The innovative study comprised a comparative evaluation of phenotypic and anatomic characters of anthers in 14 citrus taxa grown in Iraq. The results revealed the classification of citrus anthers into three groups based on the apex shape—round in five taxa, round-flattened apex in three taxa, and acute apex in six taxa. The epidermis surface patterns also exhibited four groups—reticulated surface, pitted, smooth, and slightly disassembled. The tapetum was evident in three forms, viz., densely folded, folded orbicules, and almost unfolded. The anatomical study disclosed that the cross-section shape of the anther was like a butterfly in all taxa. The anther wall of the studied citrus taxa consisted of four distinct cell layers. The endothecium cells of the studied citrus taxa had the characteristic of semi-circular outline thickenings with needle-shaped crystals appearing in the anther tissue in some taxa. The stamen filament was irregular in the citrus taxa, comprising an epidermis with cuticle, followed by the cortex with raphides crystals, with the vascular bundle located in the center. The results confirmed that the citrus anther micromorphology and anatomy represent effective tools in supporting taxonomy and breeding by facilitating the differentiation of taxa and improving the understanding of relationships within Citrus.
Citrus taxa, citrus anther, Iraqi citrus, anther anatomy, SEM
Classification tools vary to differentiate taxonomic taxa down to the smallest structure; therefore, the anther’s adoption morphologically and anatomically served as one of the distinguishing marks between citrus taxa, and with hybridization, their characterization resulted in a high degree of convergence and similarity.