COMBINING ABILITY ESTIMATES OF MAIZE (ZEA MAIZE) …

J Agric. Res., 2016, Vol. 54(3):447-465 ISSN: Online: 2076-7897, Print:0368-1157

http://www.jar.com.pk

COMBINING ABILITY ESTIMATES OF MAIZE (ZEA MAIZE) GENOTYPES TO CONTEST WATER STRESS IN PAKISTAN

Taufiq Ullah and Ijaz Rasool Noorka*

ABSTRACT

The objective of the present study was to estimate general and specific

combing ability in different crosses of maize genotypes by line × tester analysis

in two seasons of 2012 under normal and stress water conditions. In total

twelve parents including eight lines and four testers; were crossed to produce

32 F1 hybrids. Parents and their hybrids were evaluated in CRD with three water

treatments under controlled conditions. Different results were obtained for

general and specific combining ability studied for yield and its related

parameters i.e. ear leaf area, number of kernel rows per ear, 100 grain weight,

biological yield, vegetative dry matter and anthesis-silking interval. General

combining ability effects indicated that lines DR-187, DR-177, DR-198, DR-194

and testers Pak Afgoee and EV-6098 had strong potential to be used in

hybridization program for development of water resistant varieties. While

specific combining ability results indicated that crosses DR-177 × EV-6098, DR-

198 × EV-1098 and DR-198 × EV-6098 were the hybrids with outstanding

heterotic performance. The significant estimates of GCA and SCA suggested

the importance of both additive and non-additive gene actions for expression

of the traits under study for the selection of parents to be used for the

development of synthetics and hybrids resistant to water stress conditions in

Pakistan.

KEYWORDS: Maize; Zea maize; water stress; tester analysis; general

combining ability; specific combining ability.

INTRODUCTION

Globally maize is one of the high yielding crops among the cereals. The demand for food is increasing owing to rapid increase in population and income growth, accompanied by increased urbanization of developing countries (37). The rapid development of poultry and animal feed industry in Pakistan is also a major reason behind the significant increase in maize demand. There are many limiting factors for low yield of maize especially in

*Department of Plant Breeding and Genetics, University College of Agriculture,

University of Sargodha, Pakistan.

T. Ullah and I. R. Noorka

J. Agric. Res., 2016, 54(3)

448

developing countries like Pakistan; including various kinds of biotic and abiotic stresses (2). Water shortage is one of the important abiotic factors causing the major reduction in yield of crops (27, 28). This presents a challenge for plant breeders to develop new genotypes that are better adapted to adverse climatic conditions (Ashraf, 2010). For this, the selection of parental lines should be essentially based on general and specific combining ability effects (12) providing important genetic information on the basis of their hybrids performance (10, 38).The momentous breeding programs in maize are estimation of general and specific combining abilities of inbred lines, in the first generation (6, 42). General combing ability estimates of parents provide potential utilization for generating superior genotypes (22) while SCA designate deviation of certain crosses on the basses of average performance of the parents (Sprague and Tatum, 1942; Falconer and Mackey, 1996). The combining ability analysis gives an indication of the variance owing to GCA and SCA representing a relative measure of additive and non-additive gene actions respectively (11). High GCA value either positive or negative indicates that the parental mean is superior or inferior to the general mean and gives information about the concentration of dominant gene with additive effects whereas SCA gives non-additive interactions. The frequency of favorable genes increases with best combination of high GCA effects and favorable SCA effects in hybrids (26) and populations with high frequency of favorable alleles are good source for plant selection (39). Low GCA and SCA effects can be improved through intra and inter population breeding. The higher GCA effect indicates that these parental lines may be desirable for selection and hybridization programs. The best specific combiner for yield and its related traits can be used to produce efficient hybrids. These hybrids are expected to produce desirable segregates in the subsequent generations. So, these hybrids could be improved through a recombination breeding program (16). This study will provide the genetic information for selection of various varieties useful for maize breeding under water stress conditions in Pakistan.

In the next section materials and methodology is presented followed by results and discussion and conclusion in the subsequent sections.

MATERIAL AND METHODS

A total 44 genotypes including 32 crosses and 12 parents were sown in the polythene bags (45 × 30 cm) filled with mixture of soil (Soil, Silt and organic

Combining ability estimates of maize genotypes to contest water stress

J. Agric. Res., 2016, 54(3)

449

matter, in equal amount) having (pH 8.2 and EC.0.4) in wire-house of Department of Plant Breeding and Genetics, University College of Agriculture, University of Sargodha, Pakistan, under three water treatments given under.

Water treatment 1 T1 Eighty percent of field capacity Water treatment 2 T2 Sixty percent of field capacity Water treatment 3 T3 Forty percent of field capacity

All recommended agronomic, cultural and plant protection measures were kept uniform for all treatments except irrigation water. For the control of shoot fly and borer, insecticide was applied. Following Two Factorial Triplicate Randomized Complete Designs; each genotype was sown in three lines per replication per treatment in two seasons i.e. March, 2012 and August, 2012. Three water treatments were applied following Kirda et al., (24) and Aslam et al., (4). The data for the six yield related traits were recorded at appropriate time. Ear leaf area (E.L.A) of five randomly selected maize plants was measured in cm

2 by using leaf area meter (ΔT-MK2, England). Number of

kernel rows (N.K.R) per ear from five randomly selected maize plants per treatment was counted and then average was computed. An electronic balance (OHAUS-GT 4000, USA) was used to weigh 100-grain weight ((100 G.wt), biological yield (B.Y) and vegetative dry matter (V.D.M) in grams of the five randomly selected maize plants per treatment. Anthesis- Silking Interval (A.S.I) was measured through difference between anthesis and silking dates; calculated for all the maize genotypes separately.

Biometrical Approaches The recorded data on maize genotypes were subjected to line × tester

analysis as outlined by Kempthorne (1957). General and specific combining abilities effects were calculated according to the following formulae;

Estimation of GCA Effects

Lines: gi = { ( x.j./tr ) } – ( x…/ 1tr ) }

Testers: gi = { ( x.j..1r) } – (x… / 1tr)} Estimation of SCA Effects

Si = { ( xij.) / r) – ( xi.. / tr ) – ( x. j. / lr ) + x … / l tr


J. Agric. Res., 2016, 54(3)

450

RESULTS AND DISCUSSION In cereal crops, contribution of flag leaf photosynthesis is 30 to 50 per cent of the assimilates for grain filling (35) and initiation of grain filling coincides with the onset of senescence, therefore rate of senescence becomes important factor for determining grain yield (20, 23, 12). Genotypes capable to sustain photosynthesis for a longer time in the ear leaf have a greater tendency to yield better as assimilation of photosynthesis is totally dependent on leaf area (1, 7) and a sudden water stress diminishes more yield than gradual change (34). Water stress at flowering and grain filling stage reduces the number of kernel rows per ear and kernel size respectively (13, 22, 40) owing to decreased photosynthesis (9) and causes more lose at early stages of grain filling than later stages (33). Grain weight is also directly related to yield in maize that decreases with amplified water deficiency (8, 29). Biological yield (B.Y) and vegetative dry matter (V.D.M) are also the components of yield directly related to water use efficiency (7, 36). Kumar et al., (25), Joshi et al., (17) and Perez-Velasquez et al., (31), concluded that maize grain yield and flowering traits were under the control of non-additive type of gene action i.e. (SCA effect). Water stress at reproductive stage of maize, decreases the silk growth rate and time of silk opening for the pollination that further extends the anthesis-silking interval and decreases the chance of seed development (18). Therefore short anthesis-silking interval is a desired trait in maize production (5). Results of genotypes, parents, crosses, parents vs. crosses, lines, testers and lines × testers for the six traits, mentioned in materials and methods studied under three water treatments in season I and II, are presented in Table 1. Genotypes exhibited significant results for all traits under three water treatments in both seasons. Parents and crosses showed the significant result in both seasons except for parents for A.S.I under T1 and T3 in season I. Parents Vs Crosses revealed significant differences for all traits apart from 100 G. Wt under T1 in both seasons and for A.S.I under T3 in season I and for T1, T2 in season II. Lines and Testers exhibited notable deviations among the most of the traits under study in both seasons. Significant results were revealed for E.L.A and 100 G. Wt under all water treatments except for T1 for later in both seasons. For Number of kernel rows (N.K.R) insignificant difference was found under T1 in both seasons and T3 in season I. Whereas for Lines for B.Y showed significant difference under all three water treatments in season I while insignificant in season II. For V.D.M lines showed similar behavior in both seasons i.e. significant except for T1 in season II and for A.S.I insignificant result was found only under T1 and T3 in


J. Agric. Res., 2016, 54(3)

451


J. Agric. Res., 2016, 54(3)

452


J. Agric. Res., 2016, 54(3)

453

season I. Testers had significant results under T1 in both seasons and under T2 in season I for Ear leaf area but insignificant for N.K.R under all treatments in both seasons except for T2 in season I. Results of 100 G. Wt and V.D.M showed the same pattern for Testers in both seasons i.e. significant for T1. While for Biological yield and A.S.I testers showed deviation as B.Y was significant only under T1, T3 in season I and A.S.I in season II under all treatments. Lines × Testers had significant results for all traits in both seasons except for A.S.I under T2, T3 in season II. Results of general combining ability for the lines are presented in Table 2. GCA effects of lines and testers showed variable direction and magnitude. Line DR-187 had significant positive GCA effects for ear leaf area and significant negative for 100 G.wt and B.Y in both the seasons for all water treatments. A significant GCA effect was observed for DR-187 for N.K.R only under T1 in season I and for V.D.M under T2, T3 and for A.S.I under T3 in season II. Line DR-177 depicted significant effects for E.L.A, B.Y and V.D.M grown under three treatments in two seasons but negative in season II for B.Y and V.D.M except for later under T1. An insignificant GCA effect was shown for N.K.R excluding T1 in season I while significant for 100 G.wt except for T2 in season II under all three treatments. Whereas a positive significant effect was seen for A.S.I under T3 in season I and T1 in season II. A positive significant GCA effect was seen for ear leaf area and biological yield and insignificant for N.K.R and A.S.I under three water treatments in both seasons for Line DR-198. While a significant effect was observed for 100 G. Wt in season I and V.D.M in season II. DR-194 had insignificant GCA effect for E.L.A under T3 (season I), T1 (season II), for N.K.R under T2 (season I) and for B.Y in T3 (season I). A positive significant GCA effect was seen for 100 G. Wt in T3 (season I) and T2, T3 in season II while insignificant for V.D.M and A.S.I under T2 and T3 in season II. Line DR-158 revealed a significant but negative for E.L.A and B.Y while insignificant GCA effect for N.K.R under all three water treatments in both seasons. For 100 G. Wt an insignificant and for A.S.I a significant GCA effect was seen only under T1 in both seasons and season I respectively. DR-185 for Ear Leaf Area and 100 G. Wt had negative significant GCA effect in both seasons but insignificant for B.Y in two treatments i.e. T2 and T3 in season II. While; a positive significant GCA effects was seen for N.K.R and V.D.M only in T1 (season I) and T3 (season II) respectively but a negative for A.S.I. in T3 (season I) and T1 (season II). Line DR-189 for E.L.A revealed negative significant GCA effect under T1 in both seasons while positive significant in T3 (season II). A significant effect was seen for N.K.R. and B.Y under all treatments but negative for B.Y in season I. Under T1 and T2 a significant effect was found


J. Agric. Res., 2016, 54(3)

454


J. Agric. Res., 2016, 54(3)

455

for 100 G.wt and A.S.I in both seasons but negative for former. For V.D.M a negative significant effect was present under T1, T2 in season I and positive significant for T2, T3 in season II. A negative significant effect was revealed by DR-159 for E.L.A, N.K.R and B.Y under three water treatments except for N.K.R under T1 (season I) and B.Y under T3 (season 2). While a positive significant effect was observed for 100 G. Wt. under T2, T3 in both seasons. In season I this line expressed positive significant result for V.D.M only under T2 but in season II under T2 and T3 both. A positive significant effect was found for A.S.I in T1, T2 in season I but negative in T1 (season II).

The GCA effects for testers given in Table 3 showed that Pak Afgoee expressed a positive significant effect for E.L.A and insignificant for N.K.R. under all treatments in both seasons. A similar trend was depicted for 100 G.wt. as under T1 a positive significant and under T3 a negative significant effect was found in both seasons. Results for Biological yield were absolutely different in both seasons as significant for season I and insignificant in season II. In season I Pak Afgoee showed a positive significant GCA effect for V.D.M under all treatments but negative significant under T2, T3 in season II. In season I a negative significant effect was seen under treatment T1, T2 for A.S.I and a positive significant under T1 in season II. Tester Sadaaf revealed a negative significant result for E.L.A and B.Y and insignificant for N.K.R under all water treatments in both seasons. Whereas a negative significant effect was exhibited for 100 G. wt. under T1, T2 in both seasons but positive significant effect for V.D.M under T2 and T3 (season I) and T3 (season II). For the trait A.S.I, a positive significant effect was observed only under T3 in season I. Tester Ev-1098 revealed negative significant effect for E.L.A except for T2 (season II) but insignificant for N.K.R and V.D.M in both seasons. A similar trend was shown for 100 G.wt in both seasons i.e. negative significant for T1 while B.Y was negative significant in season I and positive significant in season II under all treatments. GCA effect was positive significant for A.S.I under T1, T2 in season I and negative significant under T1, T3 in season II. Ev-6098 has revealed negative significant GCA effect for T1 but positive for T3 in season I while insignificant for all treatments in season II. Effect of GCA was insignificant for N.K.R and A.S.I but positive significant for 100 G.wt and B.Y in both seasons. For V.D.M a negative significant effect was found under all water treatments in season I but positive under T2 and insignificant under T3 in season II. Line DR-198 had the highest positive significant GCA effect for biological yield and DR-187 for ear leaf area while DR-159 for 100 grain weight and vegetative dry matter both. Among testes Pak Afgoee had the highest


J. Agric. Res., 2016, 54(3)

456


J. Agric. Res., 2016, 54(3)

457

positive significant GCA effects for all the traits except number of kernel rows per ear and anthesis-silking interval. Variations among GCA effects may be due to additive, additive × additive and higher order additive interactions while SCA effects may be due to non-additive genetic variances (Falconer, 1960). Positive GCA effect means that a continuous improvement is possible through breeding (Golparvar, 2013). Results of specific combining ability for 32 newly developed crosses are presented in Table 4. It is clearly evident that SCA effects varied both in sign and magnitude. A positive significant SCA effect was seen for the cross DR-194 × EV- 6098 for ear leaf area, cross DR-185 × EV-1098 in season-I and DR-198 × EV-6098 in season-II for number of kernel rows per ear and cross DR-177 × EV-6098 for 100 grain weight in both the seasons. For biological yield cross DR-194 × Pak Afgoee in season-I and cross DR-158 × Pak Afgoee in season- II showed positive SCA effects. cross DR-187 × EV-1098 in season-I and DR-177 × Pak Afgoee in season-II for vegetative dry matter, cross DR-158 × Sadaaf in season-I and cross DR-185 × EV-1098 in season-II had positive and significant SCA effects for anthesis-silking interval under normal water application. Crosses in which one of the parents had significant GCA indicated the presence of additive genetic effects controlling that character. Crosses DR-177 × EV- 6098, DR-158 × EV-1098, DR-185 × EV-6098 and DR-177 × Sadaaf showed high SCA effects for grain yield and its components. For the selection of lines as parents, only SCA effects had limited value. Therefore, SCA effects are used in combination with parameters like hybrid means and GCA of the respective parent. The cross combination with good mean, favorable SCA and at least one parent with significant GCA effects, tend to increase favorable alleles. Hybrids were evolved through high × high such as DR-177 × EV-6098, DR-198 × Pak Afgoee, DR-177 × Sadaaf and high × low like DR-185 × EV-6098, DR-194 × Pak Afgoee, DR-187 × EV-1098 and low × low general combiners i.e. DR-158 × EV-1098 for 100 grain weight. It was observed that high positive SCA effects were observed in hybrids DR-177 × EV-6098 and DR-198 × Pak Afgoee for 100 grain weight in which both the parents had positive GCA effects. Crosses DR-177 × Sadaaf, DR-185 × EV-6098 and DR-194 × Pak Afgoee for 100 grain weight had high positive GCA value at least for one parent. None of the parents had high GCA effects for 100 grain yield in crosses DR-187 × EV-1098 and DR-158 × EV-1098 which indicate that any combination of parents with high or low GCA effects can result in high SCA effects. It is clear that hybrid combinations were not always due to best GCA effects but hybrid means and GCA effects of both


J. Agric. Res., 2016, 54(3)

458


J. Agric. Res., 2016, 54(3)

459


J. Agric. Res., 2016, 54(3)

460


J. Agric. Res., 2016, 54(3)

461


J. Agric. Res., 2016, 54(3)

462

parents are considered together. Petrovice (1998) also produced positive and significant SCA effects from combination of lines with significant positive or negative GCA effects. Testers had also revealed significant positive GCA effects for 100-grain weight. High means of hybrids with favorable SCA effects along with parents having high GCA effects was actually due to high concentration of favorable alleles, a good sign for plant breeders.

CONCLUSION In the present study, genetic variability existed among different maize genotypes for the various traits. The discrimination of genetic material under normal and water stress conditions on the basis of general combining ability effects suggests that lines DR-177, DR-198, DR-194 and testers Pak Afgoee and EV-6098 can successfully be recommended for hybridization program in future studies and specific combining ability effects indicates that the crosses DR-177 × EV-6098, DR-198 × EV-1098 and DR-198 × EV-6098 are the hybrids with outstanding heterotic performance.

ACKNOWLEDGEMENT The authors acknowledge the management of Maize and Millet Research Institute Sahiwal for providing maize seeds for this study. We are also highly grateful to the management of Fodder Research Institute, Sargodha and Plant Breeding and Genetic Department, University of Agriculture, Faisalabad, Pakistan, for facilitating this research.

REFERENCES

1. Araus, J.L., G. A. Slafer., C. Royo and M. D. Serret 2008. Breeding for

yield potential and stress adaptation in cereals. Critical Reviews in plant Science. 27:377-412.

2. Atkinson, N.J. and P.E. Urwin. 2012 The Interaction of Plant Biotic and Abiotic Stresses: from Genes to the Field. J. of Exp. Bot. 63(10):3523–3544

3. Ashraf, M. 2010. Inducing drought tolerance in plants; recent advances. Biotechnology Advances. 28:169-183.

4. Aslam, M., I.A. Khan, M. Saleem and Z. Ali. 2006. Assessment of water stress tolerance in different Agriculture Water Management. 80:212-214. maize accessions at germination and early growth stage. Pak. J. Bot. 38(5):1571-1579.


J. Agric. Res., 2016, 54(3)

463

5. Banziger, M., G.O. Edmeades, D. Beck and M. Bellon. 2000. Breeding for drought and nitrogen stress tolerance in maize: from theory to practice. D. F: CIMMYT. Mexico

6. Batool, A., I. R. Noorka, M. Afzal and A. H.Syed. 2013. Estimation of heterosis, heterobeltiosis and potence ratio over environments among pre and post green revolution spring wheat. J. Basic Appl. Sci. 9:36-43

7. Blum, A. 2011. Plant breeding for water limited environment. Berlin: Springer.

8. Borrell, A. K., Graeme L. Hammer and R. G. Henzell. 2000. Does maintaining green leaf area in sorghum improve yield under drought? II. Dry matter and yield. Crop Science. 40:1037-1048.

9. Carmo-Silva, A.E., S.J. Powers, A. J. Keys and M.C. Arrabaca. 2008. Photorespiration in C4 grasses remains slow under drought conditions. Plant, Cell and Environment.31:925-940.

10. Chezhian, P., S. Babu and J. Ganesan. 2000. Combining ability studies

in egg plant. Tropical Agric. Res. 12:394-397.

11. Dar,S.H., Rather, A.G., Ahanger, M.A., Sofi, N.R., and Talib, S. (2014)

Gene Action and Combining Ability Studies for yield and component

traits in Rice (Oryza sativa L.): A Review. Journal of Plant and Pest

Science, 1(3):110-127

12. Divan R., S. K. Khorasani, A. Ebrahimi and S. Bakhtiari. 2013. Study on

combing ability and gene effects in inbred lines and single cross hybrids

of forage maize (Zea mays L.). Intl. J. Agron. Plant. Prod. 4 (6):1290-

1297.

13. Edmeades, G.O., J. Bolanos, M. Hernandez and S. Bello. 2003.

Causes for silk delay in low land tropical maize population. Crop

Science. 33, 1029–1035.

14. Falconer D.S. 1960. Introduction of Quantitative Genetics. Ronald

Press Cor., New York, USA.

15. Falconer, D.S. and T. F. C. Mackay. 1996. Introduction to quantitative

Genetics, 4th Edn. Longman Group Ltd.

16. Jebaraj, S., A. Selvakumar and P. Shanthi. 2010. Study of gene action

in maize hybrids. Ind. J. Agri. Res. 44(2):136-40.

17. Joshi, V. N., N. K. Pandiya and R. B. Dubey. 1998. Heterosis and

Combiningability for quality and yield in early maturing single cross

hybrids ofmaize. Ind. J. of Gen. and Pl. Br. 58:519-524.

18. Ghooshchi, F., M. Seilsepour and P. Jafari. 2008. Effect of water stress

on yield and some agronomic traits of maize (SC 301). Amer.-Eur J. of

Agr. and Environ. Sci. 4:302-305.


J. Agric. Res., 2016, 54(3)

464

19. Golparvar R.A. 2013. Genetic control and combining ability of flag leaf area and relative water content traits of bread wheat cultivars under drought stress condition. Genetika, 45(2):351-360

20. Gregersen, P. L. and Holm, P.B. 2007. Transcriptome analysis of senescence in the flag leaf of wheat. J. of Pl. Biotech. 5:192-206.

21. Kempthorne, O. 1957. An Introduction to Genetic Statistics, John Wiley, New York, 458-471.

22. Kenga, R., S. O. Alabi and S. C. Gupta. 2004. Combining ability studies in tropical sorghum (sorghum bicolor L.). Field Crop Research. 88:251-260.

23. Khaliq. I., A. Irshad, and M. Ahsan. 2008. Awns and flag leaf contribution towards grain yield in spring wheat (Triticum aestivum L.). Cereal Research Communication. 36(1):65-76.

24. Kirda, C., S. Topeu, H. Kaman, A. C. Ulger, A.Yazici, M. Cetin and M. R. Derici. 2005. Grain yield response and N-fertilizer recovery of maize under deficit irrigation. Photosynthetica. 19:312-319.

25. Kumar, A., M. G. Gangashetti and N. Kumar. 1998. Gene effects in some metric traits of maize. Ann. of Agri. and Bio. Res. 3:139-143.

26. Marilla, C. F., T. C. Servio, O. R. Valter, V. Clibas and T. M. Siu. 2001 Combining ability for nodulation in common bean (Phaseolus vulgaris L.) genotypes from Andean and middle American gene pools. Euphytica. 118:265-270.

27. Mittler, Ron. 2006. Abiotic stress, the field environment and stress combination. Trends in plant science. 11(1):15-19.

28. Noorka, I. R. and S. Tabasum. 2013. An empirical approach to get the vitality of a genotype to water stress tolerance in yield and yield contributing traits. Amer. J of Pl. sci. 4(5):32128, 5.

29. Passioura, J. B. 1996. Drought and drought tolerance. In: Belhasssene (ed). Drought Tolerance in Higher Plants. Genetical, physiological and molecular biological analysis. Kluwer Academic Publisher, Dordrecht, the Netherlands, 1-7.

30. Petrovic, Z. 1998 Combining abilities and mode of inheritance of yield and yield components in maiz (Zea mays L.). Novi Sad (Yugoslavia).

85(34):1399-1406 31. Perez-Valasquez, J.G., S. Ceballo, S.H. Paindey and C.D.

Amaris.1996. A diallel cross analysis of some quantitative characters in maize. Crop Science. 36:572-578.

32. Sprague, G.F. and L.A. Tatum. 1942. General versus specific combining ability in single crosses of corn. J. Amer. Soci. Agro. 34:923-928.


J. Agric. Res., 2016, 54(3)

465

33. Stone, P. J. and M. E. Nicholas. 1995a. Effect of timing of heat stress during grain filling on two wheat varieties differing in heat tolerance. I Grain growth. Aus. J. of Pl. Phys. 22:927-934.

34. Stone, P.J. and M. E. Nicholas. 1995b. Comparison of sudden heat stress with gradual exposure to high temperature during grain filling in two wheat varieties differing in heat tolerance. I. Grain growth. Aust. J. of Pl. Phys. 22:935-944.

35. Sylvester, B. R., R. K Scott and C.E.Wright. 1990. Physiology in the production and improvement of cereals. Home-Grown Cereals Authority Res. Rev., HGCA, London, 18:205-211.

36. Tambussi, E.A., J. Bort and J.L. Araus. 2007. Water use efficiency in C3 cereals under Mediterranean conditions: a review of physiology aspects. Annals of Applied Biology. 150:307-32.

37. Trostle, R. and R. Seeley. 2013. Developing Countries Dominate World Demand for Agricultural Products. Farm Economy. USDA 2013 Available online at http://www.ers.usda.gov

38. Virmani, S.S. 1994. Heterosis and hybrid rice breeding. Monographs on theoretical and applied genetics. Springer-Verlag. 22:1-38.

39. Wali, M. C., R. M. Kachapur, C. P. Chandrashekhar, V. R. Kulkarni and N. S. B. Devara. 2010. Gene action and combining ability studies in single cross hybrids of maize (Zea mays L.). K J AS. 23:557-562.

40 Zarco, P. E., H. V. A. Gonzalez, P. ta. M. Lopez and S. M. Y. Cristinay. 2005. Physiologcal markers for drought tolerance in maize (Zea mays L.). Agrociencia. 39:517-528.

Received: December 1, 2014 Accepted: August 26, 2015

***

CONTRIBUTION OF AUTHORS:

Taufiqullah : Conducted the research and writeup

Ijaz Rasool Noorka : Guided and supervised the research

http://www.ers.usda.gov/ers-staff-directory/ronald-trostle.aspx




http://www.ers.usda.gov/ers-staff-directory/ralph-seeley.aspx

http://www.ers.usda.gov/

Documents

COMBINING ABILITY ESTIMATES OF MAIZE (ZEA MAIZE) …