Owuor, E.D.,1 Kimani, P.M,2 Mendlinger, S., 3 Chweya, J., 2 and Olsvig-Whittaker, L. 4
1 - Current contact, Institute of Evolution, University
of Haifa, Mt. Carmel, 31905 HAIFA, Israel, email: dedward@research.haifa.ac.il
2 - Department of Crop Science, University of Nairobi, CAVS
POB. 29053, Nairobi, Kenya
3 - Institutes for Applied Research, Ben-Gurion University of
the Negev, 1025 Beer Sheva, 84110 Israel
4 - Current contact, Israel Nature Reserve Authority, Jerusalem,
Israel.
In order to assess the extent and structure of genetic variation in wild barley, several quantitative traits were studied in 385 individual plants, representing six and seven populations of Hordeum spontaneum from Turkmenistan and Israel respectively. The populations were sampled from Jericho, Yeruham, Sde Boqer, Yavne, Ein Yochean, Dead Sea, Dimona, in Israel and Canal, Commune, Cemetery, 35Km NW, L. Ruderal in Turkmenistan. The quantitative trait measurements were taken over both the vegetative and reproductive periods of plant growth and development. A parallel allozymic study was realized through the analysis of seventeen loci in three buffer systems, Tris borate, Tris malate and Poulik. Through nested (hierarchical) analysis of variance, the variability in quantitative and allozyme phenotypes were apportioned into the respective contributing fractions.
The quantitative trait measures presented a higher intra-populational component of genetic variation over both inter-populational and regional fractions. The traits that displayed this pattern of variation were: initial vegetation scores (intra-,79.4%), spikelet weight (intra-, 68.4%), days-to-awn-appearance (intra-, 80.6%), spike length (intra-, 84.6%), awn length (intra-, 44.0%), panicle length (intra-, 75.2%), culm length (intra-, 60.0%), total plant height (intra-, 98.1%), number of nodes (intra-, 80.0%), internode length (intra-, 83.6%), flag leaf length (92.2%) and total number of reproductive tillers (intra-, 69.6%). The exceptions were: tiller heights (inter-, 54.3%) and average seed weight (inter-, 64.1%). 85.7% of the studied quantitative traits provided evidence for a higher and statistically significant intra-populational genetic variation in all the thirteen population.
The days to awn appearance which determines the ability to escape stress e.g. drought, was found to be much lower in the desert populations. In this case, Dead Sea and Sde Boqer offered the least number of days for the first awns to appear. There was also a higher variability for this trait, in all the assayed populations, which means that genetic gain can be realized in improvement programs exploiting this character.
These results show a similar pattern to that achieved in the same populations, at the same time, with the scored 17 allozyme loci (Owuor, 1994; Owuor et al., 1996), and are again in agreement with Lewontin, (1972) with the intra-group component being more significant and Buth, (1984) for initial vegetative scores as a measure of compensatory growth following slight shock, in this case transplanting shock.
However, the results differed with those reached by Laura and Brody (1984); Brody and Snow, (1986). Also, in durum wheat, Pecetti et al., (1992) obtained significant inter-populational variation in most characters, except spike length and protein characters. This ratifies our allozyme results while deviating from the quantitative trait patterns.
Some of the numerical traits were able to distinguish between the two regions, with sampling implications. The high variability manifested in Hordeum spontaneum for almost all the traits (quantitative and protein) emphasize its potential as a gene-pool for barley improvement programs.
References
Brody T. and Snow, L., 1986 Structuring of genetic variation in Hordeum spontaneum (Poaceae): genotypic variation within populations. Pl. Syst. Evol. 158, 1-10.
Buth Donald G., 1984 The Application of Electrophoretic Data in Systematic Studies. Ann. Rev. Ecol. Syst. 15, 501-522.
Laura S. and Brody, T., 1984 Genetic Variation of H. spontaneum in Israel: Eco-Geographical Races , Detected by Trait Measurements. Pl. Syst. Evol. 145, 15-28.
Lewontin R.C., 1972 The Apportionment of Human Diversity. Evol. Biol. 6, 381-398.
Owuor, E.D., 1994 Comparative studies of the extent and structure of genetic variation in wild barley, Hordeum spontaneum populations from Israel and Turkmenistan. Msc thesis, University of Nairobi.
Owuor E.D., Kimani P.M., Mendlinger, S., Chweya, J., and Olsvig-Whittaker, L., 1996 Comparative allozymic multilocus analysis of genetic diversity in wild barley from Turkmenistan (former USSR) and Israel: implications on sampling strategies. BGN 25, 10-12.
Pecetti L., Damania A.B. and Kashour G., 1992 Geographic variation for spike and grain characteristics in durum wheat germplasm adapted to dryland conditions. Genetic Resources and Crop Evolution. 39, 97-105.
Acknowledgement: The principal author would like to express appreciation to Mashav division of the Ministry of Foreign Affairs, Israel for sponsoring the Msc research grant and Mr. Haim the field Assistant in Dr. Mendlinger's laboratory, Ben-Gurion University.