Euphytica

, Volume 122, Issue 3, pp 491–502

Diversity and adaptation in rice varieties under static (ex situ) and dynamic (in situ) management

  • H.Q. Tin
  • T. Berg
  • Å Bjørnstad
Article

Abstract

This study compares genebank-conserved and farmer managed populations of the same farmers' varieties of rice. Seven varieties that had been collected twice, in the early 1980s and in 1991, were recollected in 1997 after having been grown continuously in farmers' fields. Since the first genebank collection, rice cultivation in the Meking delta has been intensified with a rather abrupt switch from single to double cropping, more use of chemical fertilisers, improved water management, and more market oriented production. Many farmers' varieties have been maintained as a second crop but with a considerably delayed planting time compared to previous practice. In this experiment, the ex situ materials represent adaptation to pre-intensification conditions while the in situ populations have been exposed to the intensive production system for a number of years. The materials were tested in the wet season of 1997 under current farmers' management practices in an on-farm field experiment within the area where the varieties originated. Agronomic, stress resistance and morphological traits and variation at 7 isozyme loci were observed in the field or laboratory. Analysis of variance (ANOVA) and Principal Component Analyses (PCA) were used to study differences in agronomic and morphological traits between ex and in situ populations. Isozyme variation was analyzed by Nei's diversity indices and Wright's F-statistics. Farmer-managed populations showed a general trend of later flowering and maturity time, more uniformity of grain quality, lower frequency of undesired off-types, and reduced drought stress tolerance compared with corresponding ex situ populations. There were no significant differences in grain yield or tolerance to biotic stresses. Allelic frequencies of isozymes showed no consistent differences that could be related to changes of the farming system. These results are interpreted as an adaptation to the changed farming system and include natural and farmers' selection for maturity time (all varieties are photoperiodic)and market standards. The poorer drought tolerance may reflect the fact that such stress was common before intensification but is not normally a factor under the current water management regime. For in situconservation strategies this case sheds some light on the survival of allelic diversity vs. adaptedness. Isozyme data indicate maintenance of allelic diversity. Adaptedness, however, is at risk under on-farm conservation. Natural and intentional selection will normally not remain constant over time. Consequent genetic changes include loss of adaptation to past conditions and building up of adaptation to new. In this case such changes have happened surprisingly fast. However, changes are limited to adaptation to factors of the environment and to market-relevant quality traits. Yield seems to be unaffected. Considering needs for crop improvement this case has kept the materials `updated' with respect to adaptation and unchanged with respect to yield potential.

adaptation Convention on Biological Diversity in situ management of genetic resources isozymes rice 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Allard, R.W., 1988. Genetic change associated with the evolution of adaptedness in cultivated plantsand their wild progenitors. J Hered 79: 225–238.PubMedGoogle Scholar
  2. Allard, R.W., 1990. The genetics of host-pathogencoevolution: Implications for genetic resource conservation. J Hered 81: 1–6.PubMedGoogle Scholar
  3. Bellon, M.R., 1997. On-farmconservation as a process: An analysis of its components. In: Sperling, L. & M. Loevinsohn (Eds.), Using Diversity, Enhancing and Maintaining Genetic Resources On-Farm. Proc of a workshop held on 19–21 June 1995, New Delhi, India. International Development Research Center.Google Scholar
  4. Bellon, M.R., J.L. Pham & M.T. Jackson, 1997. Genetic conservation:a role for rice farmers. In: N. Maxted, B.V. Ford-Lloyd & J.G. Hawkes (Eds.), Plant Conservation: the in situ Approach, pp. 263–289. Chapmann and Hall, London.Google Scholar
  5. Brown, A.H.D., 2000. The genetic structure of crop landraces andthe challenge to conserve them in situ on farms. In: S.B. Brush (Ed.), GENES in the FIELD. On-Farm Conservation of Crop Diversity, Chapter 2, pp. 19–48. Lewis Publishers, IDRC and IPGRI.Google Scholar
  6. Brown, A.H.D. & D.R. Marshall, 1995. Abasic sampling strategy: Theory and practice. In: L. Guarino, V. Ramanatha & R. Reid (Eds.), Collecting Plant Genetic Diversity, ppl. 75–91. Cabi, Technical Guidelines.Google Scholar
  7. Brush, S.B., 1995. In situ conservation of landraces in centers ofcrop diversity. Crop Sci 35: 346–354.CrossRefGoogle Scholar
  8. Dempsey, G.J., 1996. In Situ Conservation of Crops and TheirRelatives: A Review of Current Status and Prospects for Wheat and Maize. CIMMYT, Natural Resource Group, Paper 96–08.Google Scholar
  9. FAO, 1998. The state of the world's plant genetic resources for food and agriculture. FAO, Rome.Google Scholar
  10. Friis-Hansen, E., 1999. Tanzania's forgotten farmers. Seedling, 16, 4 December 1999.Google Scholar
  11. Glaszmann, J.C., B.G. de los Reyes & Kush, 1988. Electrophoretic variation of isozymes of plumules of rice (Oryza sativa L.). A key to the identification of 76 alleles at 24 loci. IRRI, Los Banos, Laguna, Philippines.Google Scholar
  12. IRRI, 1988. Standardevaluation systems for rice. 3rd ed.Google Scholar
  13. Jana, S. & B.S. Khangura, 1986. Conservation and diversity in bulkpopulations of barley. Euphytica 35: 761–776.CrossRefGoogle Scholar
  14. Kasuga, M., Q. Liu, S. Miura, K. Yamaguchi-Shinozaki & K. Shinozaki, 1999. Improving plant drought, salt and freezing tolerance by gene transfer of a single stress-inducible transcription factor. Nature Biotech 17: 287–291.CrossRefGoogle Scholar
  15. Le Boulc'h, V., J.L. David, P. Brabant & C. de Vallavieille-Pope, 1994. Dynamic conservation of variability: Responses of wheat populations to different selective forces including powdery mildew. Genet Sel Evol 26(suppl. 1): 221–240.Google Scholar
  16. Pasteur, N. & G. Pasteur, 1988. Practicalisozyme genetics. Ellis Horwood Limited, Publisher Chichester, Halsted Press: A division of JOHN WILEY & SONS, New York - Chichester - Brisbane - Toronto, pp. 62–163.Google Scholar
  17. Soleri, D. & S.E. Smith, 1995. Morphological andphenological comparisons of two hopi maize varieties conserved in situ and ex situ. Economic Bot 49(1): 56–77.Google Scholar
  18. Suliman, K.M. & R.W. Allard, 1991. Grain yield of composite cross populations of barley: Effects of naturalselection. Crop Sci 31: 705–708.CrossRefGoogle Scholar
  19. Suneson, C.A., 1956. An evolutionary plant breeding method. AgronJ: 188–191.Google Scholar
  20. Swofford, D.L. & R.B. Selander, 1989. BIOSYS-1, version 1.7. A programme packagereleased by the University of Illinois, Urbana, USA.Google Scholar
  21. Vaughan, D.A. & T.T. Chang, 1992. In situ conservation of ricegenetic resources. Economic Bot 46(4): 368–383.Google Scholar
  22. Wright, S., 1978. Evolution and the Genetics ofPopulations. University of Chicago Press, Chicago.Google Scholar

Copyright information

© Kluwer Academic Publishers 2001

Authors and Affiliations

  • H.Q. Tin
    • 1
  • T. Berg
    • 2
  • Å Bjørnstad
    • 3
  1. 1.Department of Biodiversity Conservation, Farming Systems Research and Development InstituteCantho UniversityVietnam
  2. 2.Center of International Environment and Development Studies (Noragric)Agricultural University of NorwayNorway
  3. 3.Department of Horticulture and Plant ScienceAgricultural University of NorwayNorway

Personalised recommendations