Document Type : Original Article
Authors
1 MSc. in Plant Breeding, Agronomy & Plant Breeding Department, Faculty of Agriculture, Yasouj University, Yasouj, Iran
2 Associate Professor in Plant Breeding, Agronomy & Plant Breeding Department, Faculty of Agriculture, Yasouj University, Yasouj, Iran
3 Assistant Professor in Crop Physiology, Fars Agriculture and Natural Resources Research Center, Agronomic and Horticultural Science Research Department, Zarghan, Iran
Abstract
Introduction
With the increasing population, ensuring food security is one of the most important challenges for humans. Oilseeds are considered strategic crops, and due to the role they play in providing fats, proteins, and vitamins, they are among the most important food sources. Water deficit and drought stress severely reduce crop production and are the most significant abiotic stress worldwide, posing a crisis in Iran. Seed production and the sustainability of sunflower (Helianthus annuus) under drought stress are limited especially in arid and semi-arid regions. To understand the effects of stress on crops, it is essential to consider drought stress conditions in breeding programs to identify tolerant genetic materials. The response of sunflowers to drought stress depends on genotype, stress intensity, and the time of occurrence. Due to the annual damage caused by drought stress and the lack of sufficient information regarding the tolerance levels of different sunflower genotypes, the present study aimed to evaluate some common genotypes of sunflower under drought stress.
Materials and methods
This research was conducted in 1401 in the Dasht-e Roum region of Boyer-Ahmad County, Kohgiluyeh and Boyer-Ahmad Province, with geographical coordinates of 30° 34ʹ north latitude and 51° 31ʹ east longitude, at an altitude of 2095 m. Two separate experiments were performed in a randomized complete block design with three replications. The first experiment was conducted under non-stress conditions (providing 100% of the water requirement), and the second experiment was conducted under stress conditions (providing 50% of the water requirement). The experimental treatments included 10 genotypes, including oilseed sunflowers (Lakomka, Progress, Shams, Qasim, Golsa, Biotech, and Zarrin) and nut sunflowers (Shamshiri, Kalleh Ghoochi, and Pakan Bazaar). In April 1401, plowing operations were carried out, followed by the creation of furrows at a distance of 50 centimeters. Plots with dimensions of 4x3 meters were considered, and oilseed sunflowers were planted with a spacing of 20 centimeters between rows, while nut sunflowers were planted with a spacing of 25 centimeters. The planting depth was 5 centimeters in the last of June. Irrigation regimes were applied after the plants reached the 4 to 6-leaf stage.
Results and discussion
Based on the analysis of variance, the effect of genotype on the head diameter was not significant under stress conditions, but it was significant at the 1% level of probability under non-stress conditions. Under non-stress conditions, nut genotypes including Shamsiri, Local Pakan Bazar, and Kallegouchi did not show any significant difference in head diameter. Among the oilseed genotypes, Shams had the highest head diameter, although it did not show a significant difference compared to other genotypes except for the Zarrin genotype. Based on the combined analysis of variance, the main effect of genotype and irrigation regime was significant at a 1% level of probability on the number of filled grains per head. The comparison of the mean effect of the irrigation regime showed that with the application of drought stress, the number of filled grains per haed decreased by 20.03%. Among the oilseed genotypes, Ghassem had the highest and Biotech had the lowest number of filled grains per head. Among the nut genotypes, the local Pakan Bazar genotype had the highest number of filled grains per head, while the Kalleh Qouchi genotype had the lowest. The combined analysis of variance showed that the percentage of seed oil, hundred-seed weight, seed yield, and biological yield of sunflower were significantly influenced by genotype-by-irrigation regime interaction with 99% confidence. The comparison of mean oil percentage for genotypes at different levels of irrigation regime showed that under non-stress conditions, the Ghassem genotype had the highest oil percentage among the oilseed genotypes. Among the nut genotypes, the local Pakan Bazar genotype had a higher oil percentage compared to the Shamsiri and Kalleh Qouchi genotypes. Under stress conditions, the Golsa genotype showed the highest oil percentage. Among the nut genotypes, the Kalleh Qouchi and local Pakan Bazar genotypes had a higher oil percentage compared to the Shamsiri genotype. Under non-stress conditions, the Biotech genotype had the highest hundred-seed weight. Additionally, among the nut genotypes, the Shamsiri genotypes had the highest hundred-seed weight under this irrigation condition. Under stress conditions, among the oilseed genotypes, the Biotech genotype showed the highest hundred-seed weight. Similarly, among the nut genotypes, the Shamsiri genotype had the highest hundred-seed weight. The results of comparing the mean of genotypes at different levels of irrigation regime indicated a decrease in seed yield with the occurrence of stress. Under non-stress and stress conditions, among the nut genotypes, the Shamsiri genotype had the highest seed yield, while among the oilseed genotypes, the Shams genotype had the highest seed yield. Under non-stress conditions, the Shams genotype had the highest biological yield, although the local Pakan Bazar genotype did not show a significant statistical difference compared to the Shamsiri genotype. Under stress conditions, among the oilseed genotypes, the Shams and Golsa genotypes had the highest biological yield. Among the nut genotypes, the Shamsiri genotype also had the highest biological yield.
Conclusion
Based on the obtained results and the response of different sunflower genotypes in the present study, the Shams genotype among the oilseed types and the Shamsiri genotype among the nut types can be considered tolerant genotypes to water deficit for cultivation.
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