Agronomy and Horticulture Department


First Advisor

Prof. Dr. Ismail Dweikat

Date of this Version



A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Agronomy, Under the Supervision of Professor Ismail Dweikat. Lincoln, Nebraska: January, 2022

Copyright © 2022 Sevgi Saylak


Consequent to the increasing world population, food sources are needed to be increased to meet the nutritional needs. However, due to natural processes and agricultural activities, the most destructive environmental factors that limit crop production, soil salinity, and drought-exposed areas are growing. As one of the major oilseed crops, sunflower (Helianthus annuus L.), is considered to be moderately tolerant to salt and drought. Although it can grow in arid to semi-arid regions, increasing salinity and drought might adversely affect sunflower production. This study aimed to investigate several sunflower germplasms' morphological responses to salt and drought stresses. For this purpose, greenhouse and field trials were conducted at University of Nebraska-Lincoln facilities during 2020-2021. For the greenhouse salinity experiment, germplasms PI 539899, PI 539900, PI 539901, PI 539902, PI 539903, and PI 599984 were used and exposed to three different salt concentrations (0, 150, and 250 mM). In addition, PI 632338/HA 429 and PI 632339/HA 430 were tested for drought response under three different irrigation levels for drought experiments in both greenhouse and field. For the greenhouse, treatments consisted of full irrigation (2L/pot), limited irrigation of 50% (1L/pot), 25% irrigation (.5L/pot), and while for the field, full irrigation treatment (FIT), limited irrigation treatment (LIT), and rain-fed (RF) treatments were applied. In the greenhouse experiments, while the plant height was observed as the highest under the 150 mM salinity treatment, it was seen in the 50% irrigation treatment for the drought experiment. The salt treatment effect was significant with the Soil Plant Analysis Development (SPAD), and the Normalized Difference Vegetation Index (NDVI) with a downward trend over time, and canopy temperature showed an upward trend for salinity and drought trials. In the field experiment, irrigation treatments were not found significant for over time data, however, the effect of time was significant in all data sets, while the germplasm effect and its interaction on canopy temperature, and NDVI was significant. In the salinity experiment, the treatment effect was found to be significant for dry root and shoot weight, while only the germplasm effect was found statistically significant for dry head weight. Different irrigation treatments for the greenhouse drought experiment were only significant for dry shoot weight and head weight. In the field trial, the highest values for head diameter, head weight, whole seed weight g/head, and hundred seed weight were observed in full-irrigated plants. Post-harvest data for the field experiment, different irrigation applications significantly affected the oil amount, and not the crude protein and fatty acids composition. This study indicated that there are differences in genotypes' response to both drought and salinity that could be used for sunflower improvement.

Advisor: Ismail Dweikat