Do Pollination and Pollen Sources Affect Fig Seed Set and Quality? First Attempt Using Chemical and Vibrational Fingerprints Coupled with Chemometrics

Abstract

This research investigates whether pollination and pollen sources separately and simultaneously influence fig seed set and quality, as being thus far the less studied part of the fig trees. This is the first research that tries to answer and verify the above hypothesis through a combined approach of vibrational spectroscopy along with lipo-biochemical and ionomic fingerprinting. Results showed that pollination and pollen source significantly impacted seed set as it was higher in fertilized seeds than that in the control. A similar pattern was obtained with oil yield, which generally ranged between 25.93 and 32.59%. Caprification also displayed a substantial effect on seeds' phenolic components, which was more driven by pollen carbohydrates, involved in the phenolic biosynthesis in the endosperm and embryo tissues. This biosynthesis is also activated by minerals, which are cofactors for large varieties of enzymes that are involved in the phenolic synthesis pathways. Ca and Zn did not follow this pattern and have recorded high levels in figs fertilized by the pollen of OZ and FD4 caprifigs pollen, respectively. Vibrational spectroscopy using Fourier transform infrared (FTIR) spectroscopy coupled with total attenuated reflectance (ATR) also showed a similar pattern to the seed sets and their lipo-biochemical attributes. Thus, the fertilized seeds displayed high vibrational intensity compared to the control in all fingerprint regions. Peaks at 2928 and 1747 cm−1 had a higher intensity and were attributed to lipids CH2 and CH3 stretching vibration and C=O of the carbonyl groups belonging to the triacylglycerols, respectively. Principal component analysis showed high throughput classification with quite similar patterns for both FTIR-ATR fingerprinting and ionomic and biochemical analysis. As many areas of how caprification impacts other seed aspects still need to be investigated further, this research suggests the importance of caprification in seed valorization for oil extraction and as a functional ingredient.