Effect of Early Heat Stress on Wheat Genotypes
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Date
2020-02
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CCSHAU, Hisar
Abstract
The present investigation was carried out to study the effect of early heat stress on
germination characters, plant growth and yield parameters along with the seed quality of progeny seeds
in twelve wheat genotypes during the years 2016-2019. The seeds were germinated under four different
temperatures viz. 20°C, 25°C, 30°C and 35°C and then their germination and the vigour potential was
assessed after 8 days. In an another experiment, seeds of all genotypes were sown in trays containing
sand, cocopeat and vermi-compost and kept in the germinators under above said temperatures
continuously for 8 days. The seedlings were then transplanted in field at timely and late sown
conditions and different plant growth and yield characters were recorded. The seeds obtained from
these plants were further evaluated for seed quality. The results revealed that the highly significant
mean squares confirmed the presence of substantial amount of variation and significant difference for
all the factors involved in the study. Standard germination along with other vigour parameters were
affected by different temperature treatments. Genotypic differences prevailed and the genotypes viz.
WH 730, WH 1123, EC 277134 and HD 2967 maintained above 90% germination even at 35°C while
PBW 725 and WH 1105 were unable to tolerate heat at the germination stage and their germination
reduced drastically at higher temperatures. However, germination percentage at 20°C and 25°C was
found statistically at par in all the genotypes. Other vigour parameters were maximized at 25°C. This
study concluded that wheat sowing can be done at a mean temperature of around 25°C, this could be a
strategy to escape the terminal heat stress by providing the crop a little more time to mature. The
catalase and SOD enzymes activities continuously increased with temperature and CAT was found
maximum at 35°C and SOD was maximized at 30°C, then it decreased at 35°C. In the second
experiment, results revealed that plant height and tillers per plant were highest at 20°C and reduced at
higher temperatures. The spike parameters increased with temperature and found highest at 35°C
treatment and lowest at 20°C. The overall best performance was shown by the plants germinated at
25°C under both timely sown and late sown environments. The highest grain yield was recorded in the
genotype WH 1105 under normal conditions while overall mean highest yield through all the
temperatures was obtained in the genotype EC 277134. For all the characters studied, timely sown
condition was found better than late sown conditions. Seeds obtained from 20°C treated plants were
found best for most of the seed quality parameters. However, standard germination, root length and
vigour index-II had maximum values at 25°C treatment. Seeds obtained from 35°C treatment had
higher membrane integrity as shown by their lowest electrical conductivity. Treatment of heat under
late sown conditions has shown thermo-priming effect and enhanced the standard germination and
speed of germination of progeny seeds.