Mapping and transfer of GENES/QTLs for nematode (Meloidogyne graminicola) resistance from Oryza glaberrima into Oryza sativa L.
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Date
2020
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Punjab Agricultural University, Ludhiana
Abstract
Rice root knot nematode (Meloidogyne graminicola) is one of the emerging constraints for rice
production, causes about 50% yield losses in field conditions and 98% yield losses in pot
experiments. The identification and exploitation of resistant rice genotypes is one of the economic
and sustainable option to minimize the yield losses caused by M. graminicola infestations. The
present investigation was undertaken to identify the QTLs associated with rice root knot nematode
resistance as well as the transfer of resistance to elite rice cultivars. A total of 42 accessions of O.
glaberrima along with O. sativa cultivar PR121 were screened in triplicates during kharif 2016
and kharif 2017 in nematode infested sick plot at initial nematode population density of one
juvenile per gram of soil. Reproduction factor of rice root knot nematode among O. glaberrima
accessions was found to be <1 while in O. sativa cultivar PR121, reproduction factor was >1. Out
of 42 accessions, three accessions (IRGC102196, IRGC102538 and IRGC102557) were found to
be highly resistant, thirty-three accessions were resistant, and six accessions were moderately
resistant. Data on different morphological traits (plant height, root length, fresh shoot weight,
fresh root weight, dry shoot weight and dry root weight) revealed that no statistically significant
differences were found among O. glaberrima accessions whereas PR121 exhibited significant
reduction in all growth parameters in nematode infested sick plot as compared to controlled
conditions. The BC1F1 population derived from the cross of O. glaberrima acc. IRGC102206 ×
PR121 was used for mapping of rice root knot nematode resistance. The BC1F1 plants were
screened against M. graminicola in triplicates and genotyped using 84 polymorphic SSR markers.
Both phenotypic data and genotypic data was analyzed and a total of 13 QTLs associated with gall
number, gall index and different morphological traits were mapped on chromosomes 1, 3, 4, 5, 6
and 8. Out of 13 QTLs, three QTLs associated with gall number were identified; two QTLs
designated as qGN4.1and qGN4.2 were mapped on chromosome 4 and one QTL, qGN6.1, was
mapped on chromosome 6. QTL associated with gall index (qGI6.1) was found to be co-localized
with qGN6.1. Similarly, qGN6.1 QTL was co-localized with plant height and root length. Due to
less coverage by SSR markers, we simultaneously performed BSA-QTLseq (Bulked segregant
analysis coupled with QTL-seq approach) analysis and identified QTLs for nematode resistance
on chromosomes 1, 2, 3, 4, 5, 6, 11 and 12. The genomic interval of all QTLs was narrowed down
to 1–2 Mb using QTL-seq analysis. The development of SNP based molecular markers from
identified QTL regions will further help to saturate the linkage map and to identify closely linked
markers to rice root knot nematode resistance. The identified markers will further fasten the
improvement of genotypes for rice root knot nematode resistance through marker assisted
breeding approach. Based on introgressed genomic regions from O. glaberrima carrying QTLs for
nematode resistance the BC1F1 resistant plants were selected and backcrossed to generate BC2F1
and subsequently BC3F1 progenies for transfer of nematode resistance in the background of
PR121. The data generated from this study can serve as valuable genomic resources for rice
breeding programmes.
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Citation
Gurwinder Kaur (2020). Mapping and transfer of GENES/QTLs for nematode (Meloidogyne graminicola) resistance from Oryza glaberrima into Oryza sativa L. (Unpublished Ph.D. Dissertation). Punjab Agricultural University, Ludhiana, Punjab, India.