Gene Action and Combining Ability of Cellular Thermotolerance in Bread Wheat (Triticum aestivum L.)

( Mahmoud A. El-rawy ),( Mohamed I. Hassan ),( Mohamed F. Omran ),( Mohamed M. El-defrawy ) 한국육종학회 2018 Plant Breeding and Biotechnology Vol.6 No.3

Heat stress is one of the most important factors limiting growth and productivity of wheat. In the present study, gene action, general (GCA) and specific (SCA) combining ability of cellular thermotolerance were studied in a nine-parent half diallel cross of bread wheat evaluated under normal (1 ^st sowing date) and heat stress (late sowing date) conditions. The cellular thermotolerance was estimated based on cell membrane thermostability (CMS) and tetrazolium chloride (TTC) reduction. Grain yield/plant (GYP), 1000-kernel weight (TKW), stem diameter (STD) and heat tolerance index (HTI) were measured. Compared with their parents, F1 hybrids significantly produced higher GYP, CMS, TTC and HTI. Highly significant mean squares of GCA and SCA effects were observed for all traits with GCA mean squares being much larger than that of SCA. Highly significant additive (a) and non-additive (b) gene actions were observed for all the traits with a predominance of the additive gene actions. However, the dominance genetic variance of CMS and TTC was greater than the additive variance. Moderate to high narrow-sense heritability was obtained for CMS (0.52), TTC (0.57) and HTI (0.71). GYP was significantly correlated with CMS (r = 0.62), TTC (r = 0.63) and HTI (r = 0.60). A highly significant positive correlation was obtained between CMS and TTC (r = 0.73), supporting that CMS and TTC could be used as efficient criteria for selecting wheat genotypes under heat stress. The parents P₉, P₁ and P₂ were identified as best general combiners for CMS, TTC and HTI respectively. Six crosses were identified as best promising combinations for CMS (P₁ × P₈ and P₅ × P₉), TTC (P₄ × P₉ and P₅ × P₆) and HTI (P₁ × P₂ and P₈ × P₉). Thus, inclusion these superior genotypes into breeding programs could be useful for improvement of heat tolerance in wheat.

Effectiveness of Drought Tolerance Indices to Identify Tolerant Genotypes in Bread Wheat (Triticum aestivum L.)

Mahmoud A. El-Rawy,Mohamed I. Hassan 한국작물학회 2014 Journal of crop science and biotechnology Vol.17 No.4

In order to assess efficiency of drought tolerance indices, 50 bread wheat genotypes were evaluated under three environments:normal (clay fertile soil, E1), 100% (E2), and 50% (E3) field water capacity in sandy calcareous soil. A total of 14 drought toleranceindices including grain yield/plant, grain yield/spike, 1000-kernel weight, spike length, no. of tillers, plant height, flowering time,stomata frequency, stomata width, stomata length, drought susceptibility index (DSI), stress tolerance index (STI), yield stabilityindex (YSI), and harmonic mean (HM) were estimated. A moderate to high broad-sense heritability was obtained for 1000-kernelweight (0.47), spike length (0.38), plant height (0.54), flowering time (0.73), stomata frequency (0.59), and stomata length (0.54). Grain yield/plant was strongly positively correlated with grain yield/spike, no. of tillers, plant height, flowering time, stomata length,STI, YSI, and HM, while negatively correlated with stomata frequency and DSI in E2 and E3, respectively. Thus, highly heritabletraits strongly correlated with grain yield under stress conditions especially stomata frequency and length could be used as reliableindices for selecting high-yielding genotypes tolerant to drought stress. Cluster analysis based on morpho-physiological traits suggestedthe group 3 genotypes in E2 as the most tolerant genotypes to be used for developing improved varieties

Assessment of Genetic Diversity in Durum and Bread Wheat Genotypes Based on Drought Tolerance and SSR Markers

( Mahmoud A. El-rawy ),( Mohamed I. Hassan ) 한국육종학회 2021 Plant Breeding and Biotechnology Vol.9 No.2

Six durum and twelve bread wheat genotypes were evaluated under favorable and drought-stressed field conditions, and screened with thirty simple sequence repeats (SSR) markers. The traits studied were stomata frequency (STF), relative water content (RWC), flag leaf area (FLA), flag leaf weight (FLW), flag leaf dry matter content (FLD), chlorophyll a content (Chl.a), chlorophyll b content (Chl.b), grain yield/plant (GYP) and 1000-kerenl weight (TKW). Highly significant differences were observed among wheat genotypes for all the traits, indicating considerable genetic variation. Moderate to high broad-sense heritability estimates were observed for the studied traits. Under drought stress, GYP was positively correlated with RWC, FLA, FLW and TKW, whereas negatively correlated with STF. G3 (Svevo) and G6 (WK-12-1) were the most drought-tolerant durum wheat, whereas G11 (L.S-15) and G16 (SIDS-1) were the most drought-tolerant bread wheat genotypes. SSR markers analysis indicated considerable genetic variation between and within durum and bread wheat genotypes. The percentage of polymorphism ranged from 14.3% (Xgwm174-5D) to 100% (Xgwm294-2A and Xgwm573-7B), with an average of 61.4%. The polymorphism information content (PIC) ranged from 0.20 (Xwmc596-7A) to 0.48 (Xgwm294-2A), with an average of 0.33.The highest polymorphism (77.1%) was observed in the B genome followed by A (57.8%) and D (50.0%) genomes. Cluster analysis based on phenotypic data distinguished the most drought-tolerant genotypes (G6 and G11) from the remaining genotypes. Cluster analysis based on SSR markers distinguished durum from bread wheat genotypes. The study indicated that phenotypic data and SSR markers were effective in assessing the genetic diversity in the studied genotypes.

A Diallel Analysis of Drought Tolerance Indices at Seedling Stage in Bread Wheat (Triticum aestivum L.)

( Mahmoud A El-rawy ),( Mohamed I Hassan ) 한국육종학회 2014 Plant Breeding and Biotechnology Vol.2 No.3

Drought is one of the most important abiotic factors affecting wheat production and development of tolerant genotypes is limited by the lack of effective selection criteria. A genetic analysis of drought tolerance indices at seedling stage (i.e. root length, shoot length, root/shoot ratio and seedling dry weight) was performed for a seven-parent half diallel cross of bread wheat (Triticum aestivum L.) in Egypt. The parents and their F2 progenies were evaluated in the laboratory under osmotic stress induced by polyethylene glycol (PEG) with five treatments (i.e. 0, 5, 10, 15 and 20% PEG-6000). Grain yield per spike was also evaluated under drought stressed field conditions. The parent P7 had maximum root and shoot lengths under stress conditions, highest root/shoot ratio under 20% PEG and higher grain yield per spike than the other parents suggesting that P7 possessed stress tolerance genes. Grain yield/spike was significantly correlated with root length (r= 0.41, P<0.05) and seedling dry weight (r= 0.46, P<0.05) at 15% PEG. Both additive and non-additive gene effects were involved in the genetic control of all traits. Rather low to moderately narrow-sense heritability was obtained for root length (0.18 and 0.12) and shoot length (0.19 and 0.12) at 15 and 20% PEG, respectively; root/shoot ratio (0.15) and seedling dry weight (0.16) at 15% PEG. Moderate genetic advance was observed for root length (41.24%) and shoot length (29.96%) under stress conditions suggesting that selection could be practiced on both traits for improving drought tolerance in wheat breeding programs.

Evaluating Interspecific Wheat Hybrids Based on Heat and Drought Stress Tolerance

Mohamed I. Hassan,엘자에드 압델몬세프 모하메드 이스마엘,Mahmoud A. El-Rawy,Karam A. Amein 한국작물학회 2016 Journal of crop science and biotechnology Vol.19 No.1

Three durum and three bread wheat genotypes were crossed to produce three tetraploid, three hexaploid and nine interspecific (pentaploid) F1 hybrids. All genotypes were evaluated for heat tolerance in the field and for drought using polyethylene glycol in vitro. Chromosome numbers and meiotic behavior in pentaploid F1 hybrids (2n=5x=35, genomes AABBD) were confirmed. Heat stress significantly reduced grain yield/plant and 1000-kernel weight (1000-KW), while grain protein content (GPC) was increased. Drought caused a significant reduction in root length, shoot length and seedling fresh weight, whereas root/shoot ratio was increased. P3 (durum), P4 (bread) and their pentaploid F1 hybrid could be considered as the most heat-tolerant genotypes. However, P2 (durum), P6 (bread) and their F1 were most tolerant to drought. The addition of a D genome single dose into pentaploid F1 hybrids obviously reduced grain yield/plant, 1000-KW and seedling traits, however GPC was increased. Moderate to high broad-sense heritability and genetic advance were obtained for the most investigated traits. Grain yield/plant was strongly positively correlated with stress tolerance index (STI), yield index (YI), mean productivity (MP), geometric mean productivity (GMP) and harmonic mean (HM) under heat stress and with root length under drought condition, suggesting that STI, YI, MP, GMP and HM are powerful indices for heat tolerance, while root length is most effective for drought. Successful interspecific hybridization obtained in the study is only an initial step for desired genes introgression. Successive progenies are going to be evaluated for further genetic studies aiming at improving abiotic stress tolerance in wheat.

Impacts of Selection for Spike Length on Heat Stress Tolerance in Bread Wheat (Triticum aestivum L.)

Asmaa M. Mohamed,Mohamed K. Omara,Mahmoud A. El-Rawy,Mohamed I. Hassan 한국육종학회 2019 Plant Breeding and Biotechnology Vol.7 No.2

Two consecutive cycles of selection were imposed on five F2 populations of bread wheat. The first cycle was a divergent selection for spike length conducted in favorable environment (optimal sowing date) and the response was measured under favorable and heat stress conditions of a late sowing date. Positive responses to selection for longer spikes were obtained under favorable (13.43%) heat stress (8.66%) conditions, whereas the responses for shorter spikes were 2.24 and 5.02% in the two environments, respectively. The realized heritability of spike length was greater under favorable conditions (0.25-0.56) than under heat stress (0.18- 0.41). Concurrent positive responses to selection for longer spikes were obtained in grain yield per spike under favorable (25.35%) and heat stress (13.65%) environments. Selection for greater number of grains per spike imposed on F3 plants selected for spike length under heat stress resulted in significant responses (14.65%). Selection for greater number of grains per spike resulted in correlated responses in grain yield per spike (17.64%). The concurrent positive responses produced in spike length in F4 with selection for number of grains per spike (averaged 9.20%) was almost equal to that produced by the direct selection in F3 (8.66%), indicating that selection advance effected in F3 has been maintained in F4. High F4/F3 regression was obtained for spike length under heat stress (b = 0.85 ± 0.07), indicating high heritability. In conclusion, phenotypic selection for longer spikes under heat stress followed by a cycle of selection for number of grains per spike was capable of improving heat tolerance in wheat.