Background and Objectives
Drought stress is a limiting factor for sunflower. Various reports have mentioned the effect of water stress and limited irrigation on sunflower for many respects, including phonological traits, morphology, agronomic and physiological. Sunflower is a crop that can withstand a variety of environmental conditions, particularly drought and due to the developed root system. It has high efficiency in absorbing water from the soil. Sunflower is one of the most important oil crops and due to its high content of unsaturated fatty acids and a lack of cholesterol, the oil benefits from a desirable quality. The aim of this study is to investigate the genetic diversity and the heritability of agro-morphological traits in confectionary sunflower under different levels of drought stress.
Materials and Methods
56 local populations were studied in three separate experiments in rectangular lattice design (7×8) with two replications at Agricultural Research Center of West-Azerbaijan province, Urmia, Iran in 2012. Water treatments were well-watered, moderate and severe water stress conditions so that irrigation was applied with 50%, 70% and 90% depletion of available water, respectively. Various agronomic and morphological traits were calculated based on measuring traits in sunflower. Productivity effort as a physiological trait was measured by dividing the total dry weight of reproductive organs (head) to the total dry weight of plant.
The results showed that in all three different water treatment conditions, heritability of head diameter, stem diameter, plant height, grain and biological yield was more than other traits. In well-watered conditions, moderate heritability varied between 0.52% for number of seeds per head to 80.61% for plant height. In moderate drought stress condition, the maximum and minimum heritability belonged to head diameter (76.21%) and chlorophyll index (26.45%), respectively. In severe drought stress condition, the most and the least heritability was observed for stem diameter (83.64%) and number of seeds per head (0 %), respectively. Among yield components, the heritability of 1000-grain weight at three water treatment conditions was higher compared to number of seeds per head, so for increasing grain yield, selection via 1000-grain will be more efficient.
For the traits of grain yield, head diameter, stem diameter, biomass yield, chlorophyll index, dry weight of leaf, head and head with grain, the heritability in severe drought stress was higher than optimum conditions and this showed that the phenotypic variance is a large proportion of the genetic variance of more favorable traits. Due to the fixed component in the numerator and the denominator of genetic variance, environmental variance decreased in drought stress conditions in comparison with optimum irrigation conditions.