ABSTRACT
In the present investigation, phenotypic evaluation of blast disease reaction was conducted at Ponnampet and Mandya districts of Karnataka, India, which indicated that the rice varieties such as IR64, Jaya, KMP153, IR30864, Mandya Sona-1, Mandya Sona-2, KCP1, Dodda Byra, and Malgudi Sanna were susceptible to both leaf and neck blasts. Further, the rice varieties that were resistant to leaf blast such as KMP200, DHMAS70Q164-1b, Karibatta, Coimbatore Sanna and others showed susceptible reaction to neck blast only. In contrast, the varieties such as JyothixBR2655, Punkutt Kodi, Sirsi, 222 and Gangadale which were resistant to neck blast were found to be susceptible to leaf blast also. Only one variety, BR2655 showed resistance to both leaf and neck blast diseases. The genotypic studies using simple sequence repeat markers showed that the analysis of the distribution of resistance genes and genotyping of the selected rice varieties, and traditional rice varieties from different ecological regions with allele specific markers helped to identify 20 major blast resistance genes. The individual gene frequencies of the 20 major rice blast resistance genes varied from 10.34 to 100%. Less and more frequency of resistance gene distribution occurred in Pi9 and Pizt gene, respectively. The result of this study would help to create strategies for improving rice blast resistance through genetic studies and plant–pathogen interaction.
ABSTRACT
The rice blast caused by the fungus Magnaporthe oryzae is one of the most devastating diseases of rice and can lead to complete failure of the crop under severe cases. The first step in breeding for blast resistance in rice is therefore to identify the novel sources of resistance and cataloguing different blast resistant genes in these genotypes. In the present study, a set of 37 rice genotypes comprising of landraces, advanced breeding lines and released varieties were first characterized for blast resistance under epiphytotic conditions and subsequently different blast resistant genes were catalogued with the help of markers tightly linked to these genes. A total of 22 different blast resistant genes were catalogued in these genotypes. Lot of diversity was found to be present for different genes in the rice genotypes studied. In addition, a set of 2–3 markers were identified which could distinguish genotypes of a particular geographic area from each other.The results are useful for identifying the right combination of genotypes in the resistance breeding programme
ABSTRACT
Finger millet plants conferring resistance to leaf blast disease have been developed by inserting a rice chitinase (chi11) gene through Agrobacterium-mediated transformation. Plasmid pHyg-Chi.11 harbouring the rice chitinase gene under the control of maize ubiquitin promoter was introduced into finger millet using Agrobacterium strain LBA4404 (pSB1). Transformed plants were selected and regenerated on hygromycin-supplemented medium. Transient expression of transgene was confirmed by GUS histochemical staining. The incorporation of rice chitinase gene in R0 and R1 progenies was confirmed by PCR and Southern blot analyses. Expression of chitinase gene in finger millet was confirmed by Western blot analysis with a barley chitinase antibody. A leaf blast assay was also performed by challenging the transgenic plants with spores of Pyricularia grisea. The frequency of transient expression was 16.3% to 19.3%. Stable frequency was 3.5% to 3.9%. Southern blot analysis confirmed the integration of 3.1 kb chitinase gene. Western blot analysis detected the presence of 35 kDa chitinase enzyme. Chitinase activity ranged from 19.4 to 24.8. In segregation analysis, the transgenic R1 lines produced three resistant and one sensitive for hygromycin, confirming the normal Mendelian pattern of transgene segregation. Transgenic plants showed high level of resistance to leaf blast disease compared to control plants. This is the first study reporting the introduction of rice chitinase gene into finger millet for leaf blast resistance.