Wheat (Triticum aestivum l.) production under drought and heat stress – adverse effects, mechanisms and mitigation: A review

Heat and drought stresses are the most important abiotic factors that reduce crops productivity by affecting various physiological and biochemical processes. Thus, selecting cultivars with better drought or heat stress tolerance or breeding for stress tolerance will be helpful in enhancing crop productivity under harsh environments. This review elaborates the physiological basis of high temperature and drought stress tolerance in wheat which can be used as selection criteria in wheat breeding program. In addition, some agronomic selection criteria which are valid and useful in selecting stress tolerant wheat species and cultivars. The review also discussed the valid usage of stress tolerance indices (such as mean productivity (MP), geometric mean productivity (GMP), yield index (YI), yield stability index (YSI), relative productivity (RP%), stress susceptibility index (SSI), and the tolerance index (TOL)) to scan the genotypes against drought and heat stress. Beside these, exogenous application of stress signaling compounds, osmolytes, or certain inorganic salts play a vital role for alleviating adverse effects of abiotic stresses for sustainable wheat production. In addition, applications for soil amendments will also helpful in increasing wheat crop productivity under stressful conditions. All these strategies may be helpful to meet the food demands of the increasing population.Fil: El Sabagh, A.. University of Kafrelsheikh; EgiptoFil: Hossain, A.. Bangladesh Agricultural Research Institute; BangladeshFil: Barutçular, C.. University of Çukurova; TurquíaFil: Islam, Mohammad Sirajul. Hajee Mohammad Danesh Science and Technology University; BangladeshFil: Awan, S. I.. University of the Poonch; PakistánFil: Galal, A.. University of Kafrelsheikh; EgiptoFil: Iqbal, M. A.. University of the Poonch; PakistánFil: Sytar, O.. Slovak University of Agriculture; EslovaquiaFil: Yildirim, M.. Dicle University; TurquíaFil: Meena, R. S.. Inistitute of Agricultural Sciences; IndiaFil: Fahad, S.. The University of Swabi; PakistánFil: Najeeb, U.. The University of Queensland; AustraliaFil: Konuskan, O.. Mustafa Kemal University; TurquíaFil: Habib, R. A.. Bahauddin Zakariya University; PakistánFil: Llanes, Analia Susana. Universidad Nacional de Rio Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Investigaciones Agrobiotecnológicas - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones Agrobiotecnológicas; Argentina. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Ciencias Naturales; ArgentinaFil: Hussain, S.. University of Agriculture; PakistánFil: Farooq, M.. Sultan Qaboos University; OmánFil: Hasanuzzaman, M.. Sher-e-Bangla Agricultural University; BangladeshFil: Abdelaal, K. H.. Kafrelsheikh University; EgiptoFil: Hafez, Y.. Kafrelsheikh University; EgiptoFil: Cig, F.. Siirt University; TurquíaFil: Saneoka, H.. Hiroshima University; Japó

Recent advancements in the breeding of sorghum crop: current status and future strategies for marker-assisted breeding

Sorghum is emerging as a model crop for functional genetics and genomics of tropical grasses with abundant uses, including food, feed, and fuel, among others. It is currently the fifth most significant primary cereal crop. Crops are subjected to various biotic and abiotic stresses, which negatively impact on agricultural production. Developing high-yielding, disease-resistant, and climate-resilient cultivars can be achieved through marker-assisted breeding. Such selection has considerably reduced the time to market new crop varieties adapted to challenging conditions. In the recent years, extensive knowledge was gained about genetic markers. We are providing an overview of current advances in sorghum breeding initiatives, with a special focus on early breeders who may not be familiar with DNA markers. Advancements in molecular plant breeding, genetics, genomics selection, and genome editing have contributed to a thorough understanding of DNA markers, provided various proofs of the genetic variety accessible in crop plants, and have substantially enhanced plant breeding technologies. Marker-assisted selection has accelerated and precised the plant breeding process, empowering plant breeders all around the world

Photosynthesis and Productivity of Old and Modern Durum Wheats in a Mediterranean Environment

Genetic variability of leaf net photosynthesis rate (An) and its relation to productivity in durum wheat (Triticum turgidum L. var. durum) is not well defined. Two field experiments were conducted at the experimental area of the Faculty of Agriculture, in the University of Çukurova, Turkey, to evaluate the differences between old and modern cultivars in A n and productivity. Experiments with sowing dates in November 1996 and February 1997 were performed under rainfed and irrigated conditions, respectively. Measurements included leaf gas exchange and agronomic traits. Old cultivars (OC) were later flowering and taller than modern cultivars (MC) and their harvest indexes were lower. Before the onset of leaf senescence, most of the OC exhibited higher An values than most of the MC, but the extent of variability was not great. High An was correlated with high stomatal conductance (gs), but no overall correlation between An and the ratio of internal [CO2] to [CO2] in the air was observed. In spite of higher An, OC showed no superiority in grain yield. The results indicate that mesophyll conductance rather than gs has an effect on variation in An, and that preanthesis dry matter distribution and total flag leaf photosynthesis and its duration appear to be more relevant than An for grain yield, especially under drought

Grain protein and grain yield of durum wheats from south-eastern Anatolia, Turkey

High grain protein in durum wheat [Triticum turgidum ssp. turgidum L. conv. Durum (Desf.)] is one of the main goals of breeding programs. Landraces may be very useful germplasm for achieving this goal. To examine their potential as a source of high grain protein content, 11 genotypes, including 7 landraces, were evaluated in 8 environments. Environment, genotype, and the interaction of the two (G x E) significantly influenced the variation in grain yield, grain protein content, and grain protein yield. The environmental effect was the strongest, mostly due to differences in water supply. Grain yields of the modern genotypes were higher than those of landraces. Yields of the modern genotypes tended to respond more strongly to the higher yielding environments, but they varied more than the yields of landraces. With the exception of VK.85.18, the grain protein content of the high-yielding genotypes was almost as high as that of the best landraces. Moreover, grain protein content of these bred genotypes tended to respond more strongly to the higher protein environments. Differences in grain protein yield were closely related to the differences in grain yield. The results indicate that it is possible to improve grain protein content without grain yield being adversely affected. The results also indicate that potential gene sources should be compared over a number of environments before they can be used as breeding material or as crop varieties producing high grain protein yields

Possible heat-tolerant wheat cultivar improvement through the use of flag leaf gas exchange traits in a Mediterranean environment

BACKGROUND: Flag leaf traits are associated with performance of wheat (Triticum aestivum L.) genotypes in heat-stress environments. Fifteen cultivars were evaluated during 3 years with two sowing dates under irrigated conditions so as to examine the relationship between the flag leaf traits and performance in a Mediterranean environment. RESULTS: It became possible to assess a heat susceptibility index (HSI) for each cultivar by altering the sowing date, exposing the crops to different temperatures. The cultivars showed significant differences for all measured traits except canopy temperatures and chlorophyll fluorescence, though not all were consistent. Excluding two cultivars that differed in development, yield, grain number, harvest index and leaf A n (net CO2 assimilation rate), gs (stomatal conductance to water vapor), mc (apparent mesophyll conductance of CO2) and ash content were negatively associated with HSI, whereas leaf area and width were positively associated. Traits showing the best correlation with HSI were An, followed by area, gs, m c, width and ash content. High An was associated with smaller leaf size. CONCLUSION: It is worthwhile to select high ear grain number and harvest index. In addition, flag leaf gas exchange traits and ash content can be used as complementary selection criteria after the possible pleiotropic associations of these traits with leaf size are clarified. © 2008 Society of Chemical Industry

Variations in morphological and physiological traits of bread wheat diallel crosses under timely and late sowing conditions

Four wheat cultivars and their F1 hybrids, at full diallel design, were sown timely and late to represent non-stress and stress conditions. The objectives of this study were to (1) investigate gas exchange (An, gs, Ci, An/Ci), canopy temperature depression (CTD), chlorophyll content measured by SPAD-502 chlorophyll meter (SPAD, soil plant analysis development) and certain agronomic traits, (2) to determine the relationships among all traits, and (3) to obtain genetic information on physiological traits via diallel analysis. Gas exchange at the medium milk development stage and SPAD measurements at the heading and late milk development stages were made on flag leaf. CTD was measured at medium milk development at three different times of day: late morning, noon and early afternoon. All gas exchange parameters decreased under late sowing conditions, except An/Ci. The CTD was higher under the late sowing conditions compared with the timely sowing conditions. The plants were cooler at early afternoon than at the other measurement times. The SPAD chlorophyll at the heading time for timely sowing was higher than for late sowing, while the SPAD chlorophyll at the late milky stage decreased for timely sowing and increased for late sowing with respect to the measurement at heading time. Compared with the parents, the hybrids had higher values for grain yield, CTD, SPAD chlorophyll and all agronomic traits under both conditions. Significant reciprocal differences were observed in all gas exchange parameters (under both non-stress and stress conditions), except for Ci under non-stress conditions, while reciprocal effects were not observed for SPAD chlorophyll. Reciprocal effects for CTD were significant at noon and early afternoon under stress conditions. SPAD chlorophyll at heading and late milk development correlated significantly with grain yield under stress conditions. All CTD and SPAD chlorophyll measurements showed corresponding correlations with grain yield under non-stress conditions. The data indicate that SPAD chlorophyll has the potential, as an indirect selection criterion in early segregating generations, to improve high grain-yielding genotypes under stress conditions. © 2012 Elsevier B.V

Membrane thermal stability at different developmental stages of spring wheat genotypes and their diallel cross populations [Yazlık bugday genotipleri ve diallel melez populasyonlarının farklı gelisme dönemlerinde yüksek sıcaklık membran kararlılıgı]

Membrane thermal stability (MTS) can be a significant selection criterion for heat stress tolerance. MTS is determined by measuring of electirical conductivity of aquause phase in which leaf tissue exposure to high temperature. This research was conducted to investigate the membrane stability assay measured by two different methods, namely MTS and relative injury (RI). The second objective of this experiment was to determine the effects of different growth stages of four spring wheat parents and their six half F2 diallel cross progenies grown in the field on membrane stability. Measurements were taken at different growth stages (seedling, stem elongation and early milk). The MTS and RI assays gave similar results at the three different growth stages. However, growth stages significantly affected the MTS and RI values of genotypes. Membrane stability parameters of genotypes decreased during the later developmental stages. Specific combining ability effects were superior to general combining ability effect for all measurements, indicating that membrane thermal stability was mediated mainly by non-additive gene actions. Membrane stability of flag leaf at the early milk stage was significantly correlated with grain yield. The parent of Genç 99 and 84ÇZT04 had low yield potential, whereas Chil's and Seri 82 had high yield potential. Grain yield, spike yield and kernel weight of F2 population were found higher than their parents. These results suggest that genetic variation among genotypes for membrane stability can be utilized in wheat breeding in heat-stressed environments

Trends in performance of Turkish durum wheats derived from the International Maize and Wheat Improvement Center in an irrigated West Asian and North African environment

Turkey is one of the most important durum wheat (T. turgidum L. var. durum Desf.) producers in West Asia and North Africa (WANA). There appears to have been a lack of progress in wheat yields in WANA over recent decades. Most of the modern cultivars grown in WANA are related to crosses produced by the International Maize and Wheat Improvement Center (CIMMYT). During 1999 and 2000, a chronological set of 11 cultivars related to CIMMYT crosses was evaluated using two irrigation regimes near Şanliurfa, Turkey. Average yields ranged from 386 g/m2 (local cultivar, Karakilçik-33) to 614 g/m2 (Ege-88). When wheat cultivars were grown with irrigation until physiological maturity, cessation of irrigation near anthesis reduced average grain yields of all cultivars by 6.2-25.7%. Since the introduction of the first generation of CIMMYT cultivars in 1975, CIMMYT grain yields have increased by about 0.60% per year compared with that of Karakilçik-33. This rate increased up to 1.08% per year until 1988. No further progress in yield was measured for varieties released in the 1990s. The average rate was 0.76% per year. After the introduction of the CIMMYT cultivars, yield changes fitted better in a quadratic function. Compared with Karakilçik-33, the yield increases of CIMMYT cultivars have resulted from an increase in harvest index associated with reduced height and the development of more and heavier grains. Grain quality traits decreased with the introduction of the first CIMMYT cultivar but recovered slightly thereafter with no clear trend. The results are discussed with consideration of breeding priorities and specific WANA conditions. © 2006 Cambridge University Press

Harvest index is a critical factor influencing the grain yield of diverse wheat species under rain-fed conditions in the Mediterranean zone of southeastern Turkey and northern Syria

Environmental and plant factors critical to the grain yields of bread (Triticum aestivum L.), durum (T. durum L.) and emmer (T. dicoccum L.) wheat cultivars were investigated at two Mediterranean rain-fed field sites: Adana in southeastern Turkey (2009 and 2010) and Aleppo in northern Syria (2009). The grain yield (GY) and biological yield (BY) of most cultivars were higher in Adana than in Aleppo, and the lower GY in Aleppo resulted from lower harvest index (HI) and lower BY due to higher temperatures and lower rainfall. The variations in the HI among cultivars were greater in Adana than in Aleppo. The GY was closely related to the HI but not the BY across cultivars at each site, and a higher GY was accompanied by a superior conversion-efficiency of incident radiation during the grain filling period for grain yield [GY/Ra, where Ra is the cumulative radiation for 30 days after heading (D 30 )] across all observations. The GY/Ra correlated negatively with the average temperature for D 30 , and higher HI values resulted in higher GY/Ra. In Adana, the time from anthesis to physiological-maturity decreased as the average temperature for D 30 increased, resulting in a lower HI. Cultivars exhibiting the early heading trait can effectively escape the negative impacts of terminal high-temperature and water-shortage conditions on the HI. The results suggested that the HI is a critical factor for GY across diverse wheat cultivars under terminal high-temperatures and water-shortages in Mediterranean areas, and the BY is also an important factor under severe water-limitation conditions. © 2018 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group