SciELO - Scientific Electronic Library Online

 
vol.32 número2La Denominación de Origen Pisco en Chile: algunos problemas nacionales e internacionalesDistribución espacial de la calidad fisiológica de semillas de café Arábica cultivar Catuaí índice de autoresíndice de materiabúsqueda de artículos
Home Pagelista alfabética de revistas  

Servicios Personalizados

Revista

Articulo

Indicadores

Links relacionados

  • En proceso de indezaciónCitado por Google
  • No hay articulos similaresSimilares en SciELO
  • En proceso de indezaciónSimilares en Google

Compartir


Idesia (Arica)

versión On-line ISSN 0718-3429

Idesia vol.32 no.2 Arica mayo 2014

http://dx.doi.org/10.4067/S0718-34292014000200008 

Volumen 32, Nº 2. Páginas 57-63 IDESIA (Chile) Marzo-Mayo, 2014

INVESTIGACIÓN

Response of wheat genotypes to osmotic stress in terms of seed germination and growth of seedling

Efecto del estrés osmótico en la germinación y crecimiento de plántulas en distintos genotipos de trigo

 

Masoud Ezzat-Ahmadi1, Ahad Madani2*, Abdolreza Alimohammadi2

1 Razavi Khorasan Agriculture and Natural Resources Research Center, Mashhad, Iran.
2 Islamic Azad University, Gonabad Branch, Gonabad, Iran. * Corresponding author: amadani@iau.ac.ir


ABSTRACT

To compare the wheat genotypes in terms of seed germination and growth of seedling under osmotic stress conditions, a laboratory experiment was conducted using a completely random design with factorial arrangement. The wheat genotype (G) consisted of eight genotypes numbered as (G1) 9103, (G2) 9116, (G3) 9203, (G4) 9205, (G5) 9207, (G6) 9212, (G7) C-81-10 and (G8) cross-shahi. The osmotic potential factor (Ψs) consisted of five levels (-1.2,-0.9,-0.6,-0.3 and 0 MPa). Genotypes G2, G6 and G7 prevailed in terms of germination percentage (GP) up to Ψs = -1.2, while genotype G8 and genotype G6 were only prevalent at Ψs = 0 and up to Ψs = -0.9, respectively. The two genotypes of G1 and G4 had lower GPs at Ψs = 0 compared to other genotypes but these two genotypes had no significant difference with resistant genotype G7 in terms of GP at Ψs = -0.3. This trend continued in case of genotype G1 up to Ψs = -1.2, while genotype G4 had the lowest GP value next to G8 cultivar from Ψs = -0.6 to Ψs = -1.2. Interaction effect of Ψs x genotype was significant for Coleoptile Length (CL), Radicle Length (RL), Plumule Length (SL). G7 prevailed in terms of CL with a significant difference at Ψs = -1.2 while G1 lost its dominance. The same trend was observed in interaction effect of Ψs x genotype for SL. According to GP and CL and SL values, modern genotype G7 was the most resistant genotype to osmotic stress while old genotype G8 was the most sensitive one.

Key words: wheat, germiantion, seedling growth, osmotic stress.


RESUMEN

El estudio tuvo como objetivo comparar, bajo condiciones de laboratorio, la germinación de semillas y el crecimiento de plántulas bajo condiciones de estrés osmótico de distintos genotipos de trigo. El diseño experimental fue de bloques completamente al azar con arreglo factorial y tres repeticiones. Se evaluaron ocho genotipos de trigo (G): 9103 (G1); 9116 (G2); 9203 (G3); 9205 (G4); 9207 (G5); 9212 (G6); C-81-10 (G7) y, cross-shahi (G8). El potencial osmótico ( Ψs) fue evaluado en cinco niveles (-1,2, -0,9, -0,6, -0,3 y 0 MPa). Los genotipos G2, G6 y G7 obtuvieron un mayor porcentaje de germinación (PG) a -1,2 MPa. Los genotipos G1, G4 y G5 tuvieron el menor porcentaje de germinación con Ψs = 0. El efecto de la interacción de Ψs x genotipo fue estadísticamente significativa para longitud de coleóptilo (CL), longitud de radícula (RL) y longitud de la plúmula (SL), según genotipo. De acuerdo con los análisis de resultados el genotipo G7 fue el más resistente al estrés osmótico y G8 fue el genotipo más sensible.

Palabras clave: trigo; germinación; crecimiento de las plántulas; estrés osmótico.


Introduction

Both seed germination and establishment properties of seedlings are regarded as applied attributes that are used to evaluate the wheat genotypes under osmotic stress (Hubbard et al., 2012; Rauf et al., 2007). The germination percentage and establishment of seedlings considerably decrease when the soil water potential is less than -1.5 MPa (Qayyum et al., 2011). Gonzalez et al., (2005) and Almansouri et al., (2001) reported a reduction in the lengths of radical, plumule and coleoptile as well as a decrease in germination percentage due to the increase in intensity of moisture stress while also suggesting that the germination percentage in resistant reaction of wheat cultivars to drought stress may not be considered an appropriate indicator for selection of resistant cultivars. The initial growth strength in modern short-statured wheat cultivars is less compared to that of the old long-statured wheat cultivars, with the length of coleoptile and leaf surface area having decreased during the initial stages of growth (Pereira et al., 2002). The decrease in length of coleoptile leads to poor germination and the subsequent low establishment of plant, thus making it impossible to cultivate at lower depths in order to utilize the soil moisture storage, the increase in length of coleoptile would result in larger sizes of initial leaves and accelerate the germination rate (Hakizimana et al., 2002;). A highly positive and significant correlation was reported between the germination percentage and the lengths of radical, plumule, coleoptile as well as the dry weights of radical and plumule (El-Moneim et al., 2008). These properties were evaluated during the course of this test in order to compare the seed germination and seedlings growth of seven modern wheat genotypes with those of an old l Cal genotype (cross-shahi) under osmotic stress conditions in order to determine the resistant and sensitive genotypes to osmotic stress in terms of each one of the aforesaid properties and to compare the modern cultivars and old cultivar in terms of seed germination and growth of seedling under osmotic stress conditions.

Materials and Methods

Test Scheme

This study was conducted using a completely random design with factorial arrangement with 3 replications. The wheat genotype (G) consisted of eight genotypes numbered as (G1) 9103, (G2) 9116, (G3) 9203, (G4) 9205, (G5) 9207, (G6) 9212, (G7) C-81-10 and (C8) cross-shahi. The osmotic potential factor (Ψs) consisted of five levels (-1.2, -0.9, -0.6, -0.3 and 0 MPa). The pedigree of genotypes is presented in Table 1.

Table 1. Studies genotypes.

* "Cross-shahi" is an old local genotype with not specified pedigree.

Applying osmotic stress treatments

Osmotic stress treatments were applied through adding polyethylene glycol osmotic solution to petri dishes containing 20 seeds of each genotype placed on two filter papers. Seeds of Genotypes were disinfected by agitating in a solution of sodium hyp Chlorite for 5 minutes, prior to application of osmotic stress treatments (Sapra et al., 1991). Then, the amount of polyethylene glycol required for preparation of -0.3, -0.6, -0.9 and -1.2 MPa osmotic solutions was determined through equation (1) as follows (Michel & Kaufmann, 1973):

Where WP is the osmotic potential of polyethylene glycol in bars, C is polyethylene glycol concentration in terms of g per kg water, and T is the temperature in Celsius. The amounts of polyethylene glycol required to prepare -0.3, -0.6, -0.9 and -1.2 MPa osmotic solutions at 20 degrees Celsius were 143.18, 213.64, 267.97 and 313.88 grams of polyethylene glycol per 1 liter of distilled water, respectively.

The petri dishes containing two layers of filter paper were placed in aut Clave for 4 hours prior to application of osmotic stress treatments.Then, a number of 20 seeds of genotypes that had already been disinfected by 10% sodium hyp Chlorite solution were placed in each petri dish and the osmotic stress treatments were applied through osmotic solutions. Then, the petri dishes were placed in the germinator at temperature of 20 degrees Celsius in darkness.

Measured properties

In order to determine the germination percentage, the germinated seeds were counted on a daily basis. The seeds with radical lengths about 3 mm were considered as germinated seeds (Sapra et al., 1991). The percentage of germination was ultimately derived from the ratio of germinated seeds to the number of seeds (20) in the petri dish. The ultimate lengths of radical and coleoptile and their respective dry weights as well as the dry weight of shoot parts and ratio of shoot parts to the root were measured and calculated after heating them in the oven at 85 degrees for 24 hours.

Mean germination time (M.G.T) was calculated through equation (2) (Sapra et al., 1991).

Where D is the number of days during which the germinated seeds were counted, n is the number of germinated seeds in each day and N is the ultimate number of germinated seeds. Having obtained the M.G.T, the germination rate would be derived from equation 3 (Sapra et al., 1991).

12 hours of light were also all Cated to the incubator environment from day 4 onward so that the coloration of leaves Ccurs, making them distinct from the coleoptile. Using 5 random seedlings from each petri dish and a scale ruler, the length of coleoptile was measured and its mean value was recorded. All the petri dishes were removed from the germinator after 10 days and the lengths of radical and plumule were measured using 10 random seedlings. Both radical and plumule were detached from the seed and placed in separate envelopes and then heated at 76 degree Celsius for 24 hours. When dried, the samples were weighed through a highly sensitive laboratory scale (0.0001g accuracy) and their mean values were calculated and recorded.

Variance analysis was performed through application of SAS software based on the hypotheses of factorial test and Duncan's Multiple Range Test was applied in order to compare the mean values through interaction effects slicing while the EXCEL software was used in order to plot and pr Cess the data. Angular conversion was used in case of values that were calculated in percentage.

Results and Discussion

Germination Percentage (GP) and Germination Rate (GR)

GP and GR showed significant reduction as the osmotic potential (Ψs) was decreased (Table 2). The decrease thresholds of GP and GR were Ψs = -0.3 and Ts = -0.6, respectively (Table 2). There was a significant difference between all Ψs treatments in terms of GP (Table 2).

Table 2. The simple effect of osmotic stress and Genotype on seed germination and growth of seedling in wheat.

P:
Ψs and G: osmotic stress and genotype, respectively. Ψs 5 to Ψs 1: -1.2, -0.9, -0.6, -0.3 and 0 MPa.
Genotypes: (G1) 9103, (G2) 9116, (G3) 9203, (G4) 9205, (G5) 9207, (G6) 9212, (G7) C-81-10 and (G8) cross-shahi.
GR (germination percentage); SG (speed of germination); CL, RL and SL: coleptile, radical and pulmule length, repectively; RDW,
SDW and SLDW: radical, plumule and seedling dry weight, respectively.

The GP decreased from 93.1% at Ψs = 0 to 88.5% and 55.8% at Ψs = -0.3 and Ψs = -1.2, respectively (Table 2). Genotypes were significantly different in terms of GP (Table 2). The GP of genotypes varied from 84.0% for G7 to 71% for G8 (Table 2). There was no significant difference in GP of G1, G2, G6 and G7 genotypes (Table 2).

The GR decreased from 33.3 (percentage of daily germinated seeds) at Ψs = 0 to 20.7 (percentage of daily germinated seeds) at Ψs = -1.2 (Table 2). Interaction effect of Ψs x genotype was significant for GP (Table 2). At Ψs = 0, the genotypes G2, G5, G6, G7 and G8 had higher GPs than the other three genotypes (Table 3). Genotypes G2, G6 and G7 prevailed in terms of GP up to Ψs = -1.2, while genotype G8 and genotype G6 were only prevalent at Ψs = 0 and up to Ψs = -0.9, respectively (Table 3). The decreasing trend of GP due to reduction of Ψs was not identical in case of three genotypes of G2, G6 and G7 in that germination did not decrease as a result of Ψs reduction from -0.3 to -0.6 in G7 which reflects the higher resistance of this genotype (Table 3). The two genotypes of G1 and G4 had lower GPs at Ψs = 0 compared to other genotypes but these two genotypes had no significant difference with resistant genotype G7 in terms of GP at Ψs = -0.3 (Table 3). This trend continued in case of genotype G1 up to Ψs = -1.2, while genotype G4 had the lowest GP value next to G8 cultivar from Ψs = -0.6 to Ψs = -1.2 (Table 3). According to GP values, genotypes G7> G6 = G2 were resistant to osmotic stress while genotypes G1 and G8 were sensitive. The genotypes did not differ significantly in terms of GR (Table 2). Interaction effect of Ψs x genotype was insignificant for GR (Table 2). Thus, the germination rate is not a proper characteristic for comparison of genotype resistance to osmotic stress. The G8 genotype which is a long-statured and old cultivar was anticipated to yield better germination percentage and rate under osmotic stress conditions compared to the other seven short-statured and modern genotypes, but the results proved the opposite. Ghodsi (2004) reported that wheat cultivars under various osmotic potentials differ with each other in terms germination characteristics in that the medium-statured Mexican cultivars have higher percentage and rate of germination and are thus more resistant to drought during germination stage, an assertion that is consistent with the results of this study.

Table 3. The interaction effect of osmotic stress and Genotype on seed germination and growth of seedling in wheat.

Ψs and G: osmotic stress and genotype, respectively.
Ψs5 to Ψs1: -1.2, -0.9, -0.6, -0.3 and 0 MPa.
Genotypes: (G1) 9103, (G2) 9116, (G3) 9203, (G4) 9205, (G5) 9207, (G6) 9212, (G7) C-81-10 and (G8) cross-shahi.
GR (germination percentage); SG (speed of germination); CL, RL and SL: coleptile, radical and pulmule length, repectively; RDW, SDW and SLDW: radical, plumule and seedling dry weight, respectively.

Coleoptile Length (CL), Radicle Length (RL), Plumule Length (SL)

Effect of Ψs on CL, RL and SL was significant (Table 2). Osmotic stress had more effect on SL decrease than that of the CL. Moreover; RL reaction to Ψs stress was different than those of CL and SL. There was a significant difference in CL and SL among all Ψs treatments while there was no significant difference in RL between Ψs = 0 and Ψs = -0.3 (Table 2). Reduction thresholds due to osmotic stress were at Ψs = -0.3 for CL and SL and at Ψs = -0.6 for RL (Table 2). As the osmotic potential decreased from Ψs = 0 to Ψs = -1.2, the CL, RL and SL decreased up to 67.7%, 42.2% and 83.1%, respectively (Table 2). This decrease was respectively 18.2% and 22.5% for CL and RL at Ψs = -0.3 while it was 12.9% for RL at Ψs = -0.6 (Table 2). There was a significant difference between genotypes in terms of SL, CL and RL (Table 2). Genotypes G1 and G7 had the highest CL, SL and RL while genotype G8 had the lowest SL and RL with genotype G3 having the lowest CL (Table 2). Interaction effect of Ψs x genotype was significant for CL, SL and RL (Table 2 and 3). As the osmotic potential reduced, CL decreased up to 47.0% and 49.2% at Ψs = -0.1 in genotypes G7 and G1, respectively (Table 3). With Ψs decreasing from Ψs = -.1 to Ψs = -1.2, the CL respectively reduced to 25.0% and 40.8% for G7 and G1 so that G7 prevailed in terms of CL with a significant difference at Ψs = -1.2 while G1 lost its dominance (table 3).

The CL in genotype G8 was higher than other genotypes up to Ψs = -0.3 but as the Ψs decreased, the CL in this genotype dropped lower than that of the other genotypes to the extent that it attained the lowest CL at Ψs = -1.2 with only G3 genotype having a lower CL at Ψs = 0 (Table 3).

According to CL values, genotypes G7 and G1 were thus resistant to osmotic stress while genotypes G8 and G3 were sensitive. The same trend was observed in interaction effect of Ψs xgenotype for SL. Genotypes G1 and G7 that were prevalent at Ψs = 0 in terms of SL maintained this dominance up to Ψs = -1.2, except for G1 at Ψs = -0.3 (Table 3).

But genotype G8 lost the dominance it once had at Ψs = 0 as it showed the least SL compared to other genotypes from Ψs = -0.6 to Ψs = -1.2 (Table 3). According to SL values, genotypes G7 and G1 were thus resistant to osmotic stress while genotypes G8 was sensitive. Interaction effect Ψs x genotype was significant for RL (Table 2). The value of RL increased in genotypes G2, G6 and G7 as the osmotic potential dropped to Ψs = -0.3 while it contrastingly decreased as the osmotic stress increased (Table 3). Genotype G1 and G7 that were dominant in terms of RL at Ψs = 0 maintained this trend up to Ψs = -1.2, except for G1 at Ψs = -0.3 (Table 3). Genotype G2 also showed no significant difference under osmotic potential from Ψs = -0.3 to Ψs = -1.2 (Table 3). Genotype G8 had the lowest RL among other genotypes from Ψs = -0.3 to Ψs = -1.2 (Table 3). Thus according to RL values, genotypes G2<G1<G7 were resistant to osmotic stress while G8 was sensitive. Although the height of genotype G7 was less than the long-statured G8 cultivar, but it was longer in terms of CL, RL and SL which is consistent with the report of Calderini et al. (1999). Dhanda & Behl (2004) evaluating 30 bread wheat genotypes subject to osmotic stress also reported that the length of coleoptile and plumule decreased subsequent to increase in osmotic stress while the radicle length of cultivars increased up to average levels of osmotic stress. They concluded that the coleoptile and plumule are more sensitive than the radicle under osmotic stress which is consistent with the results obtained in this study. Dhanda & Behl (2004) also suggested that the lesser decrease in length of radicle under stress compared to that of the plumule is a basic mechanism of plant whereby the root system is developed more than the aerial parts in order to attain more soil moisture.

Plumule Dry Weight (SDW), Radicle Dry Weight (RDW) and Seedling Dry Weight (SLDW)

The effect of Ψs and genotype as well as the interaction effect of Ψs x genotype on SDW, RDW and SLDW was significant (Table 2). RDW had a significant increase up to Ψs = -0.3 (7.57 to 7.82 Kg) and then decreased so that it showed a significant increase of 6.4% and 36.1% at Ψs = -0.6 and Ψs = -1.2, respectively (Table 2). An increase of 2.2, 10, 9.7 and 8.7 % in RDW was observed at Ψs = -0.3 for genotypes G1, G3, G4 and G5, respectively (Table 3). SWD and SLDW had declining trends as the Ψs decreases in that SDW was respectively 33.2% and 82.4 % at Ψs = -0.3 and Ψs = -1.2, while SLDW underwent significant decreases of 18.6% and 63.9%, respectively (Table 2). Hence, RDW has shown greater response to osmotic stress than SDW and SLDW. The maximum and minimum SDW, RDW and SLDW were observed in Genotypes G7 and G8, respectively (Table 2). G7 had no significant difference with genotypes G2 and G1 in terms of SDW and with genotype G6 in terms of RDW (Table 2). Genotype G8 also had no significant difference with genotypes G3 and G4 in terms of SDW and SLDW (Table 2). Genotypes G6 and G7 maintained their dominance in terms of SDW and SLDW over the entire Ψs treatments,except for G6 for SLDW at Ψs = -0.6 (Table 3).

Genotypes G1, G2 and G7 maintained their dominance in terms of SDW over the entire Ψs treatments, except for G1 for SLDW at Ψs = -1.2 (Table 3). Genotype G8 had the least RDW among other genotypes from Ψs = -0.6 to Ψs = -1.2 (Table 3). Genotypes G8, G3 and G4 had the least SDW up to Ψs = -0.6 and the least SLDW up to Ψs = -1.2 while genotype G4 and genotypes G5, G4 and G1 had the least SDW at Ψs = -0.9 and Ψs = -1.2, respectively (Table 3).

According to the integrated results of RDW, SDW, and SLDW, genotypes G7, G6 and G1 were the most resistant and genotypes G4, G3 and G8 were the most sensitive to osmotic stress.

Radicle length to plumule length ratio (RL/ SL), Radicle dry weight to plumule dry weight ratio (RDW/SDW) and plumule dry weight to seedling dry weight ratio (SDW/SLDW) are important characteristic representing the compatibility of plant to stress conditions. This characteristic is highly correlated with performance and could be considered a criterion for initial selection of cultivars under moisture stress conditions (Dhanda & Behl, 2004). The effect of Ψs and genotype on RL/SL and effect of Ψs, genotype and interaction effect of Ψs x genotype on RDW/SDW, RDW/SLDW and SDW/SLDW was significant (Table 1). RL/ SL, RDW/SDW and RDW/SLDW respectively increased up to 3.46, 3.69 and 1.75 times from Ψs = 0 to Ψs = -1.2 while SDW/SLDW decreased up to 2.03 times (Table 2). Although the effect of genotype on SDW/SLDW was significant (Table 2), its value remained within the limited range of 0.42 to 0.45 (Table 2). The amounts of RL/SL, RDW/ SDW and RDW/SLDW were higher in case of the resistant G7 while it was lower in case of sensitive G8 (Table 2).

Literature Cited

Almansouri, M.; Kinet, G.M.; Lutts, S. 2001. Effect of salt and osmotic stresses on germination in durum wheat (Triticum durum). Plant and Soil, 231 (2): 243-254.         [ Links ]

Calderini, D.F.; Reynolds, M.P.; Slafer, G.A. 1999. Genetic gains in wheat yield and main physiological changes ass Ciated with them during the 20th century. In: Satorre, E.H., and G.A. Slafer, (eds). Wheat: Ecology and physiology of yield determination. New York. Food Products Press.         [ Links ]

Dhanda, G.S.; Behl, R.K. 2004. Indices of drought tolerance in wheat genotypes at early stages of plant growth. Journal of agronomy and crop science. 190: 1-6.         [ Links ]

El-Moneim, D.A.A.; Mohamed, I.N.; Belal, A.H.; Atta, M.E. 2008. Screening bread wheat genotypes for drought tolerance. 1-Germination, radical growth and mean performance of yield and its components. Annals of Agricultural Science (Cairo). 53 (1): 171-181.         [ Links ]

González, L.M.; Argental, L.; Zaldívar, N.; Ramírez, R. 2005. Effects of simulated drought induced by PEG-6000 on the germination and growth of two wheat varieties. Cultivos Tropicales, 26 (4): 49-52.         [ Links ]

Hakizimana, F.; Haley, S.D.; Turnipseed, E.B. 2000. Repeatability and genotype x environment interaction of coleoptile length measurements in winter wheat. Crop Science, 40: 1233-1237.         [ Links ]

Hubbard, M.; Germida, J.; Vujanovic, V. 2012. Fungal endophytes improve wheat seed germination under heat and drought stress. Botany, 90 (2): 137-149.         [ Links ]

Pereira, M.J.; Pfahler, P.L.; Barnett, R.D.; Blounet, A.R.; Wofford, D.S.; Littell, R.C. 2002. Coleoptile Length of Dwarf Wheat Isolines. Crop science, 42 (5): 1483-1478.         [ Links ]

Qayyum, A.; Razzaq, A.; Ahmad, M.; Jenks, M.A. 2011. Water stress causes differential effects on germination indices, total soluble sugar and proline content in wheat (Triticum aestivum L.) genotypes. African Journal of Biotechnology, 10 (64): 14038-14045.         [ Links ]

Rauf, M.; Munir, M.; Hasan, M.; Ahmad, M.; Afzal, M. 2007. Performance of wheat genotypes under osmotic stress at germination and early seedling growth stage. African Journal of Biotechnology, 6 (8): 971-975.         [ Links ]

Sapra, V.T.; Savage, E.; Anaele, A.O.; Beyle, C.B. 1991. Varietal differences of wheat and triticale to water stress. Journal of Agrononmy and Crop Science, 167: 23-28.         [ Links ]


Fecha de Recepción: 20 Enero, 2014. Fecha de Aceptación: 13 Marzo, 2014.