CHARACTERIZATION OF THE FIRST PEA (PISUM SATIVUM L.) NATURAL STRIGOLACTONE-DEFICIENT MUTANT RESISTANT TO CRENATE BROOMRAPE (OROBANCHE CRENATA FORSK.)

Crenate broomrape (Orobanche crenata Forsk.) is a devastating parasitic weed threatening the cultivation of legumes in the Mediterranean basin and in the Middle East, which can lead to up to 100% yield losses. In pea germplasm, only moderate level of resistance has been found and all commercial cultivars are prone to broomrape infestation. As a result of a large germplasm screening, we identified a pea landrace showing high level of resistance to O. crenata, from which we developed a line which was named ROR12. The branching phenotype of ROR12 prompted us to quantify its content of strigolactones, a new class of plant hormones which is known to have a key role in the control of apical dominance as well as in stimulating the germination of Orobanche seeds. Notably, we determined a very low amount of the three main pea strigolactones orobanchol, orobanchyl acetate and epoxy-orobanchol acetate in ROR12 root tissues and root exudates compared to three commercial cultivars. Orobanche seeds germination tests with root exudates from different genotypes provided final prove that ROR12 is a strigolactone deficient line. Two years replicated trials in non infested fields indicated that the ROR12 line does not have markedly lower yield potential with respect to commercial cultivars, and therefore can be conveniently used for breeding purposes. Two large segregant F2 population are being currently analyzed aiming to resistance gene/QTL mapping and cloning.