Plant Breeding 112, 199208 (1994) 1994 Paul Parey Scientific Publishers, Berlin and HamburgISSN 0179-9541

Variation in Rate and Duration of GrowthAmong Spring Barley Cultivars'

J. LEON and G. GEISLER

Institut fiir Pflanzenbau und Pflanzenzuchtung, Christian-Albrechts-Universitat, Olshausenstr. 40,D-24118 Kiel, Germany.

With one figure and 3 tahles

Received April 19, 1993 I Accepted December 3, 1993Communicated hy W. E. Weher

AbstractTen two-rowed spring barley cultivars {Hordeumvulgare L.) were evaluated for growth parameters,i.e. crop growth rate, crop growth duration, grainfilling rate, grain filling duration, vegetative growthrate, vegetative growth duration, single caryopsisfilling rate, single caryopsis filling duration. Fieldstudies were conducted on a sandy loam at Hohen-schulen. Northern Germany with three levels ofnitrogen fertilization and three sowing rates in 1986to 1988. Cultivar effects were observed for allgrowth parameters except for crop growth rate andvegetative growth rate. But only crop growth dura-tion and grain filling duration showed positive corre-lations with grain yield. No growth rate parameterwas related to yield. Biomass was correlated to cropgrowth duration and not to crop growth rate, whileaverage caryopsis weight was strongly related tocaryopsis filling rate and only moderately to caryop-sis filling duration. Comparing grain filling rate andduration to individual caryopsis filling rate and dura-tion, only grain filling rate and duration appeared tobe relevant to grain yield. Since genetic variabilityfor crop growth rate was lacking in the spring barleymaterial tested, further improvement of yield wouldonly result from increase in harvest index and/orlonger crop growth duration.

Key words: Hordeum vulgare grain filling vegetative growth caryopsis growth genotypicvariability

The yield of cereal crops can be separated intocomponents in at least three ways: (1) grainyield as the product of its yield components.

Dedicated to Professor Dr. Dr. F. W. SCHNElLonthe occasion of his 80th birthday.

(2) grain yield as the product of biomass andharvest index, and (3) grain yield as the pro-duct of average grain filling rate (dry matterincrement per unit ground area per unit time)and grain filling duration. FEIL (1992) reviewedthe plant breeding progress in yield compo-nents for small grain cereals and found thatmodern cultivars produce more caryopses perunit area, while for individual grain weights nogeneral tendencies could be observed. Regard-ing grain yield as the product of harvest indexand biomass, it has been shown that yieldimprovement of small grain cereals by meansof plant breeding has been accompanied by anincrease in harvest index with little or nochange in biomass (e.g. AUFHAMMER and FISCH-BECK 1964, AUSTIN et al. 1980, RIGGS et al.1981). AUSTIN et al. (1980) stated that furtherimprovements by increasing harvest index maybe limited by a maximal harvest index. Theyield improvements through an increased har-vest index may be restricted because consider-able amounts of carbohydrates are required tobuild up an efficient plant canopy and a stableculm, and disproportionately heavy ears ofhigh harvest index genotypes may lead to lodg-ing (HELSEL 1985). TAKEDA et al. (1987) studiedharvest index and grain yield of Fs-derivedlines of oat crosses and found an optimal har-vest index for oat at 0.45, which is much lowerthan the maximal harvest index of 0.60 givenby AUSTIN et al. (1980) for wheat. Further-more, ROSIELLE and FREY (1975) showed thatharvest index had little value as a selectioncriterion for grain yield improvement when itwas the only character used for selection. Aus-

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200 and GEISLER

TIN et al. (1980) therefore stated that biomassincrease may contribute to a further yield im-provement. Biomass can be defined as the pro-duct of average crop growth rate and cropgrowth duration. Consequently, the yield ofcereals can also be defined as the product ofcrop growth rate, crop growth duration andharvest index (TAKEDA and FREY 1976), a for-mula which also uses growth parameters, aswith the separation of grain yield into theproduct of grain filling rate and grain fillingduration. These growth parameters may beuseful as a selection criterion as has been dem-onstrated by HELSEI, and SKRDLA (1983) andJOHNSON et al. (1983) for vegetative growthrates in oats.

The object of the present study was to evalu-ate cultivar differences of two-rowed springbarley in growth rate and duration. Vegetativegrowth rate and duration, crop growth rateand duration and grain filling rate and duration(based on unit ground area and on grainweight) were compared as selection criteria.

Materials and MethodsTen two-rowed spring barley {Hordeum vulgare L.)cultivars, 'Apex' (breeder: Cebeco-Handelsraad),'Arena' (Schweiger), 'Aura' (K. & J. Breun), 'Beate'(Saaten-Ring Pfeuffer-von Rlimker), 'Berolina' (H.-V. Heege), 'Dorett' (Schweiger), 'Golf (Nicker-son), 'Harry' (Weibull), 'Klaxon' (Nickerson) and'Lerche' (von Lochow-Petkus), were tested in fieldstudies at three levels of nitrogen fertilization andthree sowing rates in 1986 to 1988. Following fababeans in rotation, levels of N-fertilization were 0 kgN/ha, 50 kg N/ha and 100 kg N/ha in 1986 and 1987and following sugar beets the levels were 30, 80 and130 kg N/ha in 1988. Sowing rates were 200, 350 and500 caryopses per m'^ . The field studies were con-ducted on a sandy loam at Hohenschulen, the ex-perimental station of the Institute of Crop Scienceand Plant Breeding near Kiel, Northern Germany.There were two replicates. Experimental design wasa split-plot design with N-levels as main plots andcultivar-seeding rate combinations as subplots. Plotsizes were 10.0 m^ (2.50 m x 4.00 m) in 1986 and1987 and 10.8 m^ (1.80 m x 6.00 m) in 1988. Tocontrol diseases, fungicides (Corbel, Calixin) weresprayed on to the plants once or twice each year.Further fertilization and treatments (e.g. herbicides)were carried out according to the local standard.

Plant samples were harvested from the three leafstage to physiological maturity on a twice-weekly

basis (usually Monday and Thursday) from predesig-nated sampling sites. Sample sizes were 0.4 m (1986,1987) and 0.6 m (1988) of a row, respectively. Fromflowering to maturity the sample size was halved andreproductive and vegetative dry matter were deter-mined. At maturity, plant samples of 0.6 m^ wereharvested, dried and threshed. Grain yield was com-puted from the dry weight of the threshed caryopses.For each sample, the biomass, and following anthesisthe grain dry matter too, was recorded and con-verted into g m .^ Individual caryopsis dry matterweight was determined, beginning from anthesis upto maturity. Accumulated growing degree days(GDD) were calculated by summing daily degree-days. Daily degree-days were calculated according toCOLVILLE and FREY (1986), but we used a basetemperature of 5 C (LALUKKA et al. 1978, RussEl.l.Eet al. 1984, STRAND 1987).

A "repeated measure analysis of variance" wasapplied to test whether the factor steps showedparallel growth curves and whether the growthcurves of the factor steps showed differences in levelheight (HARTUNG and El.PEIT 1986). Severalmathematical models are capable of describing theobserved growth. Since biomass, grain dry matterand to a lesser extent grain weight decreased afterreaching a maximum, polynomial or the Boguslaws-ki-Schneider equation had to be used (BOGUSLAWSKIand SCHNEIDER 1962, DARROCH and BAKER 1990).In order to compare the results with other investiga-tions the cubic polynomial equation was applied.From the polynomial equation the growth durationand growth rate were calculated. In this study thegrowth was considered to start at emergence (0 %)and anthesis for reproductive growth (0 %), respec-tively, and to be complete on reaching a maximum(100 %) of biomass or grain yield. The interval from10 to 90% of this period (Fig. 1) was used tocalculate the crop growth rate and crop growthduration from the equations of the biomass curve.The grain filling rate and grain filling duration wascalculated from the equations of the grain dry mattercurve and the single caryopsis filling rate, and singlecaryopsis filling duration from the equation of thecaryopsis dry matter weight. In order to calculatevegetative growth rate and vegetative growth dura-tion the estimation of biomass was terminated atflowering and the interval of 10 % of growing(Fig. 1) to flowering was used. These growth ana-lyses were applied to each plot. In the statisticalanalysis the factors cultivars and years were consid-ered as random and the N-fertihzation and sowingrate as fixed. Although cultivars were random, forreaders, who are interested in comparing specialcultivars, results of multiple range test are given inTable 1. Correlations were based on cultivar means.Heritabilities were calculated using variance compo-nents for cultivars, cultivar by years interactions anderror (NYQUIST 1991).

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ResultsBefore calculating growth rate and growth du-ration from estimated growth curves, a "re-peated measure" analysis of variance was usedto evaluate whether the growth curves of cul-tivars were parallel or different in level height.The analyses were conducted for each yearseparately. The Wilks Lambda-Test revealedthat the growth curves of the cultivars were notparallel for biomass, grain dry matter and cary-opsis weight within each year. Furthermore,significant differences in level of biomass, graindry matter and caryopsis weight-curves (ex-cept biomass and grain dry matter in 1988)were shown. With these cultivar effects on thegrowth curves a further examination of thegrowth of cultivars was justified.

In order to estimate growth rate and dura-tion, the growth curves were fitted forbiomass, grain dry matter and caryopsisweight. Several equations can be used to de-scribe crop growth. However, a descriptiveanalysis showed that biomass, grain dry matterand caryopsis weight decreased after havingreached a maximum. The degree of the de-crease differed between years and was highestfor biomass followed from grain dry matterand was only moderate for caryopsis weight.Due to this decrease, the biomass, grain drymatter and caryopsis weight data were fitted to

a cubic polynomial curve, which served tocalculate the growth rate and duration. Coeffi-cients of determination for the plotwise fitwere high for biomass and caryopsis weight(> 0.90) and medium for grain dry matter(> 0.70).

Cultivars were different from each other forthe growth parameters measured except forrate of crop growth and vegetative growth(Table 1). The cultivar 'Harry' can be distin-guished from all other cultivars tested due to acombination of high caryopsis filling rate, veg-etative growth rate and short growth duration(crop growth, grain filling, caryopsis filling).Cluster and principal component analysisshowed that 'Golf, 'Klaxon' and 'Apex' can beclustered into one subgroup, again with rela-tively high growth rates (esp. grain filling,caryopsis filling) and shorter growth duration.'Beate' on the other hand was separated bycluster analysis possibly because of the longgrowth duration (esp. crop growth, grain fil-ling). Cultivars with high growth rate andmedium to short growth duration or withmedium to low growth rate and long growthduration existed but no cultivar with highgrowth rate and long growth duration or lowgrowth rate and short growth duration wasdetected (except perhaps 'Harry' with highvegetative growth rate and medium to longvegetative growth duration).

Variation in Rate and Duration of Growth Among Spring Barley Cultivars 203

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