 1000-grain weight. Ecotype E7 under normal conditions had the highest plant height, number of branches, number of full capsules, and seed weight per plant, but in severe stress conditions, it showed the lowest height, number of branches, number of full capsules, seed weight per plant, 1000-seed weight, straw and seed yield per unit area and was the most sensitive ecotype to drought stress. Ecotype E6 had the least decrease in plant height, number of branches, seed weight per plant, straw and seed yield per unit area, and harvest index in both stress conditions and was the most tolerant to drought stress. Estimation of the ideal genotype selection index (SIIG) and Multi-trait genotype–ideotype distance index (MGIDI) for different ecotypes showed that the E6 ecotype with the highest SIIG value and the lowest MGIDI value in all three stress conditions was the most tolerant, and E3 and E8 ecotypes were in the next rank and were classified as ecotypes with relatively high drought tolerance. Also, in both moderate and severe stress conditions, ecotype E7 with the lowest value of SIIG and the highest value of MGIDI showed high sensitivity to drought stress.

In general, the E6 ecotype was desirable in both normal and stress conditions and was one of the ecotypes with high drought tolerance. Also, in both moderate and severe stress conditions, Eotype E7 showed high sensitivity to drought stress