Drought is the most confining factor in agricultural productions in waterless and semi-arid parts. This research was conducted to analyze 19 facultative and winter wheat genotypes under normal irrigation ( N ) , blossoming ( S1 ) and post-anthesis ( S2 ) drought conditions utilizing randomised complete block design with three reproductions at Karadj, Arak and Jolgehrokh Agricultural Research Stations in Iran in 2008-11 cropping seasons. Based on consequences, drought emphasis reduced meats figure per spike, spike weight, thousand meats weight, grain weight per spike, crop index, entire biomass weight and grain output. However, remobilization, efficiency of remobilization and pre-anthesis photoassimilate part to grain ( PAPCG ) were increased under drouth emphasis status. Effect of environment, irrigation and genotype on most of the traits including grain output, was important. Correlation coefficients between grain output and remobilization, efficiency of remobilization and PAPCG were significantly positive under N, S1 and S2 conditions. Based on MP, GMP, STI, SSI and TOL, genotype 6 was determined as the most tolerant genotype. Among the genotypes, genotype 6 had the highest value for remobilization, efficiency of remobilization and PAPCG under drouth emphasis status, hence selected as the most stable and tolerant line under mild and terrible drouth emphasis.
Cardinal words: Bread wheat, Grain output, Drought emphasis,
Drought emphasis as an of import environmental phenomenon adversely affects public presentation and output of cereals ( Rang et al. , 2011 ) . In Iran, drought emphasis in irrigated wheat Fieldss due to no equal entree to underground H2O resources ( Mohammadi and Karimpour Reihan, 2008 ) occurs chiefly during terminal growing phases of wheat ( Jalal Kamali et al. , 2009 ) which intensify harvest failure and economic loss to husbandmans. Harmonizing to the Emberger definition, Iran with one-year mean precipitation of 240 millimeter is located in the semi-arid and waterless countries of the universe ( Kardavani, 1988 ) . In fact significant parts of 2.4 million hour angle of irrigated wheat in Iran suffer from the deficit of irrigation H2O particularly in post-anthesis or through grain filling period ( Jalal Kamali et al. , 2009 ) . Drought emphasis happening in vegetive phases of harvest development decreases works tallness, leaf country, figure of tillers and biomass ( Nouri et al. , 2011 ) , while generative phases of harvest development in cereal harvests, including wheat ( Triticum aestivum L. ) , are more sensitive to drought emphasis than vegetive phases ( Shpiler and Blum, 1986 ) . Abiotic emphasiss such as drouth at anytime of harvest development, lessening foliage chlorophyll and photosynthesis, and hasten aging ( Dulai et al. , 2006 ) . Wheat harvest failure in impermanent drought conditions may be compensated subsequently by some output constituents depending chiefly on genotype. So, the best option to achieve stable production under drought emphasis status would be to develop drought tolerant genotypes through physiological attacks which need a deeper apprehension of the output finding traits and procedures. But, the battalion of traits involved in wheat response to drought emphasis makes it hard to supply a complete trial of drought tolerance. Hence, the drouth tolerance in wheat can be improved through specifying drouth job of the mark country, placing drought tolerance traits and developing choice standards to suggest ideotypes.
Drought emphasis at blossoming lessenings seed set in wheat by bring oning pollen asepsis ( Ji et al. , 2010 ) . Drought emphasis frequently occurs during the grain filling period of a wheat harvest development phase doing terrible output loss in most of the wheat turning countries of the universe ( Altenbach et al. , 2003 ) . The grain filling period is besides extremely sensitive to drought emphasis ( Yang et. al. , 2001 ) . Drought at the grain filling period besides decreases single grain weight but the lessening is frequently due to diminish in grain filling continuance instead than diminish in grain filling rate ( Wardlaw and Willenbrink, 2000 ) .
Drought tolerance or susceptibleness indices as steps or maps of output decrease through comparing of genotypes in drouth and normal conditions have been used to test drought tolerant or susceptible genotypes ( Mitra, 2001 ; Fernandez, 1992 ; Blum, 1996 ) . Hall ( 1993 ) defined drought tolerance as the comparative output of genotypes exposed to similar drouth emphasis. Under drought emphasis status, current photosynthesis diminutions during grain filling period of wheat and accordingly demands of remobilization additions ( Blum,1998 ) .
Rosielle and Hamblin ( 1981 ) presented stress tolerance ( TOL ) as the differences in output between the emphasis ( YS ) and auxiliary irrigation ( YP ) environments, and average productiveness ( MP ) as the mean output of YS and YP. Fischer and Maurer ( 1978 ) suggested stress susceptibleness index ( SSI ) for wheat cultivars. Fernandez ( 1992 ) defined a new advanced index of emphasis tolerance index ( STI ) to place high giving genotypes under both emphasis and auxiliary irrigation conditions. Geometric average productiveness ( GMP ) and average productiveness ( MP ) are two other output based steps of drouth tolerance. Breeders which frequently use GMP, are interested in comparative public presentation of a genotype due to the fluctuation in drought emphasis badness in field environment over old ages ( Ramirez and Kelly, 1998 ) . Clarke et Al. ( 1992 ) used SSI to measure wheat genotypes for drought tolerance and found year-to-year fluctuation in SSI for genotypes and their superior form.
The aim of this survey was to measure consequence of drouth emphasis on grain output and some morpho-physiological traits and choose the superior genotypes.
Materials and Methods
To measure post-anthesis drouth emphasiss tolerance in wheat genotypes, this research was conducted at Karadj, Arak and Jolgehrokh agricultural research Stationss in Iran in 2008-11 cropping seasons. The experimental design was split-plot based on RCB with three reproductions in which irrigation interventions [ normal irrigation ( N ) , irrigation was cut-off during post-anthesis ( S1 ) and irrigation was cut off 20 yearss after blossoming ( S2 ) ] were as main-plots and 19 winter and facultative wheat genotypes as sub-plots. The lineages of the wheat genotypes are given in Table 1. The secret plan size for each genotype was 7m2 ( 1.2 m x 6 m ) which sown by an experimental seed plantation owner ( WintersteigerTM ) utilizing 450 seeds m-2 with the concluding crop country of 6m2 ( 1.2 m x 5 m ) by an experimental secret plan combine reaper ( WintersteigerTM ) . The experimental field was under two old ages cereal-fallow rotary motion and the dirt readyings included stubble mulch autumn cultivated land and following spring cultivated land with mouldboard plough, harrowing, two times perpendicular land grading, fertiliser spreading and doing beds as furrows. Application of fertilisers were harmonizing to the dirt trial recommendations with the NPK expression of 120-90-50 kg ha-1 using urea ( every bit base and top-dressed ) , potassium sulphate and di-ammonium phosphate beginnings. The irrigation interventions in three old ages of experiments were the same for all the chief secret plans as one clip irrigation in autumn after seting but different in spring times i.e. 6, 2 and 4 irrigations for N, S1 and S2 interventions, severally. All the necessary field directions and informations aggregations were done throughout the turning seasons. To measure and analyze the morpho-physiological traits in genotypes, in three growing phases i.e. at blossoming, 20 yearss after blossoming and physiological adulthood, works samples were indiscriminately taken from the secret plans including 20 complete roots ( dwelling foliages and the spike ) . The samples were dried in a forced air oven for 72 hours at 70 & A ; Acirc ; & A ; deg ; C and so the traits such as entire dry affair weight, spike weight, peduncle unit length weight, kernel figure per spike, 1000s kernel weight, kernel weight per spike and harvest index were measured. The traits of remobilization from root to the grains and efficiency of remobilization were estimated as follows:
( Ehdaie, 1998 ; Kobata et al. , 1992 ) ( 1 )
SaGR: Root assimilate to grain remobilization.
SdWA: Stem dry weight in post-anthesis.
SdWM: Stem dry weight in adulthood.
( 2 )
( Palta et al. , 1994 )
SGRE: Root to grain reserve remobilization efficiency
CGR: Culm to grain remobilization.
SWA: Stem dry weight in post-anthesis
( 3 )
( Niu et al. , 1998 )
Pre-anthesis photoassimilate part to grain = ( PAPCG )
CGR: Culm to grain remobilization
GWM: Grain weight at adulthood.
After informations aggregation, the combined ANOVA for three conditions ( N, S1 and S2 ) was carried out to find chief effects of irrigation, genotype and their interaction on the studied traits. To measure drought tolerance of the genotypes, the indices of tolerance ( TOL ) , average productiveness ( MP ) ( Rossielle and Hamblin, 1981 ) , stress susceptibleness index ( SSI ) ( Fisher and Maurer, 1978 ) , stress tolerance index ( STI ) and geometric mean productiveness ( GMP ) ( Fernandez, 1992 ) were used. The correlativity coefficients between the traits in normal ( N ) and drought emphasis conditions ( S1 and S2 ) were besides calculated.
Table 1. Name or lineage of genotypes.
Consequences and Discussion
Consequences of combined ANOVA showed that chief effects of environment, genotype and irrigation were important on grain output and most of the traits ( Table 2 ) . However among the interactions, merely interaction consequence of genotype x environment was found important on grain output. The mean grain output of 19 genotypes under normal irrigation ( N ) , and blossoming ( S1 ) and post-anthesis ( S2 ) drought stress conditions were 5936, 4139 and 5162 kilogram ha-1, severally ( Table? ) . As the consequences show, genotypes significantly produced less grain output under blossoming ( S1 ) drought emphasis than post-anthesis ( S2 ) drought emphasis and normal irrigation ( N ) conditions. These findings are non in understanding with the consequences of Calhoun et Al. ( 1994 ) and van Ginkel et Al. ( 1998 ) who reported a higher grain output under early drouth than late drought emphasis conditions. The ground for lower grain output under blossoming instead than post-anthesis drouth emphasis conditions was chiefly due to a decrease in 1000 meat weight which determined after blossoming and grain figure per spike which determined before and after blossoming. Thousand kernel weight under N, S1 and S2 drought stress conditions was 37.8, 29.8 and 34.5 ; and figure of grain per spike was 40.8, 37.7 and 38.9, severally. These consequences were consistent with consequences of Inness et Al. ( 1981 ) and Plaut et Al. ( 2004 ) . Plaut et Al. ( 2004 ) besides reported that 1000 meats weight was more badly decreased by H2O shortage than by heat emphasis in wheat assortments, i.e. the rate of dry affair accretion by meats was well decreased by H2O shortage. Genotype no. 6 significantly had the highest grain output in both stress conditions with 4737 and 5713 kilogram ha-1, severally. However, genotype no. 15 produced the highest grain output ( 6265 kg ha-1 ) in normal irrigation status.
The drouth emphasis strengths were 0.30 and 0.13 under blossoming ( S1 ) and post-anthesis ( S2 ) drought stress conditions, severally, i.e. applied drought emphasis at blossoming was more terrible than in post-anthesis. Mean of all the traits were reduced in stressed conditions ( S1 and S2 ) compared to normal irrigation. Furthermore, the decrease was higher in S1 than S2 for all traits except for PWA and PWM which the agencies remained the same in both stressed conditions and for BWA which the mean value was somewhat and non-significantly higher in S1 than S2.
Pre-anthesis photoassimilate part to grain ( PAPCG ) in N, S1 and S2 was estimated 14.3, 25 and 19.1 % , severally which indicated higher remobilization in terrible emphasis status ( S1 ) . In all three conditions, genotype no. 6 had the highest PAPCG.
Consequences of susceptibleness and tolerance indices at blossoming ( S1 ) and post-anthesis ( S2 ) drought stress conditions are presented in tabular array. Genotype 6 was the highest giving up at S1 and S2 conditions with 4737 and 5713 Kg ha-1, severally. This genotype had the best and absolute value of rank for all indices at S1 and S2 conditions, so that its average rank ( ) and standard divergence of rank ( SDR ) for MP, GMP, STI, SSI and TOL at both stress conditions ( S1 and S2 ) were 1 and 0, severally. Drought emphasis conditions resulted higher SaGR, SGRE and PAPCG than normal status ( Table ) in which S1 ( terrible emphasis ) had higher value than S2 ( mild emphasis ) . Among genotypes, the highest value of SaGR, SGRE and PAPCG in N, S1 and S2 conditions were belonged to genotype 6, so that 42.2, 30.1 and 21 % of its grain output resulted from SaGR, SGRE and PAPCG, severally ( Table ) . However, Shahryar assortment ( no.1 ) was the lowest giving up and weakest in all susceptibleness and tolerance indices at both S1 and S2 conditions ( Table ) .
The mean grain output and some morpho-physiological traits of wheat genotypes under three conditions of blossoming, post-anthesis drouth and normal ( table ) , genotype no.6 with grain output of 5517 kg per hectare showed highest public presentation and explained by its highest tonss in crop index ( 46.3 % ) , remobilization ( 0.38 g ) , remobilization efficiency ( 19.65 % ) and PAPCG ( 31.14 % ) . There was a important difference among genotypes in grain output ( Table ) . Drought emphasis reduced grain output so that the grain output for normal, blossoming and post-anthesis emphasis were 5936, 5162 and 4139 kilogram ha-1, severally. Grain yield decrease due to post-anthesis drouth has been antecedently reported ( Gooding et al, 2004 ; Ozturk and Aydin, 2003 ) . Grain yield increase observed in wheat line no.6 seems to be related to its highest remobilization, PAPCG and harvest index in drouth emphasis status. Drought emphasis by and large reduced harvest index ( Ehdaei, 1993 ) , while they were 43.35 % , 38.8 % and 44.8 % in blossoming, station blossoming and normal conditions, severally ( Table ) . The consequences of decrease in grain output due to drought emphasis comparing to normal status ( Gooding et al. , 2003 ; Ozturk and Aydin, 1993 ) was the same for all the mensural features of 1000 grain weight ( 37.86, 34.48 and 29.8 g ) ; entire works weight ( 3.44, 3.12 and 2.89 g ) ; spike weight ( 2.2, 2 and 1.7 g ) ; peduncle weight ( 0.27, 0.26 and 0.26 g ) ; figure of seeds per spike ( 40.8, 38.9 and 37.7 ) and seeds weight per spike ( 1.54, 1.34 and 1.13 g ) in normal, blossoming and post-anthesis drouth conditions, severally.
Harmonizing to the consequences there was a positive correlativity between grain output and most studied traits such as remobilization, efficiency and breakdown of the remobilized root militias to the grain in all three conditions. Papakosta and Gagianas ( 1991 ) besides reported the same consequences of positive correlativity between remobilized root militias and grain output. The remobilized assimilates were 0.2, 0.24 and 0.26 g in each studied root for normal, blossoming and post-anthesis drouth conditions, severally. Drought emphasis increased remobilization efficiency from 9.58 % in normal conditions to 11.34 % and 12.03 % in post-anthesis and blossoming drouth emphasis conditions which are in conformity with the consequences reported by Ehdaei et Al. ( 2006 ) . This increase due to the consequence of drouth emphasis was the same for breakdown of remobilized assimilates ( 14.29, 19.07 and 24.99 % ) in normal, blossoming and post-anthesis drouth conditions, severally and has been ported by Yang et Al. ( 2000 ) and Yang and Zhang, 2006 ) . Based on the above-named findings, the highest values measured in studied features in wheat line no.6 comparing with other genotypes resulted in less grain output decrease in this genotype. Another advantage for the referred wheat line was more trust on root militias for grain filling period particularly in blossoming and post-anthesis drouth conditions. By and large, drought emphasis causes less photosynthesis and more remobilization in grain filling period. So, efficient assortments in remobilization may hold less grain loss in drouth affected environments and more drought opposition ( Niu et al. , 1998 ; Yang et. al. , 2000 ) .
Harmonizing to consequences of drought opposition and susceptibleness indices, wheat line no.6 was the most drought immune line, while its remobilization rate, efficiency and breakdown was highest amongst studied genotypes. It seems the stableness and drouth opposition observed in line no.6 can be attributed to its rate, efficiency and breakdown of remobilization.
Hatim and Majidian ( 2012 ) reported that grain output was chiefly influenced by TGW in studied wheat genotypes in both normal irrigation and H2O emphasis conditions, while HI was non significantly different in genotypes that may be due to the declared grounds of all being ideal genotypes with high HI and with minimal fluctuation and important differences in grain output merely in H2O emphasis status.
Gupta et al. , ( 2011 ) stated that mobilized dry affair and mobilisation efficiency were higher in the internodes of tolerant cultivar, both under control and emphasis conditions, which boosted translocation of root militias to the grains. It is by and large accepted that root reserve mobilisation or per centum of root militias in grains is affected by sink size, environment and cultivar ( Blum, 1998 ) . In other words the high sum of root modesty in a assortment does non needfully intend that assortment has a good remobilization in drought environment so the sink activity and demand for root militias are really much of import features in drouth tolerant assortments. The mentioned parametric quantities are indirectly observed and related to higher TGW, entire works weight ( pre-anthesis biomass ) , spike, peduncle and seeds weight per spike ) which are wholly help lessening grain output loss in wheat line no.6. It may be due to the capableness of this genotype to synthesise and hive away higher concentration of soluble saccharides in the roots prior to blossoming ( Conocono, 2002 ) .
Zhang et al. , ( 2013 ) believe that H2O shortage addition WSC accretion and remobilization, remobilization efficiency, and part to grain output in non-leaf variety meats.
Lopes et al. , ( 2012 ) consequences suggested that if drouth and heat adaptative traits are brought together in one genotype, outputs can be farther increased peculiarly in low giving up environments.
Consequences of deliberate indices of MP, GMP, STI, SSI and TOL in the studied genotypes showed that line no.6 was the most drought immune line, because the highest rate, efficiency and breakdown of remobilization belonged to this line. Therefore, the stableness and drought opposition of line no.6 may be associated to high values in its rate, efficiency and breakdown of remobilization. We concluded that wheat line no.6 ( Alvd/Aldan/Ias58*2/3/Gaspard ) as the most drought tolerant genotype with higher grain output in both normal and drought stressed conditions and recommended to the husbandmans for onfarm experiments in both normal and blossoming and station blossoming drouth emphasis environments.