Genetic diversity in Morocco’ sunflower “Helianthus annuus L.” gene-bank for autumn-early winter plantation conditions: Agro-morpho-physiological screening

Despite Morocco’s reliance on sunflower as an oilseed crop, little is known about its agronomic performance when sown in autumn or early winter. This knowledge gap is critical, as spring-sown varieties have shown declining performance in recent years under intensifying climate stress. Therefore, targeted breeding strategies could discover genotypes suitable for autumn or early winter sowing, with cold tolerance as a key selection criterion. Currently, ‘Ichraq’ is the only autumn-planted sunflower variety officially registered in Morocco, although efforts to release additional tolerant varieties are underway. This study evaluated 31 genotypes (MGB1 to MGB31) selected from various environments under autumn planting conditions and conserved in the Moroccan Gene Bank. These genotypes were planted in early winter at a mountainous site known for its pronounced winter cold. Eighteen Morphological, physiological and agronomic parameters including initial vigor, leaf area, seed yield, oil content etc., were assessed using both univariate and multivariate statistical approaches. Analysis of variance revealed significant genotypic differences across most traits, indicating substantial genetic variation. Notably, seed oil content ranged from 23.28% (MGB26) to 43.88% (MGB5), and seed yield from 1,400 kg/ha (MGB7) to 5,400 kg/ha (MGB8). Principal component analysis (PCA) identified that the first principal component, accounting for over 24% of the total phenotypic variance, exhibits a strong positive loading of yield-related traits and chlorophyll content, while displaying a pronounced negative loading for oil content variables. This opposing gradient indicates a clear trade-off between vegetative productivity and oil accumulation across the evaluated genotypes. Hierarchical cluster analysis resolved the germplasm into two principal clusters with high within-group similarity, each further partitioned into relatively homogeneous subgroups. Notably, several genotypes outperformed the control variety Ichraq, underscoring their potential for autumn or early winter cultivation. Nonetheless, essential multi-environment trials remain to validate their phenotypic stability and to ascertain their value as genetic resources for sunflower breeding programs in Morocco and other Mediterranean agro-ecosystems. • Early sowing of sunflower remains effective to avoid periods of droughts and CC effects • Assessing genetic diversity in Moroccan sunflower Gene-Bank for winter sowing varieties • Several genotypes outperformed ‘Ichraq’ the only autumn-planted variety registered in Morocco. • Significant differences among genotypes traits indicating substantial genetic diversity • Yield, oil content, and chlorophyll content traits, explained over 21% of genetic variation