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THE INFLUENCE OF FUSARIUM OXYSPORUM F.SP. PISI ON SOME CYTOGENETIC PARAMETERS OF PEA PLANTS

A SOCHIRCA and G LUPASHKU

Institute of Genetics, Academy of Sciences, Padurilor str. 20, Chisinau 2002 MD, Republic of Moldova

Background and objectives
The chromosome apparatus makes a greater contribution to the maintenance of the plant organism homoeostasis compared with other cell structures. Hence it is especially important to study the influence of various factors on cell nuclear structures [1]. Most reports in this area are devoted to the effects of pesticides and mutagens of various kinds [2]. As Fusarium disease is very harmful to the pea crop in the Republic of Moldova, and the cytological aspects of the problem are little studied, we tried to identify the influence of F. oxysporum f.sp. pisi on meiotic cells and to develop a test system to assess the resistance of forms of pea to this disease.

Results and conclusions
It has been established that artificial infection with F. oxysporum f.sp. pisi under field conditions increases the frequency of chromosome aberrations in meiotic cells of pea genotypes differing in resistance. At the first (optimum) sowing period the frequency of chromosome aberrations in infected plants increased by 3.7 and 5.2% in susceptible and resistant genotypes, respectively, compared with the control, i.e. the increase was approximately similar. At the second period (high temperature contributing to disease manifestation) the increase was 11.5 and 6.3%. This means that the fungus and unfavourable temperature have a significant effect on the mutation level in the susceptible genotype, remaining practically at the some level in the resistant one. It was discovered that the frequency of chromosomes scattered in cytoplasm, chromosome lagging and chromatid bridges predominated in the range of chromosome aberrations in both genotypes in both control and experimental treatments. In the second period the frequency of single fragments increased sharply in the susceptible genotype (24.8%) in comparison with the resistant one (2.3%). This regularity was observed over 2 years. Consequently, the frequency of single fragments and the total mutation index in meiotic cells under the action of Fusarium fungi and high temperature may serve as test parameters of pea resistance to Fusarium disease.

References
1. Oku H, 1994. Plant Pathogenesis and Disease Control. Lewis Publishers, Boca Raton, Florida, USA.
2. Njadi GD, Gopalan HM, 1981. Cytology 46, 1-2, 169-172.