Plant traits to complement selection based on yield components in wheat

Caracteres da planta para complementar a seleção baseada em componentes de rendimento em trigo

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CROP PRODUCTION

Plant traits to complement selection based on yield components in wheat¹

Caracteres da planta para complementar a seleção baseada em componentes de rendimento em trigo

Lauro Akio Okuyama^I,2; Luiz Carlos Federizzi^II; José Fernandes Barbosa Neto^II

^IInstituto Agronômico do Paraná, IAPAR, CP 481, 86001-970, Londrina, Paraná, Brasil. E-mail: [e-mail]

^IIFaculdade de Agronomia da Universidade Federal do Rio grande do Sul. CP 776, 91501-970, Porto Alegre, Rio Grande do Sul, Brasil

ABSTRACT

The aim of the present study was to investigate the relationship between plant traits and yield per spike in wheat genotypes. The measured plant traits were: length of flag leaf blade, peduncle extrusion, peduncle, spike and sheath, culm diameter and plant height. Data were analyzed with correlation and path coefficient analysis. Yield per spike correlated positively with spike length and culm diameter. Path coefficient analysis indicated that, under irrigated condition, yield per spike had a positive direct effect and a positive correlation with spike length and culm diameter and, under non-irrigated condition, yield per spike showed a positive direct effect and a positive correlation with culm diameter, spike length and plant height. Culm diameter and spike length, under irrigated condition, and also plant height, under late season water stress condition, were the plant traits most related to higher grain yield per spike in wheat.

Key words: correlation, path analysis, water stress, irrigation.

RESUMO

O objetivo do presente trabalho foi investigar as relações entre caracteres da planta e produção de grãos por espiga em genótipos de trigo. Foram avaliados os comprimentos da lâmina da folha bandeira, da parte do pedúnculo extrusado, do pedúnculo, da espiga e da bainha, o diâmetro do colmo e a estatura da planta. Os dados foram analisados por meio de correlações e análises de trilha. A produção de grãos por espiga correlacionou-se positivamente com o comprimento da espiga e o diâmetro do colmo. Análises de trilha indicaram que, sob condição irrigada, a produção de grãos por espiga teve um efeito direto positivo e correlação positiva com o comprimento da espiga e diâmetro do colmo e, sob condição não-irrigada, a produção de grãos por espiga apresentou efeito direto positivo e correlação positiva com o diâmetro do colmo, comprimento da espiga e estatura da planta. O diâmetro do colmo e o comprimento da espiga, sob condição irrigada, e também a estatura da planta, sob condição de deficiência hídrica no final do ciclo, foram os caracteres de planta mais relacionados com a maior produção de grãos por espiga em trigo.

Palavras-chave: correlação, análise de trilha, estresse hídrico, irrigação.

INTRODUCTION

Development of suitable varieties for variable moisture stressed environments has been a difficult task of wheat breeding programs. A major limitation has been the lack of a technique to identify drought tolerance that is repeatable and that can be used in populations where genetic segregation is present. The multitude of factors involved in plant response to water stress makes it difficult to provide a test of drought tolerance (MOUSTAFA et al., 1996).

Drought tolerance in cereals can be improved through: defining drought problem and proposing ideotypes, identifying drought tolerance traits and developing screening techniques, evaluating trait heritabilities and their relationship with yield, screening germplasm for suitable sources of the trait and using appropriate sources of genetic variability in breeding programs (CLARKE, 1987; ORTIZ-FERRARA et al., 1991).

Concerning plant traits, the following considerations should be taken into account: there seems to be no single plant trait conferring stress resistance in the form of avoidance or tolerance but there are responses to a combination of traits; some traits which help improve the performance of a plant under stress conditions are constitutive (always present) while others are adaptive, i.e. they will be expressed only under a given set of environmental stimuli; plant performance is the result of a combination of constitutive and adaptive traits; the response depends on the stress history of the plant since acclimation (short-term responses) may also be present; if adaptive traits are important to plant response under stress, a target environment for the breeder’s selection is needed; there seems to be a tradeoff between yield and stress resistance (ACEVEDO, 1987).

Plant traits contributing to grain yield and plant adaptations under various drought patterns were evaluated by several researchers. In bread wheat under Mediterranean terminal drought stress condition, the traits considered as important for durum wheat grain yield increase were: the displacement from optimal heading date (absolute difference of days from the mean heading date of three control cultivars) and kernels per spike (ANNICCHIARICO & PECETTI, 1998); increased leaf rolling, cooler leaf canopy, longer peduncle, increased plant height and early heading (ORTIZ-FERRARA et al., 1991). Under warm northwestern México condition, above ground biomass at maturity, days from emergence to anthesis and to maturity, number of grains m^-2 and ground cover estimated visually after heading showed associations with wheat grain yield (REYNOLDS et al., 1998). In India, the ear:stem ratio was not as efficient as harvest index in selecting for drought susceptible and tolerant wheat genotypes (RANE et al., 2001).

For each pattern of drought stress, a particular and often different plant trait contributed to specific adaptation to the distinct drought stress conditions (VAN GINKEL et al., 1998). Under continuing moisture stress, where grain yield might be only a fraction of yield potential, traits that improve water-use efficiency deserve priority. In contrast, when moisture supply is adequate and energy capture becomes more important as a yield-limiting factor, traits that alter canopy profile deserve higher priority (RASMUSSON, 1991).

Under water stress condition, most tillers abort or linger to form green, immature, nuisance heads at harvest. Thus, the plant traits of the main tiller may play important role in determining the grain yield. The objective of this study was to evaluate the association of plant traits of the main tiller with grain yield per spike in wheat genotypes grown under irrigated and non-irrigated field conditions.

MATERIAL AND METHODS

Field experiments were conducted at the Experimental Station of the Instituto Agronômico do Paraná (IAPAR), in Londrina (latitude 23°23'S, longitude 50°01'W, altitude 556m). The field design for each sowing date was a split-plot arranged in a randomized complete block with six replications. Water regimes, irrigated and non-irrigated (rainfed), were allocated to the main plots and genotypes to the subplots. Each subplot consisted of six rows with five meters, spaced 17cm apart and seed density of 350 grains m^-2. The genotypes were 10 spring wheat (Triticum aestivum L.), one durum wheat (Triticum durum L.) and one triticale (X Tritosecale Wittimack). The characteristics of these genotypes are as follows: BR 37 has high vigor and spikes without awns, IA 9122 shows a higher capacity to roll leaves during drought periods, IAC 5–Maringá is an old cultivar with high vigor and low yield potential, IAPAR 6-Tapejara was largely sown in North and West of Paraná due to its high yield potential and good adaptation to soils with moderate aluminum, IAPAR 17-Caeté was largely grown in the North of Paraná, IAPAR 28- Igapó is originated from Veery’s that has shown good adaptability and drought tolerance (RAJARAM et al., 1996), IAPAR 29-Cacatú has medium drought tolerance, Nesser is considered drought tolerant under dry conditions of Syria (ORTIZ-FERRARA et al., 1991; RAJARAM et al., 1996), OCEPAR 7-Batuíra is an early cultivar that has apparent lower drought tolerance, OCEPAR-14 has performed well under early-season drought in the northern region of Paraná, DP-885 is a durum wheat that exhibited good yield potential at Cambará Experimental Station (north of Paraná State) and IAPAR.23-Arapoti is a triticale highly adapted and grown in Paraná.

Plant managements, irrigation control and climatological conditions were described in OKUYAMA et al. (2004). In each subplot, a sample of one row with 1m in length was used to randomly selected 10 main tillers for the following determinations: flag leaf length (distance from base to tip of the flag leaf blade), peduncle extrusion length (distance from insertion of flag leaf blade to basal node of spike), peduncle length (distance from upper node to the basal node of spike), spike length (distance from the base to the end of spike), sheath length (difference of peduncle length and peduncle extrusion length) and plant height (distance from the ground to the tip of the spike). Yield per spike was computed as the average grains weight of 10 spikes, with moisture corrected to 13%, and the culm diameter as the average distance of 10 stems aligned tightly together and measured at 10cm above ground level.

Data were submitted to variance and path analysis (CRUZ, 1997). Path analysis was carried out with genotypic correlation considering grain yield per spike as the dependent variable and length of flag leaf, peduncle extrusion, peduncle, spike and sheath, culm diameter and plant height as the causal variables. Tests of significance of water regimes by F test and phenotypic correlation coefficients of yield per spike and plant traits by t-test were obtained through the Statistical Analysis System (SAS, 1990).

RESULTS AND DISCUSSION

In the first sowing of 1994, there were significant differences among irrigated and non-irrigated water regimes only for yield per spike and spike length, while in the second sowing significant differences were found for yield per spike, length of flag leaf, peduncle extrusion, peduncle and sheath, and plant height. In the first sowing of 1995, yield per spike, length of flag leaf, peduncle extrusion, peduncle and spike, culm diameter and plant height revealed significant differences among irrigated and non-irrigated water regimes, while in the second sowing all the traits exhibited non-significant differences (Table 1).

Regardless of sowing date, year and water regime, yield per spike had a positive phenotypic correlation with spike length and culm diameter (Tables 2 and 3). Other positive correlations were observed between flag leaf length and peduncle extrusion length, peduncle extrusion length and peduncle length, spike length and culm diameter, sheath length and plant height, and culm diameter and plant height. The only significant and negative correlation was between flag leaf length and spike length. Regarding the effect of flag leaf on grain yield, contradictory results are reported in the literature. No association was found between flag leaf blade length and grain yield or components of yield in parental, F1 and F2 populations in field spaced plants (HSU & WALTON, 1971; CHOWDHRY et al., 1976; MCNEAL & BERG, 1977). On the other hand, positive correlation was found between flag leaf area and grain yield in wheat plants under greenhouse condition (MONYO & WHITTINGTON, 1973). Flag leaf area by itself is not a very good index of plant performance. The spikes, including awns, leaf sheaths, and remaining leaf area also need to be considered as supplier to grain yield (MCNEAL & BERG, 1977). Under Mediterranean terminal drought stress condition, longer peduncle was found to be an important trait for bread wheat (ORTIZ-FERRARA et al., 1991) and for two rowed barley genotypes (ACEVEDO et al., 1991). In this study, the drought intensity and period of water stress were probably not long enough to obtain large differences in plant growth and development. The correlation studies of the present paper showed that to increase grain yield per spike, the most important traits are culm diameter and spike length. As spike length correlated positively with culm diameter, selection for greater spike length will also increase culm diameter. Larger culm diameter may be selected from taller plants, due to positive correlation among these two traits. However, taller plants under non-limiting water conditions normally have lower grain yield potential caused by higher lodging, lower number of spikes m^-2 and inferior harvest index (ARNAU & MONNEVEUX, 1995).

Path coefficient analysis under irrigated condition revealed that flag leaf length, peduncle extrusion length and sheath length had a high direct positive effect on yield per spike, but due to the negative effect through other plant traits, the total correlation was very low (Table 4). Peduncle length had high negative direct effect and low total correlation with yield per spike. Spike length and culm diameter had high direct effect and moderate positive total correlation with yield per spike. Plant height had a high negative direct effect and moderate positive total correlation with yield per spike. Path coefficient analysis under non-irrigated condition showed that yield per spike had a positive direct effect in one out of four experiments and a moderate positive total correlation with spike length, and a high positive direct effect and a high positive total correlation with culm diameter, and a medium positive direct effect and moderate positive total correlation with plant height. Furthermore, yield per spike had an inconsistent direct effect and low total correlation with length of flag leaf, peduncle extrusion, peduncle and sheath (Table 5).

Under both water regimes, culm diameter and spike length were associated with yield per spike. Culm diameter had higher positive direct effect and higher positive correlation with yield per spike. This result indicated that direct selection of plants with a thicker culm might contribute to increase grain yield per spike. Moreover, a thicker culm might reduce lodging, allow greater water flow in the plant and accumulate a larger amount of assimilates. Wheat grain filling under water stress may be improved by stem reserve mobilization (EHDAIE & WAINES, 1996; BLUM, 1998; FOULKES et al., 2002). This may represent an important adaptation for grain yield, mainly in those areas where dry periods are likely to occur during the grain filling stage. The spike length contributions for higher grain yield per spike were not consistent in all environments, so the indirect effects should be taken into account, mainly culm diameter under non-irrigated condition. Positive association between grain yield per spike and spike length was also found (HSU & WALTON, 1971). Plant height was related to higher yield per spike only under non-irrigated condition. Thus, path analysis provided additional information on component interrelationships that had not been obtained in analysis of correlation coefficients. Taller plants have best performance under water stress conditions (ORTIZ-FERRARA et al., 1991). In the present paper, the correlation studies showed a positive relationship between plant height and culm diameter, hence taller plants may be used to indirectly select for thicker culms, mainly under water stress conditions.

In a previous paper (OKUYAMA et al., 2004) was reported that the number of spikes m^-2 and the number of grains per spike, followed by the above-ground biomass.m^-2 should be taken into account to enhance wheat grain yield. This paper provides evidence that some plant traits may be used to complement selection based on yield components in wheat. Yield per spike may be increased, under irrigated condition, by selecting plants with thicker culm and longer spike and, under non-irrigated late season water stress conditions, by choosing taller plants with thicker culm and longer spikes.

Received 11.08.04

Approved em 05.11.05

• ACEVEDO, E. Assessing crop and plant attributes for cereal improvement in water-limited Mediterranean environments. In: SRIVASTAVA, J.P. et al. (Ed). Drought tolerance in winter cereals Chichester: J. Wiley, 1987. p.303-320.
• ACEVEDO, E. et al. Traits associated with high yield in barley in low-rainfall environments. J Agric Sci, v.116, n.1, p.23-36, 1991.
• ANNICCHIARICO, P.; PECETTI, L. Yield vs. morphophysiological trait-based criteria for selection of durum wheat in a semi-arid Mediterranean region (northern Syria). Field Crop Res, v.59, n.3, p.163-173, 1998.
• ARNAU, G.; MONNEVEUX, P. Physiology and genetics of terminal water stress tolerance in barley. J Genet & Breed, v.49, n.4, p.327-331, 1995.
• BLUM, A. Improving wheat grain filling under stress by stem reserve mobilization. Euphytica, v.100, n.1-3, p.77-83, 1998.
• CHOWDHRY, A.R. et al. Relations between flag leaf, yield of grain and yield components in wheat. Exp Agric, v.12, n.4, p.411-415, 1976.
• CLARKE, J.M. Use of physiological and morphological traits in breeding programmes to improve drought resistance of cereals. In: SRIVASTAVA, J.P. et al. (Ed). Drought tolerance in winter cereals Chichester : J. Wiley, 1987. p.171-189.
• CRUZ, C.D. Programa genes: aplicativo computacional em genética e estatística Viçosa : Universidade Federal de Viçosa, 1997. 442p.
• EHDAIE, B.; WAINES, J.G. Genetic variation for contribution of preanthesis assimilates to grain yield in spring wheat. J Genet & Breed, v.50, n.1, p.47-55, 1996.
• FOULKES, M.J. et al. The ability of wheat cultivars to withstand drought in UK conditions: formation of grain yield. J Agric Sci, v.38, p.153-169, 2002.
• HSU, P.; WALTON, P.D. Relationships between yield and its components and structures above the flag leaf node in spring wheat. Crop Sci, v.11, n.2, p.190-193, 1971.
• MCNEAL, F.H.; BERG, M.A. Flag leaf area in five spring wheat crosses and the relationship to grain yield. Euphytica, v.26, n.3, p.739-744, 1977.
• MONYO, J.H.; WHITTINGTON, W.J. Genotypic differences in flag leaf area and their contribution to grain yield in wheat. Euphytica, v.22, n.3, p.600-606, 1973.
• MOUSTAFA, M.A. et al. Response of four spring wheat cultivars to drought stress. Crop Sci, v.36,n.4, p.982-986, 1996.
• OKUYAMA, L.A. et al. Correlation and path analysis of yield and its components and plant traits in wheat. Ciência Rural, v.34, n.6, p.1701-1708, 2004.
• ORTIZ-FERRARA, G. et al. Identification of agronomic traits associated with yield under stress conditions. In: ACEVEDO, E. et al. (Ed). Physiology breeding of winter cereals for stressed Mediterranean environments Paris: INRA, 1991. p.67-88.
• RAJARAM, S. et al. CIMMYTS approach to breed for drought tolerance. Euphytica, v.92, n.1-2, p.147-153, 1996.
• RANE, J. et al. Evaluation of ear: stem weight ratio as a criterion for selection of drought-tolerant wheat (Triticum aestivum) genotypes. Indian Journal of Agricultural Sciences, v.71, n.8, p.505-509, 2001.
• RASMUSSON, D.C. A plant breeders experience with ideotype breeding. Field Crop Res, v.26, n.2, p.191-200, 1991.
• REYNOLDS, M.P. et al. Evaluating physiological traits to complement empirical selection for wheat in warm environments. Euphytica, v.100, n.1-3, p.85-94, 1998.
• SAS INSTITUTE INC. SAS - Procedures guide, Version 6. 3.ed. Cary : SAS Institute, 1990. 705p.
• VAN GINKEL, M. et al. Plant traits related to yield of wheat in early, late, or continuous drought conditions. Euphytica, v.100, n.1-3, p.109-121, 1998.

1

Extraído de parte da tese de doutorado do primeiro autor.

2

Autor para correspondência.

Publication Dates

• Publication in this collection
  16 Sept 2005
• Date of issue
  Oct 2005

History

• Accepted
  11 May 2005
• Received
  08 Nov 2004