Wheat developmental traits as affected by the interaction betweenEps-7Dand temperature under contrasting photoperiods with insensitivePpd-D1background

Abstract

Earliness per se (Eps) genes are important to fine tune adaptation, and studying their probable pleiotropic effect on wheat yield traits is worthwhile. In addition, it has been shown that some Eps genes interact with temperature. We studied two NILs differing in the newly identified Eps-7D but carrying insensitive Ppd-D1 in the background under three temperature regimes (9, 15 and 18 °C) and two photoperiods (12 h and 24 h). Eps-7D affected time to anthesis as expected and the Eps-7D-late allele extended both the period before and after terminal spikelet. The interaction effect of Eps-7D × temperature was significant but not cross-over: the magnitude and level of significance of the difference between NILs with the late or early allele was affected by the growing temperature (i.e. difference was least at 18 °C and largest at 9 °C), and differences in temperature sensitivity was influenced by photoperiod. Rate of leaf initiation was faster in NIL with Eps-7D-early than with the late allele which compensated for the shorter duration of leaf initiation resulting in similar final leaf number between two NILs. Eps-7D-late consistently increased spike fertility through improving floret primordia survival as a consequence of extending the late reproductive phase.

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

“…The fact that the Eps-7D × Ppd-D1 interactions would be clearer at some temperatures as opposed to others is also something that could have been expected as both Eps-7D [ 1 ], as well as other Eps [ 7 , 9 , 14 , 15 , 34 , 35 ], and Ppd genes [ 12 , 36 , 37 ] have shown to interact with temperature.…”

“…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.…”

“…For details, please see the companion paper [ 1 ]. To recap briefly, treatments considered in this paper comprised four NILs differing in the alleles for Eps-7D and Ppd-D1 (i.e., Eps-7D-late + Ppd-D1a ; Eps-7D-late + Ppd-D1b; Eps-7D-early + Ppd-D1a ; Eps-7D-early + Ppd-D1b ); grown at three temperatures (namely, 9, 15 and 18 °C) from seedling emergence to anthesis.…”

“…As mentioned in the introduction of the companion paper [ 1 ], and elsewhere [ 2 , 3 ], the main genetic factors controlling wheat developmental traits are photoperiod- and vernalisation-sensitivity genes ( Ppd and Vrn ), both critical for coarse tuning phenology, and the earliness per se ( Eps ) gene, responsible for fine-tuning development [ 4 ]. Furthermore, these genetic factors controlling the duration of the developmental phases may have pleiotropic effects on yield traits [ 5 , 6 ], explaining a selective advantage of certain genes over others.…”

“…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.…”