Reduction In Grain Yield Research Articles

Evaluation of different post-emergence herbicides in chickpea (Cicer arietenum L.)

A field experiment was conducted during rabi season of 2018-2019 at research farm of Bihar Agricultural University, Sabour, Bhagalpur to assess the effect of various post-emergence herbicides in chickpea. The results indicated that among different herbicides, post-emergence application of imazethapyr + imazamox @ 60 g a.i. ha-1 at 20 days after sowing recorded significantly lowest weed density & weed dry weight at 60 days after sowing and highest weed control efficiency at harvest, which was statistically at par with quizalofop-ethyl + imazethapyr @ 60+50 g a.i. ha-1 at 20 days after sowing. As a consequence of effective weed control, quizalofop-ethyl + imazethapyr @ 60+50 g a.i. ha-1 at 20 days after sowing recorded significantly highest grain yield, straw yield and harvest index which was significantly superior over hand weeding twice at 30 and 50 days after sowing. In weedy check, uncontrolled weed growth caused significant reduction in grain yield of chickpea. Net returns and B:C ratio was found maximum with quizalofop-ethyl + imazethapyr @ 60+50 g a.i. ha-1 at 20 days after sowing which was significantly superior over weedy check.

Response of Plant Spacing and Balanced Fertilization on Growth and Yield of Maize (Zea mays L.) in Red Laterite Zone of Purulia District of West Bengal

The experiment was conducted at Krishi Vigyan Kendra Kalyan, Purulia adopted village namely Jambad in Purulia District of West Bengal during kharif season of 2019. The experiment was laid out in nine strip plots with plot size of 48 sq m2. m including three different doses of Nutrients viz. N: P2O5:K2O - 120:60:60, 150:60:60 and 150:75:60 at densities comprising of 55,555 plants/ha (60 X 30 cm), 66,666 plants/ha (60 X 25 cm) and 83,333 plants/ ha (60 X 20 cm) by using of four row multi-crop planter with the objective of observing the effect of plant spacing on yield attributes and yield of maize hybrids. The yield attributing factor as cob length was determined and initially the yield was recorded for application of different doses of nutrients. In case of plant spacing with the optimum doses of nitrogen and phosphorus the only factor contributing to increase in grain yield per unit area was the number of plants grown in the area, so the maximum grain yield (7.5 t/ha) was obtained at (60 X 20 cm) spacing with application of nutrient doses of 150:75:60. Drastic reduction in grain yield occurred at wider plant spacing i.e. (60 X 30 cm). It was due to the reason that increase in cob length did not occur proportionately to the reduction in plant population.

Salicylic acid and thiourea mitigate the salinity and drought stress on physiological traits governing yield in pearl millet- wheat.

Plant growth is often affected with hampered physiological and cellular functioning due to salinity and drought stress. To assess the effectiveness of plant bioregulators (PBRs) in mitigating abiotic stresses, a double spilt plot field study was conducted with three replications at ICAR-CSSRI, research farm, Nain, Panipat. The study comprised of three deficit irrigation regimes viz., 100, 80 and 60% of crop evapo-transpiration (ETc) (I1, I2 and I3), four levels of irrigation water salinity i.e. 2, 4, 8, 12 dS m−1 (S0, S1, S2 and S3) and two PBRs salicylic acid (SA; G1) and thiourea (TU; G2). Irrigations, as per regimes and salinity, were applied at identified critical stages of wheat and if needed in pearl millet. PBRs were applied as seed priming and foliar sprays at two sensitive stages of respective crops. The trend of plant height, and physiological and biochemical traits was similar under different treatments at both stages, but differed significantly only at reproductive stage. Water deficit caused significant reduction in pearl millet (5.1%) and wheat (6.7%) grain yields. The reduction in grain yield under 8 and 12 dS m−1 was 12.90 and 22.43% in pearl millet and 7.68 and 32.93% in wheat, respectively compared to 2 dS m−1. Application of either SA (G1) or TU (G2) significantly enhanced plant height and grain yield, but magnitude of the increment was higher with SA in pearl millet and with TU in wheat. Application of SA and TU increased grain yield by 14.42 and 12.98 in pearl millet, and 12.90 and 17.36% in wheat, respectively. The plant height, RWC, TC, MI, LP, proline, Fv/Fm and Na/K ratio significantly reduced by salinity stress in pearl millet and both water and salinity stress in wheat. Application of both PBRs proved beneficial to mitigate adverse effect of water deficit and salt stress by significantly improving physiological traits, biochemical traits and ultimately grain yield in both crops.

Evaluating the integrative response of moringa leaf extract with synthetic growth promoting substances in maize under early spring conditions

The performance of spring maize is severely hampered by high temperature at reproductive phase, causing marked reduction in grain yield. Early sowing of spring maize can be a good adaptive approach however, due to low temperature causes adverse effect on germinating seeds and young seedlings, thus being detrimental to early planting. Exogenous application of natural and synthetic growth promoting substances may induce tolerance against temperature constraints. For this purpose, field experiment was conducted to explore the potential of moringa leaf extract (MLE, 3%), sorghum water extract (SWE, 10 ml L − 1), ascorbic acid (ASA, 50 mg L − 1), salicylic acid (SA, 50 mg L − 1) and hydrogen peroxide (H2O2, 2 µM) as priming agents on maize hybrid under early and optimum sowing dates. The performance of early planted maize crop was severely influenced by low temperature in comparison to optimum sown crop nevertheless exogenous application of growth promoting substances proved effective in improving stand establishment, phenotypic behavior, key physiological and biochemical attributes of maize crop. Low temperature persuaded inhibition in growth of maize was mainly ameliorated by seed priming with MLE + H2O2 and SWE + ASA. It can be concluded that application of growth promoting substances as priming agents proved to be the most successful strategy in conferring better thermotolerance at early sowing through improved antioxidant defense system and physiological mechanism of spring maize. Better crop performance with combined application of natural and synthetic growth enhancers was linked to improvement in crop stand establishment, better growth and development, dry matter partitioning and yield attributes.

Detopping in Maize: A Review

The scope of increasing the cultivated area under forages is rather limited, because of mounting pressure on need for food and commercial crops, but there is a large demand for green and dry fodder from livestock industry. Hence, fodder production has to be increased per unit area per unit time. By practicing the de-topping in commercial grain maize we can increase the fodder production, quality and it also reduces the deficit of fodder to some extent. Reviews indicated that by de-topping of maize, there may be slight reduction in grain yield of maize but by doing it at right stage/time and at right plant height it gives highest net returns than no de-topped treatments. De-topping at 30 days after silking; removing the top 6 leaves or after physiological maturity; removing all the leaves above the cob or de-topping above 10th internode gives highest fodder yield and net returns with slight or no reduction in grain yield.

A synergistic increase in water and nitrogen use efficiencies in winter wheat cultivars released between the 1940s and the 2010s for cultivation in the drylands of the shaanxi Province in China

Although soil water and nutrients are two of the most important factors affecting growth and production of winter wheat, genetic improvement for wheat responses to water and nitrogen (N) levels has been rarely studied. In this paper, five dryland winter wheat cultivars representative of widely cultivated varieties released from the 1940s to the 2010s in Shaanxi Province, China, were grown in an open rainout shelter (which could be closed when rain threatened) under four contrasting water/N treatment combinations. Yield-related parameters, biomass accumulation, crop water productivity (WUE), and nitrogen use efficiency (NUE) were determined. The results indicated that water deficit and low N treatment caused a significant reduction in grain yield and flag leaf photosynthesis in the five wheat cultivars studied. However, NUE, grain protein content, and partial factor nitrogen productivity were significantly improved by N application under water deficit. Our results confirm the genetic improvement for plant growth, N accumulation, and grain yield in wheat cultivars released from the 1940s to the 2010s; newergenotypes showed the highest NUE under water deficit combined with N limited conditions. Additionally, based on principal component analysis, we found that the newer genotypes, i.e. those from the 2000s and the 2010s, are more sensitive to low nitrogen and water stress compared with the older genotypes from the 1980s, which are more sensitive to the combined effect of water and N limitations. Our findings provide a theoretical support for further improvement of the wheat yield potential, selection, and breeding of high-efficiency varieties in arid and semi-arid areas.

Modeling Aceria tosichella biotype distribution over geographic space and time.

The wheat curl mite, Aceria tosichella Keifer, one of the most destructive arthropod pests of bread wheat worldwide, inflicts significant annual reductions in grain yields. Moreover, A. tosichella is the only vector for several economically important wheat viruses in the Americas, Australia and Europe. To date, mite-resistant wheat genotypes have proven to be one of the most effective methods of controlling the A. tosichella-virus complex. Thus, it is important to elucidate A. tosichella population genetic structure, in order to better predict improved mite and virus management. Two genetically distinct A. tosichella lineages occur as pests of wheat in Australia, Europe, North America, South America and the Middle East. These lineages are known as type 1 and type 2 in Australia and North America and in Europe and South America as MT-8 and MT-1, respectively. Type 1 and type 2 mites in Australia and North America are delineated by internal transcribed spacer 1 region (ITS1) and cytochrome oxidase I region (COI) sequence differences. In North America, two A. tosichella genotypes known as biotypes are recognized by their response to the Cmc3 mite resistance gene in wheat. Aceria tosichella biotype 1 is susceptible to Cmc3 and biotype 2 is virulent to Cmc3. In this study, ITS1 and COI sequence differences in 25 different populations of A. tosichella of known biotype 1 or biotype 2 composition were characterized for ITS1 and COI sequence differences and used to model spatio-temporal dynamics based on biotype prevalence. Results showed that the proportion of biotype 1 and 2 varies both spatially and temporally. Greater ranges of cropland and grassland within 5000m of the sample site, as well as higher mean monthly precipitation during the month prior to sampling appear to reduce the probability of occurrence of biotype 1 and increase the probability of occurrence of biotype 2. The results suggest that spatio-temporal modeling can effectively improve A. tosichella management. Continual integration of additional current and future precipitation and ground cover data into the existing model will further improve the accuracy of predicting the occurrence of A. tosichella in annual wheat crops, allowing producers to make informed decisions about the selection of varieties with different A. tosichella resistance genes.

Alleviation of Field Low-Temperature Stress in Winter Wheat by Exogenous Application of Salicylic Acid

Low temperature in later spring severely limits plant growth and causes considerable yield loss in wheat. In this study, the impacts of exogenous salicylic acid (SA) on plant growth, grain yield and key physiological parameters of wheat plants were investigated under field low-temperature conditions using a field air temperature control system (FATC). The results showed that low-temperature stress significantly decreased leaf net photosynthetic rate, plant height and biomass production of wheat plants at the jointing stage, resulting in a reduction in grain yield. Moreover, the growth period of wheat plants was prolonged by low-temperature stress. However, SA-treated plants significantly improved the photochemical efficiency of photosystem II, accumulation of osmo-protectants, activities of enzymatic antioxidants, and pool of non-enzymatic low molecular substances compared with non-SA-treated plants under low-temperature stress. Pretreatment with SA effectively alleviated low-temperature-induced reduction in leaf net photosynthetic rate, plant height, biomass production and grain yield as well as prolonging of growth period of wheat plants. However, SA-treated plants had no significant effects on the expression levels of cold-responsive genes compared with non-SA-treated plants under low-temperature stress. Our results demonstrated that exogenous application of SA is an appropriate strategy for wheat to resist late spring low-temperature stress under field conditions.

Parthenium weed (Parthenium hysterophorus) competition with grain sorghum under arid conditions

AbstractParthenium weed is an invasive species in a growing number of countries where it infests numerous crop fields, including sorghum. Two field studies were conducted to quantify the effect of parthenium weed on the performance of grain sorghum at different weed densities (0, 5, 10, 15 and 20 plants m−2) and durations of weed-crop competition (season-long weed-free, weed-free after 2, 4, 6 or 8 weeks, and season-long weedy). Our aim was to identify the density threshold and ideal duration to control parthenium weed in sorghum fields. Both field experiments were planned in a randomised complete block design each with three replications in 2016 and were repeated in 2017. Parthenium weed biomass increased significantly with increasing density and competition duration. The increasing parthenium weed density had a linear negative effect on sorghum growth, yield and yield-contributing traits. The highest yield loss, of up to 66%, was recorded at the highest parthenium weed density of 20 plants m−2 when compared to weed-free treatment. In addition, the season-long competition of this weed with sorghum caused 81% reduction in grain yield over weed-free treatment. According to our results, parthenium weed should be managed below a density of 5 plants m−2 and throughout the crop growth duration in grain sorghum fields as it can cause serious yield losses even at low densities and through strong competition at early as well as late growth stages of the crop.

Alternate furrow irrigation can maintain grain yield and nutrient content, and increase crop water productivity in dry season maize in sub-tropical climate of South Asia

Water scarcity is becoming a major constraint for maize cultivation and increasing maize yield globally. Water-saving irrigation methods are required to increase crop water productivity (CWP) without reducing grain yield and nutrient uptake. We evaluated the effects of different methods and levels of irrigation on crop dry matter, grain yield, nutrient uptake and CWP of maize (cv. ‘BARI Hybrid Bhutta-9′) in field condition in a sub-tropical environment in Bangladesh. The experiment was laid out in a nested plot design with three replications during 2014−15 and 2015−16. The treatments were three irrigation levels (I1: 100 % field capacity, FC; I2: 80 % FC; I3: 60 % FC) and three irrigation methods (AFI: alternate furrow irrigation; SFFI: skip-fixed furrow irrigation; and TFI: traditional furrow irrigation). Results indicate that both the irrigation method and level had significant effects on dry matter, grain yield, nutrient uptake, and CWP. The AFI technique maintained similar grain yield (8.1 t ha−1) to TFI but reduced irrigation water by 37 % for irrigation applied at 100 % of FC. Both AFI and TFI had significantly higher (p ≤ 0.05) grain yield compared to SFFI at the irrigation level of I2. The interactive effect of irrigation level and method also had a significant effect (p ≤ 0.05) on maize yield. The uptakes of macronutrients (N, P, K, S, Ca, and Mg) and micronutrients (B, Zn, Fe, and Mn) by maize grain were not significantly different between AFI and TFI under I1. Irrigation level was the main driver for determining the patterns in grain yield but irrigation method controlled the patterns in CWP. The AFI technique resulted in higher CWP compared to TFI or SFFI. Results demonstrate that AFI is an effective water-saving technique, which can increase the CWP without a significant reduction in grain yield and nutrients uptake by maize grain. The AFI method in conjunction with a reduced amount of irrigation water can be adapted in the sub-tropical climates of South Asia where maize production in the dry season is heavily dependent on repeated irrigation with limited water supplies.

Rice Cultivar Response to Florpyrauxifen-Benzyl When Applied with Imazethapyr and a Cytochrome P450 Inhibitor

Understanding cultivar responses to a new herbicide is crucial to determining appropriate herbicide use and management practices. Florpyrauxifen-benzyl is a new rice herbicide developed to control troublesome weeds in rice production. Little research has been conducted to characterize rice cultivar responses to florpyrauxifen-benzyl, and thus, a field experiment was conducted at the Pine Tree Research Station (PTRS) in 2017 and 2018 and at the Rice Research and Extension Center (RREC) in 2018 to determine rice cultivar tolerance to florpyrauxifen-benzyl as influenced by herbicide rate, the addition of imazethapyr, and rice growth stage. Another experiment was conducted in 2018 at PTRS and RREC to assess crop response when florpyrauxifen-benzyl at different rates is applied with and without malathion, a known cytochrome P450 inhibitor. Three cultivars were evaluated in both experiments: a long-grain variety “CL111,” a medium-grain variety “CL272,” and a long-grain hybrid “CLXL745.” Injury in the first experiment was higher when florpyrauxifen-benzyl was applied at 60 g ae ha−1 than at the labeled rate of 30 g ha−1, with the most injury being 10% when averaged over growth stage at the time of application. Generally, applications made at the 3-leaf growth stage resulted in the most injury; however, this injury was at most 14%. Additionally, there was no reduction in grain yield for any cultivar, indicating florpyrauxifen-benzyl can be used safely in conjunction with imazethapyr in imidazolinone-resistant rice. In the second experiment, there was no more than 10% injury and no reduction in grain yield, with the addition of malathion not causing an increase in rice injury. Results from these experiments indicate florpyrauxifen-benzyl can be mixed with imazethapyr and the addition of malathion will not lead to increased risk for injury to rice.

Allelopathic potential of marshpepper residues for weed management and yield of transplant Aman rice

An experiment was conducted at the Agronomy Field Laboratory, Bangladesh Agricultural University, Mymensingh, during the period from June to December 2016 to evaluate the effect of marshpepper (Polygonum hydropiper L.) crop residues on weed management and crop performance of transplant aman rice. The experiment consisted of three cultivars viz. BR11, BRRI dhan33 and BRRI dhan49 and five marshpepper crop residues treatment such as 0, 1.0, 2.0, 3.0 ton ha-1 and hand weeding. The experiment was laid out in a randomized complete block design (RCBD) with three replications. Five weed species belonging to four families infested the experimental plots. Weed population and weed dry weight were significantly affected by cultivar and crop residues treatment. The highest percent inhibition of all the studied weed was found by hand weeding. The second highest percent weed inhibition was found with the application of marshpepper residues at 3.0 t ha-1 which was 63.43, 63.43, 52.85, 52.40 and 59.12 percent for sabuj nakful (Cyperus difformis), chesra (Scirpus juncoides), shama (Echinochloa crusgalli) panikachu (Monochoria vaginalis) and panishapla (Nymphaea nouchali ) respectively. The maximum weed growth was noticed with the cultivar BRRI dhan33 variety and the minimum was found in the cultivar BRRI dhan49. The grain yield as well as the yield contributing characters produced by BRRI dhan49 was the highest among the studied varieties. The highest reduction of grain yield was obtained in no crop residue treatment. The highest number of effective tillers hill-1, number of grains panicle-1, 1000-grain weight, grain and straw yields were observed in marshpepper residues in hand weeding followed by 3.0 t ha-1 marshpepper crop residue. BRRI dhan49 produced the highest grain and straw yields under hand weeding followed by marshpepper residues 3.0 t ha-1 treatment. Results of this study indicate that marshpepper residues showed potentiality to inhibit weed growth and it has a significant effect on the yield of transplant aman rice. Therefore, marshpepper residues might be used as an alternative way for weed management effective and sustainable crop production.
 Progressive Agriculture 30 (4): 379-386, 2019

Increased arbuscular mycorrhizal fungal colonization reduces yield loss of rice (Oryza sativa L.) under drought

Drought reduces the availability of soil water and the mobility of nutrients, thereby limiting the growth and productivity of rice. Under drought, arbuscular mycorrhizal fungi (AMF) increase P uptake and sustain rice growth. However, we lack knowledge of how the AMF symbiosis contributes to drought tolerance of rice. In the greenhouse, we investigated mechanisms of AMF symbiosis that confer drought tolerance, such as enhanced nutrient uptake, stomatal conductance, chlorophyll fluorescence, and hormonal balance (abscisic acid (ABA) and indole acetic acid (IAA)). Two greenhouse pot experiments comprised three factors in a full factorial design with two AMF treatments (low- and high-AMF colonization), two water treatments (well-watered and drought), and three rice varieties. Soil water potential was maintained at 0 kPa in the well-watered treatment. In the drought treatment, we reduced soil water potential to − 40 kPa in experiment 1 (Expt 1) and to − 80 kPa in experiment 2 (Expt 2). Drought reduced shoot and root dry biomass and grain yield of rice in both experiments. The reduction of grain yield was less with higher AMF colonization. Plants with higher AMF colonization showed higher leaf P concentrations than plants with lower colonization in Expt 1, but not in Expt 2. Plants with higher AMF colonization exhibited higher stomatal conductance and chlorophyll fluorescence than plants with lower colonization, especially under drought. Drought increased the levels of ABA and IAA, and AMF colonization also resulted in higher levels of IAA. The results suggest both nutrient-driven and plant hormone-driven pathways through which AMF confer drought tolerance to rice.

Grazing and Cutting under Different Nitrogen Rates, Application Methods and Planting Density Strongly Influence Qualitative Traits and Yield of Canola Crop

Canola crop has the potential for both seeds and grazing. Optimal planting density, time of nitrogen (N) fertilizer application and rates are the major aspects for successful qualitative traits and canola yield formation. In this content, optimization of planting density, N levels and its time of application in dual purpose canola are needed. This study was carried out in RCB design with split pot arrangement having three repeats during winter 2012–2013 and 2013–2014. The study evaluated N levels (120 and 80 kg N ha−1), cutting treatment, N application timings and planting density (20 and 40 plants m−2) effects on qualitative traits and yield of canola. No-cut treatment had 7.02%, 2.46%, and 4.26% higher, glucosinolates, oil, and protein content with 31.3% and 30.5% higher biological and grain yield respectively, compared with grazed canola. Compared with no-cut canola, grazed canola resulted in 7.74% of higher erucic acid. Further, application of N at 120 kg N ha−1 had 8.81%, 5.52%, and 6.06% higher glucosinolates, percent protein, and seed yield, respectively than 80 kg N ha−1. In-addition, the application of N into two splits was most beneficial than the rest application timings. Cutting had 15% reduction in grain yield of canola and fetched additional income of 143.6 USD compared with no-cut. Grazing resulted in a 23% reduction in grain yield while had additional income of 117.7 USD from fodder yield. Conclusively, the application of N in two splits at 120 kg N ha−1 combined with 20 plants m−2 is a promising strategy to achieve good qualitative attributes and canola yield under dual purpose system.

The influence of different intensities of chalky spot damage on seed germination, grain yield and economic returns of red lentil

Chalky spot damage caused by Dolycoris baccarum (L.) and Piezodorus lituratus (F.) causes significant losses to productivity and marketing lentil (Lens culinaris Medik.) in southeastern Anatolia region, Turkey. The chalky spot-damaged grains attract lower price in the market, which decreases productivity. Limited is known about the influence of varying intensities of chalky spot damage on seed germination, productivity and economic returns of lentil in the region. The current study was conducted to assess the influence of varying intensities of chalky spot damage, on seed germination, yield and economic returns of lentil in laboratory and field. Seeds of different lentil cultivars (5 for laboratory and 2 for field studies) were sorted to get 0, 25, 50, 75 and 100% damaged seeds with chalky spot. The data relating to grain weight, reduction and percent reduction in 1000-grain weight were collected. Seed germination of Altintoprak, Cagil, Firat-87, Seyran and Tigris with varying chalky spot damage intensities was inferred in laboratory, whereas seed germination and yield of Cagil and Tigris cultivars was observed under field conditions. The 1000-grain weight, seed germination percentage under laboratory and field conditions, grain yield and gross income were linearly decreased with increasing intensity of chalky spot damage. The cultivar Cagil observed lower reduction in grain yield and gross income compared to Tigris cultivar. It is recommended that non-damaged, certified seeds should be sown in the region to get higher grain yield and economic returns of lentil.

Growth performance of wheat varieties under different pruning intensities of Dalbargia sissoo based Agri-silviculture system

A field experiment was carried out at Dusty Acre Research Farm, Department of Forestry, JNKVV, Jabalpur to assess the growth performance of wheat varieties in 13 year old Dalbergia sissoo plantation. Maximum grain yield of wheat was recorded when grown under open condition (27.20 q ha-1). Among different pruning intensities, significantly maximum grain yield was recorded under 75% pruning (24.4 q ha-1) which inturn was significantly superior to 50% pruning (21.27 q ha-1) and 25% pruning (19.47 q ha-1). No pruning recorded significantly lowest grain yield (17.74 q ha-1). The percent reduction in grain yield under no pruning 25%, 50% and 75%. Pruning as compared to open condition was 34.75%, 28.41%, 21.80% and 10.29% respectively. Wheat varieties showed no significant effect on straw yield, however variety Sujata recorded higher straw yield as compared to variety MP 3173 and MP 3288. Different wheat varieties showed significant effect on harvest index. Variety MP 3288 recorded significantly higher harvest index (34.96) followed by MP 3288 (33.90). Variety Sujata recorded lowest harvest index (32.51).

English

Wheat (Triticum aesum L.) production in Bangladesh is often impaired by heat stress. Therefore, it has been a priority to develop heat tolerant wheat variety for Bangladesh. An investigation was carried out to evaluate locally cultivated wheat genotypes for heat tolerance based on morpho-physiological and molecular markers. A pot experiment was carried out with ten locally cultivated wheat genotypes. Heat treatment was imposed, 5 days after anthesis, in a plant growth chamber at 35°C and 70% RH for 3 days. The heat stress affected all the yield contributing characters and ultimately led to a reduction in grain yield. BARI gom-29, BARI gom-30 and BARI gom-28 emerged as heat tolerant variety on the basis of susceptibility index and tolerance efficiency. While, Shatabdi, BARI gom-23, BARI gom-26 and BARI gom-24 were heat susceptible. Twenty six wheat genotypes were screened for heat tolerance through seven linked SSR markers that generated 44 alleles among the 26 wheat genotypes with an average of 6.28 alleles per locus. Overall polymorphism information content (PIC) and Nei’s gene diversity were 0.68 and 0.72, respectively. Similarity indices based unweighted pair group method with arithmetic mean (UPGMA) analysis separated 26 genotypes into five different clusters. Two morphologically identified tolerant genotypes namely BARI gom-29, BARI gom-30 and one moderate genotype BARI gom-22 were grouped in cluster 2. Therefore, these three varieties can be suitable for cultivation in the north-western part of Bangladesh as heat tolerant cultivars. Key words: Diversity, heat tolerance efficiency, heat susceptibility index, SSR marker.

Optimizing wheat (Triticum aestivum L.) management under dry environments: A case study in the West Pampas of Argentina

Water shortage, caused by large variations in the amount, frequency and timing of rainfall during the crop cycle, is one of the major abiotic stresses limiting crop production. In this context, environmental variability represents a significant challenge for farmers as optimal management practices vary from season to season. The aim of this study was to optimize wheat (Triticum aestivum L.) management practices considering rainfall variability in the West sandy Pampas of Argentina. This region is characterized by a high annual rainfall variability with predominant summer rainfall and probable deficits during winter and early spring in analogy with many other regions around the world. Two commercial cultivars, commonly used by farmers, with different time to flowering (LF: late flowering; EF: early flowering), under three initial soil water conditions (well-watered, moderately-watered and dry conditions) at three sowing dates were simulated with CERES-WHEAT for a series of 39 years. Wheat yield was higher for the LF than the EF cultivar under average (LF = 5437 vs. EF=5112 kg ha−1) and no-water restriction years (LF = 7915 vs. EF=6956 kg ha−1), while the opposite was observed in dry years (EF = 4128 vs. LF=3255 kg ha−1). Reductions in grain yield were associated with reductions in grain number, mainly explained by a lower partitioning to reproductive organs, principally limited by water shortage. The LF cultivar used more water than the EF cultivar before anthesis depleting soil water reserves (p < 0.05) and losing the yield potential advantage in dry years. Genotypic differences were more evident under initial soil well-watered conditions (16 %) compared to moderately-watered (13 %) or dry conditions (9%). Therefore, cultivar selection could partially compensate the deleterious impacts of water deficit on wheat yield under early water stress pattern environments. These results highlight the relevance of design management practices under variable water scenarios in order to reduce yield gaps.

Nitrogen supply modulates nitrogen remobilization and nitrogen use of wheat under supplemental irrigation in the North China Plain

Excessive nitrogen (N) input and irrigation exacerbate N leaching in winter wheat production in the North China Plain (NCP). To explore the optimal N for better N remobilization and higher N utilization of wheat under water-saving irrigation will be conductive to less environmental contamination. A field experiment was conducted at 300 (N300), 240 (N240), 180 (N180), and 0 (N0) kg N ha−1 of N application under supplemental irrigation (SI) that brought the relative soil water content (RSWC) to 70% at jointing and 65% at anthesis. Compared with N0, N180 improved the free amino acid content in the flag leaf and grain after anthesis, dry matter and plant N accumulation at maturity, N translocation amount of vegetable organs and its contribution to grain from anthesis to maturity. Compared to N240 and N300, N180 increased the N translocation efficiency of vegetable organs, and reduced the soil NO3-N residue in the 60–180 cm soil layer, which contributing to no significant reduction in grain yield and grain protein yield, but higher grain N recovery efficiency (GREN), N recovery efficiency (REN), and N partial factor productivity (PFPN). Positive relationships were found between leaf N translocation efficiency and grain yield, grain protein yield, PFPN, GREN, and REN. Therefore, N180 is appropriate to obtain a steady grain yield over 7.5 t ha−1 for at least 2 years under SI based on RSWC in the NCP.

The Integration of Spring and Winter Wheat Genetics With Agronomy for Ultra-Early Planting Into Cold Soils

Early seeding has been suggested as a method of increasing the grain yield and grain yield stability of wheat (Triticum aestivum L.) in the Northern Great Plains. The point at which early seeding results in a decrease in grain yield has not been clearly identified. Changes in climatic conditions have increased frost-free periods and increased temperatures during grain filling, which can either be taken advantage of or avoided by seeding earlier. Field trials were conducted in western Canada from 2015 to 2018 to evaluate an ultra-early wheat planting system based on soil temperature triggers as opposed to calendar dates. Planting began when soil temperatures at 5 cm depth reached 0°C and continued at 2°C intervals until 10°C, regardless of calendar date. Conventional commercial spring wheat genetics and newly identified cold tolerant spring wheat lines were evaluated to determine if ultra-early wheat seeding systems required further development of specialized varieties to maintain system stability. Ultra-early seeding resulted in no detrimental effect on grain yield. Grain yield increased at sites south of 51° latitude N, and was unaffected by ultra-early seeding at sites north of 51° latitude N. Grain protein content, kernel weight, and bulk density were not affected by ultra-early seeding. Optimal seeding time was identified between 2 and 6°C soil temperatures. A greater reduction in grain yield was observed from delaying planting until soils reached 10°C than from seeding into 0°C soils; this was despite extreme environmental conditions after initial seeding, including air temperatures as low as −10.2°C, and as many as 37 nights with air temperatures below 0°C. Wheat emergence ranged from 55 to 70%, and heads m−2 decreased with delayed seeding while heads plant−1 did not change. Cold tolerant wheat lines did not increase stability of the ultra-early wheat seeding system relative to the conventional spring wheat check, and are therefore not required for growers to adopt ultra-early seeding. The results of this study indicate that growers in western Canada can successfully begin seeding wheat earlier, with few changes to their current management practices, and endure less risk than delaying seeding until soil temperatures reach 10°C or greater.