Estimation of Variability, Heritability and Genetic Advance for Phenological, Physiological and Yield Contributing Attributes in Wheat Genotypes under Heat Stress Condition

The investigation was carried out in focusing the genetic variability for different traits of wheat influenced by heat tolerance mechanism to find out relationships among phenological, physiological and yield contributing traits. Spring wheat cultivar of 25 genotypes were selected and cultivated under late sowing condition at the Regional Wheat Research Institute, Shympur, Rajshahi, Bangladesh from December, 2016 to April, 2017. Significant variability among the genotypes exposed for different traits related to heat tolerance. Results showed that the genotypes G24, G10, G01, G13, G16, G25 and G14 ranked as better category considering maximum number of traits in mean performance indicating their tolerance to heat stress under late sowing condition. Phenotypic variances (σg2) of all traits were greater than those of genotypic variances (σg2). The same trends were also found in their co-efficient of variances. The phenotypic co-efficient of variances (PCV) of all traits were greater compare to those of genotypic co-efficient of variances (GCV) and their values were closer to each other. The heading days (HD), canopy temperature at vegetative stage (CTvg), canopy temperature at grain filling stage (CTgf), biomass, plant height (PH), spike/m2 (SPM), spikelet/spike (SPS), grain/ spike (GPS), thousand grain weight (TGW) and yield exhibited higher heritability (hb2) estimated under irrigated late sowing (ILS) condition. Under the same ILS condition SPAD, SPM, SPS, GPS, TGW and yield showed moderate to high genetic advance (GA) obtained through computing their mean percentage (%) and the rest traits HD, maturity days (MD), CTvg, CTgf, biomass, PH and harvest index (HI) exposed smaller genetic advance (% mean). The co-efficient of variation (CV%) of all attributes in all genotypes were significantly lower (1.36 - 6.96). Both heritability and genetic advance were found lower for MD, SPAD and HI indicated their non additive genetic effects for which these traits might not be recommended for selection. However, spike/m2, spikelet/spike, grain/spike, thousand grain weight and yield belonged to higher heritability and high to moderate genetic advance in mean percentage (%) along with wide genetic variation and lower environmental influence in heat stress situation indicated the most likely heritability due to the effects of additive genes that might be suggested as effective process of selection for these traits in heat stress condition.

Estimation of New Wheat Genotypes for Salt Tolerance Which Induced through Plant Breeding Programs

Salinity of soils or water poses an increasing threat to food production due to climate change. Plant breeding programs were applied to improve salt tolerance in new wheat genotypes to overcome this problem. The aim of this research work is to estimate the realized improvement in salt tolerance of the selected genotypes through plant breeding programs. The comparison experiments were conducted in salinized soils at two locations for two years as compared with two local cultivars. All the selected genotypes derived from F2 populations after six cycles of exposure to high salinity level were tested for salt tolerance during all growth stage. At harvest stage, seed yield and its components were studied for the comparison. Results showed that there were significant differences between all selected genotypes and local eultivars in their overall sensitivities to soil salinity. All selected genotypes were superior in seed yield and its components at maturity to those of the local cultivars at the two location and years. Clearly, all the selected genotypes exhibited more than twice seed yield/m2 compared with that obtained from local cultivars. The results also indicated that there were differences among selected genotypes in their responses to soil salinity between locations and years, but not significant. Important thing is significant improvement in selected genotypes was achieved in their salt tolerance through six cycles of screening and selection to high salinity level. The conclusion is a strong possibility to improve salt tolerant genotypes of wheat with high salt tolerance through plant breeding programs.

Comparative Study on Photoinhibition Between Two Wheat Genotypes

Changes in the efficiency of the primary light energy conversion, fluorescence quenching parameters and contents of photosynthetic pigments were compared between two wheat ( Triticum aestivum L.) genotypes in response to high light stress. The contents of chlorophyll and carotenoid in “Jing_411' were slightly higher than those in “Xiaoyan_54'. Under high light stress, photoinhibition as indicated by a sustained decrease in PSⅡ photochemical efficiency was more pronounced in “Jing_411' than in “Xiaoyan_54'. The content of ascorbate and the activity of the deepoxidase were higher in “Xiaoyan_54' than in “Jing_411'. The genotypic difference in resistance to photoinhibition is related to the capacity to dissipate the excess energy nonradiatively.

Drought Tolerant Criterion of Wheat Genotypes Using Carbon Isotopes Discrimination Technique

Drought tolerant analysis using carbon isotopes discrimination could be useful tool to decide a genotype with high adaptation to drought. A pot culture experiment was conducted in glass house at the IAEA （International Atomic Energy Agency） laboratories, Seibersdorf, Austria to analyze drought tolerant of wheat genotype using carbon isotopes discrimination technique. Four wheat genotypes viz., LU-26s, Bhittai, Roshan, Taifu, were tested. There were two treatments： Control （normal irrigation） and Drought （@ 30% field capacity of the control treatment）. Drought treatment was imposed after two weeks of germination. The experiment was continued up to 10 weeks after germination and was terminated at flowering stage. The data were recorded in terms of plant height, number of tillers, shoot dry weight and carbon isotopic ratio （δ）. Results showed that genotype LU-26s was found to have best performance under drought condition, with minimum decrease in the growth parameters i.e., plant height, number of tillers and shoot dry weight. High CID （carbon isotopes discrimination） values were also observed in genotype LU-26s, showing close positive correlation between SDW （shoot dry weight） and CID. It is therefore concluded that carbon isotopes discrimination can be an important criterion for the selection of wheat genotypes for drought prone areas.

Genotype Environment Interaction (G ×E) of Heat Tolerant Wheat Genotypes over Locations and Years

Twenty heat tolerant wheat genotypes were evaluated in three heat stress environments of Bangladesh such as Wheat Research Center (WRC), Nashipur, Dinajpur, Regional Wheat Research Center, BARI, Gazipur, Regional Wheat Research Center, RARS, Jashore in 2015-2016. The experiments were conducted in RCBD with three replications in 2015-2016. The stability and response to change of location and sowing time of the genotypes were assessed through AMMI model and regression coefficient analysis on seven characters, viz. days to heading, days to maturity, plant height (cm), spikes m-2, grains spike-1, 1000-grain weight (g) and yield (kg·ha-1). Among the linear interactions, sowing time alone exerted the maximum sum of square (335,388,000.00**) and among the non-linear interactions, location × year paid the highest effect (7,676,490.00**), which was followed by year × location × sowing time interaction (3,956,500.00**). The highest grain yield (4475.3 kg·ha-1) was obtained from the genotype G13, followed by the genotypes G17 (4460.8 kg·ha-1) and G19 (4404.7 kg·ha-1). The genotype G8 had the smallest interaction effect, while the genotype G14 followed by G10 responded vigorously to amelioration. The genotypes G13, G18 and G19 showed averagely high yield and showed stability over the environmental modifications. The other two genotypes G20 and G12 exhibited great reduction of yield potential under unfavorable environment. The environment 121 proceeded by J121 and G131 appeared as favorable environments. The genotypes G13 and G19 produced high yield (kg·ha-1) in the favorable environments. The genotypes G16 and G18 high IPCa1 scores, indicated sensitive to mega-environmental changes. The best genotype with respect to environment was genotype G13. Genotypes G17 and G19 were best for site E1;genotypes G14, G16 and G18 were best for site E2.

Comparison of Responses to Mn Deficiency Between the UK Wheat Genotypes Maris Butler, Paragon and the Australian Wheat Genotype C8MM

Wheat grown in Mn-deficient soil has been widely observed to produce much reduced yields. Breeding for Mn-efficient wheat genotypes adapted to Mn-deficient soils would represent a long-term solution for wheat agronomy. To characterize the physiological basis of Mn efficiency in wheat genotypes would facilitate the breeding programs for producing Mn-efficient wheat. Using a solution culture and a soil culture system in the present study, a Mn-efficient UK wheat genotype Maris Butler and a Mn-inefficient UK wheat genotype Paragon have been compared with a Mn-efficient Australian wheat genotype C8MM in the responses to Mn deficiency in order to characterize the Mn efficiency in these wheat genotypes. Results showed that in solution culture, Marls Butler grown under Mn deficiency had 77% relative dry matter yield of control plants that were grown under Mn sufficiency, whereas CSMM and Paragon had 60% and 58% relative dry matter yield of their respective controls. Results from the soil culture demonstrated that relative dry matter yield remained high for Maris Butler and C8MM （53% and 56%, respectively）, whereas the value for Paragon dropped to 33%. In terms of dry matter yield and photosynthetic efficiency, Maris Butler demonstrated Mn efficiency in both solution culture and soil culture, whereas C8MM showed Mn efficiency only in soil culture. Results also demonstrated that under Mn-depleted supply in soil, plants of C8MM had a significantly higher ability in Mn uptake, whereas plants of Marls Butler showed a higher internal Mn use efficiency in comparison with plants of Paragon. Results from the present study indicate that the ability of C8MM to accumulate higher amounts of Mn is the basis of the improved Mn efficiency of this genotype in comparison with Paragon, and in Marls Butler there is a higher internal use of Mn expressed as an improved photosynthetic efficiency in conferring its Mn efficiency. It is suggested that more than one mechanism has arisen in wheat to confer tolerance to Mn deficiency.

Assessing the Suitability of Various Physiological Traits to Screen Wheat Genotypes for Salt Tolerance

Success of improving the salt tolerance of genotypes requires effective and reliable screening traits in breeding programs. The objective was to assess the suitability of various physiological traits to screen wheat genotypes for salt tolerance. Thirteen wheat genotypes from Egypt, Germany, Australia and India were grown in soil with two salinity levels （control and 150 mmol/L NaCI） in a greenhouse. The physiological traits （ion contents in leaves and stems, i.e. Na^＋, Cl^-, K^＋, Ca^2＋）, the ratios of K^＋/Na^＋ and Ca^＋/Na^＋ in the leaves and stems, net photosynthesis rate, stomatal conductance, transpiration rate, chlorophyll content （SPAD value）, and leaf water relations, were measured at different growth stages. The physiological traits except for Na^＋ and Cl^- in stems and the leaf transpiration rate at 150 mmol/L NaCI showed a significant genotypic variation, indicating that the traits that have a significant genotypic variation may be possibly used as screening criteria. According to the analysis of linear regression of the scores of the physiological traits against those of grain yield, however, the physiological traits of Ca^2＋ and Ca2^＋/Na^＋ at 45 d and final harvest with the greatest genotypic variation were ranked at the top. From a practical and economic point of view, SPAD value should be considered to be used as screening criteria and/or there is a need to develop a quick and practical approach to determine Ca^2＋ in plant tissues.

Critical phosphorus concentrations in winter wheat genotypes with various phosphorus efficiencies

Under greenhouse conditions, a pot experiment was conducted to seek critical phosphorus concentrations of wheat genotypes with high and low phosphorus use efficiency. Results indicated that low efficient genotype was much more sensitive to phosphorus deficiency, with low or without phosphorus application, seed yield and dry matter of biomass were much lower. The yield of all the genotypes gradually got higher as application rate increased, but high efficient genotype——Lofflin produced relatively higher yields of seeds and biomass with low or without phosphorus input. Highly tolerate to low availability of soil phosphorus and efficient activation and absorption for soil unavailable phosphorus had been displayed. As application rates increased, yields of both genotypes were increased but high efficient genotype maintained stable while low efficient one showed continuously increase with remuneration decrease progressively. Critical phosphorus concentrations in high efficient genotypes of winter wheat were lower than that in low efficient ones and changed with various development stages, for example, at seedling state, the concentrations of high efficient genotype were 4.50—4.60 g/kg while low efficient one was 5.0 g/kg. They were 2.25—2.30 g/kg and 2.52 g/kg at flower stage, 1.96—2.05 g/kg and 2.15 g/kg at maturity respectively. But the values in seeds were reversal, higher in high efficient genotype(4.05—4.10 g/kg) than that in low efficient(3.90 g/kg). Therefore, phosphorus high efficient genotypes belong to the phosphorus resource saving type.

Phosphorus Uptake and Utilisation Efficiencies of Different Wheat Cultivars Based on a Sand-Culture Screening System

A sand-based culture system using rock phosphate (P) was developed to simulate the situation in alkalinesoils, with respect to the dominant P form, and five wheat cultivars (Excalibur, Brookton, Krichauff, Westoniaand Sunco) were tested in this screening system to compare their P uptake and utilisation efficiencies. Resultsshowed that these cultivars differed significantly in their ability to acquire P from the sparingly available form(rock phosphate in this case). The accumulation of P by Brookton was three times that by Krichauff. Pconcentrations in plant tissues did not differ significantly, indicating that all cultivars were similar in Putilisation efficiency. A further experiment showed that the greater ability of a cultivar to take up P fromsparingly available form was related to the ability of a cultivar to acidify the rhizosphere. Seed P content wasa confounding factor in this system, and the use of relatively uniform seed with similar P content, preferablylow, was conducive to a successful outcome of the screening process.

Statistical Analysis of Leaf Water Use Efficiency and Physiology Traits of Winter Wheat Under Drought Condition

Five statistical methods including simple correlation, multiple linear regression, stepwise regression, principal components, and path analysis were used to explore the relationship between leaf water use efficiency （WUE） and physiological traits （photosynthesis rate, stomatal conductance, transpiration rate, intercellular CO2 concentration, etc.） of 29 wheat cultivars. The results showed that photosynthesis rate, stomatal conductance, and transpiration rate were the most important leaf WUE parameters under drought condition. Based on the results of statistical analyses, principal component analysis could be the most suitable method to ascertain the relationship between leaf WUE and relative physiological traits. It is reasonable to assume that high leaf WUE wheat could be obtained by selecting breeding materials with high photosynthesis rate, low transpiration rate, and stomatal conductance under dry area.

Breeding and Selection of Some Lines of Bread Wheat for Salt Tolerance

The aim of this experimental work is to select wheat progenies tolerant high levels of salinity. Studies were conducted to determine the realized response in salt tolerance of some selected progeny （F3） through one cycle of screening and selection and the extent of variability for salt tolerance among selected progeny （F3） of wheat. All the selected progeny （F3） derived from （F2） populations after exposure are to high salinity level, were tested for salt tolerance during all growth stages in sand cultures salinized with 0, 100, 175 mM NaCI as compared with the unselected progeny （F2）. Results showed that the selected progeny （F3） were in all cases except one, superior in yield at maturity and in most cases significantly so, both at 100 and 175 mM NaCl, to the yield of the unselected progeny （F2） controls. In this study, some selected progeny exhibited more than twice the seed yield compared with that obtained from unselected progeny at 175 mM NaCl, and their seed yield was also significantly higher than that at 0 mM NaCl. Results also indicated that the highest value percentage of realized response in salt tolerance was in （F3AS1） and （F3AS2） at 175 mM NaCI. It is important to bear in mind that the significant improvement in selected progeny was achieved just in a single cycle of selection. There is then a strong possibility that further increases in tolerance may be obtained through further cycles of selection till reaching F6 or F7 where would show genetics stability.

Cloning and characterization of a novel UDP-glycosyltransferase gene induced by DON from wheat

Fusarium head blight（FHB）,caused primarily by Fusarium graminearum,is a destructive disease of wheat throughout the world.However,the mechanisms of host resistance to FHB are still largely unclear.Deoxynivalenol（DON）produced by F graminearum which enhances the pathogen to spread could be converted into inactive form D3 G by UDP-glycosyltransferases（UGTs）.A DON responsive UGT gene,designated as TaUGT4,was first cloned from wheat in this study.The putative open reading frame（ORF） of TaUGT4 was 1386 bp,encoding 461 amino acids protein.TaUGT4 was placed on chromosome 2D using a set of nulli-tetrasomic lines of wheat cultivar Chinese Spring（CS）.When fused with eGFP at C terminal,TaUGT4 was shown to localize in cytoplasm of the transformed tobacco cells.The transcriptional analysis revealed that TaUGT4 was strongly induced by F graminearum or DON in both of FHB-resistant cultivar Sumai 3 and susceptible cultivar Kenong 199,especially in Sumai 3 under DON treatment.Similar increase of TaUGT4 expression was observed in Sumai 3 and Kenong 199 in response to salicylic acid（SA） treatment.But interestingly,the transcripts level of TaUGT4 in Sumai 3 showed significantly higher than that in Kenong 199 after treated with methyl jasmonate（MeJA）.According to the expression patterns,TaUGT4 might lead to different effects between FHB-resistant genotype and susceptible genotype in the process against F graminearum inoculation.It had also been discussed in this paper that JA signaling pathway might play a significant role in the resistance against F.graminearum compared to SA signaling pathway.

Soil properties drive the bacterial community to cadmium contamination in the rhizosphere of two contrasting wheat(Triticum aestivum L.)genotypes

Cadmium(Cd)bioavailability in the rhizosphere makes an important difference in grain Cd accumulation in wheat.Here,pot experiments combined with 16S rRNA gene sequencing were conducted to compare the Cd bioavailability and bacterial community in the rhizosphere of two wheat(Triticum aestivum L.)genotypes,a low-Cd-accumulating genotype in grains(LT)and a high-Cd-accumulating genotype in grains(HT),grown on four different soils with Cd contamination.Results showed that there was non-significant difference in total Cd concentration among four soils.However,except for black soil,DTPA-Cd concentrations in HT rhizospheres were higher than those of LT in fluvisol,paddy soil and purple soil.Results of 16S rRNA gene sequencing showed that soil type(52.7%)was the strongest determinant of root-associated community,while there were still some differences in rhizosphere bacterial community composition between twowheat genotypes.Taxa specifically colonized in HT rhizosphere(Acidobacteria,Gemmatimonadetes,Bacteroidetes and Deltaproteobacteria)could participate inmetal activation,whereas LT rhizosphere was highly enriched by plant growth-promoting taxa.In addition,PICRUSt2 analysis also predicted high relative abundances of imputed functional profiles related to membrane transport and amino acid metabolism in HT rhizosphere.These results revealed that the rhizosphere bacterial community may be an important factor regulating Cd uptake and accumulation in wheat and indicated that the high Cd-accumulating cultivar might improve Cd bioavailability in the rhizosphere by recruiting taxa related to Cd activation,thus promoting Cd uptake and accumulation.

Genetic Analysis of Grain Yield in a 7×7 Diallel Cross F_2 Population of Wheat(T.Aestivum L.)

In order to obtain genetic information for grain yield, seven genetically diverse wheat cultivars were crossed in an incomplete diallel to study the inheritance of grain yield using F_2 progenies for two years. Significant differences were observed among genotype, year and genotype × year interaction for grain yield, and both general combining ability(GCA) and specific combining ability(SCA) were also highly significant for grain yield, suggesting that the trait was controlled by both additive and non-additive effect. The GCA estimates revealed that the best combiners for grain yield were Yangmai 5 and Ningmai 9. Adequacy tests revealed that data of grain yield was fully adequate for genetic interpretation. Over-dominance genetic effects were important for the expression of grain yield. Grain yield exhibited moderately high value of narrow sense heritability(h_N^2=66.98% and h_N^2=72.37%).