Chapter 4: Heterotic Classification and Combining Ability of Local and Exotic Medium
4.5 Conclusions
4.4.4 Heterotic grouping based on SCA
Basing on SCA data and significance from zero (p < 0.05), collections were also classified into four heterotic groups in the medium and highland. In this case, nine accessions were classified to belong to Pool A, ten to Pool B, 12 to KSII and 11 to EC 573
In comparison between classifications using SCA and percentage heterosis, Pool B and KSII had almost the same accessions being grouped similarly by both methods. Pool B had only one accession, Murumba, that was classified by SCA to belong to Pool B but percent heterosis classified it as not belonging to Pool B. Kitale synthetic II had three accessions only being classified differently by both methods. Pool A and EC 573 had more variations in their classification of the accessions compared to Pool B and KSII.
Pool A had five while EC 573 had seven accessions being classified differently. Although SCA and percentage heterosis classification slightly varied, in overall they classified most accessions similarly. Therefore the two methods can effectively be used separately but it is better to compare the two for verification.
In this study the overall classification depended on percentage yield heterosis as this was the primary factor for classification since SCA data did not capture all the crosses that were made. In cases where all data is captured then it is better to compare the two methods.
Table 4.5.1: Identified heterotic groups of collections Heterotic groups
Pool A Pool B KSII EC 573
Sipindi Bunyore LR 385 Sipindi LR 1/99 Mwala Cheborosinik LR 585 LR 306 B LR 43
No. 8 LR 1/99 LR 9 A LR 43 Maragoli
Illonga composite LR 43 LR 42 Murumba Murumba Chiapas LR 585 Costorica Mwala LR 301 Tuxpeno MASR 9A Illonga comp. LR 40, LR 301A R12 S
V 37 Mwala MSR 9A Embu Pool B
Randago V37 Costorica
LR 29 Kawanda D. Ear
Taiwan, Chitdze
These populations and collections are highly heterotic to each other in terms of yield, GLS and PLS in the right direction with significant from zero (p<0.05) positive and negative heterosis for yield and the two diseases, respectively. Resistant and high yielding hybrids can be developed from these populations and collections. In line with this the following testcrosses with high yields and resistant to GLS and PLS were identified; Embu 12 x Pool A, Taiwan x Pool A, Chalco x Pool B, Embu Pool B x KSII and Cheborosinik x EC 573. These crosses are recommended for further evaluation on- farm. Very high variations in GLS and PLS resistance were observed in these collections, on average with scores less than 2. Collections Embu 12, Taiwan and Cheborosinik have been recommended for infusion in these populations to improve GLS and PLS resistance.
Both GCA and SCA effects were significant indicating the importance of additive and non-additive gene actions, making recurrent selection methods useful in improvement of traits in these populations. Specific combining ability, accounted for more than 50% of the total variations in GLS, PLS, yield and less than 50% in days to 50% silk and anthesis and in ear height. This implied that there is high heterosis between collections and populations. Development of top cross hybrids for on-farm evaluation and inbred lines for hybrid development is recommended.
High heterosis among collections and populations for GLS, PLS, yield, ear height, days to 50% silk and anthesis was observed, implying there is wide scope for broadening the genetic base of these populations. The high variations also implied that more cycles of selection can be made in these populations by infusing local collections that are better adapted with identified desirable traits. High heterosis present in these populations should be exploited to develop top cross hybrids. More collections in the future should be pursued to capture more favourable traits present in this germplasm to improve individual populations as the study established that collections belonged to distinct heterotic groups.
Reference
Anderson, B.M. 1995. Gray leaf spot resistance- why do we need it? How do we get it?
p. 186-94. In Proceedings of the 31st Illinois Corn Breeders School, University of Illinois at Urbana-Champaign, Illinois, USA..
Betran, F.J., J.M. Ribaut, D. Beck, and D. Gonzalez de Leon. 2003. Genetic diversity, specific combining ability, and heterosis in tropical maize under stress and non stress environments. Crop Science 43:797–806.
Bubeck, D.M., M.M. Goodman, W.D. Beavis, and D. Grant. 1993. Quantitative trait loci controlling resistance to gray leaf spot in maize. Crop Science 33:838-847.
CIMMYT. 2001. Maize inbred lines released by CIMMYT. A compilation of 454 CIMMYT maize lines (CMLs), CML1 – CML454. August 2001. 2nd draft. CIMMYT, Mexico. D.F.
Coates, S.T., and D.G. White. 1994. Sources of resistance to gray leaf spot of corn. Plant Disease 78:1153-5.
Derera, J. 2005. Genetic effects and associations between grain yield potential, stress tolerance and yield stability in Southern African Maize (Zea Mays L.) base germplasm p 60-105. PhD. Thesis. University of Kwa Zulu Natal, South Africa.
Elwinger, G.F., M.W. Johnson, R.R.Jr. Hill, and J.E. Ayers. 1990. Inheritance of resistance to gray leaf spot of corn. Crop Science 30:350-358.
Enoki H., H.Sato, K. Koinuma. 2002 SSR analysis of genetic diversity among maize inbred lines adapted to cold regions of Japan. Theoretical Applied Genetics 104:1270-1277.
Gevers, H.O., and J.K. Lake. 1994. GLS1- a major gene for resistance to gray leaf spot in maize. South African Journal Sciences 90:377-380.
Hallauer, A.R., and J.B. Miranda. 1988. Quantitative genetics in maize breeding. Iowa State University. Press, Ames.
KARI annual report. 2004. Cereals Maize breeding
LI, Y., Y. Shi, Y. Song, J. Du, R. Tuberosa, T. Wang. 2004. Analysis of genetic diversity in maize inbred lines based on AFLP markers. Maydica 49:89.
Manoel, X.dos.S., L.M. Pollak, H.W.L. de Carvalho, C.A.P. Pacheco, E.E.G. e Gama, P.
E. de Oliveira Guimarães, and R.V. de Andrade. 2001. Heterotic responses of tropical elite maize accessions from Latin America with Brazilian testers.
Scientia Agricola 58:767-775.
McCouway, K., M.C. Jones, and P.C. Taylor. 1999. Statistical modelling using using Genstat. London, U.K.
Menkir, A., and M. Ayodele. 2005. Genetic analysis of resistance to gray leaf spot of mid-altitude maize inbred lines. Crop Science 45:163-170.
Mickelson, H.R., H. Cordova, K.V. Pixley, and M.S. Bjarnson. 2001. Heterotic relationships among nine temperate and subtropical maize populations. Crop Science 41:1012-1020.
Moreno-Gonza´ lez, J. 1988. Diallel crossing system in sets of flint and germplasm.
Theoretical Applied Genetics 73:445–450. Dent inbred lines of maize (Zea mays L.). Maydica 33:37–49.
Orda’s. A. 1991. Heterosis in crosses between American and Spanish populations of corn. Crop Science 30:1182–1190.
Pilar, S., B. Orda´s, R.A. Malvar, P. Revilla, and A. Orda´s. 2003. Heterotic Patterns among Flint Maize Populations . Crop Science 43:844–849.
Pilar, S., B. Orda´s, R.A. Malvar, P. Revilla, and A. Orda´s. 2006. Combining abilities and heterosis for adaptation in flint maize populations. Crop Sci. 46:2666-2669.
Reif, J.C., A.R. Hallauer, and A.E. Melchinger. 2005. Heterosis and heterotic patterns in maize. Maydica 50:215-223.
Payne, R.W., D.A. Murray, S.A. Harding, D.B Baird, and D.M. Souter. 2006. GenStat for Windows (9th edition) introduction. VSN International, Hemel, Hempstead.
Saghai Maroof, M.A., Y.G. Zue, Z.X. Xiang, E.L. Stromberg, and G.K. Rufener. 1996.
Identification of quantitative trait loci controlling gray leaf spot disease in maize.
Theoretical Applied Genetics 93:539-46.
Singh, R.K., and B.D. Chandahany. 1977. Biometrical methods in quantitative genetic analysis, New Delhi. India.
Silva, H.P., and J.S. Moro. 2004. Diallel analysis of maize resistance to Phaeosphaeria maydis. Science Agriculture. (Piracicaba, Brazil), 61:36-42.
Ulrich, J.F., J.A. Hawk and R.B. Carroll. 1990. Diallel analysis of maize inbreds for resistance to gray leaf spot. Crop Science 30:1198-1200.
Vivek, B., K. Pixley, O. Odongo, J. Njuguna, J. Imanywoha, G. Bigirwa, and A. Diallo.
2001. Regional disease nursery (REGNUR): A unique opportunity for developing multiple-disease resistant maize. p. 66-68. In Proceedings of 7th Eastern and South African Regional Maize Conference, Addis Ababa. 11th – 15th February 2001.,Ethiopia.
Welcker, C.T., B. Andre´au, C. De Leon, S.N. Parentoni, J. Bernal, J. Fe´licite ,C.
Zonkeng, F. Salazar, L. Narro, A. Charcosset, and W.J. Horst. 2005. Heterosis and combining ability for maize adaptation to topical acid soils: Implications for future breeding strategies. Crop Science 45:2405–2413.