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J. Agric. Res., 2016, Vol. 54(1):1-14 ISSN:Online:2076-7897, Print:0368-1157 http://www.jar.com.pk ESTIMATION OF GENETIC VARIABILITY, HERITABILITY AND GENETIC ADVANCE FOR YIELD AND YIELD RELATED TRAITS IN WHEAT UNDER RAINFED CONDITIONS Muhammad Yaqoob* ABSTRACT Twenty four wheat lines developed by different research institutes of Pakistan were tested at Arid Zone Research Institute, Dera Ismail Khan, Pakistan during 2013-14 under rainfed conditions. The objective was to estimate their genetic variability for understanding the environmental effect on various plant traits through phenotypic and genotypic co-efficient of variability and heritability. The experiment was laid out in RCBD with three replications. All candidate lines alongwith well adapted local variety “Hashim-08” were planted in a six rows plot of 5 meters in length. Row to row distance was kept as 25 cm. The results revealed significant differences for all traits except number of grains per spike. The presence of considerable amount of genetic variability revealed that genotypes under study were genetically diversified as these were developed through various sources under different ecological zones. The line NR-397 proved its supremacy by producing the highest grain yield of 3437 kg per hectare. The highest estimates of GCV (17.28) and PCV (26.41) were recorded for grain yield and number of tillers per plant, respectively. The heritability estimates were high for grain yield (99.83%) and days to 50 percent heading (84.73%), moderate for plant height (45.79%) and low for number of tillers per plant (20%), number of grains per spike (26.81%), days to maturity (30.13%), spike length (36.66%) and 1000 grain weight (38.68%). Most of the traits exhibited low heritability under drought stress conditions which indicates the dominant effect of abiotic stresses on crop. High heritability accompanied by high genetic advance was recorded for grain yield indicating the presence of additive genes effect for this trait suggesting that crop can be improved through simple selection on grain yield basis. KEYWORDS: Triticum aestivum L.; wheat; genetic variability; heritability; genetic advance; yield; yield components; Dera Ismail Khan. INTRODUCTION Wheat (Triticum aestivum L.) is one of the major food staples of Pakistan cultivated on an area of about 21.465 million hectares under irrigated and *Arid Zone Research Institute, Dera Ismail Khan, Pakistan.
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J. Agric. Res., 2016, Vol. 54(1):1-14 ISSN:Online:2076-7897, Print:0368-1157

http://www.jar.com.pk

ESTIMATION OF GENETIC VARIABILITY, HERITABILITY AND GENETIC ADVANCE FOR YIELD AND YIELD RELATED

TRAITS IN WHEAT UNDER RAINFED CONDITIONS

Muhammad Yaqoob*

ABSTRACT

Twenty four wheat lines developed by different research institutes of Pakistan were tested at Arid Zone Research Institute, Dera Ismail Khan, Pakistan during 2013-14 under rainfed conditions. The objective was to estimate their genetic variability for understanding the environmental effect on various plant traits through phenotypic and genotypic co-efficient of variability and heritability. The experiment was laid out in RCBD with three replications. All candidate lines alongwith well adapted local variety “Hashim-08” were planted in a six rows plot of 5 meters in length. Row to row distance was kept as 25 cm. The results revealed significant differences for all traits except number of grains per spike. The presence of considerable amount of genetic variability revealed that genotypes under study were genetically diversified as these were developed through various sources under different ecological zones. The line NR-397 proved its supremacy by producing the highest grain yield of 3437 kg per hectare. The highest estimates of GCV (17.28) and PCV (26.41) were recorded for grain yield and number of tillers per plant, respectively. The heritability estimates were high for grain yield (99.83%) and days to 50 percent heading (84.73%), moderate for plant height (45.79%) and low for number of tillers per plant (20%), number of grains per spike (26.81%), days to maturity (30.13%), spike length (36.66%) and 1000 grain weight (38.68%). Most of the traits exhibited low heritability under drought stress conditions which indicates the dominant effect of abiotic stresses on crop. High heritability accompanied by high genetic advance was recorded for grain yield indicating the presence of additive genes effect for this trait suggesting that crop can be improved through simple selection on grain yield basis.

KEYWORDS: Triticum aestivum L.; wheat; genetic variability; heritability; genetic advance; yield; yield components; Dera Ismail Khan.

INTRODUCTION

Wheat (Triticum aestivum L.) is one of the major food staples of Pakistan cultivated on an area of about 21.465 million hectares under irrigated and

*Arid Zone Research Institute, Dera Ismail Khan, Pakistan.

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rainfed ecologies with production of 24.303 million tons annually (6). The Borlaug’s Green Revolution in late 1960s encouraged the plant breeders to develop high yielding varieties of different field crops. Pakistan is one of the states benefited from the Dr. Borlauge work (8). Consequently, a number of high yielding wheat varieties possessing resistance against various foliar diseases have been developed. The entire cultivable area of country has been classified in different zones on the basis of topographic-cum-ecological conditions. However, the average grain yield in country has not yet reached the level of satisfaction regarding more efforts to compete with the advanced countries of the world. Besides other factors, drought is the major feature sinking the grain yield. The breeders are, therefore, simultaneously addressing various biotic and abiotic problems. The genetic variability, the basic utensil of breeding tactics could be achieved through hybridization of diversified genetic material as well as introduction of exotic germplasm. The information about genetic variation of germplasm being handled is necessary to be gained for different plant traits. Singh et al. (27), Ghimirary et al. (14) and Shazly et al. (25) found significant genetic variability and higher heritability estimates with greater values of genetic advance for number of spikes, number of grains per spike, 100 seed weight, plant height and grain yield. Aafia et al. (1), however, observed low to high estimates of heritability and genetic advance for these traits except plant height. Moghaddam et al. (20) and Shafiq et al. (24) studied 53 pure lines of bread wheat and reported significant genotypic differences for most of the yield traits with high heritability estimates. The observations of Singh et al. (28) and Deshmukh et al. (12) showed high value of phenotypic and genotypic coefficient of variability, heritability and genetic advance in plant biomass, grain yield, tillers per plant, plant height and number of grains per spike assuring scope of yield improvement through selection. Some other scientists (2, 4, 5) observed significant genotypic differences for the traits including plant height, number of productive tillers per plant, number of spikelets per spike, spike length, number of grains per spike, fertility percentage, 1000 grain weight and grain yield. They also reported higher estimates of GCV, PCV and heritability for number of productive tillers per plant, number of grains per spike and grain yield per plant. Akcura M. (3) noted low heritability estimates ranging from 12.9 to 50.0 percent. He observed the highest expected genetic advance for grain yield (8.35%). The degree of heritability indicates the reliability through which the genotypes are recognized by its phenotypic expression (10). Pramoda (21) had classified the heritability values into various categories from low (<40%) to

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very high (>80%) estimates. Eid (13) observed low and medium heritability for different yield traits in wheat under rainfed conditions. Subhani et al. (30) and Shabbir et al. (23) found highly significant differences for days to heading, plant height, tillers per square meter, 1000-grain weight and grain yield in some local exotic (CIMMYT) germplasm under drought stress and irrigated conditions. They also noted high broad sense heritability for these traits under both conditions. Baranwal et al. (7) noted wide genetic variation among wheat genotypes for days to heading, plant height, tillers and grains per spike. Sajid et al. (22) released new high yielding wheat variety “BARS-09” on the basis of highly significant variability in many morphological traits in several trials conducted at various locations. Similarly, Degwioune et al. (11) studied 26 bread wheat genotypes from ICARDA-CIMMYT and reported that genotypes differed significantly for most of the yield components. High GCV alongwith high heritability and genetic advance were recorded in grain yield and days to heading. Khan (17) showed highly significant differences among wheat genotypes for days to heading and plant height, while non-significant differences were recorded for days to maturity, number of fertile tillers per plant, spike length, spikelets per spike, grains per spike and grain yield per plant. Manrya et al. (19) found highly significant differences in wheat genotypes for yield and yield components. They observed the higher GCV and PCV for grain yield, 1000 grain weight and number of grains per pike and spike length. Higher heritability was recorded for yield per plant, 1000 seed weight, grains per spike and plant height while moderate heritability was observed for days to heading, days to maturity and spike length. Present investigations were carried out to estimate the genetic variability in wheat candidate lines and further analysis of genetic components to understand the environmental effect on various plant traits through phenotypic and genotypic co-efficient of variability and heritability under rainfed conditions.

MATERIALS AND METHODS

Twenty four well-bred and improved wheat genotypes developed by different national research institutes of the country were evaluated at Arid Zone Research Institute, Dera Ismail Khan, Pakistan during 2013. Each line was planted in six rows in a 5 meters long plot having row to row distance of 25 cm. The data were recorded from middle four rows while one row on both sides was discarded. The crop was maintained under rainfed conditions, however, a soaking irrigation was applied before planting. Nitrogen (N), phosphorus (P) and potassium (K) fertilizer were applied @ 90, 100 and 120 kg per hectare, respectively. The weather data during the crop period at

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experimental site is given in Table 1. The soil of experimental field was clay loam. Analysis of variance for components were carried out for all traits using computer’s software STATISTIX 9.1. The means of all significant variables were subsequently separated through LSD at 0.05 percent level of probability to establish the level of significance (23). The genetic parameters viz. genotypic and phenotypic co-efficient of variations, heritability (h2) broad sense, genetic advance (GA) and genetic advance as percent of means (GAM) at 1 percent standardized selection differential were calculated as proposed by Burton (9), Honson et al. (15), Singh and Choudhury (26) and Johnson et al. (16), respectively. Table 1. Agro-meteorological data recorded at Arid Zone Research Institute, D. I. Khan during

2013-14.

Month Total rainfall (mm)

Average maximum

temperature (˚C).

Average minimum

temperature (˚C).

Relative humidity

(%)

Wind speed (km/day)

October 2013 6 33 21 78 46 November 2013 6 26 10 78 41 December 2013 1 22 6 82 44 January 2014 - 21 4 73 46 February 2014 38 21 7 82 59 March 2014 50 24 12 83 56 April 2014 68 23 18 67 63

RESULTS AND DISCUSSION

Days to 50 percent heading The results (Table 3) revealed that variability among candidate varieties regarding days to 50 percent heading was highly significant. The number of days to 50 percent heading ranged from 101 to 112. The line NR-439 was early in 50 percent heading availing 101 days, closely followed by lines DN-84, PR-105 and PR-109 (102 days each). The line 09FJ34 was significantly late in heading with 112 days. It was statistically at par with NIA-MB-02, AZRC-2, V-11183, DH-31 and NRL-0913 taking 110 to 112 days to complete 50 percent heading. Highly significant variability in wheat genotype have also been reported earlier (2, 4, 5, 7, 19, 22, 23, 30).

Plant height (cm) Plant height (cm) was highly significant among 24 candidate wheat varieties ranging from 73.11 to 101.22 cm (Table 2 and 3). The line NIA-MB-02 was tallest among all (101.22 cm). It was however, statistically similar to nine other wheat lines including DN-84, DH-31, 09FJ34, NRL-0913, V-12001, PR-108, HASHIM-08, PIRSABAK-05 and NARC-09 (90.78 to 96.67 cm). The line

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99172 was found as the shortest one (73.11 cm). It was statistically similar to some other lines viz; V-11183, PR-105, NR-403, NR-411, NR-402, AZRC-2 and DHARABI-2013. (76.67 to 83.56 cm) (Table 3).These results are in accordance with the findings of Aqbal et al. (2), Akhter et al. (4), Ali et al. (5), Khan (17), Manrya et al. (19), Shabbir et al. (23) and Subhani et al. (30), who reported significant genetic diversity in plant height in various wheat germplasm under different environmental conditions. Table 2. Mean squares of various wheat candidate varieties under rainfed conditions of D.I.Khan.

Source of variation

D.F Days to 50% heading

Plant height (cm) Days to maturity No. of tillers/ plant

Replications 2 25.431 98.79 35.39 0.686 Genotypes 23 34.17** 145.146** 7.475** 3.464* Error 46 1.937 41.069 3.258 1.98 Total 71 - - - - CV percentage 1.32 7.29 1.25 5.95 Source of variation

Spike length (cm)

No. of grains/spike

1000 grain weight (g)

Grain yield (kg/ha)

Replications 0.478 65.66 7.056 799438 Genotypes 3.01** 215.36N.S 41.36* 506946** Error 1.1 102.614 14.31 121154 Total - - - - CV percentage 9.98 17.07 8.63 16.77

*Significant at 0.05% level of probability, **Significant at 0.01% level of probability, N.S= Non-significant

Days to maturity

The genetic variability regarding days to maturity was found to be highly significant among 24 candidate lines ranging from 141 to 148.33 days (Table 3). Hashim-08 was found to be early as it matured within 141 days followed by line NR-397 (143.67 days). This line was statistically at par to Hashim-08 and also rest of 15 lines which matured within 144 to 146.33 days. Similarly, line NR-411 was found late with 148.33 days to maturity followed by lines NARC-09 (148 days) and V-11183 (147.33 days). All these lines were however, statistically indistinguishable to some other 10 lines (145.67 to 147 days). Previous findings (5, 11, 17, 22, 23, 25, 28, 30) are in conformity with present investigations observing significant and highly significant variation in days to maturity under irrigated and rainfed conditions in wheat genotypes.

Number of tillers per plant

The differences in number of tillers produced by various genotypes were significant ranging from 4.56 to 8.44 per plant. Hashim-08 line produced highest number of tillers per plant (8.44) closely followed by variety DHARABI-2013 (8.33 tillers/plant). Both the lines were statistically parallel to

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each other and also with some other lines including 99172, NARC-09, NR-403, NRL-0913, PR-108, NR-439 and NR-397 (6.33 to 7.33 tillers/plant). The lowest tillers were produced by lines V-12001, PR-105, W-23 and DN-84 showing less than 5 tillers per plant (Table 3). Similar results were reported by earlier scientists (4, 5, 11, 17, 19, 20). Spike length (cm) Spike length also differed significantly (8.33 to 12.67 cm) in various wheat genotypes. Maximum value (12.33 cm) was measured in line NRL-0913 followed by PR-108 (12.22 cm). These two lines were statistically identical with each other and also with other 11 lines having spike length 10.67 to 11.78 cm. The shortest spike was produced by variety Dharabi-2013, line 99172, V-11183, 09FJ34, W-23, NIA-MB-02 and NR-402 with the values of 8.33, 8.67, 9.22, 9.44, 9.73, 9.78 and 9.89 cm respectively (Table 3). These results agreed to earlier findings (24, 28, 30) where significant variation was observed in spike length in wheat germplasm. Number of grains per spike

The number of grains per spike differed non-significantly in various wheat candidate lines. Although length of spikes was significantly different in genotypes yet the number of grains per spike were statistically uniform (Table 2). This might be due to variation in size of grains and number of spikelets per spike. Number of grains per spike were numerically higher in NR-403 (69.89) and DN-84 (69.33) while lowest in AZRC-2, DHARABI-2013 and 09FJ34 (50.11, 51.33 and 51.67). Khan (17) has also reported non-significant variation in number of grains per spike in different wheat varieties. These results however, contradicted the results of Ajmal et al. (2), Subhani et al. (30) and Manrya et al. (19) who noted significant variation in number of grains per spike in various wheat genotypes. The differentiation in results might be due to different genetic material used and variable environmental conditions of experimental sites. 1000 grain weight (g) The data (Table 2) revealed that weight of grains was significantly different in various wheat lines ranging from 36 to 48.67 g per 1000 seed. The heaviest grains were produced by 09FJ34 48.67 g closely followed by Line NR-411 and variety Dharabi-2013 (48 g each) (Table 3). The lowest 1000 grain weight were produced by line AZRC-2 (36 g). Generally, smallest seeds weighing 36 to 42 g of 1000 grains were produced by nine statistically

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comparable lines while rest of 15 lines produced more than 42 g weight 1000 grains with and all these lines were statistically comparable to each other (Table 3). These results are in line with the previous studies (2, 4, 5, 7, 19, 24, 30) indicating significant variation in seed weight in wheat genotypes. Grain yield (kg/ha)

Highly significant differences were observed in various lines indicating that genotypes used in these studies were genetically divergent (Table-2). As all these lines had already been refined by the breeders, therefore, these candidate lines showed quite reasonable yield despite facing moisture deficit problem at early growth stages. The line NR-397 remained excellent with grain yield of 3437 kg per hectare and remained statistically superior to all lines (Table 3). The line DN-84 was second best with grain yield of 2571 kg per hectare (Table 3). The line DN-84 was statistically similar to other 11 lines whose yield ranged from 2042 to 2567 kg per hectare. Such types of genetic variability in yield of different wheat varieties and other germplasm accessions has also been reported by many other workers (2, 4, 5, 7, 11, 17, 19, 20, 22, 23, 24, 28, 30). The line NR-397 alongwith other lines namely; DN-84, V-11183, C-4, NR-403, O-17 and NR-407 performed better suggesting that these may be further tested and recommended for rainfed areas.

Phenotypic and genotypic variance The results (Table 4) revealed that genotypic variance ranged from 0.50 to 128597 for number of tillers and grain yield, respectively while phenotypic variance ranged from 1.74 to 128813 for spike length and grain yield, respectively. The highest genotypic and phenotypic (128597 and 128813) variances were recorded for grain yield (Table 4). This indicates that genotypic performance of these traits reflects phenotypes. These results are similar to some earlier workers (11, 17, 24). The estimates of genotypic co-efficient of variation (GCV) ranged from 0.81 (days to maturity) to 17.28(grain yield), while phenotypic co-efficient of variation (PCV) ranged from 1.48 (days to maturity) to 26.41 (number of tillers/plant). Deshmukh et al. (12) proposed that more than 20 percent PCV and GCV values are regarded as higher and values 10-20 percent are medium while those less than 10 percent are considered as low. The GCV estimates were medium for grain yield, number of tillers and number of grains per spike and low for days to 50 percent heading, plant height, days to maturity, spike length and 1000 grain weight. Similarly, PCV estimates were high for number of tillers and grains per spike, medium for grain yield, spike length and 1000 grain weight, while

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low for days to maturity, days to heading and plant height. The traits like days to heading, plant height, days to maturity, spike length and 1000 grain weight showed lower GCV indicating the least scope of improvement of these traits through selection as these traits are highly influenced by drought stress environment. PCV were higher than GCV for all traits showing the environmental effect on crop as experiment was maintained under rainfed conditions and the crop experienced severe drought stress at initial growth and tillering stage. Estimates of heritability (h2) in broad sense Pramoda and Gangaprasad (21) had classified the heritability estimates into low (<40%), medium (40-50%), moderately high (60-79%) and very high (>80%). The results of present study (Table 4) showed that heritability estimates were low for number of tillers per plant (20%), grains per spike (26.81%), days to maturity (30.13%), spike length (36.66%) and 1000 grain weight (38.68%) and moderately high for plant height (45.79%) and very high for days to 50 percent heading (84.73%) and grain yield (99.83%). Aafia et al. (1), Ajmal et al. (2) and Akcura (3) have also noted low to high estimates of heritability and genetic advance for all these traits except plant height. Similarly, Degeioone et al. (11) and Khan (17) have also observed lower heritability in days to heading, days to maturity, number of fertile tillers per plant, spike length, spikelets per spike, grains per spike and grain yield per plant. These results are, however, contradicted to some earlier reported results (14, 25, 27) where higher heritability estimates were noted for number of spikes, number of grains per spike, 1000 seed weight and plant height. Similarly, Akhtar et al. (4) and Ali et al. (5) have also noted high heritability for plant height, number of spikelet per spike, spike length, number of grains per spike, 1000 grain weight and grain yield. The differences in findings might be due to different genetic material used and incongruent climatic conditions under which the studies were undertaken. Moreover, the environmental stress dominated the genotypic performance as studies were conducted under rainfed conditions and crop experienced a moisture stress during early growth stages.

Estimates of expected genetic advance The heritability alongwith estimates of genetic advance (GA) would be more consistent and meaningful than heritability alone (19). The expected genetic advance as percent of mean (GAM) by selecting top 5 percent (high yielders)

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of 24 wheat candidate varieties ranged from 1.18 percent for days to maturity to 45.58 percent for grain yield indicating that selecting top 5 percent of population could result in an advance of 1.18 to 45.58 percent over respective population mean (Table 4). High heritability was associated with high genetic advance for grain yield suggesting that grain yield was under the control of additive genetic effects which indicate that selection on grain yield basis would be beneficial for genetic improvement in wheat yield (Table 4). Present results confirm the earlier results (14, 25, 27) which noted higher heritability estimates alongwith greater values of genetic advance for yield and other traits in wheat. High heritability (h2)was coupled with low GA for days to heading, while low h2 coupled with low GA for days to maturity, number of tillers, spike length, grain per spike and 1000 grain weight. It indicates that these traits are controlled by non-additive gene effects and may be improved through hybridization program involving genotypes with diversified genetic background. Previous studies (1, 2, 3) have showed low to high estimates of heritability and genetic advance for most of the traits in wheat except plant height. Eid (13) also observed low heritability and low genetic advance for plant height and number of grains spike in wheat under drought stress conditions. The study reveals that various candidate wheat genotypes were comparable in all the plant traits under rainfed conditions. All the genotypes were significantly different in most of the traits. The presence of considerable amount of genetic variability revealed that genotypes under study were genetically diversified as these lines were developed under different ecological zones of country. The line NR-397 excelled by producing the highest grain yield (3437 kg/ha). The highest estimates of heritability were recorded for grain yield (99.83%) and days to 50 percent heading (84.73%) while rest of the traits showed low heritability values. Lower heritability (h2) may be attributed to dominant effect of environmental stress (drought) on crop. High heritability accompanied by high genetic advance was recorded for grain yield indicating the presence of additive genes effect for these traits. It is suggested that crop can be improved through simple selection on grain yield basis.

CONCLUSION

It can be concluded that selection will be an effective tool to be used for improvement on the basis of grain yield in wheat. The traits showing significant genetic variability can be further exploited through improvement and selection followed by intra-specific hybridization among wheat genotypes for development of high yielding varieties suitable for rainfed areas.

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29. Steel, R. G. D. and J.H. Torrie. 1997. Principles and Procedures of Statistics. A Biometrical Approach.3rdEd. McGraw Hill Book Co., Inc., New York, USA.

30. Subhani, G.B., M. Hussain, J. Ahmad and J. Anwar. 2011. Response of exotic wheat genotypes to drought stress. J. Agric. Res. 48(3):293-305.

Received: September 17, 2014 Accepted: November 11, 2014

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CONTRIBUTION OF AUTHOR

Muhammad Yaqoob: Conducted research and prepared the writeup as a sole author


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