8th INTERNATIONAL WHEAT CONFERENCE

moLeCuLAR ChARACTeRIzATIoN of TeRmINAL heAT
ToLeRANCe IN WheAT
Ratan Tiwari, Rajender Singh, Sindhu Sareen,
Jag Shoran and S. S. Singh
Directorate of Wheat Research, Karnal- 132 001, Haryana, India
Email: tiwari1964@yahoo.com
Frequent incidences of sudden spurt in temperatures during the grain filling period of
wheat, has brought concerns to wheat researchers towards terminal heat stress. Development
of heat tolerant genotypes is one of the approaches to mitigate the effect and
increase production in a sustainable manner in a changing environmental regime. Keeping
this in mind a mapping population involving wheat genotypes possessing tolerance
to terminal heat stress as well as sensitive to stress has been developed at the Directorate
of Wheat Research, Karnal, India, which is being utilized for mapping components of
terminal heat tolerance. Two hundred and six Recombinant Inbred Lines developed for
the study were phenotyped along with parents for terminal heat tolerance under poly
house conditions. At heading stage, one set was transferred to poly house where average
maximum temperature was about 3-5 o C higher than ambient temperature. Data was
recorded on phenological, physiological and grain traits. Exposure to high temperature
under poly house condition at the time of grain development resulted in higher reduction
in grain weight in the sensitive genotype as compared to the tolerant one. Considerable
variability for the trait in response to high temperature as well as for grain growth period
under polyhouse environment was observed among the recombinant inbred lines. This
was evident from per cent reduction in grain weight per spike. Chlorophyll fluorescence
was recorded in RILs varying in their response to high temperatures inside and outside
the poly house. Variation among the genotype in chlorophyll fluorescence (Fv/Fm) was
also recorded. Parental screening was carried out with 188 SSR markers. This included
gwm (106), gdm (7), wmc (35), barc(33) and cfd(7). The percent polymorphism observed
varied from 21.5% (gwm) to 30.3% (barc).
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