Chromosome-scale pearl millet genomes reveal a CARLACTONOIC ACID METHYL TRANSFERASE as key determinant of strigolactone pattern and Striga susceptibility

Abstract

The yield of pearl millet, a resilient cereal crop crucial for African food security, is severely impacted by the root parasitic weed Striga hermonthica, which requires host-released strigolactones (SLs) for seed germination. Herein, we identified four SLs present in the Striga-susceptible line SOSAT-C88-P10 (P10), but absent in the resistant 29Aw (Aw). We generated chromosome-scale genome assemblies including four gapless chromosomes for each line. We found the Striga-resistant Aw lacks a 0.7 Mb genome segment containing two putative CARLACTONOIC ACID METHYL TRANSFERASE1 (CLAMT1) genes. Upon transient expression, P10CLAMT1b produced methyl carlactonoate (MeCLA), an intermediate in SL biosynthesis. Feeding Aw with MeCLA resulted in the production of two P10-specific SLs. Screening a diverse pearl millet panel confirmed the pivotal role of the CLAMT1 section for SL diversity and Striga susceptibility. Our results reveal a reason for Striga susceptibility in pearl millet and pave the way for generating resistant lines through marker-assisted breeding or direct genetic modification.