Etude des interactions riz-Magnaporthe grisea : caractérisation et clonage du gène de résistance Pi33

We identified the resistance gene corresponding to the avirulence gene ACE1 using pairs of isogenic strains of Magnaporthe grisea differing only by their ACE1 allele. This resistance gene was mapped on the short arm of rice chromosome 8 using progenies from the crosses IR64 (resistant) x Azucena (susceptible) and Azucena x Bala (resistant). We also detected this resistance gene in several rice varieties, including the differential isogenic line CIOILAC. Allelism tests permitted us to distinguish this gene from two other resistance genes (P ill and Pi- 29(t)) that are present on the short arm of the chromosome 8. Segregation analysis in F2 populations was in agreement with the existence of a single dominant gene, designated as Pi33. Finally, Pi33 was finely mapped between two molecular markers of the rice genetic map that are separated by a distance of 1.6 cM. Using this fine map, we physically mapped Pi33 using the ordered BAC library of the cultivar Nipponbare (susceptible). A two-step walk was necessary to achieve this map. We then used the markers found during this walk to physically map Pi33 in the IR64 (resistant) unordered BAC library. No resistance gene homologues (RGA) were found in the available sequence data in the area of Pi33. Moreover, no RGA were revealed in IR64 BAC clones by PCR amplification. A complementation test was performed in order to confirm the physical map and to demonstrate Pi33 cloning. Kassalath susceptible cultivar was transformed using 5 BAC clones of the IR64 library that span the area of Pi33. One of these clones seemed to confer resistance to ACE1 but this result needs confirmation. Finally, the markers generated during this work were used to study the polymorphism around Pi33 and the origin of this gene amongst the parents of the IR64 cultivar. Pi33 is probably an ancestral gene that appeared before rice domestication. In most of the resistant modem cultivars, Pi33 comes from the Taiwanese traditional cultivar TYC. Alternatively, in IR64, Pi33 comes from an accession of the wild species Oryza nivara.

Bibliographic Details

Main Author:	Berruyer, Romain
Format:	thesis biblioteca
Language:	fre
Published:	ENSAM
Subjects:	H20 - Maladies des plantes, F30 - Génétique et amélioration des plantes, Magnaporthe grisea, agent pathogène, résistance aux maladies, maladie fongique, gène, carte génétique, phylogénie, Oryza, http://aims.fao.org/aos/agrovoc/c_37090, http://aims.fao.org/aos/agrovoc/c_5630, http://aims.fao.org/aos/agrovoc/c_2328, http://aims.fao.org/aos/agrovoc/c_11042, http://aims.fao.org/aos/agrovoc/c_3214, http://aims.fao.org/aos/agrovoc/c_24002, http://aims.fao.org/aos/agrovoc/c_13325, http://aims.fao.org/aos/agrovoc/c_5435,
Online Access:	http://agritrop.cirad.fr/513520/ http://agritrop.cirad.fr/513520/1/These%20Berruyer%202002.pdf.pdf
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