QTL MAPPING FOR HEAT TOLERANCE RELATED TRAITS IN WHEAT (TRITICUM AESTIVUM L.) USING BACKCROSS INBRED LINES”
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Date
2017
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DIVISION OF GENETICS ICAR-INDIAN AGRICULTURAL RESEARCH INSTITUTE NEW DELHI -
Abstract
Mapping population of 134 backcross inbred lines (BILs) was developed crossing HD2733, which is
heat susceptible variety with WH730, a heat tolerant. The BILs population was phenotyped in two
environments late sown (LS) and very late sown (VLS) in Rabi 2016 in experimental farms of Indian
Agricultural Research Institute, New Delhi, for nine phenotypic traits i.e., days to heading (DH),
normalized difference vegetative indices (NDVI), canopy temperature (CT), thousand Kernal weight
(TKW), grain weight per spike(GWS), spike length (SL), number of spikelets per spike (NSPS),
biomass and grain yield (GY). The significant variation among genotypes observed as revealed by
ANOVA. The population distributed normally in both environments for all the characters studied
indicating the polygenic control of the traits studied. The transgressive seggregants were found for all
traits. The formation of four cluster following heirarchial clustering of BILs reflects the sufficient
variability in the population for QTL mapping and selection. Correlation and regression analysis
revealed the strong positive association of NDVI, TGW, GWS, and biomass with GY under both
environments. The CT and DH having strong negative correlation with GY under heat stress. Total of
1350 markers were surveyed for parental polymorphism and 124 markers were found polymorphic.
The population was genotyped with 95 markers. A linkage map was constructed with 95 markers
genotypic data at 149 loci, in 134 BILs using ICIM v4.0 software. The population has the average
genome content of 63.3 per cent of HD2733 and 26.2 per cent of WH730 and 10.4 per cent of
heterozygous and missing values which is in accordance with the expected 3:1 Mendelian
segregation ratio. The single marker analysis (SMA) and inclusive composite interval mapping
(ICIM) was performed, a total of 9 QTLs were discovered on 7 chromosomes. In LS condition 4
QTLs were detected and in VLS condition 5 QTLs were detected. A major QTL for DH was detected
in both the environment and methods, on 5A chromosome. QTL for DH has phenotypic variation
explained value of 23 and 26% under LS and VLS condition. For NDVI3 and NDVI4, common QTL
is found in LS and VLS respectively, explaining 8.6% phenotypic variance (PVE). A QTL for
NDVI7 was found on 7D chromosome, explaining 10% phenotypic variance. A QTL for TKW
detected on 3A chromosome by SMA, explaining 10% phenotypic variance under LS condition. The
QTL detected for GWS was co localized with TKW QTL. Two QTLs were detected for Spike length
on 2A (10.58 % PVE) and 4A (13.5 % PVE) chromosomes. One QTL for each biomass and yield
was found on 1B (8 % PVA) and 2A (5 % PVA) chromosomes respectively. The QTL detected for
DH and others can be used in MAS programme of crop improvement in wheat.
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t 9836
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