Mapping of paranodulation response QTL in rice

Abstract

Paranodules are the nodule like structures induced on roots of non-legumes. These can be induced by several methods, viz., treatment with auxins; hydrolytic enzymes etc. The paranodules thus induced can be colonized by nitrogen fixing bacteria by which non-legumes can also derive benefits of biological nitrogen fixation, like legumes. Paranodulation response in rice was found to exhibit high degree of genetic variation behaving as a heritable trait. Since, the phenotyping for the paranodulation response is tedious and time consuming; there is a need for developing molecular markers for the trait useful in Marker Aided Selection (MAS) for better paranodulation response. Keeping this in mind, an attempt was made to map the QTL responsible for paranodulation trait. Perpetuating mapping population of doubled haploid (DH) lines derived from anther culture of IR64 X Azucena was used as experimental material in the present investigation. A total of 121 DH lines were screened for paranodule induction response, by culturing the seedling roots in-vitro in Yoshida‟s rice culture medium with 2, 4-D treatment. The phenotypic landscape was super-imposed on the already established SSR marker based genomic grid (269 SSR marker data, Susan Mc Couch, per. Comm.). Analysis with „MAPMAKER/QTL‟ showed two major QTL responsible for paranodulation trait, both mapped to chromosome 9. pnodQ-1 being between the markers RM 219 and RM342b, with LOD score of 3.47 and responsible for 22.4% of variation. The other, pnodQ-2 located between RM342b and RM105, with LOD score of 4.72, responsible for 36.5 % of variation. Further analysis revealed that paranodulation trait is having recessive mode of inheritance.