Genetic basis and mapping of the resistance to rice yellow mottle virus. II. Evidence of a complementary epistasis between two QTLs |
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Authors: | G Pressoir L Albar N Ahmadi I Rimbault M Lorieux D Fargette A Ghesquière |
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Institution: | (1) Unité de Génétique, GeneTrop, ORSTOM, BP5045, 34032 Montpellier cedex 1, France, FR;(2) IER/CIRAD, BP183, Sikasso, Mali, ML;(3) LPRC, ORSTOM/CIRAD, BP5035, 34032 Montpellier cedex 1, France, FR |
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Abstract: | The genetic basis of resistance to rice yellow mottle virus (RYMV) was studied in a doubled-haploid (DH) population derived
from a cross between the very susceptible indica variety ‘IR64’ and the resistant upland japonica variety Azucena. As a quantitative trait locus (QTL) involved in virus content estimated with an ELISA test has been previously
identified on chromosome 12, we performed a wide search for interactions between this QTL and the rest of the genome, and
between this QTL and morphological traits segregating in the population. Multiple regression with all identified genetic factors
was used to validate the interactions. Significant epistasis accounting for a major part of the total genetic variation was
observed. A complementary epistasis between the QTL located on chromosome 12 and a QTL located on chromosome 7 could be the
major genetic factor controlling the virus content. Resistance was also affected by a morphology-dependent mechanism since
tillering was interfering with the resistance mechanism conditioned by the epistasis between the two QTLs. Marker-assisted
backcross breeding was developed to introgress the QTLs of chromosome 7 and chromosome 12 in the susceptible ‘IR64’ genetic
background. First results confirmed that if both QTLs do not segregate in a backcross-derived F2 population, then the QTL of chromosome 12 cannot explain differences in virus content. A near-isogenic line (NIL) approach
is currently being developed to confirm the proposed genetic model of resistance to RYMV.
Received: 20 April 1990 / Accepted: 30 April 1998 |
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Keywords: | QTL Complementary epistasis Marker-assisted selection Quantitative resistance Rice yellow mottle virus |
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