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Titre: البحث عن دور سم solanapyrone A كعامل إمراضية لفطر (Ascochyta rabiei Pass. Labrousse) Didymella rabiei Kovachevski المسبب لمرض التبقع الأسكوكيتي على نبات الحمص(Cicer arietinum L.)
Auteur(s): زروق, محمد ميهوب
Mots-clés: Ascochyta rabiei
Cicer arietinum
phytotoxins
Solanapyrone A
Date de publication: 8-oct-2018
Résumé: Cultures of A. rabiei, designated Ag1, Ag2 and Ag3, were isolated from chickpea debris left in fields near the Algerian towns of Sétif, Guelma and Oued Smar, respectively. Isolation from such plants gave rise to fungal colonies with he same morphology as the original isolates and symptoms identical to the naturally infected plants. Identity of isolates Ag1 and Ag2 was confirmed by sequencing rDNA. The sequence for Ag1 gave a perfect match for 448 bases of a reference sample AR 738 in Genbank and essentially the same result for 454 bases of Ag2. PCR of DNA from Ag1 and Ag2 with primers specific for the mating type genes of A. rabiei both gave amplicons of about 700 bp, demonstrating that they were both mating type 1. The three Algerian isolates grew well on Czapek Dox medium supplemented with cations (CDCLM). Only solanapyrone A and sometimes a trace of solanapyrone C were produced and were recognised by their retention times on HPLC and spectra. The major peak from all three Algerian isolates gave spectra that closely matched to that of authentic solanapyrone A. Solanapyrone A and culture filtrates of A. rabei inhibited the germination of chickpea seed, and this inhibition decreased with dilution. Probit % inhibition of germination was proportional to the concentration of solanapyrone A or the dilution factor of culture filtrates. The concentration of solanapyrone A that caused 50% inhibition of germination was 6.93 ± 0.21 µg/ml and the dilutions of culture filtrates of isolates Ag1, Ag2 and Ag3 required to give the same inhibition were 52.5%, 55.0% and 64.4%, respectively. The elongation of radicles and hypocotyls of chickpea seedlings was inhibited by solanapyrone A and culture filtrates of A. rabiei. The concentration of solanapyrone A that cause 50% inhibition of radicle elongation was 4.72 ± 0.30 µg/ml and the dilutions of culture filtrates of isolates Ag1, Ag2 and Ag3 required to give the same inhibition were 30%, 47.5% and 53.0%, respectively. The concentration of solanapyrone A that cause 50% inhibition of hypocotyl elongation was 6.56 ± 0.33 µg/ml and the dilutions of cultural filtrates of isolates Ag1, Ag2 and Ag3 required to give the same inhibition were 45%, 51% and 59%, respectively. Radicle elongation was the most sensitive of the three parameters to solanapyrone A, the respective values for the three tests being 7.10 ± 0.21 µg/ml for germination, 4.72 ± 0.3 µg/ml for radicle elongation and 6.56 ± 0.33 µg/ml for hypocotyl elongation. Agrobacterium tumefaciens mediated transformation of A. rabiei with strains LBA1126 and AGL1 led to the production of 498 tranformants which were resistant to hygromycin B with an efficiency of 46.8 and 35.8 transformants per 105 spores, respectively.. A total of 30 transformants was screened for the production of solanapyrone A as determined by light absorption at 327 nm, the λmax of solanapyrone A as this is essentially the only compound in culture filtrates of wild type A. rabiei grown on CDCLM which absorbs at this wavelength. If it is assumed that this is also true for the transformants, then their production of solanapyrone A varied from 2.11 ± 0.10 µg/ml to 4.32 ± 1.93 µg/ml, representing a reduction of solanapyrone A of 74.11% to 46.99% in comparison with the wild type (8.15 ± 2.99 µg/ml).
URI/URL: http://dspace.univ-setif.dz:8888/jspui/handle/123456789/2718
Collection(s) :Thèses de doctorat

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