Crop Science Journal of Natural Resources and Life Sciences Education
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

This Article
Right arrow Abstract Freely available
Right arrow Figures Only
Right arrow Full Text (PDF) Free
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via ISI Web of Science (11)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Merah, O.
Right arrow Articles by Monneveux, P.
Right arrow Search for Related Content
PubMed
Right arrow Articles by Merah, O.
Right arrow Articles by Monneveux, P.
Agricola
Right arrow Articles by Merah, O.
Right arrow Articles by Monneveux, P.
Related Collections
Right arrow Wheat
Crop Science 41:677-681 (2001)
© 2001 Crop Science Society of America

CROP BREEDING, GENETICS & CYTOLOGY

Stability of Carbon Isotope Discrimination and Grain Yield in Durum Wheat

O. Merah*a, E. Deléensb, I. Souyrisc, M. Nachitd and P. Monneveuxc

a UFR de Génétique et Amélioration des Plantes, ENSA-INRA, 2 place Viala, F-34060 Montpellier Cedex, France
b Institut de Biotechnologie des Plantes, UMR 8618, Bat 630, Université de Paris-Sud, Centre d'Orsay, F-91405-Orsay Cedex, France
c UFR de Génétique et Amélioration des Plantes, ENSA-INRA, 2 place Viala, F-34060 Montpellier Cedex, France
d CIMMYT/ICARDA Durum Wheat Program, ICARDA P.O. Box 5466, Aleppo, Syria

* Corresponding author (merah{at}ensam.inra.fr)


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 REFERENCES
 
Carbon isotope discrimination ({Delta}) has been proposed as an indirect selection criterion for transpiration efficiency and grain yield in bread wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.), with potential value for durum wheat (Triticum turgidum convar. durum Desf. MacKey). We evaluated the genetic variation for {Delta}, the relationship between {Delta} and grain yield, and the magnitude of genotype x year (G x Y) interactions in durum wheat. Field experiments were conducted under Mediterranean conditions on 144 durum wheat accessions during three successive years. Grain yield and carbon isotope discrimination of flag leaves ({Delta}F) and kernels ({Delta}K) were measured. Large genotypic and year variation was observed for {Delta}F and {Delta}K. Flag leaf {Delta} was correlated with grain yield in 2 yr characterized as having greater water limitation (r = 0.29 - 0.38, P < 0.001). Conversely, {Delta}K and grain yield were significantly correlated in all 3 yr (r = 0.49 - 0.52, P < 0.001). In addition, G x Y interactions were significant for {Delta}F, {Delta}K and grain yield. However, significant correlations (P < 0.001) were noted for {Delta}K across years. As a result, {Delta}K may serve as a better predictive criterion for higher grain yield under Mediterranean conditions.

Abbreviations: {delta}13C, Carbon isotope composition • {Delta}, carbon isotope discrimination for flag leaf ({Delta}F) and for kernel ({Delta}K) • G x E, genotype x environment interaction • G x Y, genotype x year interaction • Pi/Pa, The ratio of the intercellular and atmospheric partial pressure of CO2 • R/ET, Rainfall/Penman Evapotranspiration • TE, Transpiration efficiency


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 REFERENCES
 
THE MEDITERRANEAN CLIMATE is characterized by low and highly variable annual rainfall (200–800 mm) and typically less than 100 d of rainfall, mostly concentrated during the winter (Baldy, 1986). Water deficit and high temperatures often occur during grain filling (Loss and Siddique, 1994), causing dramatic reductions in crop yield. Hence, improvement of drought tolerance and yield stability is an important aim for breeders in this region (Monneveux and Belhassen, 1996).

During photosynthesis, plants discriminate against the heavy isotope of carbon (13C), which leads to a depletion of 13C in plant dry matter. According to Farquhar et al. (1982), {Delta} in C3 species depends on the ratio of the intercellular and the atmospheric partial pressure of CO2 (Pi/Pa). Carbon isotope discrimination was found by many researchers to be positively correlated with Pi/Pa and negatively associated with transpiration efficiency (TE), the ratio of biomass production to water transpired (Farquhar and Richards, 1984; Hubick and Farquhar, 1989; Ehdaie et al., 1991). This correlation, together with a high broad-sense heritability (Ehdaie et al., 1991; Ehdaie and Waines, 1994), suggests that {Delta} could be used in breeding programs to modify TE of water-limited C3 crops (Farquhar and Richards, 1984; Condon et al., 1987). Moreover, {Delta} has been found frequently to be positively associated with grain yield in bread wheat (Condon et al., 1987; Morgan et al., 1993; Sayre et al., 1995) and barley (Craufurd et al., 1991; Acevedo, 1993). As a result, {Delta} has been proposed as an indirect selection criterion for increased grain yield. The relationship between {Delta} and grain yield, as well as genotype x environment (G x E) interactions for {Delta}, are undocumented in durum wheat under Mediterranean conditions. Mediterranean regions are characterized by the unpredictable timing, duration, frequency, and intensity of drought stress which have a negative impact on gas exchange, growth, and yield (Loss and Siddique, 1994). Moreover, wide variation was noted for yield and several morphophysiological traits in durum wheat grown in these regions (Pecetti et al., 1992; Annicchiarico and Pecetti, 1998), which may be associated with differences in {Delta} within a large collection used in this study, as already reported for barley in these areas (Acevedo, 1993; Voltas et al., 1998).

The objectives of this study were to: (i) describe the levels of genetic variation for {Delta} in flag leaves ({Delta}F) and mature kernels ({Delta}K) of durum wheat, (ii) determine the consistency of genotype ranking for {Delta}F and {Delta}K across environments, and (iii) examine the relationships between {Delta}F or {Delta}K with grain yield, and their stability across years differing in water availability.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS AND DISCUSSION
 REFERENCES
 
Trials were conducted under rainfed conditions in Montpellier, France (4°29' E, 48° 46' N and elev. 45 m) during three successive cropping seasons (1994-1995, 1995-1996, 1996-1997). Sowings occurred on 24, 17, and 8 November, respectively, in the threee cropping seasons. The soil type was Calcixerollic Xerochrept. The experimental design for the three trials was a randomized complete block with two replicates. Each genotype was planted in two 1.5-m rows with 25-cm-row spacing and 3-cm interplant spacing. Anthesis occurred between the last week of April and the beginning of May, and maturity occurred near the end of June.

A total of 144 durum wheat accessions constituting the CIMMYT/ICARDA Durum Wheat Core Collection (DWCC) was used in this study. This collection included 66 landraces originating from 18 countries, 53 improved cultivars, and 25 CIMMYT/ICARDA advanced breeding lines. Among the advanced breeding lines, 18 were obtained from interspecific crosses and seven from intraspecific crosses. The 18 interspecific advanced breeding lines were derived from crosses with T. monococcum L., T. dicoccoïdes Körn., T. carthlicum Nevski., and Aegilops columnaris Zhuk.

For each genotype, 20 flag leaves were randomly detached at anthesis and immediately oven dried for 48 h at 80°C. At maturity, a 10-g grain sample was collected. Dried leaf and kernel samples were ground to a fine powder. Carbon isotope composition was determined with an isotope mass spectrometer (Micromass, Villeurbanne, France), and calculated as {delta}13C ({per thousand}) = [(R sample/R reference-1) x 1000], with R being the 13C/12C ratio. Carbon isotope discrimination ({Delta}) was then calculated by the following formula (Farquhar et al., 1989): {Delta} ({per thousand}) = [({delta}a - {delta}p)/(1 + {delta}p)] x 1000, where {delta}p is the {delta}13C of the leaves or kernels and {delta}a is the {delta}13C of the atmospheric CO2 (-8{per thousand}). At harvest, grain yield (g plant-1) was also determined for each accession.

Analysis of variance was performed on data pooled across years, where years, genotypes, and blocks were considered as random effects. The block effect was not significant (P < 0.05) for any trait and subsequently pooled with the experimental error. Then, for each trait, genotype means were generated for each year and phenotypic correlations were calculated to examine relationships among physiological and agronomic traits within and across years by the CORR procedure of SAS (SAS Institute, 1987).


   RESULTS AND DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
REFERENCES
 
Cumulative rainfall during the cropping cycle (November–June) was 285 mm in 1994-1995, 933 mm in 1995-1996, and 744 mm in 1996-1997 (Table 1). More than 60% of the total rainfall occurred during the first 90 d of the cropping cycle. The first year (1995) was characterized by low total rainfall, with intensive water deficit occurring from February until the end of the growing cycle (Table 1). The second year (1996) was characterized by high total rainfall (Table 1). Decreasing of rainfall and increasing of evapotranspiration were progressive, leading to mild terminal water stress (water deficits of 58 mm in May and 105 mm in June, 1996). The third year (1997) was intermediate for total rainfall. Water deficit began as soon as in 1995. In addition, the water balance was positive in June 1997 because of important rainfall (Table 1). The 3 yr (1995, 1996, and 1997) can be summarized as three environments corresponding to intensive and early water stress, mild terminal water stress, and moderate intermittent water stress, respectively. The ratio of total rainfall to Penman evapotranspiration (R/ET) during the cycle was respectively for the 3 yr 0.26, 1.75, and 0.46. More detailed weather information is reported elsewhere by Merah et al. (1999b).


View this table:
[in this window]
[in a new window]
  		Table 1. Monthly averages for mean daily temperatures (T), Penman evapotranspiration (Penman ET), and rainfall (R) during three cropping seasons at Montpellier.

 
Variation for {Delta} and Grain Yield
Significant differences among genotypes were observed for grain yield, {Delta}F, and {Delta}K (Table 3). The grain yield mean value for all genotypes was about 1.5 to 2 times higher in 1996 and 1997 than in 1995. The greatest difference between extreme genotypes for {Delta}F was observed in 1997 (3.9{per thousand}). For {Delta}K, the greatest genotype difference was found in 1995 (3.4{per thousand}). The smallest ranges of values for {Delta}F and {Delta}K were observed in 1996. Mean values of {Delta}F increased (in absolute terms) more than 2{per thousand} from both 1995 and 1997 to 1996. For {Delta}K, the mean values in 1995 were lower than those noted in 1996 and in 1997 (Table 2).


View this table:
[in this window]
[in a new window]
  		Table 3. Mean squares from the combined analysis of 144 wheat genotypes across 3 yr for {Delta}F, {Delta}K, and grain yield.

 

View this table:
[in this window]
[in a new window]
  		Table 2. Cumulated rainfall during various periods of wheat development, and mean values and standard deviation (SD) for carbon isotope discrimination of flag leaf ({Delta}F) and mature kernels ({Delta}K) and grain yield for three cropping cycles.

 
The G x Y interactions for yield, {Delta}F, and {Delta}K (Table 3) were further characterized by correlation analysis. A positive correlation was observed for {Delta}F between 2 yr (1995 vs. 1997) characterized by a drought period from February to May. For {Delta}K, positive correlations were found among all 3 yr (Table 4). These results are in agreement with those of Matus et al. (1997), who reported greater G x Y interactions for {Delta}F (sampled at anthesis and at maturity) than for {Delta}K for eight bread wheat genotypes. Highly significant G x E interactions for {Delta} measured on the peduncle were found in barley (Craufurd et al., 1991). In contrast, low G x E interactions were noted for {Delta} of the peduncle in bread wheat (Ehdaie et al., 1991; Condon and Richards, 1992) and in crested wheatgrass [Agropyron cristatum (L.) Gaertner] (Read et al., 1991), suggesting that genotypes remained relatively consistent across environments for ranking of {Delta}.


View this table:
[in this window]
[in a new window]
  		Table 4. Correlations among 3 yr for carbon isotope discrimination of the flag leaf ({Delta}F) and mature kernels ({Delta}K) of 144 wheat genotypes.

 
A positive correlation was also found between {Delta}F and {Delta}K within each year (Fig. 1), but the coefficient of correlation decreased from the driest (1995) to the wettest year (1996). Condon et al. (1987) reported that variation in {Delta} results from variation in both stomatal conductance and photosynthetic capacity. Under stressed conditions, {Delta} strongly depends on stomatal limitation (Morgan et al., 1993). In 1996, flag leaf development (March–May) was accompanied with favorable water conditions (Table 1). Under those conditions, {Delta}F variation would be relatively more influenced by differences in photosynthetic capacity than in a dry year where stomatal conductance is the primary determining factor for {Delta}. Genotypes with greater assimilation capacity would have lower {Delta}F (resulting from a lower Pi/Pa). Araus et al. (1997), Matus et al. (1997), and Merah et al. (1999a)(b) attributed differences in {Delta} measured in leaves and kernels to differences in water availability during the formation of these plant parts. In 1996, R/ET from March to June (when flag leaf achieved full development and functioning) was 0.97, decreasing to 0.33 during grain filling (May and June).



View larger version (31K):
[in this window]
[in a new window]
  		Fig. 1. Correlation between carbon isotope discrimination of the flag leaf ({Delta}F) and carbon isotope discrimination of the mature kernel ({Delta}K) for 144 wheat genotypes evaluated at Montpellier during three successive years.

 
Relationship between Grain Yield and {Delta}
Positive correlations were noted between {Delta}F and grain yield in 1995 and 1997 (Fig. 2). For {Delta}K, the correlation with grain yield was positive in all years (Fig. 3). Our results agreed with those reported for bread wheat and barley under both water-stressed and well-watered conditions (Condon et al., 1987; Craufurd et al., 1991; Ehdaie et al., 1991; Acevedo, 1993; Morgan et al., 1993; Sayre et al., 1995). As reported in bread wheat by Condon et al. (1987) and Morgan et al. (1993), the positive association between grain yield and both {Delta}F and {Delta}K suggests that these traits are mainly dependent on stomatal conductance. Higher {Delta} is caused by a higher ratio of intercellular to atmospheric concentrations of CO2 because of a larger stomatal conductance which leads to higher photosynthetic rates and higher yield (Condon et al., 1987; Morgan et al., 1993).



View larger version (30K):
[in this window]
[in a new window]
  		Fig. 2. Correlation between carbon isotope discrimination of the flag leaf ({Delta}F) and grain yield for 144 wheat genotypes evaluated at Montpellier during three successive years.

 


View larger version (32K):
[in this window]
[in a new window]
  		Fig. 3. Correlation between carbon isotope discrimination of the mature kernel ({Delta}K) and grain yield for 144 wheat genotypes evaluated at Montpellier during three successive years.

 
Nevertheless, Craufurd et al. (1991) found a negative correlation between {Delta} and grain yield in barley, under well irrigated conditions. Under those conditions, stomatal limitation is expected to be lower for all genotypes, and differences for stomatal conductance would dissipate. Simultaneously, the genetic variation in internal photosynthetic activity would be more highly expressed leading to a high assimilation per unit area and thus a negative correlation between {Delta} and grain yield. In 1996, water supply was not limited during vegetative stages (Table 1), and stomatal conductance was likely high in all accessions. Thus, variation in {Delta}F would reflect differences in the photosynthetic capacity of different genotypes (Craufurd et al., 1991).

Flag leaves sampled at anthesis represent the photosynthesis functioning during the time that their biomass was produced. In 1996, flag leaf formation (February–April) was accompanied by favorable water conditions, as suggested by R/ET of 2.69 (Table 1). This ratio was clearly lower during grain formation and filling (May–June) reaching a value of 0.33 (Table 1). These conditions probably lead to high stomatal limitation on transpiration during grain filling and thus may have influenced {Delta}K and grain yield. This could also explain the absence of a significant correlation between {Delta}F and grain yield. Araus et al. (1997) and Voltas et al. (1998) suggested that genotypes which sustain greater stomatal conductance and transpiration losses during grain filling could produce greater yield in a wide range of environments with different levels of drought stress.

In conclusion, broad genotypic variation was found in both flag leaf {Delta} and mature kernel {Delta} in the durum wheat core collection within and across environments. The year effect on {Delta}F may result from stomatal response to a decrease in water availability. Genotype x year interactions observed for {Delta}F suggest that knowledge of water availability during the cropping cycle is important for interpretation of {Delta} values. A high correlation was noted between {Delta}F and grain yield in years characterized by severe drought. On the contrary, a positive correlation was found between {Delta}K and grain yield in both stressed and favorable water conditions. Moreover, significant correlations were reported for {Delta}K across years. Consequently, {Delta}K appeared as a better predictive criterion for durum wheat grain yield. Our results confirm the potential value of {Delta} for grain yield improvement in durum wheat, especially under stressed conditions.


   ACKNOWLEDGMENTS
 
O. Merah was supported by a French-Algerian fellowship. Financial support for this study was provided by the French Ministry of Foreign Affairs through the ENSAM-INRA/UPS/ICARDA joint program "Biotechnology and Durum Wheat Breeding."

Received for publication May 18, 1999.


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 REFERENCES
 




This article has been cited by other articles:


Home page
 J Exp BotHome page
A. G. Condon, R. A. Richards, G. J. Rebetzke, and G. D. Farquhar
Breeding for high water-use efficiency
J. Exp. Bot., November 1, 2004; 55(407): 2447 - 2460.
[Abstract] [Full Text] [PDF]

Home page
 Crop Sci.Home page
J. L. Araus, D. Villegas, N. Aparicio, L. F. G. del Moral, S. El Hani, Y. Rharrabti, J. P. Ferrio, and C. Royo
Environmental Factors Determining Carbon Isotope Discrimination and Yield in Durum Wheat under Mediterranean Conditions
Crop Sci., January 1, 2003; 43(1): 170 - 180.
[Abstract] [Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Figures Only
Right arrow Full Text (PDF) Free
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via ISI Web of Science (11)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Merah, O.
Right arrow Articles by Monneveux, P.
Right arrow Search for Related Content
PubMed
Right arrow Articles by Merah, O.
Right arrow Articles by Monneveux, P.
Agricola
Right arrow Articles by Merah, O.
Right arrow Articles by Monneveux, P.
Related Collections
Right arrow Wheat

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
The SCI Journals Agronomy Journal Vadose Zone Journal
Journal of Natural Resources
and Life Sciences Education		 Soil Science Society of America Journal
Journal of Plant Registrations Journal of
Environmental Quality		 The Plant Genome