Abstract
High temperature especially affects terminal end of inflorescence during anthesis and grain filling thus significantly reducing quality and yield of wheat. The key complication with late sown wheat rises due to high temperature during reproduction process causing lower grain yield. This study was planned to screen six newly developed wheat genotypes for high temperature tolerance. The study was led at experimental Farm of NIA, Tandojam during 2011-12 where the minimum, maximum temperatures and humidity were recorded. Grain yield and associated traits in genotypes of wheat significantly decreased under late sowing. About 15.8% and 14.0% reduction was measured in days to heading and maturity, respectively in late-sown trial. Morphological traits viz., plant height, spike length, spikelets per spike, grains per spike, 1000-grain weight, biological weight and grain yield per plant also decreased by 9.4, 17.4, 11.2, 11.4, 20.4, 62.2 and 54.8 %, respectively under late planting as compared to normal sowing. Genotype MSH-36 produced significantly higher 1000-grain weight (43.0 g) and less reduction than other genotypes at late sowing, MSH-3 and NIA-8/7 gave bold seeds with less reduction. The maturity period of wheat genotypes also decreased to about 16.8% for late planted wheat.
Highlights
Wheat (Triticum aestivum L.) crop is best adapted to moderate environmental conditions, while moderate temperatures (25-32 0C) for longer and very high temperature (33-40 0C) for a shorter duration are very conjoint in subtropical situations of South-East Asia (Paulsen, 1994; Stone and Nicholas, 1994)
In Pakistan, best time of sowing wheat is the month of November and delay reduces number of tillers, seed index and grain-yield (Ansari et al, 1989) and yield losses up to 40-50 % reported in Pakistan
The normal sowing took more time for heading of the genotypes against late sowing. These findings were coincide with Irfaq et al (2005) which reported that reduction in days to heading is related with late sowing was owing to terminal heat stress
Summary
Wheat (Triticum aestivum L.) crop is best adapted to moderate environmental conditions, while moderate temperatures (25-32 0C) for longer and very high temperature (33-40 0C) for a shorter duration are very conjoint in subtropical situations of South-East Asia (Paulsen, 1994; Stone and Nicholas, 1994). The present studies were planned to observe the stress of high temperature on various morphological and physiological traits of wheat genotypes under two sowing dates. Meteorological data for minimum and maximum temperatures (Figure 1) and relative humidity (Figure 2) was recorded on daily basis throughout the cropping season. The normal sowing took more time for heading of the genotypes against late sowing. These findings were coincide with Irfaq et al (2005) which reported that reduction in days to heading is related with late sowing was owing to terminal heat stress. Similar finding reported by Moshatati et al (2012) and Ayeneh et al (200)
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