Effects of a photoperiod-response gene Ppd-D1 on yield potential and drought resistance in UK winter wheat

Using a pair of near-isogenic lines(NILs) of winter wheat (Triticumaestivum L.) contrasting for the Ppd-D1 and ppd-D1 alleles, in eachof Mercia and Cappelle-Desprez, experimentsin two seasons (1997/8 and 1998/9) on aloamy medium sand examined differences inflowering date, resource capture, biomassproduction and grain yield responses toirrigation. Drought did not occur for anysustained period in unirrigated conditionsin 1998 due to high seasonal rainfall. In1999, drought developed post-floweringunder unirrigated conditions. Ppd-D1on average advanced flowering by 12 days inMercia and 9 days in Cappelle-Desprez.Earlier flowering with Ppd-D1 was dueto a shorter thermal duration from cropemergence to GS31, with no effect on thethermal duration from GS31 to GS61. In bothgenetic backgrounds, Ppd-D1 decreasedabove-ground dry matter (AGDM) at harvestin irrigated conditions by 0.3–0.9 tha^-1 (p< 0.05), but thiswas compensated for by increases inharvest index (HI), so that grain yield wasconserved. Although Ppd-D1 decreasedmaximum green area index (GAI) by 0.8–1.9this was countered by greater maintenanceof green area after flowering, so thatradiation interception during grain fillingwas conserved. The Ppd-D1 alleledecreased season-long crop water uptake inthe Mercia NILs in irrigated conditions by39 mm. Effects of drought in 1999,averaging across NILs, were todecrease machine-harvested grain yield by 0.6 t ha^-1 in Mercia and by 1.8 tha^-1 in Cappelle-Desprez (p<0.05). The Ppd-D1 and ppd-D1NILs, though, responded similarly todrought in both genetic backgrounds. Earlyflowering with Ppd-D1 decreasedpre-flowering water uptake underunirrigated conditions by ca. 25 mm,but increased post-flowering uptake by only10 mm, compared to ppd-D1. This was aresult of smaller season-long water uptakefor Ppd-D1 compared to ppd-D1.Ppd-D1 decreased stem solublecarbohydrate measured shortly afterflowering under drought by ca. 0.3 tha^-1. Effects of Ppd-D1 onother drought-resistance traits, such aswater-use efficiency (WUE; AGDM per unitcrop evapotranspiration) and maximumrooting depth, appeared to be neutral. Itis concluded that the effects of the Ppd-D1 allele appeared to be largelyneutral on yield potential and late-seasondrought resistance in the UK's temperateenvironment in these genetic backgrounds.However, there were indications that Ppd-D1 may offer scope for breeding winterwheat cultivars with more efficientproduction of grain DM per unit seasonalcrop evapotranspiration, associated withimproved HI, compared to currentlycommercial UK genotypes.