Chromosome-scale pearl millet genomes reveal CLAMT1b 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 hormones, called strigolactones (SLs), for seed germination. Herein, we identify four SLs present in the Striga-susceptible line SOSAT-C88-P10 (P10) but absent in the resistant 29Aw (Aw). We generate chromosome-scale genome assemblies, including four gapless chromosomes for each line. The Striga-resistant Aw lacks a 0.7 Mb genome segment containing two putative CARLACTONOIC ACID METHYLTRANSFERASE1 (CLAMT1) genes, which may contribute to SL biosynthesis. Functional assays show that P10CLAMT1b produces the SL-biosynthesis intermediate methyl carlactonoate (MeCLA) and that MeCLA is the precursor of P10-specific SLs. Screening a diverse pearl millet panel confirms 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.