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| Author | : SANGAM V. S |
| Publisher | : |
| Total Pages | : 159 |
| Release | : 1994 |
| Genre | : |
| ISBN | : |
| Author | : Amir Mohamed Hussein Ibrahim |
| Publisher | : |
| Total Pages | : 150 |
| Release | : 1994 |
| Genre | : Wheat |
| ISBN | : |
Heat stress sets an upper limit to maximizing wheat yields in many irrigated, low-altitude, tropical environments. Terminal heat stress also reduces wheat yields in certain Mediterranean environments in West Asia and North Africa. A study was carried out at three different environments in Sudan and Syria to identify potential selection traits and environments for breeding purposes. Seventeen morphological, physiological, and phenological traits were used to evaluate 16 diverse bread wheat genotypes under early, terminal, and continuous heat stress conditions. A plastic house experiment was also conducted to characterize the 16 genotypes for their response to photoperiod and vernalization. Early flowering/maturity, longer peduncles, larger number of kernels/spike, larger harvest index, and larger biomass played an important role under early and terminal heat stress conditions in Northern Syria. Medium flowering/maturity, semi-dwarf stature, denser ground cover, and larger biomass conferred better agronomic performance under continuous heat stress conditions in Wad Medani, Sudan. Unlike grain and biological yields, days to f lag leaf emergence, anthesis, and maturity showed stability across the three environments. Harvest index showed some stability across environments as well. None of the 16 genotypes was sensitive to day length. The late-maturing genotypes were sensitive to vernalization. A large amount of genetic variability was found for all the traits tested in all three environments to guarantee their use in a breeding program for heat stress.
| Author | : Ganegama Lekamge Dhuanuja Neranjalee Abeysingha |
| Publisher | : |
| Total Pages | : 0 |
| Release | : 2022 |
| Genre | : Heat |
| ISBN | : |
The reproductive phase of wheat (Triticum aestivum L.) is highly sensitive to high-temperature stress. Temperatures above the growth optimum (23oC) interfere negatively with the reproductive development processes, resulting in poor grain set and yield. Crop adaptation strategies can be used to overcome the negative effects of heat stress on grain yield and can be achieved through genetic modifications and proper agronomic practices. Experiments presented in this thesis test the hypotheses that: 1) heat stress at initial flowering (35 °C for 6 h per day for 6 days) has a negative impact on grain yield and foliar auxin application (4-Cl-IAA, 1μM) has the ability to at least partially negate the negative impact of heat stress, and 2) variation in heat stress response with respect to grain yield among a wheat RIL population will allow for the identification of specific phenotypic traits and quantitative trait loci (QTL) associated with heat stress resistance. First, a controlled environment experiment was conducted to evaluate the Canadian hard-red spring and/or CIMMYTY derived parents of two recombinant inbred line (RIL) populations of wheat for heat resistance and auxin responsiveness; the first population was derived from a cross between 'Attila' and 'CDC Go', and the second between 'CDC Teal' and 'CDC Go'. The 'Attila' x 'CDC Go' RIL population (171 lines) was selected for in-depth evaluation because 1) grain yield after heat-stress differed in 'Attila' and 'CDC Go', 2) the ability of a one-time foliar 4-Cl-IAA application (prior to heat stress) to ameliorate the negative effects of heat stress with respect to grain yield was observed in 'Attila' and 'CDC Go', and 3) the 'Attila' × 'CDC Go' RIL population was more extensively characterized in the field in previous studies than the 'CDC Teal' x 'CDC Go' RIL population. The 'Attila' x 'CDC Go' RILs, the parental RIL cultivars, and seven other Canadian spring wheat cultivars were further evaluated for heat resistance and auxin responsiveness under controlled environmental conditions. 'Attila' showed greater yield stability under heat stress conditions at flowering compared to 'CDC Go'. The lower heat tolerance for 'CDC Go' when exposed to the heat stress treatment was reflected in substantial reduction in main tiller grain yield (~ 45%) associated with reductions in the number of fertile spikelets per spike, grains per spikelet and per fertile spikelet. Heat stress reduced the RIL population mean grain number and weight with a substantial reduction in fertile spikelets per spike and grain number per spikelet or per fertile spikelet. Within the RIL population, 45% (77 RILs) were categorized as heat-resistant, 20.5% as moderately heat susceptible (35 RILs) and 7.6% (13 RILs) as highly heat susceptible with respect to grain weight. Strong to minor relationships were observed between yield component traits and grain yield among the standard spring wheat cultivars and the 'Attila' × 'CDC Go' RIL population, and in some cases heat stress affected the strength of the relationships. Auxin treatment increased some yield traits (grain number and weight, fertile spikelets per spike, and grain number per spikelet or per fertile spikelet) under heat stress and/or non-temperature stress conditions in 'Attila', 'CDC Go', and RILs 18, 46, 70, 80, and 145. Inclusive composite interval QTL mapping was conducted using phenotypic data of the 'Attila' x 'CDC Go' RIL population and genotypic data obtained from a previous study conducted using a subset of (1200 SNPs) Wheat 90K SNP array together with Ppd-D1, Vrn-A1, and Rht-B1 genes. Whole spike and spike section data from non-temperature stress (NS) and heat stress (HS) treatments identified 73 QTL (NS, 37; HS, 36) on 14 of the 21 chromosomes (1A, 1B, 2A, 2B, 2D, 3A, 4A, 4B, 5A, 5B, 6A, 6B, 7B, 7D) that individually explained 1.6 to 47.5% phenotypic variation with Logarithm of Odds (LOD) values ranging from 2.5 to 25.8. Eight important QTL clusters associated with two or more important grain yield or yield-related traits were identified on chromosomes 5A, 4B, 2B, 2D and 1B. Overall, heat stress at early flowering reduced grain yield, with the magnitude of the reduction dependent on the genotype. Relationships between grain yield and other yield-component traits were modified by the heat stress in some cases, stressing the importance of cultivar trait evaluation under environments where the cultivar will be grown. One-time foliar application of auxin prior to heat stress (4-Cl-IAA at 1 μM) at the early flowering stage can increase the grain yield and/or yield component traits in some genotypes and has the potential for use as an agronomic tool to enhance wheat grain yield. QTL and QTL clusters were identified for non-temperature stress and/or heat stress, with many detected in QTL hotspots in the wheat genome for grain yield and spike architecture.
| Author | : |
| Publisher | : |
| Total Pages | : 614 |
| Release | : 2011 |
| Genre | : Agriculture |
| ISBN | : |
| Author | : Richard Esten Mason |
| Publisher | : |
| Total Pages | : |
| Release | : 2011 |
| Genre | : |
| ISBN | : |
Heat stress adversely affects wheat production in many regions of the world and is particularly detrimental during reproductive development. The objective of this study was to identify quantitative trait loci (QTL) associated with improved heat tolerance in hexaploid bread wheat (Triticum aestivum). To accomplish this objective, an analysis of both the phenotypic and genetic responses of two recombinant inbred line (RIL) populations was conducted. RIL populations Halberd x Cutter and Halberd x Karl 92 (H/K) both derive heat tolerance from Halberd and segregate in their response to heat stress. A heat susceptibility index (HSI) was calculated from the reduction of three yield components; kernel number, kernel weight, and single kernel weight, following a three-day 38 degrees C heat stress treatment during early grain-filling. The HSI, as well as temperature depression of the main spike and flag leaf were used as measurements of heat tolerance. Genetic linkage maps were constructed for both populations and were used in combination with phenotypic data and statistical software to detect QTL for heat tolerance. In a comparison across the two across populations, seven common QTL regions were identified for HSI, located on chromosomes 1B, 3B, 4A, 5A, 5B, and 6D. Subsequent analysis of temperature depression in the H/K population identified seven QTL that co-localized for both cooler organ temperature and improved HSI. Four of the beneficial alleles at these loci were contributed Halberd. The genetic effect of combining QTL, including QHkw.tam-1B, QHkwm.tam-5A.1, and QHskm.tam-6D showed the potential benefit of selection for multiple heat tolerant alleles simultaneously. Analysis of the H/K population in the field under abiotic stress detected QTL on chromosome 3B and 5A, which were in agreement with results from the greenhouse study. The locus QYld.tam-3B was pleiotropic for both temperature depression and HSI in both experiments and was associated with higher biomass and yield under field conditions. The results presented here represent a comprehensive analysis of both the phenotypic response of wheat to high temperature stress and the genetic loci associated with improved heat tolerance and will be valuable for future understanding and improvement of heat stress tolerance in wheat.
| Author | : Marina Castro Derényi |
| Publisher | : |
| Total Pages | : 220 |
| Release | : 2005 |
| Genre | : Wheat |
| ISBN | : |
Wheat (Triticum aestivum L.) plants exposed to higher than usual temperatures during ripening show altered agronomic and grain quality characteristics. Given that seasonal variation in quality creates difficulties in the marketing and processing of grain, improving the genetic adaptation of wheat cultivars to heat stress is an important objective in breeding programs. Some genotypes have been reported to have a thermo tolerant response and could be used as genetic sources for heat tolerance. Six spring wheat cultivars and four elite experimental lines were evaluated in Uruguay. Two field experiments were conducted in years 2001 and 2002 to determine response under natural heat stress conditions, and two greenhouse experiments were conducted to vary duration and timing of heat stress. Grain protein concentration increased with moderate (field conditions) and high heat stress (controlled environment). Heat stress imposed early in grain fill had the greater effect. In field conditions, moderate to high heat stress at mid-grain fill increased test weight and thousand kernel weight. Higher heat stress under controlled environment caused a decrease in thousand kernel weight, without any difference in relation to duration or timing of stress. Rheological properties were affected by heat stress in field conditions. While moderate heat stress throughout grain fill caused stronger dough, moderate to high heat stress at mid-grain fill produced weaker dough. These results suggest a curvilinear response to increasing heat stress for both thousand kernel weight and rheological properties. Impact of heat stress under field conditions was inconsistent on protein molecular weight distribution. Moderate to high heat stress at mid-grain fill lowered level of monomeric proteins, and increased the ratio soluble polymeric proteins/monomeric proteins. Moderate heat stress throughout grain fill decreased percentage of soluble polymeric proteins, and increased percentage of low molecular weight albumins and globulins. No effect of heat stress was detected on protein molecular weight distribution in controlled environment. However, with longer duration of stress, significant genotype x treatment interaction was detected. Cultivars with relatively stable agronomic and quality characteristics were identified and could be used as genetic sources for improving resistance to heat stress.
| Author | : Karansher Singh Sandhu |
| Publisher | : Frontiers Media SA |
| Total Pages | : 657 |
| Release | : 2023-07-20 |
| Genre | : Science |
| ISBN | : 2832529615 |
| Author | : Moaed Almeselmani |
| Publisher | : LAP Lambert Academic Publishing |
| Total Pages | : 248 |
| Release | : 2012-08 |
| Genre | : |
| ISBN | : 9783659197383 |
Mechanism of heat stress tolerance in wheat was investigated with the following objectives: study the physiological and biochemical changes and role of antioxidant enzymes, investigate the effect of heat stress on different growth parameters, yields and yields components and molecular analysis of heat stress tolerance in wheat. Significant reductions in all physiological traits (Chlorophyll content, MSI, RWC and Relaxation time T2), growth parameters (LAI, CGR, RGR, NAR, and plant height), yield and yield components under stress conditions were detected. The protective role of antioxidant enzymes was clearly seen through the significant increased in the enzymes activity in tolerant genotypes which was associated with better physiological systems and more stable yield under stress condition. The reduction in the photosynthetic rate under heat stress in susceptible and tolerant genotype was associated with reduction in Rubisco enzyme activity and low level of expression of small subunit of Rubisco particularly in PBW 343. High level of expression of HSP 101 in tolerant genotypes leads to suggestion that this particular protein might have protective role under high temperature stress.
| Author | : Jung Hwa Do |
| Publisher | : |
| Total Pages | : |
| Release | : 2010 |
| Genre | : |
| ISBN | : |
This study was conducted to identify and map QTLs for yield components and heat tolerance of wheat in response to two kinds of heat treatment (short term-and long term-heat treatment) during seed formation in a set of 62 RILs derived from a cross of '7C' (heat resistant variety) and 'Seri M82' (heat susceptible variety) in environmentally controlled growth rooms and field. Phenotypic variations of yield components (kernel number, kernel weight, spike number and grain filling duration) were evaluated as indicators of heat tolerance / susceptibility. Most of the phenotypic variations of yield components exhibited a normally distributed pattern in response to heat stress treatments. This suggests that the yield component responses to high temperature stress are likely quantitatively inherited. A transgressive segregation pattern compared to the two parents was observed in several yield traits. This suggests that genetic variation from optimal recombination from the two parents have occurred in the progeny population. The Pearson correlation coefficients revealed significant correlations between yield components. This suggests the probability of co-segregation of genes controlling each yield components. The ANOVA also revealed a significant genotype x environment effect on individual yield components in response to reproductive stage high temperature stress. The heritability of the individual yield components was low (0.42 to 25%, 0.1~ 2% for heat tolerance). One hundred two polymorphic SSRs markers among 323 SSRs markers tested were used to construct a linkage coverage and average interval distance of 1860.2 cM and 18.2 cM/marker, respectively. Eighty-one QTLs for yield components and 68 QTLs for heat tolerance were detected with high LOD values (2.50~8.35 for yield components, 2.51~ 9.37 for heat tolerance) and that explained significant phenotypic variations (7~40% for individual QTL for yield components, 2~40 % for individual heat tolerance QTLs) from seven individual environments and the four individual heat stress environments, respectively. Specifically the regions between wmc48 and wmc89, and between wmc622 and wmc332 on the chromosome 4A and 6A, respectively possessed QTLs for both yield components and heat tolerance from various environments.
| Author | : Shamima Begum |
| Publisher | : LAP Lambert Academic Publishing |
| Total Pages | : 156 |
| Release | : 2012 |
| Genre | : |
| ISBN | : 9783847322634 |
The present investigation was carried out with an aim to studying some physio-morphological characters of wheat associated with yield under different soil moisture stress. The soil moisture stress as a whole reduced the yield and yield contributing characters of wheat. Correlation analysis of grain yield with yield attributing characters indicated a high positive correlation coefficient with total dry matter, crop growth rate, leaf number/plant, harvest index, spikelet number/spike and 1000 kernel weight. Growth analysis showed that both crown root initiation and heading stages were the critical and care is needed at these stages for better crop yield. However, heading stage was more critical. Stress study clearly showed that the varieties differed from one another in their tolerance to stress and among the varieties studied, Gaurab was comparatively least susceptible one while Aghrani was the highest highest susceptible. Phenotypic regression analysis also showed that Gaurab had unit regression slope with low stability value for grain yield/plant, fertile tiller number and 1000 kernel weight indicating its stability to varying soil moisture treatments.
