The parasitic effects of rye B chromosomes might be beneficial in the long term

Abstract

Rye B chromosomes (Bs) have strong parasitic effects on fertility. B carrying plants are less fertile than 0B ones, whereas the Bs have no significant effects on plant vigour. On the other hand, it has been reported that B transmission is under genetic control in such a way that H line plants transmit the Bs at high frequency, whereas the Bs in the low B transmission rate line (L) fail to pair at metaphase I and are frequently lost. In the present work we analyse variables affecting vigour and fertility considering not only the number of Bs of each plant, but also its H or L status and the B number of its maternal parent. Our results show that the Bs not only decrease female fertility of the B carrier, but the fertility of its progeny, with the exception of 0B plants coming from a 4B mother, which are the most fertile. In this way B chromosomes can be considered as a selective factor. Pollen abortion was higher in B carriers, in the progeny of B carriers and in H plants, but 4B plants coming from B carrying mothers produce less aborted pollen, indicating that a high B number is more deleterious if it is transmitted in the pollen grains. A similar result was obtained for endosperm quality estimated as grain weight, because it is negatively influenced by the Bs in 4B plants coming from a 0B mother. H plants were always less fertile than L ones, indicating that alleles increasing the loss of Bs in the L line will be probably selected as a defence of the A genome against the invasive Bs of the H line. Flower number is not affected by the Bs.

Genetic Behavior of Distinct B Chromosome in Safflower

“…Although reports show that the B chromosomes were mostly inert in nature having no effect of their own, when their number exceeds they can clearly effect the vigor and fertility of the plant (Camancho et al 2000, Green 2004), expect in the case of Plantago coronopous where a single B chromosome induced total male sterility (Paliwal and Hyde 1959), and in Haplopapus gracilis where the color of achene was changed by the presence of a single B chromosome (Jackson and Newmark 1960). Our results, showing a decrease in pollen fertility with an increase in the number of Bs as regard to plants carrying 0B s were in concordance with studies conducted by González-Sánchez et al (2004) in rye.…”

Selfish genetic elements and sexual selection: their impact on male fertility

“…Supernumerary chromosomes in lilies (Lilium sp. ), for example, are associated with reduced pollen fertility (Kimura and Kayano 1961), and in rye (Secale cereale), male fertility is negatively related to number of B chromosomes (González-Sánchez et al 2004). …”

Genomic Characterization of a B Chromosome in Lake Malawi Cichlid Fishes

“…Despite the fact that B chromosomes add significant amounts of genetic material to the genome, B chromosomes have rarely been associated with novel phenotypes, the most frequent exception being an effect on fertility [2,6,20,21,22]. With a limited list of known B-specific sequences and few or no visible phenotypes beyond drive, the prevalent view has been that B chromosomes carry few genes [14,23].…”