Correlation and principal component analysis of bixin content and yield-related traits in Annatto (Bixa orellana L.)

Abstract

Annatto (Bixa orellana L.) is an important dye-yielding species harbouring huge variations in qualitative as well as quantitative traits. Identification of factors influencing bixin content and seed yield is an important breeding aspect, considering the economic importance of annatto for selection of elite genotypes based on morphological traits. Thirty-one trees plus were selected for the study, and sixteen quantitative traits were recorded for two years (2021 and 2022) to understand their association with bixin content and seed yield. Annatto has bivalve pods; however, trivalve pods were also observed during the study. A positive and significant association (r = 0.65) between bixin content and seed yield was observed from the correlation analysis. The study revealed that bixin content was highly correlated and influenced directly by the number of primary and secondary branches and hundred seed weight, while tree height, basal diameter, and the number of primary and secondary branches exhibit a significantly positive direct effect on seed yield, suggesting these traits as a reliable morphological marker for selecting highly productive genotypes. The thirty-one plus trees were grouped through hierarchical clustering into six clusters, with maximum bixin content and seed yield in Cluster I and Cluster III. The genotypes TNBi 0020, TNBi 0021, TNBi 0022, TNBi 0023, TNBi 0024 and TNBi 0037 can be utilized for mass multiplication and popularization for commercial cultivation of Bixa orellana.