African Journal of
Agricultural Research

  • Abbreviation: Afr. J. Agric. Res.
  • Language: English
  • ISSN: 1991-637X
  • DOI: 10.5897/AJAR
  • Start Year: 2006
  • Published Articles: 6712

Full Length Research Paper

The search for productivity and pre-harvest sprouting tolerance in wheat

Rafael Nornberg
  • Rafael Nornberg
  • Department of Plant Science, Faculty of Agronomy Eliseu Maciel - FAEM, Federal University of Pelotas - UFPel, Zip Code: 96001-970, P. O. Box 354, Pelotas, Rio Grande do Sul, Brazil.
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Henrique de Souza Luche
  • Henrique de Souza Luche
  • Department of Plant Science, Faculty of Agronomy Eliseu Maciel - FAEM, Federal University of Pelotas - UFPel, Zip Code: 96001-970, P. O. Box 354, Pelotas, Rio Grande do Sul, Brazil.
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Eder Licieri Groli
  • Eder Licieri Groli
  • Department of Plant Science, Faculty of Agronomy Eliseu Maciel - FAEM, Federal University of Pelotas - UFPel, Zip Code: 96001-970, P. O. Box 354, Pelotas, Rio Grande do Sul, Brazil.
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Rodrigo Danielowski
  • Rodrigo Danielowski
  • Department of Plant Science, Faculty of Agronomy Eliseu Maciel - FAEM, Federal University of Pelotas - UFPel, Zip Code: 96001-970, P. O. Box 354, Pelotas, Rio Grande do Sul, Brazil.
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Rodrigo Lisboa Santos
  • Rodrigo Lisboa Santos
  • Department of Plant Science, Faculty of Agronomy Eliseu Maciel - FAEM, Federal University of Pelotas - UFPel, Zip Code: 96001-970, P. O. Box 354, Pelotas, Rio Grande do Sul, Brazil.
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Ricardo Garcia Figueiredo
  • Ricardo Garcia Figueiredo
  • Department of Plant Science, Faculty of Agronomy Eliseu Maciel - FAEM, Federal University of Pelotas - UFPel, Zip Code: 96001-970, P. O. Box 354, Pelotas, Rio Grande do Sul, Brazil.
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Jose Antonio Gonzalez da Silva
  • Jose Antonio Gonzalez da Silva
  • Department of Agrarian Studies, Regional University of Northwestern State of Rio Grande do Sul, Comercio Street, Zip Code: 98700-000, P. O. Box 3000, Ijui, Rio Grande do Sul, Brazil.
  • Google Scholar
Moacir Cardoso Elias
  • Moacir Cardoso Elias
  • Department of Agroindustrial Science and Technology, Faculty of Agronomy Eliseu Maciel - FAEM, Federal University of Pelotas - UFPel, Zip Code: 96001-970, P. O. Box 354, Pelotas, Rio Grande do Sul, Brazil.
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Luciano Carlos da Maia
  • Luciano Carlos da Maia
  • Department of Plant Science, Faculty of Agronomy Eliseu Maciel - FAEM, Federal University of Pelotas - UFPel, Zip Code: 96001-970, P. O. Box 354, Pelotas, Rio Grande do Sul, Brazil.
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Antonio Costa de Oliveira
  • Antonio Costa de Oliveira
  • Department of Plant Science, Faculty of Agronomy Eliseu Maciel - FAEM, Federal University of Pelotas - UFPel, Zip Code: 96001-970, P. O. Box 354, Pelotas, Rio Grande do Sul, Brazil.
  • Google Scholar


  •  Received: 12 November 2014
  •  Accepted: 01 April 2015
  •  Published: 02 April 2015

 ABSTRACT

The pre-harvest sprouting (PHS) in wheat Triticum aestivum L. is a phenomenon that reduces productivity, degrades starch and depreciates the quality of flour. The objective was to evaluate the per se performance of traits linked to grain yield and tolerance to pre-harvest sprouting in wheat genotypes from different breeding programs in Brazil. Besides, to use indirect selection based on traits showing beneficial relationships and greater heritability than the target as a selection strategy. The study was conducted in the years 2010 and 2011 using randomized complete block design with three replications. Thirty-three genotypes of different wheat breeding programs in Brazil were evaluated. The BRS 194 and Frontana genotypes are sources of tolerance to pre-harvest sprouting in wheat. The cultivar TBIO Alvorada has PHS tolerance and high grain yield, and cultivar TBIO Ivaí presenting high grain yield. The percentage of sprouted grains has negative direct relationship with the falling number in adverse cultivating environments. The falling number shows greater heritability than the percentage of sprouted grains, indicating greater reliability in selection for PHS tolerance.

 

Key words: Triticum aestivum, pre-harvest sprouting (PHS), sprouted grains, falling number.


 INTRODUCTION

The pre-harvest sprouting (PHS) in wheat is the phenomenon of germination of seeds attached to the plant mother leading to degradation of starch in the conversion into sugar (Kulwal et al., 2012), a condition that makes the flour inadequate to the baking process (Emebiri et al., 2010). The higher tolerance to pre-harvest sprouting is directly linked to the rate of water absorption, level of seed dormancy and the ability to reserve mobilization during germination (Emebiri et al., 2010; Martynov and Dobrotvorskaya, 2012; Zhang et al., 2014a). Among the main assessment methodologies PHS highlights the counting of sprouted grains (Rasul et al., 2012) and the measurement of the enzyme alpha-amylase expressed by the falling number on whole flour (Gooding et al., 2012; Zhang et al., 2014b). It is a challenge to select plants with tolerance to PHS since the trait is quantitatively inherited and strongly affected by environmental conditions (Fofana et al., 2009; Rasul et al., 2012). The analysis of the per se performance in elite genotypes is critical to quantify the variability in grain yield traits (Luche et al., 2013) and tolerance to PHS (Ogbonnaya et al., 2008). The selection gain on these traits via correlation with the path analysis can be also decisive, highlighting the direct and indirect effects of secondary traits on the primary trait (Wright, 1921; Vesohoski et al., 2011). Furthermore, the heritability is an important property to quantify the contribution of genetic and environmental effects on the phenotype and define the selection pressure on the traits of interest (Ogbonnaya et al., 2008; Fofana et al., 2009; Krüger et al., 2011). Estimates of genetic parameters and heritability can be obtained by analysis of variance components in experiments with the same number of replications or plants in the plot (Carvalho et al., 2001; Luche et al., 2013).
 
The understanding of relationships and heritability of grain yield with the characters of PHS tolerance in wheat can trigger new strategies to simultaneously get more adjusted plants to meet farmer and industrial requirements. This condition reports the necessity of understanding the direct and indirect effects between traits and their stability regarding genetic and environmental effects. These effects and their interactions are important modulators of the expressed phenotype. The objective was to evaluate the per se performance of traits linked to grain yield and pre-harvest sprouting tolerance in wheat genotypes from different breeding programs in Brazil. Moreover, in the proposition of selection strategies based on indirect selection over traits of interest evidencing beneficial relationships and greater heritability.


 MATERIALS AND METHODS

Experimental site and plant materials
 
The experiments were conducted in two successive seasons 2010 and 2011, in the field located in the city of Capão do Leão, Rio Grande do Sul, Brazil. The city is situated 31° 52' 00'' latitude south and 52°21' 24'' longitude west; at an altitude of 13.24 m, at an average annual pluviometric precipitation of 1280.2 mm. The soil is classified as Red Yellow Podzolic unit in Mapping Pelotas, which its U.S. equivalent is Typic Hapludalf (USDA, 2010). Thirty-three genotypes of wheat developed by leading Brazilian breeding programs were evaluated: TBIO Tibagi, TBIO Ivaí, TBIO Pioneiro, TBIO Itaipú, TBIO Alvorada, TBIO Sinuelo ‘S’, TBIO Mestre and TBIO Seleto (Biotrigo Genética Ltda); Topazio, Turquesa and Ametista (OR Melhoramento de Sementes Ltda); Quartzo, Mirante, Marfim, Valente and Supera (joint partnership  of  Biotrigo Genética Ltda and OR Melhoramento de Sementes Ltda); BRS Guamirim, BRS 248, BRS 194 and BRS 220 (Empresa Brasileira de Pesquisa e Agropecuária - Embrapa); Fundacep Raízes, Fundacep Horizonte, Fundacep Cristalino, Fundacep Campo Real, Fundacep Bravo, TEC Veloce, TEC Frontale, TEC Vigore, TEC Triunfo, CEP 07-136, CEP 06-167 and CEP 07-31 (Cooperativa Central Gaúcha Ltda - CCGL TEC) and Frontana (Beckmann, 1965). The cultivar Frontana released in 1940 is considered the greatest contribution of the Brazilian breeding for wheat in the world, mainly for resistance to leaf rust, the natural threshing and pre-harvest sprouting (Sousa, 2004).
 
Experiment design and management
 
The experimental design was randomized complete blocks with three replications and the sowing was performed at three different times in ten day intervals. Therefore, it enabled the harvesting of spikes at physiological maturity in the same period, even from genotypes with differences in cycle length. At harvest, only plants where the spikes had lost their green color, except the nodes of the culms, were selected. The seeding was performed in the conventional system with a density of 300 viable seeds per square meter, the experimental unit consisted of five rows of 5 m length and spaced by 0.20 m. Two applications of fungicide Folicur (tebuconazole) were performed in both years of cultivation. The fertilization and liming were carried out based on technical recommendations for the crop in the states of RS and SC (CBQFS, 2004). The control of weeds and pest plants were performed according to the recommendations of the Brazilian Commission for Research in Wheat and Triticale (RCBPTT, 2010).
 
Laboratory analysis
 
In the years 2010 and 2011 the spikes were harvested and dried at room temperature for seven days in a protected place. Subsequently, they were placed in plastic bags and stored in a freezer at -20°C. In the analysis for characterization of pre-harvest sprouting tolerance the sprouted grain (SG, in %) and falling number (FN in seconds) were evaluated. In the analysis of the SG a randomized complete block design with three replications was used, with each replicate consisting of ten spikes. The spikes were placed immersed in distilled water for eight hours and then removed and placed on paper towel to remove water excess. In the spikes the fungicide (Vitavax®) vitavax-thiram [Active Ingredient (carboxin + thiram): 200 + 200 g L-1] was applied, as recommended by the manufacturer. The spikes were rolled in the vertical position in sheets of germination paper previously soaked in distilled water. By forming rollers with spikes, these were placed in plastic bags so that no moisture loss occurred. They were then placed to incubate for seven days at 20 ± 1°C in a growth chamber Biological Oxygen Demand (BOD). After that, the rolls with the spikes were removed from the growth chamber, and dried in a drying chamber at 50°C for 72 h. With the end of drying, threshing and the evaluation of the number of sprouted grains and total number of grains were performed.
 
In evaluating the FN, the sample of spikes was threshed and later the grains were conditioned to 15% moisture and, after 24 h, ground on Chopin mill trial (model CD1, França). After grinding of grain, 7 g were taken for the evaluation. The FN is the assessment that measures the activity of the enzyme alpha-amylase, and expresses the intensity of sprouted grains in wheat before the radicle emerges, or makes the rupture of the pericarp. The FN was determined by the falling number apparatus according to the method number 56-81B AACC (1995). The value expressed in seconds measures indirectly the enzyme activity, meaning that the shorter   the  fall  time,  the  greater  content and enzyme activity. In 2010, the assessments were performed in the FN handset Falling Number Perten Instruments (model Fungal 1200, France). In 2011 the assessments were performed in the FN automatic apparatus Falling Number Perten Instruments (model Fungal 1500, France). In the analysis of traits related to grain yield, the traits measured were: grain yield (GY, in kg ha-1); test weight (TW, in kg hl-1) and thousand grain weight (TGW, in grams). The GY, TW and TGW evaluations were performed in the laboratory after harvesting three central rows of each plot on the experimental field.
 
Data analysis
 
The data obtained were subjected to analysis of variance to estimate the components of variance in the determination of heritability according to Carvalho et al. (2001). On differentiation between genotype groups it was used the averaged plus or minus one and two standard deviations in the different traits. Analysis of Pearson correlation for the magnitude and direction of associations between traits was performed according to Falconer and Mackay (1996). The significance of correlations was assessed at p≤0.01 and was adopted, the t test described by Steel and Torrie (1980), with n ? 2 degrees of freedom, according to the model t = r/[(1 ? r2)/(n ? 2)]0,5, where r is the correlation coefficient between X and Y traits, and the number of degrees of freedom in the levels of treatments considered, A total of n = 198 units of observation were obtained: two years, thirty-three genotypes with three replications. The correlations were outspread in direct and indirect effects of secondary traits on the main traits (SG and FN), the proposal described by Wright (1921). Analyses were performed with the aid of the computer software Genes (Cruz, 2006). 


 RESULTS AND DISCUSSION

Performance of individual genotypes
 
On Table 1, the SG and FN traits showed phenotypic classes of one and two standard deviations plus or minus the average of genotype standards. In 2010, the genotypes TEC Triunfo, CEP 06-137 and CEP 07-31; in 2011, FUNDACEP Bravo, FUNDACEP Raízes, TBIO Alvorada and TBIO Itaipú along with BRS 194 by joint analysis showed the lowest SG. Higher values of SG ??indicate seeds with lower accumulated dormancy, featuring advanced level of germination process (Gelin et al., 2007; Rasul et al., 2012). The analysis of sprouted grains in the spike was shown as an efficient trait in detecting genetic variability for tolerance to PHS (Franco et al., 2009; Rasul et al., 2012). It is noteworthy that the variability may be due to differences in the absorption of water by the grain or by differences in tolerance to germination (Chen et al., 2014). Another factor is the amount of genes of tegument color in wheat, grains of white color are more sensitive to PHS compared to red, and however, the mechanisms of action of the genes of the seed coat color have not been clearly described (Bi et al., 2014). On Table 1, the best FN values were obtained for the genotypes TBIO Mestre and BRS Guamirim (2010) and TBIO Pioneiro, FUNDACEP Cristalino and TEC Veloce (2011). Also, cultivar Frontana showed superior values   in   the   two  years  of  evaluation.   Pre-harvest sprouting and late maturity of alpha-amylase are highlighted as key factors related to the falling number in wheat. The variability of FN may be due to genetic, environmental and genotype x environment interaction effects, that is, genotypes, genotype origin and the growing environment (Rasul et al., 2012; Zhang et al., 2014b). The balance between the hormones abscisic acid (ABA) and gibberellic acid (GA) which act on the alpha-amylase present in the aleurone layer is crucial. GA stimulates and ABA inhibits formation of alpha-amylase in dormant grains of wheat. A genetic variability for the expression of PHS was reported, identifying a strong relationship with the dormancy and balancing of hormones linked to germination (Lohwasser et al., 2013).
 
BRS 194 and Frontana genotypes were the most stable and PHS tolerant in per se analysis. It is emphasized that concerning the traits linked to the expression of PHS, the genotypes that showed lower SG were not those that showed higher values ??of FN, leading to an inconsistency between the indicator traits. Thus, analyzing the behavior of the cultivar Frontana, an internationally recognized standard for PHS tolerance (Sousa, 2004), a good fitting was observed in the FN values. Since the PHS tolerance is a quantitative trait, difficult to assess, however, the FN was shown to be the most reliable measure for PHS tolerance in wheat (Lohwasser et al., 2013; Zhang et al., 2014b). On Table 1, superior genotypes for GY were TBIO Sinuelo ‘S’, TBIO Seleto and FUNDACEP Cristalino (2010); TBIO Alvorada and Topazio (2011) and TBIO Ivaí (2010 and 2011). It is evident that the cultivars released in the Brazilian market have ceiling of grain productivity higher than the achieved in the field conditions, generally linked to absence of investment or limiting environmental conditions (Bredemeier et al., 2013; Valério et al., 2013). As reported previously, the expression of PHS is considered one of the most important factors limiting grain yield in wheat. Thus, among the PHS tolerance genotypes, TBIO Alvorada also showed higher GY, a possible source of genes for increased PHS tolerance with grain yield. Cultivar Frontana, a standard genotype for PHS tolerance was one of those that indicated reduced expression in grain yield. Although, it is important as a source of genes for PHS tolerance, Frontana does not show accumulation of favorable alleles for GY as the current cultivars, indicating the need of transferring PHS tolerance by a backcrossing strategy.
 
On Table 1, TBIO Sinuelo ‘S’ (2010) and CEP 06-167 and CEP 07-31 (2010 and 2011) stood out as PHS tolerant and showed significant values ??of TW. The cultivar BRS 194 (2010); and TBIO Tibagi, TBIO Sinuelo ‘S’, TBIO Seleto, Mirante and Marfim (2011) and Valente and Frontana in the two years of cultivation showed high TGW. It is emphasized that the TW is used in the classification and marketing of wheat in Brazil (Schmidt et al., 2009). Moreover, the TGW is important trait in wheat, showing the yield components (grain number and grain weight), closely related to the effectiveness of per se performance of  the  genotypes  (Valério et al., 2013).  In wheat, strong interaction between genotype and environment on the phenotypic expression of GY, TW and TGW have been detected. It is necessary a continuous evaluation of performance per se in the identification of possible sources of alleles for these traits (Schmidt et al., 2009; Luche et al., 2013). Climatic variables of maximum temperature and pluviometric precipitation (Figure 1) affected the growth and development of wheat, directly influencing the productivity and quality of grain traits. In wheat the temperature rise to a limited extent in the grain filling period may increase the GY, TGW and FN, but reducing the TW. Intense pluviometric precipitation has the most drastic impact on this species, reducing the values ??of GY, TGW, TW, and FN (Guarienti et al., 2005). 
 
 
 
Correlation between grain yield and PHS traits
 
In  order  to better  understand  the relationships between traits related to grain yield and PHS tolerance, a correlation analysis was performed (Table 2). In 2010, positive phenotypic correlation was obtained for FN with TGW and SG, but with a negative association with TW. In 2011, FN showed negative association with SG and TW, indicating an inconsistency in the direct relationship between SG and FN. In the joint correlation analysis, an association of SG and FN was not observed (Table 2). The SG showed positive association with the GY, TW and TGW, while the FN showed a negative association with TGW. Also, positive correlations between GY, TW and TGW were found. TW has shown a positive association with FN, since they are important traits in the classification of wheat at the time  of  marketing  (Schmidt et al., 2009). Moreover, it indicates efficiency for indirect selection to the increment of the grain yield. Negative correlations between TW and FN are possibly due to crop conditions, since for determining the TW the grains were obtained in the harvest maturation, the spikes staying more time exposed to high pluviometric precipitation and maximum temperatures (Figure 1). On the other hand, following standard methodology, spike sampling for determining FN was performed at physiological maturity, avoiding the most adverse environmental conditions at the end of the cycle. Also, the phenotypic correlation simultaneously includes parts attributed to genetic and environmental effects and the inclusion of sources of variation can  provide  more  effective correlations among the traits (Krüger et al., 2011). 
 
 
Path analysis between grain yield and PHS traits
 
In the partition of the correlations into direct and indirect effects by path analysis positive effects of FN and TGW on the percentage of SG were observed in 2010 (Table 3). Also, a positive direct effect of SG on FN was observed with reduced indirect effects of other traits. Therefore, the FN and SG show a negative relation of cause and effect, corroborating results from other experiments (Rasul et al., 2012).
 
The TGW and the GY in 2010 and the TGW and TW in 2011 showed positive direct effects on the SG, suggesting a direct effect of those three variables on the analysis and, therefore, a close relationship with SG. The TW showed negative direct effect on the FN (Table 3). In 2010, there was a negative direct and indirect effect via SG on FN. In 2011, there were negative direct effects of minor relevance with indirect effects on SG and TGW via TW and FN. In the joint analysis, the main contribution was the negative direct effect of TW on the FN. Therefore, it is perceived a negative association between TW and FN, contradicting other reports that showed this close positive relationship (Schmidt et al., 2009). 
 
 
Heritability of traits
 
In the analysis of heritability, the SG and FN showed high individual heritability (Table 4). On the other hand, the heritability was reduced in the joint analysis. Because of that, one can observe that in 2011 high pluviometric precipitation occurred during the grain filling stage (Figure 1), and the method of FN proved to be adjusted in identifying genotypes more tolerant to adverse environmental conditions. Thus, it is a challenge to, identify wheat genotypes with stable expression of traits related the PHS in different growing conditions, given it is a quantitatively inherited trait (Fofana et al., 2009; Rasul et al., 2012). In the joint analysis, FN showed higher heritability than SG, indicating greater reliability in assessing PHS tolerance in wheat. However, some studies showed that the heritability for SG was considered high (Ogbonnaya et al., 2008). Studies via FN indicated high heritability in five environments evaluated, indicating a more stable and consistent trait in detection for PHS tolerance wheat (Zhang et al., 2014b). Therefore, the method of SG showed high heritability in individual, environments and reduced genetic effects on joint analysis, while the FN showed greater stability, and it can be the most suitable method for the detection of the PHS tolerant genotypes in genetic improvement of wheat.
 
In 2010, the heritability of GY and TW proved intermediate (Table 4). The heritability for the GY was greater than TW in 2010, while in 2011, TW was superior. It is emphasized that all the traits showed lower heritability in the combined analysis, however, heritability become more stable and reliable when estimated in more environments (Ogbonnaya et al., 2008). The expression of the GY is complex and influenced by many genes, where the genetic variance is similar to environmental variance (Hussain et al., 2013). The heritability of GY tends to be reduced when in adverse environmental conditions (Luche et al., 2013). Moreover, heritability achieves higher values ??in test weight and thousand grains weight (Barnard et al., 2002). Higher heritability values ??are indicative of a strong contribution of genetic variation on environmental expression of the phenotype and bring more effective gains on selection. 
 


 CONCLUSIONS

BRS 194 and Frontana genotypes are a source of tolerance to pre-harvest sprouting in wheat. Cultivar TBIO Alvorada has PHS tolerance and high grain yield. Cultivar TBIO Ivaí has high grain yield. The percentage of sprouted grains has negative direct association with the falling number in adverse environments of cultivation. The falling number shows greater heritability than the percentage of sprouted grains, indicating greater reliability in selection for PHS tolerance.


 CONFLICT OF INTEREST

The authors have not declared any conflict of interest.


 ACKNOWLEDGMENTS

The authors wish to acknowledge the CNPq, CAPES, FAPERGS, UFPel and UNIJUÍ by providing financial resources, structural, scholarship and research productivity fellowships.



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