Reduction In Grain Yield Research Articles

Impact of high night temperature stress on different growth stages of wheat

Increasing temperature especially the High night temperature (HNT) is a major constriction for sustaining global food production under changing climate scenario. Recent climate change has resulted into events of abrupt night temperature rise either throughout the crop period or at specific growth stage. Historical temperature observations and model projections have predicted a more pronounced increase in night temperature [minimum temperature (Tmin.)] compared to that of day temperatures [maximum temperature (Tmax.)]. Hence, the present study was carried out to identify the most critical growth stage affected by HNT and their effects on physiological, growth and yield traits of wheat. A unique field-based movable temperature controlling system was designed to enhance the night temperature by 5 °C than ambient temperature. The three critical phenological stages of wheat i.e. at GS 15 (before tillering initiation), GS 45 (booting) and GS 75 (grain filling) of Zadok’s scale were separately subjected to HNT treatment. The results reveals that GS 75 (grain filling) was the most sensitive stage affected by HNT, which has recorded remarkable reduction in grain yield (GY), Harvest Index (HI), Thousand grain weight (TGW) and grain weight per spike (GWPS) compared to control treatment. Pearson correlation analysis showed that breeders can choose lines with higher TGW, GWPS and grain number per spike (GNPS) for obtaining better GY under HNT conditions and vegetative/booting stage HNT in field condition may not attribute for any significant yield loss.

Estimation of evapotranspiration for paddy under alternate wetting and drying irrigation practice*

AbstractCrop evapotranspiration (ETC) of rice under an alternate wetting and drying (AWD) irrigation practice may be different from conventional (CON) irrigation methods due to the drying (water stress) phase. The focus of this study was to identify a suitable approach for estimating ETC for a rice crop under AWD practice. Field lysimeters were used for estimating daily ETC under AWD and CON practices during monsoon and non‐monsoon seasons. Lysimeter‐based evapotranspiration (ETC_Lys) was compared with that resulting from the product of reference evapotranspiration (FAO‐56 Penman–Monteith equation), crop coefficient (FAO tabulated values‐KC_Tab and FAO equation‐KC_Eqn) and soil water stress coefficient (linear equation‐KS_Lin; FAO equation‐KS_FAO; logarithmic equation‐KS_Log). The KC_Eqn and KS_FAO methods were found to be better estimates for KC and KS, respectively, for AWD practice. The mean KC in initial, mid and late season for AWD were found to be very close to CON practice. The KS was observed to vary from 1 to 0.15 for AWD. Overall, AWD irrigation practice saved 10–20% irrigation water with about 2% reduction in grain yield and 13% reduction in ETC. The reduction in ETC indicated that KS must be considered when calculating the ETC in rice under AWD irrigation practice.

Investigation of Heat-Induced Changes in the Grain Yield and Grains Metabolites, with Molecular Insights on the Candidate Genes in Barley

Heat stress is one of the abiotic stresses that cause a significant reduction in barley yield. Climate change will increase the number of heatwaves, which will result in more deterioration in the agricultural sector. Therefore, understanding the physiological changes that occur in the plant to tolerate heat stress is very important. A collection of 60 Egyptian spring barley genotypes has been tested for heat stress under field conditions. To quantify the changes in yield-related traits and the grain-reserve parameters as indicators for heat tolerance, several traits were scored. The causative genes that regulate the variation of all traits of interest were identified via single-marker analysis using 16,966 single nucleotide polymorphisms (SNP). Heat stress reduced yield-related traits, while some physiological traits (chlorophyll index, soluble carbohydrates, amino acids, and proline contents) increased. The genotypes were classified into four classes, A, B, C, and D, based on a reduction in grain yield per spike (GYPS) of 10%, 20%, 30%, and 40%, respectively. The physiological aspects were extensively studied in each group. The tolerant genotypes (class A) retained high yield-related traits as well as high reserved metabolites relative to the sensitive class D. The single-marker analysis and gene annotations revealed that the most effective markers and genes resided on chromosomes 1H and 4H. One of these markers, S4_250499621, was found to be associated with increased proline content, increased chlorophyll content, and decreased reduction in grain yield per spike and thousand kernel weight. This study is a part of our extended evaluation of this collection under various abiotic stresses at different developmental stages to develop climate-resilient crops.

Performance of Grain Sorghum and Forage of the Genus Brachiaria in Integrated Agricultural Production Systems

Forages of the genus Brachiaria stand out among those used in integrated systems. Little is known about the potential value of new species and cultivars when intercropped with sorghum and planted in the second crop season. The objective of this study was to evaluate the performance (agronomic characteristics) of grain sorghum and the production and nutritional characteristics of forage plants of the genus Brachiaria in an integrated agricultural production system in the second season. The experiment had a randomized block design with four replicates. The treatments consisted of the intercropping of sorghum with forage plants of the genus Brachiaria (Ruziziensis grass, Marandu, Xaraes, Piata, Paiaguas palisadegrass and Ipypora grass), in addition to an extra treatment with sorghum in monoculture. The results showed that sorghum intercropping with Ruziziensis grass, Paiaguas palisadegrass, Piata, and Ipypora grass did not cause a reduction in grain yield. The Xaraes, Piata, and Paiaguas palisadegrass showed higher forage production. However, the Paiaguas, Piata palisadegrass, and Ipypora grass showed better nutritional value. The sorghum intercropping with forage plants of the genus Brachiaria were promising alternatives for grain and forage production in the off-season. The right forage grass combined with sorghum in an integrated system can intensify agricultural production, optimizing the use of the area and increasing sustainability.

Can extended phenology in wheat cultivar mixtures mitigate post-anthesis water stress?

Wheat cultivar mixtures have a well-explored potential for improving crop diversity, yield stability, and agronomic features. However, it is unclear whether heterogeneity of phenological traits in such mixtures may help to cope with increasing environmental stresses and uncertainties. To investigate the option of using wheat cultivar mixtures with different ripening patterns for mitigating the adverse effects of post-anthesis water stress, a two-year field experiment was conducted during 2014−15 and 2015−16 growing seasons at the research field of School of Agriculture, Shiraz University, Iran. The factorial experiment was a Randomized Complete Block Design with 3 replicates, in which 15 mixture treatments including monocultures and every 11 possible mixtures of four early- to middle-ripening wheat cultivars were grown under two normal and post-anthesis deficit-irrigation conditions. The results indicated that under the stressful conditions, heterogeneity in the ripening pattern of mixtures was diminished. Consequently, dissimilarities in grain yields as well as various agronomic characteristics of mixture treatments were also lessened. Although cultivar mixtures showed some casual beneficial effects, such advantages were not consistent across all conditions. Besides, cultivar mixtures could not mitigate the post-anthesis water stress significantly. However, only when the total averaged values of Susceptibility Index across the two seasons were assessed, a tendency for decreasing SI (up to 5.9 %) was observed in response to the extended phenology, which may suggest further studies for investigating the cultivar mixtures in long-term cropping systems. Despite the general expectation for beneficial ecological services from cultivar mixtures, in many cases there were disadvantageous blends, which led to a considerable reduction in grain yield and water productivity in single growing seasons. Therefore, it is suggested that unless the performance, and preferably the involved mechanisms of cultivar mixtures are fully understood, use of blends as an alternative for conventional high-input wheat cropping systems may lead to adverse results.

Effect of Weed Management Practices on Weed Dynamics, Yield Attributes and Yield of Maize

A field experiment was conducted at Research Farm of Agricultural Research Station, Ummedganj, Kota (Agriculture University, Kota), Rajasthan, India during kharif 2019 to find out the most effective herbicide combination for limiting the menace of weeds in maize. Results showed that density of monocot weeds were observed more than dicot weeds during the experimentation. The prominent weeds were Echinochloa colona, Cyperus rotundus, Digera arvensis, Amaranthus viridis, Acalypha indica and Trianthema portulacastrum etc. caused about 58.3% reduction in grain yield as over two hand weeding at 20 and 40 DAS. In general, grassy weeds were better controlled by herbicides than broad leaves weeds. Among herbicides, maximum weed control efficiency (72.18%) was achieved with application of atrazine 500 g a.i. ha-1 (PE) followed by topramezone 25.2 g a.i. ha-1 at 20-25 DAS (72.18%) which is very close to two hand weeding at 20 and 40 DAS. Furthermore, this treatment also produced higher grain (3496 kg ha-1) and stover yield (6460 kg ha-1) which was at par with atrazine 500 g a.i. ha-1 (PE) followed by tembotrione 120.75 g a.i. ha-1 (20-25 DAS) and atrazine 500 g a.i. ha-1 (PE)+hand weeding 30 DAS with in-situ weeds mulching. Thus, pre-emergence application of atrazine 500 g a.i. ha-1 (PE) followed by topramezone 25.2 g a.i. ha-1 at 20-25 DAS is recommended for better weed control and yield of maize.

RESEARCH OF CONSTRUCTIVE-TECHNOLOGICAL PARAMETERS OF WORKING BODY FOR SCATTERING BULK MATERIALS

Machines used in world practice for surface application of mineral fertilizers are often equipped with centrifugal devices with vertical or horizontal location of the axis of rotation. Having high productivity and reliability of technological process, they cannot always provide reception of a necessary dose and uniformity of scattering of fertilizers on width. In Ukraine, currently produced machines for the application of mineral fertilizers, which we have not previously produced. Since about 2/3 of all available mineral fertilizers, as well as most of the limestone and gypsum-containing materials are applied in a continuous manner, it is necessary to have a certain fleet of machines for applying fertilizers available to consumers. Fertilizer application in a continuous manner is carried out by land and aviation. One of the main agrotechnical requirements for machines for the application of bulk materials (mineral fertilizers) is their uniform distribution on the field surface. From uneven application of fertilizers, the reduction in grain yield reaches 10 ... 15%. The main disadvantages of the machine for applying mineral fertilizers are: imperfect design of the spreading mechanism, which leads to uneven scattering of fertilizers on the field surface; a large number of gears, which affects the metal content and cost of manufacture and complicates the design. Chain transmissions that drive the spreading device and the conveyor (during operation the chain is stretched, which requires the use of tension rollers, and take-off from the sprockets, especially on the drive of the spreading device); significant uneven application of fertilizers due to imperfect design of the spreading disc. The main reason for the low quality of fertilizer distribution by scattering machines, most researchers see a significant impact on the technological process of external random factors: field relief, wind speed and direction, humidity, elastic, frictional, hygroscopic and particle size distribution of fertilizers. Therefore, the improvement of the technological process of fertilizer scattering, in order to ensure a given uniformity of their distribution on the field surface in the conditions of real functioning, is an urgent scientific and practical task. In order to eliminate these shortcomings, a new spreading working body is proposed.

Evaluating the Impact of Alternative Cropping Systems on Groundwater Consumption and Nitrate Leaching in the Piedmont Area of the North China Plain

The overexploitation of groundwater and the excessive application of nitrogen (N) fertilizer under the intensive double cropping system are responsible for the groundwater level decline and potential contamination in the North China Plain (NCP). Alternative cropping systems have the potential to alleviate current groundwater and N problems in the region, while there are limited studies simultaneously focusing on the impact of a change of cropping systems on crop yields, groundwater consumption, and N leaching. In this study, Field observed experiments of double-cropping system (i.e., winter wheat–summer maize) and mono-cropping system (early sowing maize) were used to calibrate and validate the Root Zone Water Quality Model (RZWQM2). Then, the validated RZWQM2 model was used to evaluate the long-term crop growth and environmental impact under the local winter wheat–summer maize rotation system with practical irrigation (WW-SM_pi) and auto-irrigation (WW-SM_ai), and three alternative cropping systems (single early maize, SEM; winter wheat–summer maize and single early maize, WW-SM-SEM; winter wheat-summer maize and double single early maize, WW-SM-2SEM). The net consumption of groundwater and N leaching under WW-SM_pi were 226.9 mm yr−1 and 79.7 kg ha−1 yr−1, respectively. Under the local rotation system, auto-irrigation could increase crop yields and N leaching. Compared with the WW-SM_ai, the alternative cropping systems, WW-SM-SEM, WW-SM-2SEM, and SEM, significantly decreased the net consumption of groundwater by 49.3%, 63.0%, and 97.8%, respectively (147.5–292.9 mm), and N leaching by 53.5%, 67.5%, and 89.6%, respectively (50.0–83.7 kg ha−1). However, the yields of the three alternative cropping systems were reduced by less than 30% (12.2%, 20.1%, and 29.7%, respectively). The simulated results indicated that appropriately decreasing the planting frequency of winter wheat is an effective approach to reduce groundwater overexploitation and N contamination with a relatively limited reduction in grain yields. The results could provide a scientific basis for cropping system adjustment in guaranteeing sustainable regional water and grain policy.

Analysis of Drought Susceptibility Index in Indian Mustard [Brassica juncea (L.) Czern and Coss

Background: Climatic variations such as drought have high level of impingement on the yield of rain-fed crops like mustard. A drought is an extended period of months or years when region notes a deficiency in its water availability. Water stress causes heavy yield losses in Indian mustard (17-94%). Low water availability during stem elongation, flowering and pod development causes reduction of pods per plant leading to reduction in grain yield. Very meagre efforts have been made towards improving drought tolerance of this crop. Hence there is an urgent need for, development of water use efficient genotypes. Drought Susceptibility Index (DSI) is a measure of drought, based on loss of yield under drought conditions in comparison to the yield under normal conditions. It expresses the separate effects of yield potential and drought susceptibility on yields under drought. In these terms, lower DSI is considered synonymous with higher drought tolerance. In view of above facts, present study is aimed at investigating the effects of drought on yield attributing traits with, the objective of identifying Indian mustard genotypes and their hybrids which can withstand water stress with minimum loss in yield. Methods: Nine Indian mustard genotypes and their F1s were evaluated under irrigated and rainfed conditions to study the effect of drought by calculating DSI, on yield and yield traits and to characterize their relative tolerance against drought at the Agriculture Research Farm, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi during Rabi 2017-18 season. Observations were made for different yield and yield related traits. Result: Genotype RB-50 was found as tolerant for seed yield per plant with DSI 0.38 while hybrids RB-50×RH-749 and RB-50×Giriraj were exhibiting tolerant DSI values for siliqua per plant, 1000 seed weight, seed yield per plant and oil content. These parents and F1s would serve as useful donors and hybrids respectively, in mustard breeding programmes for improving drought tolerance.

Desempenho de cultivar de soja de crescimento determinado em diferentes arranjos espaciais

The adoption of different plant arrangements in the soybean crop can promote morphological changes in the plants, which may influencethe grain yield. In this context, the spatial arrangement allied to a determined growth and higher cycle variety may be an alternative for the management of the soybean crop under adverse edaphic-climatic conditions. In this way, the objective of this work was to evaluate the agronomic performance and the productive components of the BRS Valiosa RR®soybean cultivar, with determinedgrowthin different plant populations and between rows. The trial was installed in Rio Verde/GOat2012/13 agricultural year. A randomized complete block design was used in a factorial arrangement4x4with four replications. It was evaluated four spacing between rows(20; 40; 20/40 and 20/60 cm) associated with four plant populations (200,000, 300,000, 400,000 and 500,000 ha-1plants). The BRS Valiosa RR® cultivar showed potential to reduce the plant population without causing reductions in grain yield, regardless of the spacing between rows.

Impact of deficit irrigation strategies on winter wheat in semi-arid climate of sindh

The scarcity of water for agriculture in arid and semi-arid regions increases the need for technologies to improve water use efficiency and also discover some means to increase the production from less and more reliable access to water. This research was conducted during 2017–18 and 2018–19 to assess the effect of deficit irrigation (DI), applied at appropriate critical growth stages of winter wheat (Triticum aestivum L.) by reducing 50 % of the water applied in control. The treatments were scheduled as, T1 = 100 % irrigation at all six growth stages (Ick 100), T2 = 50 % deficit irrigation at the initiation stage of the crown root (ICRS50), T3 50 % deficit irrigation at tillering stage (ITS 50), T4 = 50 % deficit irrigation at booting stage (IBS50), T5 = 50 % deficit irrigation at the heading stage (IHS 50), T6 = 50 % deficit irrigation at milky stage (IMS50), T7 = 50 % deficit irrigation at grain maturity stage (IGMS50). The highest grain yield (4558.8 kg ha−1) was achieved with full irrigation treatment Ick100. The statistical analysis conferred a significant change (p < 0.05) of deficit irrigation on grain yield, above- ground biomass, water use efficiency, plant height, spike length, grain number spike-1 and grain weight Spike-1. The maximum (17 %) reduction in grain yield was observed at the tillering stage of wheat crop when DI was applied at this stage. The IGMS50 treatment achieved 98.5 % yield with higher water use efficiency and produced almost similar grain yield to Ick100 treatment. The tillering stage (42 days after sowing) has identified as the hypersensitive and critical growth stage of the wheat crop for attaining higher yield and water use efficiency. It is recommended that water deficiency should be avoided at least at the tillering stage. However, this study concluded that 50 % water deficit at the grain maturity stage, can be an effective irrigation strategy to improve the WUE with very less yield reduction and can be implemented under semi-arid climatic conditions of Sindh and elsewhere.

Fenotipeo y selección de líneas S1 segregantes de maíz tolerantes a estrés hídrico

La sequía reduce el rendimiento de grano del maíz; se requiere obtener líneas tolerantes a sequía para formar híbridos o variedades sintéticas. Los objetivos fueron: 1) fenotipear la población segregante en ambientes contrastantes de humedad, 2) seleccionar líneas de rendimiento alto y ASI corto con base a sequía y riego; y 3) determinar la heredabilidad y correlación de caracteres. El germoplasma fueron 193 líneas S1, progenitores y testigo; estos se evaluaron bajo riego y sequía inducida bajo el diseño látice alfa con dos repeticiones en dos localidades del Estado de Morelos, México. Las variables fueron floración masculina (FM) y femenina (FF), intervalo antesis-emergencia de estigmas (ASI), altura de planta (AP) y mazorca (AM); y rendimiento de grano (RG). Se observó reducción del 40 % en RG bajo sequía (0.75 t ha-1) con respecto a riego (1.26 ton ha-1), el ASI fue de 5 y 2 d en sequía y en riego, respectivamente. La heredabilidad para RG y ASI fue de 0.41. Existen líneas con herencia transgresiva para RG y ASI. La correlación del RG con FF y ASI fue de -0.23**y -0.37**, respectivamente. Existe germoplasma para generar una variedad sintética tolerante a estrés hídrico o iniciar un programa de hibridación.&#x0D; &#x0D;

Response of Greengram to Climate Change in Northern Transition Zone of Karnataka: DSSAT Model Based Assessment

Background: Rise in temperature and expected changes in erratic rainfall patterns projected under future climates are going to affect the performance and productivity of most crops, especially under rainfed condition. But, extent of adverse effect would vary from location to location and crop to crop. Greengram is an important Kharif season crop of Northern Transition Zone (NTZ) of Karnataka mainly grown under rainfed conditions. Methods: Calibrated and validated DSSAT-CROPGRO model was used to study response of greengram to climate change in NTZ of Karnataka. A combination of three temperature (control, +1°C and +2°C) and three rainfall (control, -10% and -20%) scenarios resulting nine combinations were used to simulate phenology, yield and total biomass using weather data for the period of 32 years (1985-2016). Result: Model based seasonal analysis showed that the greengram is more sensitive to change in rainfall than temperature. Rise in temperature by 1-2°C, reduced days to physiological maturity by 2 to 3 days and yield by 1.7 to 3.5%. On the contrary, reduction in 20% rainfall alone reduced grain yield and total biomass by 9.5% and 10.48%, respectively. Combined effect of reduced rainfall (-20%) and elevated temperature (2°C) resulted in 16.36 and 21.16% reduction in grain yield and total biomass, respectively. This indicates that, rainfall plays greater role on kharif greengram yield in NTZ.

Wheat Cultivars With Contrasting Root System Size Responded Differently to Terminal Drought.

In the Mediterranean-type environment of Australia and other parts of the world, end-of- season or terminal drought is the most significant abiotic stress affecting wheat grain yields. This study examined the response of two wheat cultivars with contrasting root system size to terminal drought and the effect of terminal drought on grain yield and yield components. The cultivars were grown in 1.0 m deep PVC columns filled with soil in a glasshouse under well-watered conditions until the onset of ear emergence (Z51) when well-watered and terminal drought treatments were imposed. Terminal drought reduced stomatal conductance, leaf photosynthesis, and transpiration rates faster in Bahatans-87 (larger root system size) than Tincurrin (smaller root system size). Terminal drought reduced grain yield in both cultivars, more so in Bahatans-87 (80%) with the large root system than Tincurrin (67%) with the small root system, which was mainly due to a reduction in grain number and grain size in Bahatans-87 and grain size in Tincurrin. In the terminal drought treatment, Bahatans-87 had 59% lower water use efficiency than Tincurrin, as Bahatans-87 used 39% more water and reduced grain yield more than Tincurrin. The lesser reduction in grain yield in Tincurrin was associated with slower water extraction by the small root system and slower decline in stomatal conductance, leaf photosynthesis, and transpiration rates, but more importantly to faster phenological development, which enabled grain filling to be completed before the severe effects of water stress.

Physiological basis for yield variations in dicoccum wheat genotypes under water stress condition

A field experiment was conducted to study “Physiological basis for yield variations in dicoccum wheat genotypes under water stress condition” during rabi 2018 at Main Agricultural Research Station, University of Agricultural Sciences, Dharwad. The experiment was laid out in split plot design. The main plot consists of water regimes irrigated (providing irrigation during germination, tillering, flowering and grain filling stages) and creating stress (only two protective irrigations during germination and grain filling stages). Sub plot consists of 10 genotypes viz., DDK-50439, DDK-50427, DDK-50438, DDK-50044, DDK-50019, DDK-1044, DDK-50050, DDK-1029, HW-1098 and local. It was noticed from the investigation that, among the genotypes, DDK-1029 recorded higher grain yield (66.91 q ha-1) followed by DDK-1044 (62.229 q ha-1) as compared to other genotypes and the lowest was observed in local (44.39 q ha-1). The high yielding genotypes DDK-1029 and DDK-1044 had higher photosynthetic rate (20.62 and 19.18 µmol CO2 m-2 sec-1), transpiration rate (5.44 and 5.26 µmol H2O m-2 sec-1), stomatal conductance (0.48 and 0.38 µmol m-2 sec-1) and relative water content (84.5 and 82.21%) over other genotypes and the lowest values in these parameters were found in local. The reduction in grain yield in other genotypes was due to moisture stress where significantly reduced number of tillers, spike length and number of grains per spike. The genotypes DDK-1029 and DDK-1044 had higher grain yield in both irrigated and moisture stress conditions with minimum per cent yield reduction as compared to other genotypes. This indicates that, the genotypes DDK-1029 and DDK-1044 are to be most suited for drought tolerance.

Increased seedlings per hill compensates yield loss due to zero tillage in machine‐transplanted fragrant rice

AbstractZero tillage is a soil conservation technique. However, reduction in grain yield might be caused without the effects caused by tillage at the beginning of planting. Present study was conducted in order to test the hypothesis that increased seedlings number per hill could compensate for yield decrement under zero tillage. A two‐year field experiment was conducted between 2018 and 2019 with two fragrant rice cultivars and three treatments: convention tillage with normal seedlings number per hill (CTNS); zero tillage with normal seedlings number per hill (ZTNS) and zero tillage with high seedlings number per hill (ZTHS). The results showed that lower leaf area index, dry matter accumulation, accumulation of nitrogen, phosphorus and potassium were observed in ZTNS treatment than CTNS treatment. Compared with CTNS treatment, ZTNS treatment significantly decreased the grain yield by 11.80‐26.65%. However, the differences between ZTHS and CTNS for yield attributes (effective panicle number, grain number per panicle, seed‐setting rate and 1000‐grain weight) and grain yield were generally small during both seasons and at both sites for both cultivars. Therefore, our study indicates that increasing seedlings number per hill could be an effective strategy to compensate the potential negative effects on yield formation and grain yield of fragrant rice under zero tillage.

BIOESTIMULANTE E FERTILIZANTE FOLIAR NA REDUÇÃO DE INJÚRIAS EM PLANTAS DE SOJA CAUSADAS PELO 2,4-D

O uso de reguladores vegetais e fertilizantes foliares nas culturas tem aumentado devido aos benefícios proporcionados na nutrição das plantas e na tolerância aos estresses ambientais. Objetivou-se nesta pesquisa avaliar os efeitos de regulador vegetal e fertilizante foliar na redução de injúrias provocadas pelo herbicida 2,4-D em duas variedades de soja (M7110 IPRO e M7739 IPRO). Quatro experimentos foram conduzidos em campo, delineados em blocos casualizados, com quatro repetições. Em cada experimento, dez tratamentos foram usados: aplicação única do regulador vegetal ou fertilizante foliar aos 0, 1, 3 e 5 dias após a aplicação (DAA) do herbicida 2,4-D; aplicação de metade da dose do regulador vegetal ou fertilizante foliar aos 0, 1, 3 e 5 DAA do herbicida 2,4-D e da outra metade aos sete dias após a primeira aplicação do regulador vegetal ou fertilizante foliar; somente a aplicação de 2,4-D; e ausência de aplicação de 2,4-D, regulador vegetal ou fertilizante foliar. O 2,4-D causou leve fitotoxicidade (&lt;10%) nas plantas de soja, independente do uso de regulador vegetal ou fertilizante foliar, as quais não atenuaram as injúrias causadas pelo herbicida. As alturas de plantas e de inserção da primeira vagem, os números de ramificações, de vagens por planta, de grãos por planta e o peso de mil grãos nas plantas de soja não foram afetadas pelos tratamentos. Para a variedade M7739 IPRO houve redução do rendimento de grãos na testemunha tratada somente com 2,4-D e quando foi aplicado o regulador vegetal até 1 (um) dia após a aplicação do herbicida. Tanto o regulador vegetal quanto o fertilizante foliar não atenuaram os efeitos herbicidas do 2,4-D, na dose testada, para ambas as variedades de soja.

Fine mapping of qSdr9, a novel locus for seed dormancy (SD) in weedy rice, and development of NILs with a strong SD allele

Lack of seed dormancy, a major cause of pre-harvest sprouting in rice and other cereal crops, causes significant reductions in grain yield and quality. Weedy rice is often strongly dormant; therefore, quantitative trait loci (QTLs) related to seed dormancy in weedy rice “Ludao” could be useful for improving pre-harvest sprouting resistance in the important japonica variety “Ninggeng 4.” To identify SD QTLs in variety Ludao, we constructed an advanced backcross population (BC6F2) of Ninggeng 4 with Ludao as the donor parent by marker-assisted backcrossing followed by SD phenotyping. The consistently detected QTL qSdr9 on chromosome 9L explained 18.09% of the phenotypic variance, and the Ludao allele decreased germination percentage by 10.78%. qSdr9 was fine-mapped to a 586.60 kb region between markers QNU9–10 and RM5777. Based on the closest linked marker for locus qSdr9, we developed near-isogenic lines with the qSdr9 allele from Ludao in Ninggeng 4 background. The qSdr9 near-isogenic lines with strong SD will be useful as parents in breeding for pre-harvest sprouting resistance.

Phenotypic response of barley landrace and its wild progenitor Hordeum spontaneum from Jordan to salt stress

Populations of barley landrace [Hordeum vulgare (L.)] and wild barley progenitor [Hordeum spontaneum (L.)] were collected from 13 diverse eco-geographical regions in Jordan. In addition to two check varieties (Rum and Acsad 165) were collected from farmers’ fields. In total, 28 genotypes were evaluated during germination, early seedling and maturity stages for salt tolerance. Barley populations were exposed to tap water of 0.85 dS m-1 and saline solutions (NaCl, CaCl2 and MgSO4) of 4, 8, 12 and 16 dS m-1. Final germination percentage, the lengths of shoot and seminal root, growth and yield related traits were significantly decreased by increasing the level of salinity. Proline content was increased by increasing the level of salinity. A high level of salinity of 16 dS m-1 had a strong impact on reduction of grain yield and other agronomic traits in the examined populations. A considerable variation among populations was detectable. Barley landrace and wild barley that were collected from Tafila region were the most tolerant grown populations in Jordan. Interestingly, the ranking pattern of these two populations at the germination and seedling related-traits was consistent with the ranking pattern at the maturity phase. In conclusion, this study indicates that barley landrace and wild barley populations are potential donors for genes of salt tolerance that can be used to enhance salinity tolerance in barley.

Genetic mapping of physiological traits associated with terminal stage drought tolerance in rice

BackgroundDrought during reproductive stage is among the main abiotic stresses responsible for drastic reduction of grain yield in rainfed rice. The genetic mechanism of reproductive stage drought tolerance is very complex. Many physiological and morphological traits are associated with this stress tolerance. Robust molecular markers are required for detection and incorporation of these correlated physiological traits into different superior genetic backgrounds. Identification of gene(s)/QTLs controlling reproductive stage drought tolerance and its deployment in rainfed rice improvement programs are very important.ResultsQTLs linked to physiological traits under reproductive stage drought tolerance were detected by using 190 F7 recombinant inbred lines (RIL) mapping population of CR 143–2-2 and Krishnahamsa. Wide variations were observed in the estimates of ten physiological traits studied under the drought stress. The RIL population was genotyped using the bulk- segregant analysis (BSA) approach. A total of 77 SSR polymorphic markers were obtained from the parental polymorphisms survey of 401 tested primers. QTL analysis using inclusive composite interval mapping detected a total of three QTLs for the physiological traits namely relative chlorophyll content (qRCC1.1), chlorophyll a (qCHLa1.1), and proline content (qPRO3.1) in the studied RIL population. The QTL, qPRO3.1 is found to be a novel one showing LOD value of 13.93 and phenotypic variance (PVE) of 78.19%. The QTL was located within the marker interval of RM22-RM517 on chromosome 3. Another novel QTL, qRCC1.1 was mapped on chromosome 1 at a distance of 142.8 cM and found to control relative chlorophyll content during terminal drought stress. A third novel QTL was detected in the population that controlled chlorophyll a content (qCHLa1.1) under the terminal stress period. The QTL was located on chromosome 1 at a distance of 81.8 cM and showed 64.5% phenotypic variation.ConclusionsThe three novel QTLs, qRCC1.1, qCHLa1.1 and qPRO3.1 controlling relative chlorophyll content, chlorophyll a and proline content, respectively were identified in the mapping population derived from CR 143–2-2 and Krishnahamsa. These 3 QTLs will be useful for enhancement of terminal drought stress tolerance through marker-assisted breeding approach in rice.