Résumé
Oil palm is the first oil crop, with more than one third of world market share and generated 50 billion dollars in revenue in 2011. One major constraint that weighs heavily on yield and harvest management is the rapid oil acidification due to the high lipase activity that releases free fatty acids (FFA) in the mesocarp of bruised ripe fruits. While FFA level of crude palm oil from efficient processing facilities is usually 3 to 4%, oil from smallholders shows higher values especially in Africa where FFA level can exceed 15%. As a result, most of palm oil produced by African smallholders is not competitive on international markets. We have developed a simple and reliable assay for mesocarp lipase and showed that oil palm fruit mesocarp was the plant tissue with highest lipase activity, up to 100μmol fatty acids. min-1.mg protein-1. We screened fruits from different germplasms for triacylglycerol lipase activity and identified a few fruits with almost undetectable lipase activity. Oil was extracted from fruits bunches using conditions that mimicked that used at mills and the FFA content was 30% lower in oil from low-lipase lines than that from normal, high lipase, lines. Because these low lipase lines are elite, high yielding varieties, they can potentially be commercialized immediately. We were able to identify the lipase using a functional proteomic approach and expression studies indicated that it was almost mesocarp-specific. Low lipase activity correlated to low protein and low transcript in a segregating population and bulk segregant analysis showed a co-segregation of the lipase locus and the low/high lipase trait, thus providing a molecular marker to introgress the trait into major elite genotypes. Wide adoption of this material should significantly increase yield and improve harvest management, with highest benefits to African small-scale planters. (Texte intégral)