Morphological Relationships among Plant Architecture, Yield Components, and Seed Quality of Safflower under different Irrigation Intervals

Abstract

Safflower (Carthamus tinctorius L.) is a drought-tolerant oilseed crop with considerable potential for sustainable production in water-limited environments. This study evaluated the effects of irrigation interval and cultivar on growth, yield, biomass partitioning, seed quality, and trait relationships of two safflower cultivars (Giza and Dongla) under Sudanese conditions. A factorial experiment was conducted using three irrigation intervals (7, 14, and 21 days). Growth, yield components, biomass, harvest index, and seed quality traits were measured, and Pearson's correlation analysis was used to examine relationships among agronomic traits. Significant varietal effects (P < 0.05) were observed for several growth and yield-component traits. Giza produced significantly taller plants and greater dry matter, whereas Dongla produced significantly more heads per plant and exhibited a higher harvest index, reflecting contrasting growth and assimilate partitioning strategies. Irrigation interval significantly affected some vegetative growth traits, but had no significant effect (P > 0.05) on seed yield, harvest index, or seed quality. Likewise, although the 7-day irrigation interval produced the highest numerical seed yield, this difference was not statistically significant. Correlation analysis showed that plant height and leaf area were positively associated with seed production, whereas branch number promoted head formation but exhibited trade-offs with vegetative growth. Seed yield was more closely associated with harvest index than with total biomass, highlighting the importance of assimilate partitioning for productivity. These findings demonstrate that safflower can maintain yield and seed quality under moderate deficit irrigation, indicating that irrigation intervals of up to 21 days can reduce irrigation frequency without significant yield penalties. The results also support variety-specific cultivar selection, with Giza better suited for biomass production and Dongla for efficient reproductive allocation under water-limited conditions in Sudan.