African Crop Science Journal African Crop Science Society ISSN: 1021-9730 EISSN: 2072-6589 Vol. 4, Num. 4, 1996, pp. 497-501

SHORT COMMUNICATION

Heterotic patterns of some intermediate maturing Maize germplasm

MOSISA WORKU, LEGESSE WOLDE, BENTI TOLESSA, KEBEDE MULATU and LETA TULU^1

^1 National Maize Research Programme, Bako Research Centre, P.O. Box 3, West Shoa, Ethiopia

(Received 24 July, 1996; accepted 18 November, 1996)

Code Number: CS96092
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ABSTRACT

A comprehensive hybrid breeding system requires two diverse populations. The source germplasm of the parents of the intermediate maturing hybrids of Ethiopia are genetically divergent, but they are narrow for further improvement. This study was undertaken to synthesise a pair of intermediate maturing broad based heterotic pools and to identify superior heterotic combinations for direct use in the hybrid programme. Germplasm from East Africa and CIMMYT populations were used in the study. Parents of BH-140, i.e., Gutto LMS-5 and SC-22, were used as testers. The trial was organised and tested in a randomised complete block design at Bako, Awassa, Jimma and Arsi-Negele in 1994. General combining ability (GCA) and specific combining ability (SCA) effects for grain yield were calculated according to the Line x Tester analysis. A number of crosses outyielded BH-140, and significant differences were observed for the effects of SCA. The CIMMYT populations had better heterosis with SC-22 than with Gutto LMS-5. Based on the cross data the maize germplasm were grouped into a pair of heterotic pools. These pools may serve as source germplasm for the development of intermediate maturing maize varieties for the medium altitude areas of East Africa with sufficient rainfall.

Key Words: Combining ability, heterotic pattern, maize, Zea mays L.

RESUME

Une reproduction complete du systeme des hybrides exige deux diverses populations. La source du germoplasme des parents des hybrides intermediaires en maturite sont genetiquement divergents en Ethiopie, mais ils sont limites aux ameliorations ulterieures. Cette etude a ete initiee pour synthetiser une paire des especes heterotiques intemediaires et identifier les combinaisons des heterotiques superieurs pour l'usage immediat dans le programme des hybrides. Le germoplasme d'origine de l'Afrique de l'Est et les populations CIMMYT etaient utilises dans la recherche. Les parents du BH-140, comme Gutto LMS5 et SC-22, etaient utilizes comme agents testeurs. L'essai etait organise et teste au hasard dans le bloc a Bako, Awasa, Jimma et Arsi-Negela en 1994. La capacite generaie d'associer (General Combining ability: GCA) les effets des rendements des graines etaient calcules d'apres la ligne X du Testeur d'analyse. Un certain nombre de BH-140 ou rendement a ete enregistre, et l'on a constate de differences remarquables quant aux effets du SCA. Les populations du CIMMYT avaient de meilleurs heterogenes associes aux SC-22 par rapport au Gutto LMS-5. Base sur les donnees de croisement du germoplasme du mais, on les a groupe dans une source des heterotiques. Ces etangs ou sources peuvent servir comme source de germoplasme pour le developpement des varietes intermediaires du mais a l'etape de maturite pour les terrains d'une altitude moyenne en Afrique de l'Est avec une abondance de pluie.

Mots Cles: Asocier la capacite, echantillon heterotique, le mais, Zea mays L.

INTRODUCTION

The parents of the local commercial maize hybrids from Ethiopia were extracted from narrow based germplasm. Parents of BH-660 are based on genetically divergent populations, KS-II and EC573. In Kenya a large amount of heterosis was obtained with these two populations (Darrah et al., 1978; Ristanovic, 1988; Eberhart, 1989). In Ethiopia the hybrids developed from these populations are high yielders but they are late maturing. Intermediate maize varieties are necessary for the medium altitude areas of Ethiopia with sufficient rainfall, but no diverse source germplasm are available for the breeding programme. The source of the parents of intermediate maturing hybrid BH-140, SC-5522 of East African origin and Gutto, which was derived from Tuxpeno- 1 C 18, are too narrow for further improvement. BH- 140 involves an inbred line, SC-22 which was derived from contaminated SC-5522 and a highly selected medium maturing population, Gutto LMS-5 (Benti et al., 1993).

A comprehensive hybrid breeding system requires the development of two diverse breeding populations (Eberhart, 1989). The experience of the CIMMYT hybrid maize programme also shows the importance of developing two diverse populations for hybrid maize programme (Vassal et al., 1992a, b). Benti et al. (1990) made a diallel cross among eight locally adapted maize composites of Ethiopia and found that heterosis of the crosses was too low to justify the formation of heterotic group.

In the National Maize Research Programme of Ethiopia, diverse populations with identified heterotic patterns are necessary for further progress. Thus the objectives of this study were to synthesise a pair of intermediate maturing heterotic pools and identify superior heterotic combinations for direct use in the hybrid programme.

MATERIALS AND METHODS

Fourteen inbred lines developed from different sources and seven non-inbred populations were used for this study. The non-inbred germplasm include the locally adapted populations and some CIMMYT populations. The early populations, Katumani and Alamura white, were also included in this study. Parents of BH-140, i.e.,Gutto LMS5 and SC-22, were used as testers. BH-140 and an open pollinated variety, Beletech, were included as checks for yield comparison.

The crosses were made in 1993 at Bako Research Centre. The trial was organised and tested at four locations in 1994. The test locations were Bako (1650 masl), Jimma (1700 masl), Awassa (1700 masl) and Arsi-negele ( 1800 masl). The trial was planted with three replications in a randomised complete block design. The plot consisted of two 3m long rows spaced 75 cm apart. The spacing within the row was 30 cm. Data were recorded for grain yield and other agronomic traits.

In order to group the maize germplasm (MG) into two heterotic pools, grain yield data were used for the analysis of variance. Analysis of variance for each location and combined analysis were computed, but the checks were not included in the analyses. General combining ability (GCA) and specific combining ability (SCA) effects for grain yield were calculated according to the Line x Tester analysis (Singh and Chaudhary, 1979). Based on the cross data, the germplasm was grouped into two heterotic groups. Selected progenies were used in a diallel cross in 1996.

RESULT AND DISCUSSION

Combined analysis of variance across locations for grain yield is presented in Table 1. The effect of maize germplasm and the difference between the testers were significant (P<0.01). Significant SCA effects were also observed for the crosses.

TABLE 1. Combined analysis of variance for grain yield for some intermediate maturing maize germplasm

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Source of variation     df       MS
-----------------------------------------
Location (Loc.)          3    20990.680** 
Rep/Loc.                 8      469.889 
Maize germplasm (MG)    20      851.199** 
Testers                  1     1973.203** 
MG x Tester             20      158.447** 
MG x Loc.               60      406.980** 
Tester x Loc.            3      520.837** 
MG x Tester x Loc.      60       55.249 
Pooled error           328      116.435
------------------------------------------
CV %                             14.5
------------------------------------------
** Significant at 0.01 level of probability.
-------------------------------------------

The mean grain yield across locations ranged from 59.9 quintals (q) ha^-1 to 102.5 q ha^-1. A number of crosses outyielded the checks. The best cross outyielded BH-140 by 25.3% and Beletech by 51.9%. Eleven germplasm had positive GCA effects and six germplasm had significant positive GCA effects (Table 2).

TABLE 2. Mean grain yield (q ha-1), general combining ability (GCA) and specific combining ability (SCA) for intermediate maturing maize germplasm (MG) x Tester crosses tested at four locations of Ethiopia

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Maize       Yield    GCA   Gutto LMS-5        SC-22      Source    Status
progeny                    ------------    ------------
                           Yield   SCA    Yield    SCA
---------------------------------------------------------------------------
1. A-7025   69.7  -2.392*  67.7   0.470   71.7   -0.476  East Africa Inbred
2. A-7016   83.7   2.279*  85.0   1.571   82.4   -1.569  East Africa Inbred
3. A-7032   77.4   0.179   78.1   1.374   76.7   -1.373  East Africa Inbred
4. A-7033   77.1   0.094   76.1   0.799   78.1   -0.798  East Africa Inbred
5. F-7215   73.1  -1.242   67.0  -0.881   79.2    0.881  East Africa Inbred
6. A-7024   82.7   1.925   69.5  -3.241*  95.8    3.243* East Africa Inbred
7. F-7237   63.9  -4.312*  62.7   0.733   65.1   -0.731  East Africa Inbred
8. D-7690   67.0  -3.266*  63.0  -0.188   71.0    0.188  East Africa Inbred
9. NSCM41                                                
  1924(75)  66.6  -3.409*  71.1   2.654   62.1   -2.653  East Africa Inbred
10.NSCM41                                                
  1873(24)  78.3   0.490   75.2   0.121   81.4   -0.120  East Africa Inbred
11.D-7625   83.8   2.323*  80.5   0.048   87.1   -0.047  East Africa Inbred
12.143-5-i  92.1   5.070*  86.8  -0.621   97.3    0.622  East Africa Inbred
13.A-511    72.2  -1.563   71.6   0.955   72.7   -0.953  East Africa Populn
14.121-a    87.5   3.568*  85.2   0.380   89.8   -0.379  East Africa Inbred
15.POP-29   84.3   2.477*  71.4  -3.145*  97.1    3.145* CIMMYT  Population
16.Pozanca  73.3  -1.196   69.8  -0.014   76.7    0.015  CIMMYT  Population
17.AW-8047  70.0  -2.269*  66.1  -0.158   73.9    0.159  East Africa Populn
18.PO P-43  83.3   2.124   72.0  -2.606   94.5    2.607  CIMMYT  Population
19.Katumani 60.9  -5.320** 59.9   0.805   61.9   -0.805  East Africa Populn
20.136-d   102.2   8.441**101.9   1.044  102.5   -1.042  East Africa Inbred
21.Alamura                                
  white     64.8  -4.008*  61.1   0.091   68.5    0.091  East Africa Populn
---------------------------------------------------------------------------
MEAN        76.9  73.4     80.3
---------------------------------------------------------------------------
checks: 
  BH-140    81.8 
Beletech    67.5

Inbred = Inbred Line
Popln = Population
*, ** Significant at 0.05 and 0.01 levels of probability, respectively.
---------------------------------------------------------------------------

Significant positive SCA effect was recorded from the crosses of both non-inbred maize germplasm and inbred lines (Table 2). The non-inbred germplasm, Pop-29 had significant positive SCA effect when crossed with SC-22. Significant positive SCA effect was also recorded from the inbred cross, A-7024 X SC-22. The CIMMYT populations, Pop-29, Pop-43 and Pozarica had better heterosis with SC-22 than with Gutto LMS-5. Crosses of Katumani and Alamura white with both testers were low yielders.

The result obtained in this study provided information on the heterotic patterns of some intermediate maturing maize germplasm available at Bako Research Centre. Six selected maize germplasm which had positive SCA effect with SC-22 and negative SCA effect with Gutto LMS5 were grouped with Gutto LMS-5 whereas seven selected maize germplasm which had positive SCA effect with Gutto LMS-5 and negative SCA effect with SC-22 were grouped with S&22. Each group was recombined through diallel cross in 1996. Germplasm A-7033, A-7024, F-7237, D-7625, 143-5-i, 136-d, Katumani and Alamura white were not included in the formation of the pools. Crosses of A-7024 143-5-i and 136-d had high yield potential. However, A-7024 was susceptible to leaf disease while 143 - 5-i and 136-d were susceptible to root lodging (data not shown).

The preliminary information obtained is useful for maize research, and the source germplasm from which the parents of BH-140 were derived can be made more diversified by introgressing the selected maize materials used in this study into them. These heterotic pools may also serve as source germplasm for the development of intermediate maturing maize varieties for the medium altitude areas of East Africa with sufficient rainfall. But recurrent selection should be practised for each of the pools to increase the cross performance. The recurrent selection in KS-II and EC-573 in Kenya improved the cross performance of the two populations (Ochieng et al., 1989). In this study only combining ability for grain yield was considered for grouping the maize germplasm. In future, seed texture should also be considered. Although both inbred and non-inbred progenitors could be used to form new heterotic groups, germplasm developed from inbred progenitors will probably show a higher level of tolerance to inbreeding depression and would result in a higher frequency of superior inbred lines (Vassal et al., 1992). Thus other heterotic pools could also be formed from lines developed from these pools and other germplasm.

ACKNOWLEDGEMENT

The authors wish to thank the late Dr. Joginder Singh and National Maize Research Improvement staff for assisting in designing, organising and conducting the trial.

REFERENCES

Benti Tolessa, Kebede Mulatu, Legesse Wolde and Gezahegne Bogale. 1990. Heterosis and genetic diversity in crosses of adapted maize composites. Ethiopian Journal of Agricultural Science 12:1-8.

Benti Tolessa, Tesew Gobezayehu, MOSISA WORKU, Yigizw Desaeegne, Kebede Mulatu and Gezahhgne Bogale. 1993. Genetic improvement of maize in Ethiopia: A Review. In: Proceedings of the First National Maize Workshop of Ethiopia. Benti Tolessa and Ransom, J.K. (Eds.), pp. 13-21.5-7 May 1992, Addis Abeba, Ethiopia.

Darrah, L.L., Ebrehart, S.A. and Penny, L.H. 1978. Six years of maize selection in Kitale Synthetic II, Ecuador 573 and Kitale Composite A using methods of comprehensive breeding system. Euphytica 27: 191204.

Eberhart, S.A. 1989. A comprehensive breeding system for developing improved maize hybrids. In: Maize Improvement, Production and Protection in Eastern and Southern Africa. Proceedings of the Third Eastern and Southern Africa Maize Workshop. Birhane G/Kidan (Ed.), pp. 8-31.18-22 Sep. 1989. Nairobi, Kenya.

Ochieng, J.A.W., Mthoka, D.K. and Kamidi, R.E. 1989. Effect of selection for yield on major agronomic traits in the variety cross Kitale Synthetic II x Ecuador 573 over nine cycles of Reciprocal Recurrent Selection. In: Maize Improvement, Production and Protection in Eastern and Southern Africa. Proceedings of the Third Eastern and Southern Africa Maize Workshop. Birhane G/Kidan (Ed.), pp. 8-31. 18-22 Sep. 1989. Nairobi, Kenya.

Ristanovic, D. 1988. Maize breeding for subtropical and tropical environments. In: Maize Breeding and Production, Euromaize'88, pp. 103-118. Proceedings of a Workshop, 6-8 Oct. 1988, Belgrade.

Singh, R.K. and Chaudhary, B.D. 1979. Biometrical Methods in Quantitative Genetic Analysis. Kalyani Publishers. New Delhi, pp. 191-200.

Vassal, S.K., Srinivasan, G., Han, G.C. and Gonzalez, C. 1992a. Heterotic patterns of eighty-eight white sub-tropical CIMMYT maize lines. Maydica 37:319-327.

Vassal, S.K., Sirnivan, G., Pandey, S., Cordova, H.S., Han, G.C. and Gonzalez, C. 1992b. Heterotic patterns of ninety-two white tropical CIMMYT Maize Lines. Maydica 37:259-270.

Copyright 1996 The African Crop Science Society