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

Euphytica - Tập 122 Số 3 - Trang 491-502 - 2001
Tin, H.Q.1, Berg, T.2, Bjørnstad, Å3
1Department of Biodiversity Conservation, Farming Systems Research and Development Institute, Cantho University, Vietnam
2Center of International Environment and Development Studies (Noragric), Agricultural University of Norway, Norway
3Department of Horticulture and Plant Science, Agricultural University of Norway, Norway

Tóm tắt

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.

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Tài liệu tham khảo

citation_journal_title=J Hered; citation_title=Genetic change associated with the evolution of adaptedness in cultivated plantsand their wild progenitors; citation_author=R.W. Allard; citation_volume=79; citation_publication_date=1988; citation_pages=225-238; citation_id=CR1

citation_journal_title=J Hered; citation_title=The genetics of host-pathogencoevolution: Implications for genetic resource conservation; citation_author=R.W. Allard; citation_volume=81; citation_publication_date=1990; citation_pages=1-6; citation_id=CR2

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.

citation_title=Genetic conservation:a role for rice farmers; citation_inbook_title=Plant Conservation: the Approach; citation_publication_date=1997; citation_pages=263-289; citation_id=CR4; citation_author=M.R. Bellon; citation_author=J.L. Pham; citation_author=M.T. Jackson; citation_publisher=Chapmann and Hall

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.

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.

citation_journal_title=Crop Sci; citation_title=In situ conservation of landraces in centers ofcrop diversity; citation_author=S.B. Brush; citation_volume=35; citation_publication_date=1995; citation_pages=346-354; citation_doi=10.2135/cropsci1995.0011183X003500020009x; citation_id=CR7

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.

citation_title=The state of the world's plant genetic resources for food and agriculture; citation_publication_date=1998; citation_id=CR9; citation_publisher=FAO

citation_journal_title=Tanzania's forgotten farmers. Seedling; citation_author=E. Friis-Hansen; citation_volume=16; citation_publication_date=1999; citation_pages=4; citation_id=CR10

citation_title=Electrophoretic variation of isozymes of plumules of rice ( L.); citation_inbook_title=A key to the identification of 76 alleles at 24 loci; citation_publication_date=1988; citation_id=CR11; citation_author=J.C. Glaszmann; citation_author=B.G. de los Reyes; citation_author=null Kush; citation_publisher=IRRI

IRRI, 1988. Standardevaluation systems for rice. 3rd ed.

citation_journal_title=Euphytica; citation_title=Conservation and diversity in bulkpopulations of barley; citation_author=S. Jana, B.S. Khangura; citation_volume=35; citation_publication_date=1986; citation_pages=761-776; citation_doi=10.1007/BF00028584; citation_id=CR13

citation_journal_title=Nature Biotech; citation_title=Improving plant drought, salt and freezing tolerance by gene transfer of a single stress-inducible transcription factor; citation_author=M. Kasuga, Q. Liu, S. Miura, K. Yamaguchi-Shinozaki, K. Shinozaki; citation_volume=17; citation_publication_date=1999; citation_pages=287-291; citation_doi=10.1038/7036; citation_id=CR14

citation_journal_title=Genet Sel Evol; citation_title=Dynamic conservation of variability: Responses of wheat populations to different selective forces including powdery mildew; citation_author=V. Le Boulc'h, J.L. David, P. Brabant, C. de Vallavieille-Pope; citation_volume=26; citation_issue=suppl.1; citation_publication_date=1994; citation_pages=221-240; citation_id=CR15

citation_title=Practicalisozyme genetics; citation_publication_date=1988; citation_id=CR16; citation_author=N. Pasteur; citation_author=G. Pasteur; citation_publisher=Ellis Horwood Limited, Publisher Chichester, Halsted Press: A division of JOHN WILEY & SONS

citation_journal_title=Economic Bot; citation_title=Morphological andphenological comparisons of two hopi maize varieties conserved in situ and ex situ ; citation_author=D. Soleri, S.E. Smith; citation_volume=49; citation_issue=1; citation_publication_date=1995; citation_pages=56-77; citation_id=CR17

citation_journal_title=Crop Sci; citation_title=Grain yield of composite cross populations of barley: Effects of naturalselection; citation_author=K.M. Suliman, R.W. Allard; citation_volume=31; citation_publication_date=1991; citation_pages=705-708; citation_doi=10.2135/cropsci1991.0011183X003100030032x; citation_id=CR18

Suneson, C.A., 1956. An evolutionary plant breeding method. AgronJ: 188–191.

Swofford, D.L. & R.B. Selander, 1989. BIOSYS-1, version 1.7. A programme packagereleased by the University of Illinois, Urbana, USA.

citation_journal_title=Economic Bot; citation_title=In situ conservation of ricegenetic resources; citation_author=D.A. Vaughan, T.T. Chang; citation_volume=46; citation_issue=4; citation_publication_date=1992; citation_pages=368-383; citation_id=CR21

citation_title=Evolution and the Genetics ofPopulations; citation_publication_date=1978; citation_id=CR22; citation_author=S. Wright; citation_publisher=University of Chicago Press

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Euphytica

Tập 122 Số 3

491-502

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