Detection of stay-green QTLs in a sorghum recombinant inbred population based on cross (N13 × E36-1)

Gaikwad PS1, Mehtre SP1*, Vadez V2, Hash CT3, Santosh P Deshpande2

1 Department of Genetics and Plant Breeding, Vasantrao Naik Marathwada Krishi Vidyapeeth, Parbhani, 413402, Maharashtra, India2 International Crop research Institute for the Semi-Arid Tropics, Patancheru, 502234, Hyderabad, India3 International Crop Research Institute for the Semi-Arid Tropics, Niamey, Niger* E-mail: shivaji_pmehtre@rediffmail.com

Phenotyping RIL population 180 RILs (F3:8) of sorghum derived from

cross-(N13 × E36-1) segregating for stay-green trait, Parents (N13 and E36-1) andchecks (R16, S35 And B35) were observed atVNMKV, Parbhani, Maharashtra, India.

Field evaluation was done for two years(postrainy season of 2011 and 2012) inRCBD design in 2 meter 2 rows plot.

Treatments–CONTROL (Irrigated) andSTRESS (Water limited)

Abstract The progress in genetic improvement of post-rainy sorghum for drought tolerance using traditional plant breeding practices has been slow, and selection has not been mucheffective due to complex interaction between genotype and environment. Identification of genetic factors involved in stay-green through molecular breeding approaches would providethe basis for genetic improvement for drought tolerance. In this experiment stay-green QTLs were mapped and the effect of environment on stay-green expression was observed. Forthis a sorghum Recombinant Inbred Line (RIL) population was field evaluated for 2 years during the post-rainy season of 2011 and 2012, under two water regimes, (stress and control).A set of 200 entries, including 180 RILs, parents and checks were sown in a plot of 2 rows of 2m in RCBD design with 3 and 2 replications for stress and control treatments,respectively. Data was recorded for percent green leaf area (%GLA) with a weekly interval basis (7 counts) with starting from 50% flowering till physiological maturity. This revealssignificant genotypic variances along with high heritability. A genetic linkage map based on 176 RILs with 271 markers consisting of SSRs, DArT and two qualitative traits wasdeveloped. In total 45 QTLs were identified for seven %GLA scores in two seasons and two treatments. The phenotypic variation explained by each QTL ranged from 6.00 to 14.00%.In further across environment analysis, some QTLs may be environment specific and some may consistent across environment, such stable QTLs could be utilized through genomicsapproaches to improve drought tolerance of post rainy sorghum varieties.

Figure 1. QTLs identified for per cent green leaf area using the (N13 × E36-1)-based RIL population for 2011 and2012 postrainy season data sets under stress and control treatments

Table 1. QTLs identified for per cent green leaf area using the (N13 × E36-1)-based RIL population for 2011 and2012 post rainy season data sets under stress and control treatments

Sr.No.

Trait/ Year/ Treatment

Linkage Group

Position (cM)

Marker Interval LOD R2 (%) Additive

effect

1 % GLA at 14 Days after Flowering

2012 Stress SBI-06 4 Sb19610 - Sb18296 3.8 6.6 -1.0

2011 Control SBI-03 144 isep0843 - Sb19216 3.9 7.7 1.2

SBI-06 28 Sb15059 - Sb20374 3.3 6.4 -1.1 SBI-07 14 isep0805 - Sb18058 3.7 7.5 -1.2

2 % GLA at 21 Days after Flowering

2012 Stress SBI-03 137 Sb15076 - isep0843 4.2 7.9 1.6 SBI-03 145 isep0843 - Sb19216 3.6 7.1 1.5 SBI-06 4 Sb19610 - Sb18296 3.3 6.3 -1.4 SBI-07 16 Sb20189 - isep0328 3.4 7.5 -1.5 SBI-08 96 txp105 - isep0809 3.7 7.0 1.5

2011 Control SBI-03 145 isep0843 - Sb19216 4.4 8.9 1.7

SBI-07 17 isep0805 - Sb16143 3.3 7.1 -1.6 3 % GLA at 28 Days after Flowering

2012 Stress SBI-07 15 Sb20189 - Sb18058 4.4 9.9 -2.6 2011 Control SBI-03 145 isep0843 - Sb19216 6.8 12.7 2.2

SBI-07 19 Sb20189 - Sb16143 5.3 10.0 -2.0 SBI-07 27 Sb16143 - isep0328 3.9 8.0 -1.8

4 % GLA at 35 Days After Flowering

2011 Stress SBI-03 2 isp10282 - isep0107 3.8 8.8 -2.3 2012 Stress SBI-03 96 Sb19092 - txp114 3.4 6.6 2.8

SBI-07 32 isep0328 - Sb16133 4.3 8.5 -3.2 SBI-08 93 txp105 - Sb13986 3.7 7.8 3.0

2011 Control SBI-03 144 isep0843 - Sb19216 4.4 8.7 2.1 SBI-07 21 Sb20189 - Sb16143 3.7 7.8 -1.9

2012 Control SBI-02 26 msbCIR223-iabtp500 3.3 7.3 2.6

Sr.No

.

Trait/ Year/ Treatment

Linkage Group

Position (cM)

Marker Interval LOD R2

(%) Additive

effect

5 % GLA at 42 Days After Flowering

2011 Stress SBI-07 18 Sb20189 - Sb16143 3.9 9.6 -2.9 2012 Stress SBI-03 137 Sb15076 - isep0843 3.3 6.6 3.4

SBI-03 145 isep0843 - Sb19216 3.6 7.2 3.4 SBI-06 2 Sb19610 - Sb17708 3.1 6.0 -3.1

2011 Control SBI-03 145 isep0843 - Sb19216 3.3 6.6 1.9

SBI-05a 11 isep1133 - txp065 3.1 6.4 -1.9 SBI-07 22 Sb20189 - Sb16143 3.6 7.6 -2.0

2012 Control SBI-02 24 msbCIR223-Sb18205 4.3 10.4 3.9

SBI-06 4 Sb19610 - Sb18296 3.4 7.4 -3.3 6 % GLA at 49 Days After Flowering

2011 Stress SBI-07 9 isep0805 - Sb20189 3.1 8.7 -2.7 SBI-07 18 Sb20189 - Sb18058 4.1 9.5 -2.9

2012 Stress SBI-07 18 Sb20189 - Sb18058 3.5 7.4 -2.3 SBI-10 62 Sb15751 - txp141 3.6 8.9 -2.5

2011 Control SBI-02 18 msbCIR223-Sb18205 4.4 14.0 2.6 2012 Control SBI-02 26 Sb18205 - iabtp500 3.6 8.4 3.4

7 % GLA at 56 Days After Flowering

2011 Stress SBI-02 91 Sb16959 - Sb13645 3.1 7.6 2.3 SBI-07 21 txp312 - Sb16143 4.0 9.5 -2.6 SBI-07 30 Sb16143 - Sb19417 4.8 10.7 -2.8

2012 Stress SBI-03 145 isep0843 - Sb19216 4.5 8.9 1.6 SBI-03 151 Sb19216 - Isp10323 3.8 8.3 1.6 SBI-04 15 isep0948 - Sb17820 4.0 7.9 1.6 SBI-10 63 Sb18966 - txp141 3.6 9.2 -1.7

2011 Control SBI-02 26 msbCIR223-Sb18205 4.9 11.4 1.2

Linkage map construction The segregation data of the 271 markers

(SSRs+DArT) for 176 recombinant inbredlines (RILs) were used for the constructionof the genetic map of the (N13 × E36-1)based RIL population.

Co-segregation analysis of the markers wasperformed using the Joinmap 3.0 software.

The linkage map thus constructed has alength of 1184.23 cM with average markerinterval length 5 cM.

Acknowledgement Financial support from Generation Challenge Programme andICRISAT Dryland Cereals research program is greatly acknowledged. This work hasbeen undertaken as part of the CGIAR Research Program Dryland Cereals.

QTL mapping Mapping was done using QTL Cartographer version 2.5. Total 45 QTLs were detected for seven % GLA scores. The phenotypic variation explained by each QTL ranged from 6.00 to

14.00%. Detected QTLs for control and stress treatment of 2011 and 2012

post rainy season shown separately in Figure 1 and Table 1.Future Prospects Across season analysis will help to study interaction of QTLs with

environment. such stable QTLs could be utilized through genomics approaches to

improve drought tolerance of post rainy sorghum varieties.

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Feb 2017