Biplot analysis of drought tolerance indicators in bread wheat lanraces of Iran

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1 International Journal of Agriculture and Crop ciences. Available online at IJAC/0/-/- IN -0X 0 IJAC Journal Biplot analysis of drought tolerance indicators in bread wheat lanraces of Iran Ezatollah Farshadfar *, Bita Jamshidi and Mostafa Aghaee. College of Agriculture, azi University, Kermanshah, Iran. eed and lant Improvement Institute, Karaj, Iran * Corresponding author e_farshadfar@yahoo.com ABTACT: In order to determine the performance of landraces of bread wheat under drought stress conditions and screening quantitative indices of drought tolerance, thirty bread wheat (Triticum aestivum L.) genotypes were tested in a randomized complete block design with three replications under irrigated and rainfed conditions. ignificant positive correlation was found between grain yield in the stress condition (Ys) with indicators geometric mean productivity (GM), mean productivity index (M), stress tolerance index (TI), yield index (YI), drought response index (DI), drought resistance index (DI) and modified stress tolerance index (MTI) indicating that these indices are suitable criteria for screening drought tolerant genotypes. No significant correlation was observed between Ys with stress susceptibility percentage index (I), tolerance index (TOL), yield stability index (YI), stress susceptibility index (I), relative drought index (DI), abiotic tolerance index (ATI) and stress nonstress production index (NI), hence they can be discarded as the desirable markers for identifying drought tolerant genotypes. rincipal component analysis (CA), indicated that the first and second components justified.0% of variations between the criteria. creening drought tolerant genotypes using mean rank, standard deviation of ranks and biplot analysis, discriminated genotypes (), () and () as the most drought tolerant. Key words: bread wheat, drought tolerance, biplot, screening criteria INTODUCTION Among all the factors limiting wheat productivity, drought remains the single most important factor affecting the world security and sustainability in agricultural production. For improving yield under dry land conditions, the development of new wheat cultivars with high grain yield potential through identifying drought tolerance mechanism is of great significance (ajaram et al., ). Breeding for drought resistance is complicated by the lack of fast, reproducible screening techniques and the inability to routinely create defined and repeatable water stress conditions when a large amount of genotypes can be evaluated efficiently (amirez and Kelly, ). Achieving a genetic increase in yield under these environments has been recognized to be a difficult challenge for plant breeders while progress in yield grain has been much higher in favourable environments (ichards et al., 00). Thus, drought indices which provide a measure of drought based on yield loss under drought conditions in comparison to normal conditions have been used for screening droughttolerant genotypes (Mitra, 00). These indices are either based on drought resistance or susceptibility of genotypes (Fernandez, ). Various quantitative criteria have been proposed for selection of genotypes based on their yield performance in stress and non-stress environments. Based on these indicators genotypes are compared in irrigated and rainfed conditions or in different levels of irrigations (Taghian and Abo-Elwafa, 00). Drought resistance is defined by Hall () as the relative yield of a genotype compared to other genotypes subjected to the same drought stress. Drought susceptibility of a genotype is often measured as a function of the reduction in yield under drought stress (Blum, ) whilst the values are confounded with differential yield potential of genotypes (amirez and Kelly, ). osielle and Hamblin () defined stress tolerance (TOL) as the differences in yield between the stress (Ys) and non-stress (Yp) environments and mean productivity (M) as the average yield of Ys and Yp. Fischer and Maurer () proposed a stress susceptibility index (I) of the cultivar. Geometric mean productivity (GM) is often used by breeders interested in relative performance, since drought stress can vary in severity in the field environment over years (amirez and Kelly, ).

2 Intl J Agri Crop ci. Vol., (), -, 0 Fernandez () defined a new advanced index (TI = stress tolerance index), which can be used to identify genotypes that produce high yield under both stress and non-stress conditions. Fernandez (), divided the manifestation of plants into the four groups of (I) genotypes that express uniform superiority in non-irrigated and irrigated conditions (group A), (II) - genotypes which perform favorably only in nonstress conditions (group B), (III) - genotypes which yield relatively higher only in stress conditions (group C) and (IV) - genotypes which perform poorly in non-irrigated and irrigated conditions (group D). Fischer et al. () introduced another index as relative drought index (DI). Bidinger et al. () suggested drought response index (DI) with its positive values indicating stress tolerance. Yield stability index (YI) also was computed and suggested by Bouslama and chapaugh (). This parameter is calculated for a given genotype using grain yield under stressed relative to its grain yield under non-stressed conditions. The genotypes with high YI is expected to have high yield under stressed and low yield under non-stressed conditions (Mohammadi et al., 00). Clark et al. () used stress susceptibility I for evaluation of drought tolerance in wheat genotypes and found year-to-year variation in I for genotypes and their ranking pattern. In spring wheat cultivars, Guttieri et al. (00) used I criterion and suggested that I more than indicated above-average susceptibility to drought stress. Lan () defined new index of drought resistance index (DI), which was commonly accepted to identify genotypes producing high yield under both stress and nonstress conditions. The DI and TI consider not only the ability of genotypes to grow well under stressed environments, but also good performance in non-stressed environments. Thus, they identify materials which are compatible with stressful and optimal conditions, to achieve ideotypes that can tolerate long intervals between irrigation or possibly no irrigation at sensitive growth stages (Jafari et al., 00). Farshadfar and utka (00) improved the efficiency of TI as a modified stress tolerance index (MTI). They calculated the index ki TI, where ki is a correction coefficient which corrects the TI as a weight. Therefore, k TI and k TI are the optimal selection indices for stress and non-stress conditions, respectively. Indices ATI and I are able to separate relative tolerant and non tolerant genotypes better than previous indices, while NI is able to separate group A from others and has an emphasis on high and stable yield in both environmental conditions (Moosavi et al., 00). The objectives of the present investigation were (i) to identify drought tolerant landraces of bread wheat genotypes in Iran and (ii) screening yield based indices of drought tolerance. MATEIAL AND METHOD Thirty landraces of bread wheat (Triticum aestivum L.) listed in Table were provided from eed and lant Improvement Institute of Karaj, Iran. They were assessed in a randomized complete block design with three replications under two irrigated and rainfed conditions during 00-0 growing season in the experimental field of the College of Agriculture, azi University, Kermanshah, Iran ( N, E and m above sea level). Mean precipitation in 00 0 was 0.0 mm. The soil of experimental field was clay loam with ph.. owing was done by hand in plots with four rows m in length and 0 cm apart. The seeding rate was 00 seeds per m for all plots. At the rainfed experiment, water stress was imposed after anthesis. Non-stressed plots were irrigated three times after anthesis, while stressed plots received no water. At harvest time, yield potential (Yp) and stress yield (Ys) were measured from rows m in length. Genotype WC- WC- WC- WC- WC- WC- WC- WC-0 WC- WC-0 WC- WC-00 WC- WC- WC- Table. Name and codes of genotypes Code Genotype WC- WC-00 WC- WC- WC- WC- WC- WC- pishtaz 0 pishgam WC-0 WC- WC- WC- WC- Code 0 0 Drought resistance indices were calculated using the following relationships: (Y Y ) - tress susceptibility index = I = (Fischer and Maurer, ). (Y Y )

3 Intl J Agri Crop ci. Vol., (), -, 0 - elative drought index = DI= (Ys/Y p )/ ( Y / Y ) [(Fischer et al. ()]. - Tolerance = TOL = Y - Y (osielle and Hamblin, ). Y Y - Mean productivity = M = + (osielle and Hamblin, ). Y Y - tress tolerance index = TI = (Fernandez, ). Y - Geometric mean productivity = ( Yp)( Ys) Y - Yield index = YI = (Gavuzzi et al., ). Y GM = (Fernandez,). Y - Yield stability index = YI = (Bouslama and chapaugh, ). Y - Drought response index = DI= (Y A -Y E ) /( E ) (Bidinger et al., ). 0- Drought resistance index (DI) = Ys (Ys/Yp)/ Y ( Lan, ). - Modified stress tolerance index = MTI = ki TI, k =Y p / Y and k = Y s / (Farshadfar and utka, 00) where ki is the correction coefficient. - Abiotic tolerance index = ATI =[(Yp-Ys) / ( Y / Y )] [ ] (Moosavi et al., 00). - tress susceptibility percentage index = I=[Yp-Ys /( Y )] 00 (Moosavi et al., 00). - tress non-stress production index = NI= [ ] [ ] (Moosavi et al., 00). In the above formulas, Y, Y, Y and Y represent yield under stress, yield under non-stress for each genotype, yield mean in stress and nonstress conditions for all genotypes, respectively. Y A, Y E and E are representative of yield estimate by regression in stress condition, real yield in stress condition and the standard error of estimated grain yield of all genotypes, respectively. For screening drought tolerant genotypes a rank sum () was calculated by the following relationship: ank sum () = ank mean ( ) + tandard deviation of rank (D) and D= ( i) 0.. tatistical analysis Correlation analysis and principal component analysis (CA), based on the rank correlation matrix and biplot analysis were performed by ver., TATITICA ver. and Minitab ver.. EULT AND DICUION Data concerning yield (Yp and Ys ) and indices are given in Table. The estimates of stress tolerance attributes (Table ) indicated that the identification of drought-tolerant genotypes based on a single criterion was contradictory. For example, according to TI and GM and M genotypes, and were the most, whereas genotypes, and the least relative tolerant genotypes. For TOL and I the desirable droughttolerant genotypes were, and. As to YI genotypes, and 0 were the most and, and the least relative tolerant genotypes (Table ). According to YI, I, DI and ATI indices selected the genotypes, and as the most relatively tolerant genotypes while for DI the genotypes, and were the most relative tolerant. According to K TI the genotypes, and and according to K TI the genotypes, and 0 were the most relative tolerant. DI selected the genotypes,, 0 as the best, while the genotypes,, as the the worst relatively tolerant genotypes. Majidi et al. (0) reported that GM, TI and HM indices were similarly able to separate drought sensitive and tolerant genotypes of safflower in both mild and intense water stress environments. Talebi et al. (00) also reported that cultivars producing high yield in both drought and well watered conditions can be identified by TI, GM and M values. ireivatlou et al. (00) was also noted that TI can be a reliable index for selecting high yielding genotypes. Correlation analysis Yield in stress (Ys) condition was significantly and positively correlated with M, GM. TI, YI, DI, K TI, K TI and DI. Yield in non-stress (Yp) condition was significantly and positively correlated with TOL, Y

4 Intl J Agri Crop ci. Vol., (), -, 0 M, GM, TI, YI, DI, K TI, K TI, ATI and I indicating that these criteria were more effective in identifying high yielding cultivars under different moisture conditions (Table ). Majidi et al. (0) reported that the results under both stress environments indicated positive and significant correlations between Y with TOL, M, GM, TI, I and HM selection indices. Table. anks (), ranks mean ( ) and standard deviation of ranks (D) of drought tolerance indicators TOL I M GM TI Y Y Genotypes Table continued. ATI DI I DI DI YI YI Genotypes

5 Intl J Agri Crop ci. Vol., (), -, They reported that correlations between Y with GM, TI, and HM indicated that selection based on these indices may increase yield in stress and non stress conditions. Farshadfar et al. (00) believed that most appropriate index for selecting stress-tolerant cultivars is an index which has partly high correlation with seed yield under stress and non-stress conditions. The observed relations were consistent with those reported by Fernandez () in mungbean, Farshadfar and utka (00) in maize and Golabadi et al. (00) in durum wheat. Table. Correlation coefficients between indicators of drought tolerance Ys Yp TOL M GM TI YI YI I Ys Yp 0.** TOL ** M 0.0** 0.** 0.* GM 0.** 0.** 0.0* 0.** TI 0.** 0.** 0.* 0.** 0.** YI.00** 0.** ** 0.** 0.** YI * -0.** I ** ** DI.00** 0.** ** 0.** 0.**.00** K TI 0.** 0.** 0.** 0.** 0.** 0.** 0.** K TI 0.** 0.** 0. 0.** 0.** 0.** 0.** DI * -0.** ** -.00** ATI ** 0.** 0.** 0.** 0.** ** 0.0** I **.00** 0.0* 0.0* 0.* ** 0.** NI ** ** -0.** DI 0.0** ** * 0.0** 0.** -0.** *, **: ignificant at 0.0 and 0.0 level of probability, respectively. Table continued. K TI DI ATI I NI K TI DI 0. ATI ** I ** 0.** NI ** -0.* -0.** DI 0.** 0.** -0.** -0.** 0.** DI 0.** 0.** ** K TI 0.** ** 0.** DI amirez and Kelly () reported that selection based on a combination of both I and GM indices may provide a more desirable criterion for improving drought resistance in common beans. Guttieri et al. (00), using I criterion in spring wheat, suggested that more than unit of I value may indicate above-average susceptibility for drought stress and less than unit has below-average susceptibility. Golabadi et al. (00) found that TI, M, and GM are superior indices for selecting high yield durum wheat genotypes both under moisture stress and non-stress field environments. ourdad (00) reported that TI was the best index to identify superior cultivated safflower genotypes in conditions both with and without drought stress. creening drought tolerant genotypes and indices -rincipal component analysis method The relationships among different indices are graphically displayed in a biplot of CA and CA (Figure ). The first and second components justified.0% of the variations between criteria. The CA and CA mainly distinguish the indices in different groups. One interesting interpretation of biplot is that the cosine of the angle between the vectors of two indices approximates the correlation coefficient between them. The cosine of the angles does not precisely translate into correlation coefficients, since the biplot does not explain all of the variation in a data set. Nevertheless, the angles are informative enough to allow a whole picture about the interrelationships among the drought indices (Yan and Kang 00). NI, YI, DI and DI we refer to group = G. The Cs axes separated Ys, DI, YI, K TI, K TI, TI, GM, M and Yp in a single group (G) and ATI, TOL, I and I in a single group (G). The vector view of the biplot (Figure ) provides a summary of the interrelationships among the drought indicators. Using the biplot diagram (Figure ) genotypes,,, and were identified as tolerant and genotypes,, and were detected as sensitive to drought. A three-dimensional representation of Ys, Yp and TI is shown in Figure.The area of the D plot was divided into regions, A, B, C and D (Fernandez, ). Genotypes, 0,,,,, and were placed in a region of the plot which had the highest TI, Ys and Yp (Figure ). 0

6 Intl J Agri Crop ci. Vol., (), -, 0 Figure. Biplot analysis of drought tolerance criteria Figure. Biplot of first and second components for indices of drought tolerance Figure. Three-dimensional plot between Yp, Ys and TI election through I chooses genotypes with relatively low Y but high Y. This index ranges between 0 and and the greater this index, the greater susceptibility of the genotype to stress. The main disadvantage of this index is the lack of separation of group A from group C (Fernandez, ). YI, proposed by

7 Intl J Agri Crop ci. Vol., (), -, 0 Gavuzzi et al. (), was significantly correlated with stress yield. This index ranks cultivars only on the basis of their yield under stress and so does not discriminate genotypes of group A. YI, as Bouslama and chapaugh () stated, evaluates the yield under stress of a cultivar relative to its non-stress yield, and should be an indicator of drought resistant in the genetic materials. Clarke et al. () showed that yield-based I index did not differentiate between potentially drought resistant genotypes and those that possessed low overall yield potential. imilar limitations were reported by White and ingh (). election through TOL chooses genotype with low Y but with high Y (group C), hence, TOL deficiencies to distinguish between group C and group A (Fernandez, ). M is mean yield for a genotype in two stress and non-stress conditions. M can select genotypes with high Y but with relatively low Y (group B) and it fails to distinguish group A from group B. By decreasing TOL and increasing M, the relative tolerance increases (osielle and Hamblin, ; Fernandez, ). A high TI demonstrates a high tolerance and the best advantage of TI is its ability to separate group A from others. GM is more powerful than M in separating group A and has a lower susceptibility to different amounts of Y and Y so; M, which is based on arithmetic mean, will be biased when the difference between Y and Y is high. The higher GM value, the greater the degree of relative tolerance. The geometric mean is often used by breeders interested in relative performance since drought stress can vary in severity in the field environments and over years (Fernandez, ). The two indices namely ATI and I reveal the relative tolerance of a cultivar to drought stress. The nature of ATI and I are such that they rely on crop survival mechanisms in stress conditions although these genotypes can have either high or low yields in two conditions so, they have not exhibited a significant correlation with high Y but have shown a significant correlation with Y. The yield stability is more important than high yield in non-irrigated and irrigated conditions. In fact, this reveals the relative stability of yield with conditions changes, and the smaller ATI and I the more relative tolerance crop is. Although ATI and I have high correlation together and both of them select group C, but ATI has a more emphasis on Y than I, I and TOL (Moosavi et al., 00). ATI or I select genotypes especially on the basis of yield stability, while, selection by NI is based on two characteristics simultaneously, namely yield stability as well as high Y and Y (with more emphasis on high Y than high Y) (Moosavi et al., 00). - anking method To determine the most desirable drought tolerant genotype according to the all indices mean rank and standard deviation of ranks of all in vivo drought tolerance criteria were calculated. In consideration to all indices, genotypes (=.), (=.) and (=.) were the most drought tolerant genotypes, respectively. While genotypes (=.), (=.) and (=.) were the most sensitive to drought, therefore they are recommended for crossing and genetic analysis of drought tolerance using diallel mating design or generation mean analysis and also for the QTLs (quantitative trait loci) mapping and marker assisted selection. CONCLUION In conclusion, based on principal component and biplot analysis, the indices of group (G) Ys, DI, YI, K TI, K TI, TI, GM, M and Yp exhibited strong correlation (acute angles) with Ys and Yp, therefore, they can discriminate drought tolerant genotypes with high grain yield at the same manner under stress and nonstress conditions (group A of Fernandez). With regard to all indices using rank some method genotypes (=.), (=.) and (=.) were the most drought tolerant genotypes, respectively. EFEENCE Bidinger F, Mahalakshmi V, ao GD.. Assessment of drought resistance in millet Factors effecting yields under stress. Aust J Agric es. :-. Blum A.. lant Breeding for tress environments. CC ress Florida Bouslama M, chapaugh WT.. tress tolerance in soybean. art. Evaluation of three screening techniques for heat and drought tolerance. Crop ci. :. Clarke JM, Deauw M, Townleymith TF.. Evaluation of methods for quantification of drought tolerance in wheat. 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