Genic heterozygosity, chromosomal interchanges and fitness in rye: any relationship?

Abstract

Relationship between heterozygosity at allozyme loci, chromosomal interchanges and fitness was analyzed in a rye cultivar showing a polymorphism for such rearrangements. Nine allozyme systems (ACO, ACPH, GOT, GPI, LAP, MDH, PER, PGD and PGM) and five components of fitness (number of fertile tillers, total offspring, egg cell fertility, flowers/ear and seeds/ear) were studied. The estimated selection coefficients against interchange heterozygotes ranged from s = 0.12 to s = 0.34. A significant effect of the genic heterozygosity on some fitness components was observed in interchange heterozygotes (tillering and total offspring), in their standard homozygous sibs (flowers/ear and seeds/ear) and in the descendants of the crosses between standard karyotypes (flowers/ear, seeds/ear and egg cell fertility). However, the main effect was linked to genetic background associated to different crosses. Significant differences for Acph-1, Gpi-1, Lap-1, Mdh-1, Mdh-4, Pgd-2 and Pgm-1 loci were also found in some of these crosses although these differences were inconsistent. This suggests that probably the allozyme loci analyzed were not directly contributing to the fitness and that they are linked, in some cases, to different deleterious alleles depending on both cross and locus. This fact could support the local effect hypothesis as explanation although we do not discard the existence of some inbreeding level (general effect hypothesis) since all crosses and loci studied show a overall consistent trend of increased fitness with increased heterozygosity.

Isolation and Sequencing of Chromosome Arm 7RS of Rye, Secale cereale

“…Many chromosomes are conserved between domesticated rye and wild rye, such as the B chromosomes, which have been well studied and documented [ 35 , 36 ]. Additionally, structural heterozygosity for reciprocal translocations has been reported both in cultivated and wild rye [ 37 ]. By comparing chromosome arm 7RS from the rye donor line with the Lo7 chromosome 7 assembly, we identify gene clusters that are lost or moved to new locations after the two lines diverged.…”