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dc.contributor.authorFAROOQ, JEHANZEB-
dc.description.abstract100 genotypes of Triticum aestivum L. were screened in a plastic tunnel for heat tolerance by providing them heat stress at the time of anthesis. Selection of the genotypes was based on grain weight, number of grains per spike and grain yield per 25 spikes after computation of their relative ratios. The selected genotypes were also tested by measuring their electrolyte leakage to confirm the tolerance and susceptibility by calculating relative injuries. Seven genotypes including 3 heat tolerant, 1 moderately tolerant and 3 susceptible were crossed in a 7 × 7 diallel fashion including direct and reciprocal crosses in a randomized complete block design with three replications in two sowing dates. One set of these genotypes was sown under normal environmental conditions and other set was sown under heat stress conditions to provide temperature stress to these genotypes at the time of anthesis. Data of various morphological characters was taken at different stages of the growth period of the crop and then subjected to statistical analysis. Significant variation was found among parents and their offspring. Gene action and the percent increase or decrease of F 1 hybrids over mid parent as well as better parent value was calculated to estimate possible heterotic effects for yield and its components. Scaling tests were used to test the adequacy of the data for analyzing the additive-dominance model which showed that the additive-dominance model was fully adequate for plant traits like flag leaf area, RCI %, spike weight, spikelets per spike, number of grains per spike, biomass per plant and grain yield under normal conditions and for characters like plant height, flag leaf area, relative cell injury (%), days to maturity, number of grains per spike, 100-grain weight and harvest index under heat stress indicated that dominance was present and epistasis was absent. All the remaining traits exhibited partial adequacy under both the conditions. The results of the genetic studies showed that almost all the traits show additive genetic effects with partial dominance and with moderate to high heritability. Relative cell injury (%) calculations revealed that this is an efficient tool for screening against heat. Some of the hybrids like Maya/Pavon × Punjab-85, Maya/Pavon × Chenab-2000 and Shalimar-88 × Weebli-1 showed very useful results with relative injuries even less than their parents. The results of heterosis suggest that hybrid vigour is available for the commercial production of wheat and selection of desirable hybrids among the crosses having heterotic and heterobeltiotic effects in other characters is the best way to improve the grain yield of bread wheat. The cross combinations like Inqilab- 91 × Shalimar-88, Shalimar-88 × Maya/Pavon, Chenab-2000 × Punjab-85, Maya/Pavon × Chenab-2000, Shalimar-88 × Uqab-2000 and Uqab-2000 × Maya/Pavon are the best hybrids which can be further exploited because of their ability to perform well under normal and even diverse environments . Maximum heterosis (24.24%) and heterobeltiosis (19.95%) for number of grains per spikes was shown by the cross combination, Inqilab- 91 × Maya/Pavon under normal conditions and under heat stress maximum heterosis (36.13%) and heterobeltiosis (13.66%) was shown by the cross combinations Punjab-85 × Chenab-2000 and Weebli-1 × Uqab-2000 respectively. For 100-grain weight maximum heterosis (28.22%) and heterobeltiosis (27.87%) was recorded for cross combination Chenab-2000 × Inqilab-91. However, under stress Inqilab-91 × Weebli-1 (23.35%) followed by Maya/Pavon × Uqab-2000 (13.28%). Maximum heterosis (28.70%) and heterobeltiosis (15.58%) for grain yield per plant was shown by the cross Uqab-2000 × Punjab-85 under normal conditions but under stress Uqab-2000 × Chenab-2000 produced maximum heterosis (27.02%) and maximum heterobeltiosis (13.62%) was shown by the cross Shalimar-88 × Uqab-2000. The information obtained from these results during the current studies may be used to evolve high yielding varieties which can produce economic yield and help maintain yield sustainability in those areas where terminal heat stress is a major threat.en_US
dc.description.sponsorshipHigher Education Commission, Pakistanen_US
dc.subjectApplied Sciencesen_US
dc.subjectAgriculture & related technologiesen_US
dc.subjectPlant injuries, diseases & pestsen_US
Appears in Collections:PhD Thesis of All Public / Private Sector Universities / DAIs.

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