(1990) Differential Agronomic Response of Winter Wheat Cultivars to ...

Published September, 1990

Differential

Agronomic Response of Winter Wheat Cultivars Environmental Stress

to Preanthesis

M. H Entz and D. B. Fowler* ABSTRACT Sharmaet al., 1987). Several researchers also have reported that, compared with tall types, semidwarf Winter wheat (Tritlcumaestlvum L.) cultivarsproduced in the wheat cultivars are more productive under favorable semiarid environment of theCanadian prairiesaresubjected to variablewater stresses.Therefore, successful cultivars in this region water conditions (Syme,1969; Laing and Fisher, 1977; require botha highproduction potentialandyieldstability.This Pearmanet al., 1978; Allan, 1986) but moresusceptistudywasinitiatedto compare the agronomic performance of two ble to drought and high temperature stress (McNeal winter wheat cultivars thathaddemonstrated a differential response et al., 1972; Laing and Fischer, 1977; Woodruffand to the oftenhighdrought stress environment of Saskatchewan. Tonks, 1983). These studies demonstrate that the Eleven fieldtrials wereconducted at sevenlocations in Saskatche- yield structure of cereal plants can be affected by wanfrom1984to 1987.Measurements includeddrymatterprodrought, and that cultivar variation in drought tolerduction, yieldcomponents, grainyield,harvest index,water use,and ance for these traits can occur. wateruseefficiency.Panevaporation during the 15-dperiodimThe Chinook region of southwestern Alberta has mediately priorto anthesis(E) ranged from64to 158mm for the been the traditional winter wheat production area in 11trialsandwasusedasanindicator of environmental stress.There western Canada. In recent years, the adoption of a wasa significant(P < 0.01)negative relationship between grain snow managementsystem that utilizes noyieldandEforbothcultivars. Thedifference in grainyieldbetween practical till seeding into standing stubble has resulted in an cultivars(Norwin minus Norstar)ranged fromapproximately 500 expansion of this production area to include most of -a. to -1500kgha Asstressincreased, the grainyieldforNorwin the Canadian prairies (Fowler, 1983). Dryland winter declined at a significantlyhigher ratethanthatof Norstar. The wheat grownin the prairie region of Canadaexperidifferential response of thesecultivars to stresswasrelatedto differencesin kernelnumber m-2 (KNO). Under highE (approximately ences water conditions ranging from extreme drought 8.0mm d-a),KNO forbothcultivars wasassociated withpreanthesis to adequate moisture for the expression of high (>5 Mgha-l) yield potential (Entz and Fowler, 1989). Entz drymatterproduction. Under lowE (approximately 5.0 mm d-l), and Fowler (1988) demonstrated that drought during significantlyhigherKNO for Norwin wasattributed to a morefathe 2-wk period prior to anthesis was particularly vorable preanthesis drymatter distribution (KNO perunitof aerial drymatter present at anthesis) compared to Norstar. Other factors damagingto grain yield of winter wheat grownin this thatcontributed to theobserved genotype byenvironment interaction region. Reducedproductivity under high preanthesis -a wereharvestindexandwateruseefficiency(kggrainha-a mm drought was related to reduced dry matter accumuevapotranspiration). lation, kernel production, and HI. Winter wheat cultivars produced in the Canadian prairie region havetraditionally beentall types similar to the presently dominant cultivar Norstar (Grant, HEREHAVE BEENNUMEROUS investigations into 1980). These tall types are prone to lodging under facultivar variation in drought tolerance. Innes vorable moisture conditions. The introduction of the and Blackwell (1981) observed a differential response winterhardy semidwarf Norwin (Taylor et al., 1986) of two winter wheat cultivars to preanthesis drought, resulting primarily from a difference in kernel number has enabled the successful production of a short-statured, lodging-resistant winter wheat cultivar in this per spike. Similar results reported by Saeedand Franregion. However, Norstar has consistently outpercis (1984) indicated that temperature and rainfall beformed Norwin when produced under conditions of tween panicle initiation and anthesis accounted for a moderateto high water stress. In the present studies, significant portion of the cultivar by environmentinthe agronomic performance of Norwin was compared teraction for kernel production and grain yield in sorwith Norstar with the objective of identifying the charghum(Sorghumbicolor L.). Wells and Dubetz(1970), acters of importance in determining the adaptation of working with barley (Hordeum vulgare L.), also these two winter wheat cultivars to the environmental showeda differential cultivar response to drought at conditions prevailing on the Canadianprairies. the headingstage. However,in their experiments, differential responsesresulted primarily from differences MATERIALS AND METHODS in kernel size. Other morphologicaltraits involved in Field experiments wereconductedin central andeastern cultivar by water regimeinteractions in wheatare fillSaskatchewan at Saskatoon(52 °N107°W;silty clay Vertic eting capacity (Innes et al., 1981), ratio of spike dry Haploborolls) and Clair (52 °N 104 °W;loamyUdic Hapmatter to total dry matter at anthesis (Syme, 1969; loborolls) in 1984; Saskatoonand Kamsack (52 °N102 °W; Fischer, 1979), and harvest index (HI) (Fischer, 1979; loamyUdic Haploborolls)in 1985, Saskatoon,Clair, and CropDevel.Ctr., Univ.of Saskatchewan, Saskatoon, SK,S7N0W0, Outlook(52 °N 107 °W;fine sandy loamTypic HaploborCanada. M.H.Entzpresentaddress:Dep.of Plant Science,Univ. oils), Carlyle (50 °N 102 °W;loamyTypic Haploborolls) of Manitoba, Winnipeg, MB,R3T2N2,Canada.Supportedin part and Porcupine Plain (53 °N 103 °W;clay loam Boralfic by a grant fromthe NewCropDevelopment Fundof Agriculture Agriboralls) in 1986, and Clair and Hagen(53 °N 106 °W; Canada andin part bya grant fromthe Canada-Saskatchewan Ecoloamy,UdicHaploborolls)in 1987. nomicRegionalDev.Agreement. Received5 Oct. 1989.*CorreTwowinter wheatcultivars, Norstar and Norwin,were sponding author. included in the experiment.Thesecultivars were no-till Published in CropSci. 30:1119-1123 (1990). seededinto standingbarley, rapeseed(Brassicacampestris

T

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CROPSCIENCE, VOL. 30, SEPTEMBER-OCTOBER 1990 were described using regression analysis. Measurements of agronomic characters employed in regression analysis were average values for all replications at each location for each year. Regression lines were compared statistically using methods described by Ratkowsky (1983).

L.), or mustard (Sinapis alba L.) stubble immediately after harvest of the previous crop in late August or early September. The trial at Porcupine Plain was seeded into tilled summerfallow. Trials were seeded with a small plot hoe-press drill or a commercial minimumtillage drill at a rate of 75 kg ha-I. Plot size varied among sites and ranged from 6 to 12 m2. Phosphate fertilizer was applied with the seed at rates recommendedfor each soil type. Nitrogen (34-0-0) was topdressed in late April at recommendedrates based upon soil tests. Experimental design for all trials was a randomizedcomplete block with three or four replications. Detailed measurements of crop water balance and dry matter accumulation were made in six of the 11 trials. One neutron access tube was located in the center of each plot. Soil water from 0.1 to 1.3-m depth (1.0 m at Clair, 1984) was measured in early May (soon after resumption of growth; Zadoks stage 20-24) (Tottman, 1987), at anthesis (Zadoks stage 65), and at maturity (Zadoks stage 92-94) using a neutron probe (Troxler Laboratories, Triangle Park, NC). Surface soil water (0-10 cm) was determined gravimetrically, then multiplied by soil bulk density values to convert to volumetric basis. Evapotranspiration (ET) was expressed as precipitation plus soil water use and was calculated for two time periods, May 1 to anthesis (average anthesis date was June 26) and May 1 to maturity (average maturity date was August 11). Pan evaporation was recorded daily from a nearby Environment Canada weather station (furthest distance 60 km). Daily precipitation was recorded using a tipping bucket rain gauge (Model RG2501, Sierra Misco Inc., Berkeley, CA) connected to a Campbell Scientific CR21data acquisition system (Campbell Scientific Inc., Logan, UT). Aerial dry matter accumulation was determined at anthesis and maturity from samples taken on 1.0-m sections from each of two rows in each plot. Plot area harvested for grain yield determination ranged from 5 to 10 m2 depending on location. Maturity was similar for the two cultivars. Grain samples were dried (30 °C) to 90 g H20 -~ dry gr ain before yields were measured. Harvest index was calculated as grain yield divided by dry matter yield at maturity. Water use efficiency (WUE)was calculated as kg -~ grain yi eld mm-~ ET. A subsample of 250 kernels from each plot was used to determine kernel weight (KWT)(mg kernel-~). Kernel ber m-2 (KNO) was calculated by dividing grain yield kernel weight. Analysis of variance was used to determine the significance of treatment differences in each trial. Relationships between crop productivity parameters and environment

RESULTS AND DISCUSSION Grain Yield and Yield Components Large differences in grain yield amongtrials (Table 1) reflected the wide range of environmental conditions encountered in this study. Water stress is the primary growing season environmental limitation to grain yield in this semiarid prairie climate. Fischer (1973) has demonstrated that the critical period for water stress in wheatoccurs before anthesis. This finding has been confirmed for field-grown winter wheat in western Canada(Entz and Fowler, 1988; 1989). addition, atmospheric evaporative demandfor water (pan evaporation) during the 15-d period immediately prior to anthesis has been identified as the primary environmentalindicator of stress in this region (Entz and Fowler, 1988). A significant (P < 0.05) cultivar by trial interaction indicated that the two cultivars considered in this study did not respond the same to changes in environment. Amongthe 11 trials, Norstar significantly outyielded Norwinin the three trials that experienced the highest E (Table 1). Cultivar differences werenonsignificant for yield in the remainingtrials (Table 1). However, as E decreased, yield of Norwin improved relative to that of Norstar. As a result, while the relationship between E and grain yield was significant and linear for both cultivars (Table 2), the yield Norwinincreased at a significantly higher rate with decreases in E than that of Norstar (Table 2). This resulted in a cross-over cultivar by environmentinteraction for responseto preanthesis water stress. Similar results reported by Saeed and Francis (1984) showedthat variation in temperature and rainfall between panicle initiation and anthesis accounted for a significant portion of the cultivar by environmentinteraction for grain yield in sorghum.Differential grain yield responseto preanthesis water stress has also been

Table1. Panevaporation,average(fY) grain yield, kernel number,and kernel weight for winterwheattrials in Saskatchewan, 1984to 1987, and the difference in cultivar performance (NorwinminusNorstar= d) in each trial. Location

Year

Pan~’ evaporation --mm

Grainyield ~"

d~: -I kgha

Kernelno. ~"

Kernelwt. d

.i(

no./m2

632 Clair 1984 64 5 040a§ 520 14 906a 4 781a 221 15 593a 2 674 Kamsack 1985 68 504 9 942c 1 394 Sask~oon 1985 98 3 098d Porcupine Plain -427 12 120b -1 637 1986 106 4 057b 2 351f -125 7 753c - 181 Clak 1986 115 119 2 587ef -20 8 929d --869 Outlook 1986 2 770e -212 8 811de -3 Saskatoon 1986 120 Saskatoon 1984 123 1 531g -131 5 961f -695 Carlyie 1986 126 3 411c -1020" 10 121c -2 821" Hagen 1987 148 2 266f -607* 7 619e -3 536* Clair 1987 158 2 548ef -1457" 8 025e -3 870* *,**Cultivar differences significantat the0.05and0.01probability levels, respectively, as testedbya F-test. Panevaporation for the15-dperiodimmediately priorto anthesis. Differencein cuitivarperformance (Norwin minus Norstar). Means followedby thesameletter arenot significantlydifferentas testedbyDuncan’s newmultiplerangetest.

d mg

33.7a 30.5c 31.1c 35.5ab 30.2c 31.2bc 30.6c 25.7d 33.7a 33.2ab 32.4b

2.1" -4.4* 0.6 1.0 -0.8 1.0 0.0 0.8 -0.7 -2.1" -1.0

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ENTZ & FOWLER: AGRONOMIC RESPONSE OF WHEAT TO ENVIRONMENTAL STRESS

Table 2. Regression equations relating a) grain yield (kg -1) with pan evaporation (ram) for the 15-d period immediately prior to anthesis (E), b) kernel number -2 ( KNO) w ith E , c ) weight k nel -1 (rag) (KWT)with E, d) grain yield with KNO,and e) yield with KWTfor Norstar and Norwin winter wheat produced in Saskatchewan.

reported for other wheatcultivars (Innes et al., 1981) and for barley (Wells and Dubetz, 1970). Kernels m-2 has been reported to be the most important componentdetermining wheat yield (Fischer et al., 1977; Shanahanet al., 1984). A high positive correlation between KNOand yield indicated that KNOwas also a primary yield determinant in the present study (Table 2). The KNO was linearly related to E for both Norwinand Norstar (Table 2). However, a significant (P < 0.01) cultivar by trial interaction for K_NOindicated that Norstar and Norwindid not respond the same under the range of environmental conditions experiencedin these trials. At high stress levels, Norstar produced significantly higher K_NO than Norwin(Table 1). However,as the stress level decreased, kernel production for Norwinincreased at a significantly higher rate than for Norstar (Table 2). Syme(1969) and Pearmanet al. (1978) have reported that semidwarf wheat cultivars produce relatively higher KNO than tall types under low stress conditions. A significant (P < 0.01) cultivar by trial location interaction also was observed for KWT.However,differences in KWT were not closely associated with differences in E (Table 1 and 2), and cultivar grain yield was only weaklycorrelated with KWT (Table 2). These observations indicate that KWTdid not influence grain yield to the same degree as KNO.They also demonstrate that the differential environment responses for grain yield of Norwinand Norstar were expressed primarily through changes in KNOand not KWT.Changes in KNOalso were found to be the reasonfor differential cultivar response’to preanthesis stress in winter wheat grownin Britain (Innes et al., 1981) and sorghum(Saeed and Francis, 1984).

Cultivar

Regression equation

r

Y =a+bx Yield Yield KNO KNO KWT KWT Yield Yield Yield Yield

a. Norstar Norwin b. Norstar Norwin c. Norstar Norwin d. Norstar Norwin e. Norstar Norwin

0.89** 0.88** 0.78** 0.92** 0.33 0.28 0.98** 0.97** 0.51 0.40

5695b~" - 21.6 (E)b 7399a - 38.8 (E)a 17079b - 59.3 (E)b 23120a -119.6 (E)a 31.5a + 0.00081 (E)a 32.7a - 0.012 (E)a -715a + 0.382 (KNO)a - 110a + 0.325 (KNO)a -5404a +274.0 (KWT)a -4980a +255.1 (KWT)a

** Significantat the 0.01 probabilitylevel. t Regressioncoefficients followedbythe sameletter are not significantly different (P < 0.05).

lady to environment, Norwin consistently was most productive in low stress environments. The ratio of KNO:DMa, which is often referred to as the kernel production efficiency of a cultivar (Fischer, 1979), was similar for the two cultivars high stress levels (Table 3). However,differences KNO:DMa ratios between cultivars were significant in the twotrials that experiencedthe loweststress (Table 3). This occurred because as E decreased, KNO:DMa ratios increased (P < 0.01) for Norwin while KNO:DMa for Norstar did not change significantly (Table 4). These observations support the view that at high stress levels, KNO is associated with increases in DMa(Fischer, 1979; Jordan, 1983). However, as moisture conditions improved, Norwinhad a more favorable preanthesis dry matter distribution. Previous studies also have shownthat semidwarfwinter wheatcultivars often have a higher kernel production per unit of dry matter present at anthesis than tall types (Syme, 1969; Davidson and Birch, 1978; Fischer, 1979). Evidence of higher photosynthetic rates amongsemidwarfwheatcultivars comparedwith tall types (Morganet al., 1987) agrees with the view that semidwarfscould support a higher KNO per unit area of leaf.

Crop Growth and Water Use Measurements of crop growth and water use were madein six of the 11 trials. Dry matter production, crop height, KNO,and WUEall increased with decreasing E (Table 3). Significant (P < 0.05) trial cultivar interactions indicated differential response of the two cultivars for kernel numberkg-~ dry matter at anthesis (KNO:DMa), crop height, HI, and WUE (Table 3). Whenthe two cultivars did not respond simi-

Table 3. Trial average (f~) crop dry matter production, crop height at maturity, harvest index, evapotranspiration, water use efficiency (WUE), and kernel number kg-1 dry matter at anthesis (KNO:DMa)for winter wheat trials in Saskatchewan, 1984 to 1986, and the difference in cultivar performance(Norwin minus Norstar = d) in each trial. See Table 1 for details on grain yield, kernel number, and kernel weight for these trials. Evapotranspiration Pant evapoLocation Year ration

Dry matter at anthesis

Dry matter at maturity

Crop height at matudty

,Y

.Y(

.~"

d~

-1 --mm----kgha Clair Kamsack Saskatoon Clair Outlook Saskatoon

1984 1985 1985 1986 1986 1986

64 68 98 115 119 120

6437b~ 8021a 4720c 3926d 4817c 4114d

d

-1 kgha -2030* -3662** -561 -549 -630 -273

15871a -4382** 15452a -1921"* 10790b 147 6877d 419 8485c -1158"* 8206c -197

d

May l Harvest index to anthesis ~"

d

.Y(

d

May l to matufity

cm--

-Y(

88b 94a 73c 49e 65d 49e

-48** -53** -34** -16’ -20** -17"

mm-0.33 0.13"* 0.31 0.06* 0.29 0.04 0.34 -0.04 0.33 0.01 0.32 0.01

160b 144b 167ab 82d 178a 112c

0 -2 0 -1 -9 -9

*,**Cultivar differencessignificant at the 0.05 and 0.01 probabilitylevels, respectively, as tested by a F-test. Pan evaporationfor the 15-d period immediatelyprior to anthesis. Difference in cultivar performance(NorwinminusNorstar). Meansfollowedby the sameletter were not significantly different as tested by Duncan’snewmultiple range test.

268b -5 303a -2 227cd 13 2lid 21 302a -13 240c -6

WUE .]"

KNO:DMa d

kg ha-~ grain -~ ET mm 18.9a 3.1" 15.8b 0.7 13.7e 1.6 ll.2d -1.6 9.5d -0.3 10.$d 0.3

.]"

2.4a 2.1a 2.1a 2.0a 2.0a 2.1a

d

0.9* 1.3" 0.6 0.2 0.1 0.1

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CROP SCIENCE, VOL. 30, SEPTEMBER-OCTOBER 1990

Table 4. Regression equations relating a) kernel number kg-1 dry matter at anthesis (KNO:DMa) with pan evaporation (mm) for the 15-d period immediately prior to anthesis (E), b) harvest index (HI) with E, and c) water use efficiency (WUE — kg ha"1 grain mm'1 ET) with E for Norstar and Norwin winter wheat produced in Saskatchewan. Cultivar

Regression equation

r

ACKNOWLEDGMENTS

+ bx ——————— a. Norstar Norwin b. Norstar Norwin c. Norstar Norwin

KNOrDMa KNO:DMa HI HI WUE WUE

1.48bf 3.66a 0.18b 0.34a 23.8a 28.9a

-0.0034 (E)b -0.0134 (E)a 0.00113 (E)b 0.00008 (E)a -0.112 (E)b -0.158 (E)a

greater early season assimilation and kernel production. The observed genotype by environment interaction was related to physical measurements of the environment (pan evaporation) and specific morphological traits of the two cultivars considered.

0.21

0.98** 0.65* 0.24 0.95" 0.92"

*,** Significant at the 0.05 and 0.01 probability levels, respectively. t Regression coefficients followed by the same letter are not significantly different (P < 0.05).

Harvest index provides an estimate of the conversion efficiency of dry matter to grain yield (Baker and Gebeyehou, 1982). In the present study, HI for Norstar declined significantly (P < 0.05) as E decreased (Table 4). Therefore, while Norstar was taller in all trials (Table 3) and produced significantly more dry matter than Norwin in the two lowest stress trials (Table 3), Norstar was not able to convert as great a proportion of its dry matter to grain yield. Similar observations on the efficiency of dry matter conversion under conditions of luxuriant vegetative growth were made by Fischer (1979), Innes and Blackwell (1981), and Sharma et al. (1987). In the present study, HI for Norwin and E were not related (Table 4), indicating that dry matter conversion was more stable across environments for Norwin compared with Norstar. Superior HI for semidwarf compared with tall wheat cultivars under favorable growing conditions has previously been reported by Syme (1969), Pearman et al. (1978), and Fischer (1979). A significant (P < 0.05) trial by cultivar interaction was observed for WUE. Once again, the basis of this interaction was a diiferential cultivar response to changes in the level of preanthesis stress as indicated by level of E. As expected (de Wit, 1958), increased free water evaporation significantly decreased WUE for both cultivars considered in this study (Table 3). However, as E decreased, WUE increased at a significantly higher rate for Norwin compared to Norstar (Table 4). Greater WUE for Norwin at low stress sites could not be attributed to increased water use (deJong and Cameron, 1980), as ET was similar for both cultivars (Table 3). Greater WUE for Norwin under lower drought stress appeared to be the result of factors such as higher KNO and more efficient dry matter distribution (Table 3). In conclusion, differential yield response of Norstar and Norwin to the range of preanthesis environmental conditions encountered in the present study was reflected in a significant cross-over cultivar by environment interaction. The differential response of these cultivars to drought stress in a semiarid environment was due to differences in their ability to maximize kernel production. Under low stress conditions, higher KNO for Norwin was attributed to a more favorable pre- and postanthesis dry matter distribution compared to Norstar. However, under high preanthesis stress, higher yields for Norstar were attributed to

The technical assistance of Mr. Bruce Hodgins and Mr. Ken Greer is gratefully acknowledged.

HEICHEL & HENJUM: FALL DORMANCY IN ALFALFA

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