MARKER ASSISTED INTROGRESSION OF DROUGHT TOLERANCE QTLs INTO POPULAR HIGH YIELDING VARIETIES OF RICE (Oryza sativa L.)
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Date
2021-10-05
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Abstract
Rice (Oryza sativa L.) production is severely constrained by the drought stress. Enhancing the yield under drought condition is indeed a challenging task. However, with the advances in genotyping and phenotyping technologies, many QTLs governing yield under stress have been identified and their introgression into other elite varieties demonstrated to increase the yield under stress conditions. The present study was undertaken to transfer the QTLs for yield under drought stress from the drought tolerant variety DRT1IR64 into two high yielding varieties of Andhra Pradesh i.e., MTU1010 and NLR34449 through marker-assisted backcross breeding.
In this investigation, DRT1IR64, an introgressed line of IR64 that harbours three QTLs governing yield under drought viz., qDTY1.1, qDTY2.2 and qDTY4.1 was chosen as donor/male parent while high yielding drought susceptible varieties viz., MTU1010, and NLR34449 were used as recipient parents. For the development of introgressed lines (ILs), MTU1010 and NLR34449 varieties were crossed with DRT1IR64 parent. The resulted F1 plants were twice backcrossed to MTU1010 and NLR34449 to develop BC1F1 and BC2F1 populations followed by selfed to generate BC2F2 plants.
Before transferring of these drought QTLs it is mandatory to validate them in the donor and recipient parents for polymorphism. To this end, the three parents viz., DRT1IR64, MTU1010 and NLR34449 were screened with eight flanking markers of the targeted drought QTLs. Among all, RM551 (qDTY4.1) and RM279 (qDTY2.2) markers showed polymorphism in all the
three parents. Hence, the SSR markers, RM279 linked to qDTY2.2 and RM551 linked to qDTY4.1 were used as foreground markers for introgression of these drought tolerant QTLs into MTU1010 and NLR34449 varieties.
Foreground selection was performed with individual lines of the three backcross generations i.e., BC1F1, BC2F1 and BC2F2 using two QTL linked polymorphic markers i.e., RM279 and RM551. This resulted eight and six BC2F2 individuals of NLR34449 and MTU1010 backcross populations were found to have two QTLs (qDTY2.2, and qDTY4.1), respectively.
For background selection, a total of 396 molecular markers distributed on all 12 rice chromosomes were screened among the three parents. Out of which, 53 polymorphic markers (13.33%) between DRT1IR64 and MTU1010 and 62 polymorphic markers with 16.6 % polymorphism between DRT1IR64 and NLR34449 were obtained. These polymorphic markers were used to screen backcross populations viz., BC1F1, BC2F1 and BC2F2 of MTU1010 and NLR34449 to estimate the recovery of recurrent parent genome. Background selection was performed with BC1F1, BC2F1 and BC2F2 individuals lines, which are positive for two QTLs (qDTY2.2, and qDTY4.1) and had similar morphological character to MTU1010 and NLR34449. It was estimated that the recovery of recurrent parent genome content was found to be 83-93 % and 84-92% in the ILs of MTU1010 and NLR34449 backcross populations.
The key result of the experiment was that, it was successfully developed BC₂F₂ ILs of eight MTU1010 and six NLR34449 background were having the desired QTLs (qDTY2.2, and qDTY4.1) that showed yield advantage of 1133-2183 kg ha-1 and 2089-3145 kg ha-1over their recipient parents MTU1010 and NLR34449, respectively under moisture stress and with an acceptable yield potential under non-stress. These introgressed lines can have the potential to release as varieties in rainfed ecology after thorough evaluation. Also these ILs can be right away used as donors in existing breeding programme in rice.
Description
MARKER ASSISTED INTROGRESSION OF DROUGHT TOLERANCE QTLs INTO POPULAR HIGH YIELDING VARIETIES OF RICE (Oryza sativa L.)