The parasitic effects of rye B chromosomes might be beneficial in the long term.
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.
Departamento de Genética, Facultad de Biología, Universidad Complutense, Madrid, Spain.
M
M
González-Sánchez
M
M
Chiavarino
G
G
Jiménez
S
S
Manzanero
M
M
Rosato
M J
MJ
Puertas
D032461:Chromosomes, Plant / Q000235:genetics*; D002523:Edible Grain / Q000235:genetics; D005298:Fertility / Q000235:genetics; D035264:Flowers / Q000235:genetics; D011058:Pollen / Q000235:genetics; D011110:Polymorphism, Genetic / Q000235:genetics; D012434:Secale / Q000235:genetics*; D013995:Time