Large variation in mycorrhizal colonization among wild accessions, cultivars, and inbreds of sunflower (Helianthus annuus L.)

Arbuscular mycorrhizal (AM) fungi (AMF) establish beneficial symbioses with the roots of the majority of land plants, including major food crops. The susceptibility of sunflower (Helianthus annuus) to AMF was studied in 26 genotypes--nine wild accessions, 11 cultivars and six inbred lines--by assessing mycorrhizal root colonization in individual plants, with the aim of gaining insights into the genetic control of this trait. The analysis of genetic diversity among sunflower wild accessions, cultivars, and inbred lines, performed by retrotransposon display (multilocus fingerprinting), showed large variability among the analysed genotypes, with wild accessions more variable than domesticated genotypes. Wild accessions were also more susceptible to mycorrhizal colonization than cultivars. Nevertheless, analyses of inbred lines revealed a low repeatability value of the mycorrhizal colonization trait, suggesting the absence of a clearcut genetic control; variability should therefore mostly reflect environmental effects.