Losses In Grain Yield Research Articles

Selectivity of Iodosulfuron-Methyl Association with ACCase Inhibitors and 2.4-D in Wheat and Barley Crops

ABSTRACT: This research aimed to assess the selectivity of treatments involving the commercial formulations tank mixtures of iodosulfuron-methyl with herbicides ACCase inhibitors (fenoxaprop-p-ethyl and clethodim) and synthetic auxins (2.4-D), applied in post-emergence of wheat (Triticum aestivum) and barley (Hordeum vulgare) crops. Three experiments were conducted in the field, during the 2014 crop year. A randomized complete block design was used with 11 treatments and five replications. Treatments consisted of (g ha-1): 1) iodosulfuron-methyl (6.5), 2) fenoxaprop-p-ethyl (82.5), 3) fenoxaprop-p-ethyl + clethodim (55 + 54); 4) 2.4-D (335), 5, 6 e 7) iodosulfuron-methyl + fenoxaprop-p-ethyl (6.5 + 82.5; 6.5 + 110 and 6.5 + 165), 8) iodosulfuron-methyl + fenoxaprop + clethodim (6.5 + 55 + 54), 9) iodosulfuron + fenoxaprop-p-ethyl + 2.4-D (6.5 + 110 + 335), 10) iodosulfuron-methyl + fenoxaprop-p-ethyl + clethodim + 2.4-D (6.5 + 82.5 + 72 + 335) and 11) check without weeds. Associations of iodosulfuron-methyl + fenoxaprop-p-ethyl (6.5 + 82.5; 6.5 + 110 and 6.5 + 165 g ha-1) associations, as well as of iodosulfuron-methyl + fenoxaprop-p-ethyl + 2.4-D (6.5 + 110 + 335 g ha-1) were selective for BRS Campeiro and BRS Gralha azul wheat cultivars and did not feature symptoms of intoxication and significant losses in grain yield and hectoliter weight, when compared to the treatment with no application. For BRS Brau barley cultivar, only iodosulfuron-methyl + fenoxaprop-p-ethyl associations, in doses of 6.5 + 82.5 and 6.5 + 110 g ha-1 were feasible for selectivity. Clethodim addition in iodosulfuron-methyl + fenoxaprop-p-ethyl or iodosulfuron-methyl + fenoxaprop-p-ethyl + 2.4-D associations caused negative effects for wheat and barley crops. Commercial formulation of iodosulfuron-methyl (Hussar™) resulted in protection for damage effects of fenoxaprop-p-ethyl (Podium EW™) for studied crops.

Genetic analysis of yield and agronomic traits under reproductive-stage drought stress in rice using a high-resolution linkage map

Drought stress at the reproductive stage of rice crop leads to a huge loss in grain yield. Identification and introgression of large effect drought tolerant QTLs are necessary to develop drought-tolerant rice varieties. Compared to the high-density linkage maps, widely spaced markers lead to the identification of QTLs with large confidence intervals which are difficult to incorporate in a breeding program. A previously generated genotyping-by-sequencing (GBS) based linkage map consisting of 4748 SNP markers was used to map QTLs in Cocodrie × N-22 recombinant inbred line (RIL) population. Twenty-one QTLs were discovered for days to flowering (DTF), plant height (PH), leaf rolling score (LRS), plant dry matter content (DM), spikelet fertility (SF), grain yield (GY), yield index (YI), and harvest index (HI) under drought stress. A major QTL qPH1.38 was identified in a narrow confidence interval on chromosome 1. The QTLs, qDTF3.01 and qPH1.38, overlapped with the previously identified QTL qDTY1.1 and Hd9, respectively. Another large-effect QTL qLRS1.37 was identified close to the sd1 locus on chromosome 1. A grain yield QTL qGY1.42 located on chromosome 1 contained only 4 candidate genes. There was no overlapping of QTLs for the root traits and the yield attributes. The important candidate genes present within the large effect QTL regions are MYB transcription factors, no apical meristem protein (NAC), potassium channel protein, nuclear matrix protein1, and chlorophyll A-B binding protein. The large effect QTLs (qDTF3.01, qPH1.38, and qLRS1.37) and a novel grain yield QTL qGYS1.42 can be used to incorporate in elite breeding lines to develop drought-tolerant rice varieties.

Herbicidal activities of wheat residues in transplant Aman rice

Allelopathic potentiality of crop residues may be helpful to minimize the serious problems in the present agricultural production such as environmental pollution, unsafe products, human health concerns, depletion of crop diversity, soil sickness and reduction of crop productivity. In this phenomenon an experiment was conducted at the Agronomy Field Laboratory, Bangladesh Agricultural University, Mymensingh during June to November, 2015 to evaluate the effect of crop residues of wheat on weed management and crop performance of T. Aman rice. The experiment consisted of three varieties (cv. BRRI dhan32, BRRI dhan33 and BRRI dhan49) and five different treatments (viz. no crop residues, wheat crop residues @ 0.5, 1.0, 1.5 and 2.0 t ha-1). The experiment was laid out in a randomized complete block design with three replications. Five weed species belonging to three families infested the experimental plots. Weed population, weed dry weight and percent inhibition of weed were significantly influenced by wheat crop residues and cultivar. The maximum weed growth was noticed where no crop residues was incorporated and the minimum was found where @ 2.0 tha-1 wheat crop residues was incorporated. The grain yield as well as the other yield contributing characters produced in BRRI dhan49 was the highest among the studied varieties. The highest percent inhibition of 75.32, 58.24, 72.60, 57.45 and 82.24 was in Shama, Panishapla, Pani chaise, Panikachu and Susnishak, respectively which was caused by the application of wheat crop residues @ 2 t ha-1. The highest loss of grain yield was obtained where no crop residues were incorporated. The highest numbers of tillers hill-1, numbers of grains panicle-1, 1000-grain weight, grain yield, straw yield were observed where wheat crop residues were incorporated @ 2.0 t ha-1. The results of this study indicate that different amount of wheat crop residues showed potential activity to suppress weed growth.Progressive Agriculture 28 (4): 253-261, 2017

Genome-wide analyses of direct target genes of four rice NAC-domain transcription factors involved in drought tolerance

BackgroundPlant stress responses and mechanisms determining tolerance are controlled by diverse sets of genes. Transcription factors (TFs) have been implicated in conferring drought tolerance under drought stress conditions, and the identification of their target genes can elucidate molecular regulatory networks that orchestrate tolerance mechanisms.ResultsWe generated transgenic rice plants overexpressing the 4 rice TFs, OsNAC5, 6, 9, and 10, under the control of the root-specific RCc3 promoter. We showed that they were tolerant to drought stress with reduced loss of grain yield under drought conditions compared with wild type plants. To understand the molecular mechanisms underlying this tolerance, we here performed chromatin immunoprecipitation (ChIP)-Seq and RNA-Seq analyses to identify the direct target genes of the OsNAC proteins using the RCc3:6MYC-OsNAC expressing roots. A total of 475 binding loci for the 4 OsNAC proteins were identified by cross-referencing their binding to promoter regions and the expression levels of the corresponding genes. The binding loci were distributed among the promoter regions of 391 target genes that were directly up-regulated by one of the OsNAC proteins in four RCc3:6MYC-OsNAC transgenic lines. Based on gene ontology (GO) analysis, the direct target genes were related to transmembrane/transporter activity, vesicle, plant hormones, carbohydrate metabolism, and TFs. The direct targets of each OsNAC range from 4.0–8.7% of the total number of up-regulated genes found in the RNA-Seq data sets. Thus, each OsNAC up-regulates a set of direct target genes that alter root system architecture in the RCc3:OsNAC plants to confer drought tolerance. Our results provide a valuable resource for functional dissection of the molecular mechanisms of drought tolerance.ConclusionsMany of the target genes, including transmembrane/transporter, vesicle related, auxin/hormone related, carbohydrate metabolic processes, and transcription factor genes, that are up-regulated by OsNACs act as the cellular components which would alter the root architectures of RCc3:OsNACs for drought tolerance.

Genetic Analysis of Adult Plant Resistance Genes to Stem Rust in Some Egyptian Bread Wheat Cultivars

Adult plant resistance (APR) to stem rust in seven Egyptian wheat cultivars i.e., Giza 168, Misr 1, Misr 2, Sakha 94, Gemmeiza 12, Sids 13 and Sids 14 and five stem rust resistance genes i.e., Sr9e, Sr11, Sr13, Sr28 and SrPl, were characterized during 2014/2015, 2015/2016 and 2016/2017 growing seasons at Sids Research Station. Stem rust resistance in seven Egyptian wheat cultivars was experimentally measured using two epidemiological parameters; final rust severity (FRS %) and area under disease progress curve (AUDPC). All of these parameters were found to be lower in the partially resistant (PR) cultivars; Giza-168, Sids-14, Sakha-94 and Gemmeiza-12, rather than those in the highly susceptible or fast-rusting cultivars; Misr-1, Misr-2 and Sids-13 as well as the check variety; Morocco. The partially resistant (PR) cultivars were slightly affected by stem rust infection resulting in little or few grain yield loss (%), less than the highly susceptible or fast-rusting cultivars which were severely rusted and showed high loss in grain yield under field conditions. F1 plants resulted from the crosses between these cultivars and the five stem rust resistance genes were planted, during 2014/2015 growing season, to produce F2 seeds. The resulted F2 plants were tested under field conditions in 2016/2017 at adult stage against a mixture of Puccinia graminis f.sp. tritici races. Segregations of F2 plants indicated that the stem rust resistance gene; Sr13 was identified in all the tested wheat cultivars, except Misr 2. While SrPl was detected in the three wheat cultivars i.e., Sids 14, Sakha 94 and Gemmeiza 12, Also the three wheat cultivars; Giza 168, Sids 13 and Gemmeiza 12 proved to have the resistance gene Sr9e. The stem rust resistance gene Sr28; was found only in the two cultivars, Giza 168 and Sids 14, but Sr11 was identified in three wheat cultivars i.e., Giza 168, Sids 13 and Gemmeiza 12. A combination or pyramiding of multiple genes for stem rust resistance in one particular wheat cultivar prolonged their life expectancy and gives it the potentiality to be more durable.

Allelopathic potential of mustard crop residues on weed management and performance of transplant Aman rice

Crop allelopathy may be useful to minimize serious problems in the present agricultural production such as environmental pollution, unsafe production, human health concerns, depletion of crop diversity, soil sickness and reduction of crop productivity. In this phenomenon an experiment was conducted at the Agronomy Field Laboratory, Bangladesh Agricultural University, Mymensingh to evaluate the effect of crop residues of mustard on weed management and crop performance of T. aman rice. The experiment consisted of three cultivars of T. aman rice viz., BR11, BR23 and BRRI dhan49 and five different level of mustard crop residues such as no crop residues, mustard crop residues @ 0.5, 1.0, 1.5 and 2.0 t ha–1. The experiment was laid out in a randomized complete block design with three replications. Five weed species belonging to three families infested the experimental plots. Weed population, weed dry weight and percent inhibition of weed were significantly influenced by mustard crop residues and cultivar. The maximum weed growth was noticed with the cultivar BR23 and the minimum was found in the cultivar BR11. The grain yield as well as the other yield contributing characters produced by BR11 was the highest among the studied varieties. The highest percent inhibition of 71.17, 69.19, 80.88, 70.48 and 86.97 was in Shama (Echinochlo acrusgalli), Panishapla (Nymphaea nouchali), Panichaise (Scirpus juncoides), Panikachu (Monochoria vaginalis) and Susnishak (Marsilea quadrifolia), respectively which was caused by the application of mustard crop residues @ 2 t ha–1. The highest loss of grain yield was obtained where no crop residues were incorporated. The highest numbers of tillers hill-1, numbers of grains panicle–1, 1000-grain weight, grain yield, straw yield were observed where mustard crop residues were incorporated @ 2.0 t ha–1. BR11 cultivar with all treatments produced the highest grain and straw yield among the treatment combination. The results of this study indicate that different amount of mustard crop residues showed potential activity to suppress weed growth.J. Bangladesh Agril. Univ. 15(2): 133-139, December 2017

Rhizobium Impacts on Seed Productivity, Quality, and Protection of Pisum sativum upon Disease Stress Caused by Didymella pinodes: Phenotypic, Proteomic, and Metabolomic Traits.

In field peas, ascochyta blight is one of the most common fungal diseases caused by Didymella pinodes. Despite the high diversity of pea cultivars, only little resistance has been developed until to date, still leading to significant losses in grain yield. Rhizobia as plant growth promoting endosymbionts are the main partners for establishment of symbiosis with pea plants. The key role of Rhizobium as an effective nitrogen source for legumes seed quality and quantity improvement is in line with sustainable agriculture and food security programs. Besides these growth promoting effects, Rhizobium symbiosis has been shown to have a priming impact on the plants immune system that enhances resistance against environmental perturbations. This is the first integrative study that investigates the effect of Rhizobium leguminosarum bv. viceae (Rlv) on phenotypic seed quality, quantity and fungal disease in pot grown pea (Pisum sativum) cultivars with two different resistance levels against D. pinodes through metabolomics and proteomics analyses. In addition, the pathogen effects on seed quantity components and quality are assessed at morphological and molecular level. Rhizobium inoculation decreased disease severity by significant reduction of seed infection level. Rhizobium symbiont enhanced yield through increased seed fresh and dry weights based on better seed filling. Rhizobium inoculation also induced changes in seed proteome and metabolome involved in enhanced P. sativum resistance level against D. pinodes. Besides increased redox and cell wall adjustments light is shed on the role of late embryogenesis abundant proteins and metabolites such as the seed triterpenoid Soyasapogenol. The results of this study open new insights into the significance of symbiotic Rhizobium interactions for crop yield, health and seed quality enhancement and reveal new metabolite candidates involved in pathogen resistance.

Biocontrol of Bacterial Leaf Blight of Rice and Profiling of Secondary Metabolites Produced by Rhizospheric Pseudomonas aeruginosa BRp3.

Xanthomonas oryzae pv. oryzae (Xoo) is widely prevalent and causes Bacterial Leaf Blight (BLB) in Basmati rice grown in different areas of Pakistan. There is a need to use environmentally safe approaches to overcome the loss of grain yield in rice due to this disease. The present study aimed to develop inocula, based on native antagonistic bacteria for biocontrol of BLB and to increase the yield of Super Basmati rice variety. Out of 512 bacteria isolated from the rice rhizosphere and screened for plant growth promoting determinants, the isolate BRp3 was found to be the best as it solubilized 97 μg/ mL phosphorus, produced 30 μg/mL phytohormone indole acetic acid and 15 mg/ L siderophores in vitro. The isolate BRp3 was found to be a Pseudomonas aeruginosa based on 16S rRNA gene sequencing (accession no. HQ840693). This bacterium showed antagonism in vitro against different phytopathogens including Xoo and Fusarium spp. Strain BRp3 showed consistent pathogen suppression of different strains of BLB pathogen in rice. Mass spectrometric analysis detected the production of siderophores (1-hydroxy-phenazine, pyocyanin, and pyochellin), rhamnolipids and a series of already characterized 4-hydroxy-2-alkylquinolines (HAQs) as well as novel 2,3,4-trihydroxy-2-alkylquinolines and 1,2,3,4-tetrahydroxy-2-alkylquinolines in crude extract of BRp3. These secondary metabolites might be responsible for the profound antibacterial activity of BRp3 against Xoo pathogen. Another contributing factor toward the suppression of the pathogen was the induction of defense related enzymes in the rice plant by the inoculated strain BRp3. When used as an inoculant in a field trial, this strain enhanced the grain and straw yields by 51 and 55%, respectively, over non-inoculated control. Confocal Laser Scanning Microscopy (CLSM) used in combination with immunofluorescence marker confirmed P. aeruginosa BRp3 in the rice rhizosphere under sterilized as well as field conditions. The results provide evidence that novel secondary metabolites produced by BRp3 may contribute to its activity as a biological control agent against Xoo and its potential to promote the growth and yield of Super Basmati rice.

Mapping QTLs and meta-QTLs for two inflorescence architecture traits in multiple maize populations under different watering environments

Drought significantly affects the architectural development of maize inflorescence, which leads to massive losses in grain yield. However, the genetic mechanism for traits involved in inflorescence architecture in different watering environments, remains poorly understood in maize. In this study, 19 QTLs for tassel primary branch number (TBN) and ear number per plant (EN) were detected in 2 F2:3 populations under both well-watered and water-stressed environments by single environment mapping with composite interval mapping (CIM); 11/19 QTLs were detected under water-stressed environments. Moreover, 21 QTLs were identified in the 2 F2:3 populations by joint analysis of all environments with a mixed linear model based on composite interval mapping (MCIM), 11 QTLs were involved in QTL × environment interactions, seven epistatic interactions were identified with additive by additive/dominance effects. Remarkably, 12 stable QTLs (sQTLs) were simultaneously detected by single environment mapping with CIM and joint analysis through MCIM, which were concentrated in ten bins across the chromosomes: 1.05_1.07, 1.08_1.10, 2.01_2.04, 3.01, 4.06, 4.09, 5.06_5.07, 6.05, 7.00, and 7.04 regions. Twenty meta-QTLs (mQTLs) were detected across 19 populations under 51 watering environments using a meta-analysis, and 34 candidate genes were predicted in corresponding mQTLs regions to be involved in the regulation of inflorescence development and drought resistance. Therefore, these results provide valuable information for finding quantitative trait genes and to reveal the genetic mechanisms responsible for TBN and EN under different watering environments. Furthermore, alleles for TBN and EN provide useful targets for marker-assisted selection to generate high-yielding maize varieties.

Quantification of yield losses caused by leaf anthracnose on sorghum in Brazil

AbstractThe leaf anthracnose disease in sorghum, caused by Colletotrichum sublineolum (Henn. ex Sacc. & Trotter), is widely distributed throughout its Brazilian cultivation areas. The disease can cause significant losses in grain yield and quality. This study aimed to quantify the effects of leaf anthracnose on grain yield of different sorghum genotypes. Two elite inbred lines of sorghum, BR009 (susceptible) and BR008 (moderately resistant), and the hybrids, BR304 and MR43 (susceptible), BRS310 and DKB599 (moderately resistant) and BRS308 and AG1060 (resistant), were planted in a complete randomized block design with three replicates. The disease severity (DS) was evaluated weekly, starting from the onset of the first foliar symptoms, and yield losses were estimated using linear regression analysis. Leaf anthracnose significantly reduced sorghum yields in the susceptible genotypes. The highest yield loss of 86% was observed in the inbred line BR009, when the disease severity reached 100%. For the hybrids, the grain yield loss varied from 35% (BRS310) to 72% (BRS308). According to the adjusted model, a grain yield reduction of 23.48 kg/ha for BR304, 14.57 kg/ha for BRS310 and 15.91 kg/ha for DKB599 was observed for every 1% increase in disease severity. We demonstrate for the first time the effect of leaf anthracnose disease on grain sorghum yields under Brazilian conditions. The results from this study provide a starting point for developing new strategies for the integrated disease management of sorghum anthracnose.

Morphological and physiological responses of different wheat genotypes to chilling stress: a cue to explain yield loss.

The eco-physiological mechanism of wheat yield loss resulting from chilling stress is a fundamental scientific issue. However, previous studies have focused on hexaploid wheats, and few studies on the morphological and physiological plasticity of wheat plants. Six different wheat genotypes were tested under chilling stress to investigate the physio-morphological parameters as well as the loss of grain yield in growth chambers. Chilling stress resulted in significant loss in grain yield in all genotypes. Under chilling stress, diploid wheats generated zero harvest, and tetraploid genotypes also suffered from a pronounced loss in grain yield, compared with the control group. In contrast, hexaploid genotypes acquired relatively high maintenance rate of grain yield among three species. Diploid and tetraploid wheat genotypes maintained relatively large leaf area and high photosynthetic rates, but they were subjected to significant declines in vascular bundle number and productive tillers as a consequence of the inhibition by sink growth under chilling stress. The hexaploid wheats were found to have relatively low leaf area and photosynthetic rates. These genotypes also stored more soluble carbohydrates and exhibited stronger sink enhancement, ensuring the translocation and redistribution of assimilates. Our findings provided a new theoretical understanding of yield stabilization in the domestication process of wheat genotypes under chilling stress. © 2017 Her Majesty the Queen in Right of Canada. Journal of The Science of Food and Agriculture © 2017 Society of Chemical Industry.

English

Pearl millet is potentially prone to diseases as such downy mildew caused by Sclerospora graminicola causing losses in grain yield. Crop improvement technologies such as seed priming and fertilizer micro-dosing have only been applied to improve crop production without assessing their implications in the diseases of crops. This study examines the effects of these technologies on downy mildew of pearl millet. An experiment was conducted for three years (2012, 2013 and 2014) cropping seasons at the University of Maiduguri teaching and research farm. The experiment consisted of four pearl millet varieties Ex-Borno, SOSAT-C88, LCIC 9702 and a local check. Each was subjected to four treatments viz: primed, micro-dosed, primed + micro dosed and untreated (control). These were laid out in split-plot design with three replications. The variety served as the main plot and the treatment served as the sub-plot. Seed priming resulted in significantly higher percentage of stand establishment, reduced downy mildew severity and increased yield. However, plants from micro-dosed seeds suffered lower stand establishment, higher downy mildew incidence and lower yield than in the control seeds. The efficiency of micro-dosing alone increased only when combined with seed priming. SOSAT-C88 had the highest plant stands, the lowest disease incidence and severity, and the highest yield. The interaction of seed treatment (priming and micro-dosing) × variety on yield of pearl millet showed seed priming alone was more effective on the landrace Ex-Borno, while micro-dosing alone was more effective on the improved cultivar SOSAT-C88. Combination of seed priming with micro-dosing gave the highest yield increase in cultivar LCIC 9702. Seed priming remains a potential option for farmers in the semi-arid region of Nigeria. But more studies are needed to determine the precise effect of fertilizer on downy mildew of pearl millet. Key words: Downy mildew, severity, incidence, pearl millet, seed priming, micro-dosing.

Diallel analysis of acid soil tolerant and susceptible maize inbred lines for grain yield under acid and non-acid soil conditions

Maize is not inherently tolerant to soil acidity but due to the ever increasing demand for the crop in the developing world, production of maize on acid soils continues to expand. Breeding for maize acid soil tolerance is the best strategy to improve yield under these conditions. Therefore, the current study was done to determine the general combining ability (GCA) of eight acid-soil tolerant and susceptible inbred lines and the specific combining ability (SCA) of cross combinations of these lines for grain yield under acid and non-acid soils. The eight lines were crossed using a diallel mating design to produce 28 single cross hybrids for evaluation under acid and non-acid soils at four sites for two seasons. Line C2 was the best general combiner under both soil environments while A2/C1 and A1/C2 had the highest desirable SCA effects under optimal conditions. Loss in grain yield and sensitivity to low pH stress was higher among genotypes in light textured soils than heavy soils. Non-additive gene action was more important than additive gene action in conditioning grain yield under both environments. Results revealed that it was feasible to improve grain yield under low pH and optimum soils from the set of genotypes used in the current study.

An Atypical Thioredoxin Imparts Early Resistance to Sugarcane Mosaic Virus in Maize

Sugarcane mosaic virus (SCMV) causes substantial losses of grain yield and forage biomass in susceptible maize worldwide. A major quantitative trait locus, Scmv1, has been identified to impart strong resistance to SCMV at the early infection stage. Here, we demonstrate that ZmTrxh, encoding an atypical h-type thioredoxin, is the causal gene at Scmv1, and that its transcript abundance correlated strongly with maize resistance to SCMV. ZmTrxh alleles, whether they are resistant or susceptible, share the identical coding/proximal promoter regions, but vary in the upstream regulatory regions. ZmTrxh lacks two canonical cysteines in the thioredoxin active-site motif and exists uniquely in the maize genome. Because of this, ZmTrxh is unable to reduce disulfide bridges but possesses a strong molecular chaperone-like activity. ZmTrxh is dispersed in maize cytoplasm to suppress SCMV viral RNA accumulation. Moreover, ZmTrxh-mediated maize resistance to SCMV showed no obvious correlation with the salicylic acid- and jasmonic acid-related defense signaling pathways. Taken together, our results indicate that ZmTrxh exhibits a distinct defense profile in maize resistance to SCMV, differing from previously characterized dominant or recessive potyvirus resistance genes.

Effects of common Echinochloa varieties on grain yield and grain quality of rice

Barnyard grass, such as Echinochloa crus-galli var. mitis, Echinochloa crus-galli var. zelayensis and Echinochloa colonum, are the main troublesome weeds in rice (Oryza sativa) paddies. This study aimed to investigate the rice yield (quality and quantity) when grown with these common barnyard grass varieties. A 2-year field experiment was conducted using two high-yielding rice cultivars, Liangyoupeijiu (an O. sativa indica hybrid cultivar) and Nanjing 9108 (an O. sativa japonica cultivar) at different developmental stages from transplant to maturity. Treatments included a weed-free (control), rice grown with Echinochloa. crus-galli var. mitis (Ecm), rice grown with E. crus-galli. crusgali var. zelayensis (Ecz), and rice grown with E. colonum (Ec). The results showed that when barnyard grasses were grown with the same rice cultivar, the order of plant height of the three barnyard grass varieties was Ecz>Ecm>Ec, the growth duration was Ecm>Ecz>Ec and the dry matter accumulation of both Ecm and Ecz was greater than Ec. Compared with the weed-free control, there was no significance difference in rice tiller numbers among the treatments within the same rice cultivar. The Ecm and Ecz treatments for both rice cultivars and the Ec treatment of Nanjing 9108 had significantly lower leaf photosynthetic rate, root biomass, root oxidation activity, and dry matter accumulation at both the heading and maturity stages. Lower rice yield loss was detected for all rice grown with barnyard grass, but the loss in yield differed by treatments. Losses in grain yield of rice were 12.7–42.6% in the Ecm treatment, 22.3–55.2% in the Ecz treatment, and 1.5–12.1% in the Ec treatment. For both rice cultivars, Ecm and Ecz treatments had significantly lower grain yield compared with the control. The Ec treatment for Nanjing 9108 had significantly lower grain yield compared to the control, but there was not a significant difference between Ec and the control for Liangyoupeijiu. In general, the japonica cultivar had a greater loss in grain yield compared with the indicia hybrid cultivar under the same treatment. The degree of yield loss by barnyard grass cultivar was Ecz>Ecm>Ec. Grain quality in head rice, chalky kernel, chalky size, and gel consistency was significantly lower for both rice cultivars in the Ecm and Ecz treatments and also for Nanjing 9108 but not for Liangyoupeijiu in the Ec treatment. We conclude that the reduction in leaf photosynthetic rate, root biomass, root oxidation activity at the grain filling stage, and dry matter accumulation at maturity was caused by interference in canopy light transmission caused by barnyard grass and that these factors resulted in losses in grain yield and quality.

Post‐Flowering Drought Tolerance Using Managed Stress Trials, Adjustment to Flowering, and Mini Core Collection in Sorghum

Sorghum [Sorghum bicolor (L.) Moench] crop in the semiarid tropics often suffers from post‐flowering drought stress, which causes substantial losses in grain yield and stover quality. This research was aimed at studying the yield response of sorghum mini core accessions to post‐flowering drought stress to identify drought‐tolerant sources for sorghum improvement. Mini core accessions were grouped based on days to 50% flowering (extra early, early, medium, late, and extra late) and evaluated in two post‐rainy seasons under managed drought stress and optimally irrigated conditions. Drought tolerance index (DTI), as a standard residual after removing the known contributory effects of flowering time and grain yield under optimum irrigation (yield potential) from the grain yield under drought, was used to segregate the genotypic responses to drought stress. The residual (or restricted) maximum likelihood analysis of data revealed significant genotypic variance (σ2g) for days to 50% flowering, grain yield, and DTI (except in the extra late flowering group), in both the seasons and significant genotype × environment interactions for DTI in extra early to late flowering groups. On the basis of DTI, seven accessions, i.e., ‘IS 14779’, ‘IS 23891’, ‘IS 31714’, ‘IS 4515’, ‘IS 5094’, ‘IS 9108’, and ‘IS 15466’, were identified as drought tolerant and five accessions were sensitive to drought in both of the post‐rainy seasons. The tolerant accessions belonging to durra, caudatum, or durra‐caudatum races were of diverse geographical origins, and most yielded at par with or greater than the extensively grown cultivar ‘IS 33844’. These accessions can be employed to investigate the physiological and molecular basis of drought adaptation and to breed for drought tolerance in sorghum.

Heat stress in grain legumes during reproductive and grain-filling phases

Thermal stress during reproductive development and grain-filling phases is a serious threat to the quality and productivity of grain legumes. The optimum temperature range for grain legume crops is 10−36°C, above which severe losses in grain yield can occur. Various climatic models have simulated that the temperature near the earth’s surface will increase (by up to 4°C) by the end of this century, which will intensify the chances of heat stress in crop plants. The magnitude of damage or injury posed by a high-temperature stress mainly depends on the defence response of the crop and the specific growth stage of the crop at the time of exposure to the high temperature. Heat stress affects grain development in grain legumes because it disintegrates the tapetum layer, which reduces nutrient supply to microspores leading to premature anther dehiscence; hampers the synthesis and distribution of carbohydrates to grain, curtailing the grain-filling duration leading to low grain weight; induces poor pod development and fractured embryos; all of which ultimately reduce grain yield. The most prominent effects of heat stress include a substantial reduction in net photosynthetic rate, disintegration of photosynthetic apparatus and increased leaf senescence. To curb the catastrophic effect of heat stress, it is important to improve heat tolerance in grain legumes through improved breeding and genetic engineering tools and crop management strategies. In this review, we discuss the impact of heat stress on leaf senescence, photosynthetic machinery, assimilate translocation, water relations, grain quality and development processes. Furthermore, innovative breeding, genetic, molecular and management strategies are discussed to improve the tolerance against heat stress in grain legumes.

Productivity Of Bread Wheat Under Different Irrigation Levels And Splitting Nitrogen Fertilization In Newly Reclaimed Soils

In order to study the effect of irrigation water rates and splitting nitrogen on productivity of wheat. Three field experiments were conducted at El-Wady Al-Assiuty experimental farm in new reclaimed soil during 2013/2014 and 2014/2015 seasons using cultivar Sids 12 using sprinkler irrigation system. Each experiment subjected to one level of irrigation water requirements (100%, 75% and 50%) and each experiment contains four treatments of splitting nitrogen fertilization. Results indicated that, irrigation levels had a high significant effect on yield and its components. As when 50% of the recommended irrigation requirements was applied, the reduction of grain yield reached 44.3 and 28.9% in the first and second seasons, respectively. Moreover, splitting nitrogen fertilization affected all studied traits. As splitting nitrogen fertilization to five splits recorded the highest mean value of grain and biological yields as compared with control (3 splits) in both seasons. The interaction between irrigation levels and splitting of the nitrogen fertilizer had a significant effect on grain yield. As the highest mean value of grain yield was obtained from 5 splits with 100% of irrigation requirement in the first season while in the second season the highest grain yield was obtained from 6 splits with 100% irrigation requirements. From this study, data clarify that in sandy soils about 25% of irrigation requirements could be saved without significant losses in grain yield by splitting the nitrogen fertilization. Thus we could have additional amount of water could be used for increase the cultivation area of wheat to minimize the production consumption gap of this crop.

Effect of tolerance to Septoria tritici blotch on grain yield, yield components and grain quality in Argentinean wheat cultivars

Septoria tritici blotch (STB) caused by Zymoseptoria tritici (Mycosphaerella graminicola) is a major disease of wheat worldwide due to significant losses in grain yield and quality. Disease tolerance is the ability to maintain yield performance in the presence of disease symptoms. Therefore, it could be a useful tool in the management of the disease. Although it is known, that there is disease tolerance to STB in some wheat cultivars, this aspect has not been studied among Argentinean cultivars. The aims of this study were to evaluate genotypic differences in tolerance to STB among Argentinean cultivars, considering the relationship between the area under disease progress curve or the green leaf area or the non-green leaf area duration with the grain yield. In addition the effect of the disease on yield, yield components, test weight, grain protein concentration, wet and dry gluten concentration and the influence of tolerance on these traits was investigated. Field experiments were carried out with ten cultivars in a split-split-plot design during 2010 and 2011. Inoculation treatments were the main plots and cultivars, the subplots. STB significantly reduced grain yield, their components, test weight and increase grain protein and gluten concentration. Cultivar Baguette 10 showed major tolerance to STB, indicated by a consistent low regression slope between the green area duration and yield, while Klein Chaja was non-tolerant due to a high regression slope. However, many cultivars such as Buck Brasil, Buck 75 Aniversario, Klein Escorpion and Klein Flecha had considerably similar regression slopes to Baguette 10, provided good levels of tolerance. Other cultivars presented no significant differences. The correlation coefficient between tolerance and grain yield potential was not significant, suggesting that tolerant high-yielding cultivars can be obtained. No relationship was found between quality group or tolerance with the increase in protein and gluten concentration due to STB either.

Timing of foliar Zn application plays a vital role in minimizing Cd accumulation in wheat.

Due to chemical and biochemical similarities between cadmium (Cd) and zinc (Zn), application of Zn may minimize Cd uptake by plants and ameliorate its toxicity. However, there is poor understanding of the comparative effectiveness of the foliar Zn application at different growth stages on Cd toxicity and accumulation in wheat. The present study was carried out to compare the effectiveness of foliarly applied Zn at different stages of plant growth to minimize Cd accumulation in wheat grains. Wheat (cv AARI-2011) was grown at three levels of soil Cd (0, 2.5, and 5.0mgkg(-1)). Foliar application of Zn was carried out at either tillering, jointing, booting, heading, or grain filling stage using 0.05% w/v aqueous solution of ZnSO4 · 7H2O. Increasing soil Cd had a negative effect on growth and yield attributes, including tiller production, root length and dry weight, plant height, 100-grain weight and grain and straw yield. Zinc foliar spray increased grain yield by increasing tiller production; importantly, an application at booting was more effective than at other stages. Foliarly applied Zn decreased Cd concentration in the roots, straw, and grain. Similar to grain yield, the largest decrease (74%) in Cd concentration was associated with Zn foliar spray at booting. Grain yield was negatively related to grain Cd concentration which in turn showed a negative relationship with Zn concentration in leaves and grains. It is concluded that the booting stage is the suitable time for foliar application of Zn to (i) effectively minimize a Cd-induced loss in grain yield and (ii) decrease grain Cd concentration.