Interactions between two QTLs for time to anthesis on spike development and fertility in wheat

Abstract

Earliness per se (Eps) genes are reported to be important in fine-tuning flowering time in wheat independently of photoperiod (Ppd) and vernalisation (Vrn). Unlike Ppd and Vrn genes, Eps have relatively small effects and their physiological effect along with chromosomal position are not well defined. We evaluated eight lines derived from crossing Paragon and Baj (late and early flowering respectively), vernalisation insensitive, to study the detailed effects of two newly identified QTLs, Eps-7D and Eps-2B and their interactions under field conditions. The effect of both QTLs were minor but their effect was modulated by the allelic status of the other. While the magnitude of effect of these QTLs on anthesis was similar, they are associated with very different profiles of pre-anthesis development which also depends on their interaction. Eps-7D affected both duration before and after terminal spikelet while not affecting final leaf number (FLN) so Eps-7D-early had a faster rate of leaf appearance. Eps-2B acted more specifically in the early reproductive phase and slightly altered FLN without affecting the leaf appearance rate. Both Eps-7D and 2B affected the spike fertility by altering the rate of floret development and mortality. The effect of the latter was very small but consistent in that the -late allele tended to produced more fertile florets.

Wheat Developmental Traits as Affected by the Interaction between Eps-7D and Temperature under Contrasting Photoperiods with Insensitive Ppd-D1 Background

“…However, the NILs would have sensitive alleles in the Ppd-1 loci on the A and/or B genome. Indeed, we could not discard that a new Eps-2B could actually be Ppd-B1 [ 40 ]. These genes produce responses that are frequently less noticeable than Ppd-D1 , but still significant [ 8 , 53 , 54 , 55 ].…”

“…Recently an Eps QTL on chromosome 7D was identified in wheat which was known to influence time to heading [ 40 ]. Four NILs were generated from the cross Paragon (a modern UK commercial cultivar [ 41 ] and Baj (a CIMMYT cultivar, used frequently as check [ 42 ], both of which are spring type with no requirements of vernalisation.…”

Phenology and Floret Development as Affected by the Interaction between Eps-7D and Ppd-D1

“…This Eps-7D interacted with temperature [ 1 ] and Eps-2B [ 16 ], and the interaction effect have been shown to be effective well beyond the duration of developmental phases. Our findings suggest that it is not only important to study every newly identified Eps gene (simply because although they are all named equally, the mechanisms by which they actually modify time to anthesis may be quite different), but it is also necessary to evaluate their functions under varying backgrounds of other important genetic factors affecting wheat development to ensure repeatability of their effect and their application.…”

“…At least in part, the ambiguity of the results reported in the literature may well reflect the fact that the mechanism of each Eps gene could be quite different from one another, beyond the fact that all affect time to heading/anthesis (by definition). Final leaf number (FLN), phyllochron, plastochron, spikelet number, floret development patterns and developmental phases can be affected or not depending on the specific Eps gene studied [ 7 , 8 , 9 , 13 , 14 , 15 , 16 ]. Therefore, it is important to study and evaluate each novel Eps along with their interactions with the other genetic factors (involved in complex network of genes altering the life cycle of wheat) and the environment.…”

“…Determining to what degree the environmental condition affect the effects on phenology of a particular Eps and its interaction with the background is important if we are to predict the environment in which such a genetic combination can confer maximum benefit. For instance, in the companion paper, we showed that the environment affected the magnitude of effects of a novel Eps gene ( Eps-7D ) on phenology and spike fertility traits [ 1 ]; moreover, in a recent paper [ 16 ], we showed that these effects of Eps-7D were affected by its interaction with another Eps gene ( Eps-2B ). Quantifying the interactions with major genes coarse-tuning wheat development is relevant to determine whether it is potentially useful to exploit a particular Eps gene in a certain wheat background.…”