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Grain sorghum is a versatile crop, which can thrive under limited water and other inputs. However, crop loss from weed infestation continues to be a major constraint in grain sorghum production. Particularly, post-emergence grass weed control is a great challenge in grain sorghum due to the lack of herbicide options. Unlike in other major crops, such as maize or soybean, herbicide-resistant sorghum technology that can facilitate weed control throughout crop growing season is not available to growers yet. The development of herbicide-resistant sorghum can have potential to improve weed management, including post-emergence grass weed control. One of the major concerns in the development of such technology in sorghum is escape of resistance traits into weedy relatives of sorghum (e.g. shattercane and johnsongrass). This review focuses on sources of herbicide resistance in sorghum, the status of the development of herbicide-resistant sorghum technologies, overview of breeding methods, and limitations in the development of such sorghum technology as well as economic benefits for sorghum growers. © 2021 Society of Chemical Industry.

Increasing temperatures are adversely affecting various food crops, including legumes, and this issue requires attention. The growth of two cool-season food legumes, chickpea and lentil, is inhibited by high temperatures but their relative sensitivity to heat stress and the underlying reasons have not been investigated. Moreover, the high-temperature thresholds for these two legumes have not been well-characterised. In the present study, three chickpea (ICCVO7110, ICC5912 and ICCV92944) and two lentil (LL699 and LL931) genotypes, having nearly similar phenology with respect to flowering, were grown at 30/20°C (day/night; control) until the onset of flowering and subsequently exposed to varying high temperatures (35/25, 38/28, 40/30 and 42/32°C; day/night) in a controlled environment (growth chamber; 12 hr/12 hr; light intensity 750 μmol m−2 s−1; RH-70%) at 108 days after sowing for both the species. Phenology (podding, maturity) was accelerated in both the species; the days to podding declined more in lentil at 35/25 (2.8 days) and 38/28°C (11.3 days) than in chickpea (1.7 and 7.1 days, respectively). Heat stress decreased flowering–podding and podding–maturity intervals considerably in both the species. At higher temperatures, no podding was observed in lentil, while chickpea showed reduction of 14.9 and 16.1 days at 40/30 and 42/32°C, respectively. Maturity was accelerated on 15.3 and 12.5 days at 38/28°C, 33.6 and 34 days at 40/30°C and 45.6 and 47 days at 42/32°C, in chickpea and lentil, respectively. Consequently, biomass decreased considerably at 38/28°C in both the species to limit the yield-related traits. Lentil was significantly more sensitive to heat stress, with the damage—assessed as reduction in biomass, reproductive function-related traits (pollen viability, germination, pollen tube growth and stigma receptivity), leaf traits such as membrane injury, leaf water status, photochemical efficiency, chlorophyll concentration, carbon fixation and assimilation, and oxidative stress, appearing even at 35/25°C, compared with 38/28°C, in chickpea. The expression of enzymatic antioxidants such as superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase and non-enzymatic antioxidants declined remarkably with heat stress, more so in lentil than in chickpea. Carbon fixation (assessed as Rubisco activity) and assimilation (assessed as sucrose concentration, sucrose synthase activity) were also reduced more in lentil than in chickpea, at all the stressful temperatures, resulting in more inhibition of plant biomass (shoot + roots), damage to reproductive function and severe reduction in pods and seeds. At 38/28°C, lentil showed 43% reduction in biomass, while it declined by 17.2% in chickpea at the same time, over the control temperature (30/20°C). At this temperature, lentil showed 53% and 46% reduction in pods and seed yield, compared to 13.4% and 22% decrease in chickpea at the same temperature. At 40/30°C, lentil did not produce any pods, while chickpea was able to produce few pods at this temperature. This study identified that lentil is considerably more sensitive to heat stress than chickpea, as a result of more damage to leaves (photosynthetic ability; oxidative injury) and reproductive components (pollen function, etc.) at 35/25°C and above, at controlled conditions.

This study evaluated the long-term effects of a single application of different biochar types and quantities in combination with cow manure and annual inorganic fertilizer on soil properties and grain yield under millet monocropping and millet–peanut rotation in sandy soils of the peanut basin of Senegal. Results of over six years showed that a single application of 5–10 t ha−1 biochar (rice husk or Typha australis) and/or manure significantly increased soil pH (from 5.5 to 6.3) and total C (from 1.84% to an average of 2.69%). Soil available P increased due to all treatments. These improved soil properties were maintained for at least eight years following a single application of 5–10 t ha−1 biochar and/or manure. There was limited or slightly negative effects of biochar application on soil N and total soil microbial activity. Applications of either one-third or half of national recommended NPK rate, in combination with a single application of biochar or cow manure, increased millet grain yield up to four to five times (i.e., 100 to 450 kg ha−1), which was equivalent to the yield of treatments receiving the full national recommended fertilizer rate. Limited improvement was observed on peanut yield. This research clearly shows the synergistic benefits of applying single low rates of organic materials in combination with annual low levels of inorganic fertilizer. Treatments receiving the national recommended inorganic fertilizer rates (150 kg ha−1 NPK 15-15-15 and 100 kg ha−1 of urea four weeks after planting) did not produce more than 400 kg ha−1. Biochar application alone did not increase millet yields. With a recommended biochar application rate of 5 t ha−1, we calculate that Senegal has enough biomass available for biochar to cover all of its cropland every 4.4 to 5.5 years. Of particular importance, the 0.85% increase in stable total C has the potential to sequester 27.2 tons C ha−1 and if scaled across Senegal’s 1.6–2.0 million ha of peanut and millet cropland, this practice could sequester 43.52 to 54.4 million tons of C having mutual benefits on crop productivity and climate change mitigation.

Grain sorghum (Sorghum bicolor [L]. Moench) is a crucial crop to the world’s semiarid regions, as it can produce grain and biomass yields in precipitation-limited environments. Many genotypes have a characterized form of drought resistance known as the stay-green (SG) trait, enabling sorghum plants to resist postflowering drought stress that can severely reduce yields. Breeding for SG sorghum lines is considered vital for sorghum breeders around the world, but selecting for SG traits currently relies on methods that are labor-intensive and time-consuming. Using unmanned aerial systems capable of capturing high-resolution imagery offers a solution for reducing the time and energy required to select for these traits. A field study was conducted in Manhattan, Kansas, where 20 Pioneer® sorghum hybrids were planted in a randomized complete block design with three replications per hybrid. Imagery was collected with a DJI® Matrice 200™ equipped with a MicaSense® RedEdge-MX™ multispectral camera. Flight altitude was 30 m, and flights were collected under clear, sunny skies within ±2.5 h of solar noon. Ground-measured data included visual senescence ratings, fresh and dry plant biomass, leaf area index, and final grain yield. After correlation and regression analysis, results indicated significant relationships with the near-infrared spectral band with fresh and dry plant biomass samples, the green normalized difference vegetation index scores at flowering were the most related to final grain yield, and the visible atmospherically resistant index was the most related to visual senescence scores. Significant spectral band/vegetative indices were clustered into groups, and significant differences were found between various traits. We have developed a methodology for SG sorghum growers to collect, process, and extract data for more efficient identification of traits of interest.

Quantifying yield gaps (potential minus actual yield) and identifying management practices to close those gaps is critical for sustaining high-yielding production systems. The objectives of this study were to: 1) calibrate and validate the APSIM maize and soybean models using local field experimental data and 2) use the calibrated model to estimate and explain yield gaps in the long term as a function of management (high- vs low-input) and weather conditions (wet-warm, wet-cold, dry-warm and dry-cold years) in the western US Corn Belt. The model was calibrated and validated using in-season crop growth data from six maize-soybean rotations obtained in 2014 and 2015 in Kansas, US. Experimental data included two management systems: 1) Common Practices (CP, low-input), wide row spacing, lower seeding rate, and lack of nutrient applications (except N in maize), and 2) Intensified Practices (IP, high-input), narrow rows, high seeding rate, and balanced nutrition. Results indicated that APSIM simulated in-season crop above ground mass and nitrogen (N) dynamics as well yields with a modeling efficiency of 0.75 to 0.92 and a relative root mean square error of 18 to 31%. The simulated maize yield gap across all years was 4.2 and 2.5 Mg ha−1 for low- and high-input, respectively. Similarly, the soybean yield gap was 2.5 and 0.8 Mg ha−1. Simulation results indicated that the high-input management system had greater yield stability across all weather years. In warm-dry years, yield gaps were larger for both crops and water scenarios. Irrigation reduced yield variation in maize more than in soybean, relative to the rainfed scenario. Besides irrigation, model analysis indicated that N fertilization for maize and narrow rows for soybean were the main factors contributing to yield gains. This study provides a systems level yield gap assessment of maize and soybean cropping system in Western US Corn Belt that can initiate dialogue (both experimental and modeling activities) on finding and applying best management systems to close current yield gaps.

The quantity and quality of forage and fodder crops is the major drawback of the livestock sector in the country. There is a need to bridge the gap between the supply and demand of fodder through the adoption of specific sustainable fodder production strategies. The field experiments were conducted during kharif (rainy, June–October), rabi (post-rainy, October–February), and summer (March–May) seasons of 2018–19 and 2019–20 to identify a sustainable fodder cropping system module in randomized complete block design with fifteen fodder cropping systems in three replications. The main objective of this research was to identify the most productive cereal–legume cropping system, both in terms of quantity and quality of biomass, to reduce the gap between supply and demand of quality livestock feed around the year. Among cropping systems, Bajra–Napier hybrid intercropped with lucerne, cowpea, and sesbania recorded significantly higher green fodder (163.6, 155.2, and 144.0 t/ha/year, respectively) and dry matter yields (32.1, 30.8, and 31.3 t/ha/year, respectively). Similarly, the same perennial systems also recorded higher quality yield and ash content. However, higher crude protein content was noticed in monocrop legumes, with the highest in sesbania (22.32%), while higher ether extractable fat was found in monocrop sesbania (3.78%). The monocrop oats recorded higher non-fiber carbohydrates (36.90%) while a monocrop of pearl millet recorded higher total carbohydrates (80.75%), however they were on par with other monocrop cereal cropping systems. Cultivation of legumes as a monocrop, and their inclusion as an intercrop with cereals resulted in lower fiber fractions and improved crude protein in intercropping systems. Furthermore, this improved the dry matter intake and digestibility of fodder. With higher sustainable yield index values and land-use efficiency, perennial intercropping systems were also found to be sustainable. Thus, cultivation of the Bajra–Napier hybrid with either lucerne, cowpea, or sesbania as an intercrop will help livestock farmers to achieve higher productivity in terms of quantity and quality, and forms a viable option for overcoming livestock feed scarcity.

Small-scale irrigation in Ethiopia is a key strategy to improve and sustain the food production system. Besides the use of surface water for irrigation, it is essential to unlock the groundwater potential. It is equally important to use soil management and water-saving systems to overcome the declining soil fertility and the temporal water scarcity in the region. In this study, the solar MajiPump was introduced to enable dry season crop production in Ethiopia using shallow groundwater sources. The capacity of the MajiPumps (MP400 and MP200) was tested for the discharge head and discharge using three types of solar panels (150 W and 200 W rigid, and 200 W flexible). Besides, drip irrigation and conservation agriculture (CA) farming systems were evaluated in terms of water productivity and crop yield in comparison to the farmers&rsquo, practice (overhead irrigation and tilled farming system). Results indicated that the maximum discharge head capacity of the MajiPumps was 18 m, 14 m, 10 m when using MP400 with 200 W rigid, MP400 with 200 W flexible, and MP200 with 150 W rigid solar panels, respectively. The corresponding MajiPump flow rates ranged from 7.8 L/min. to 24.6 L/min., 3 L/min. to 25 L/min., and 3.6 L/min. to 22.2 L/min., respectively. Compared to farmer&rsquo, s practice, water productivity was significantly improved under the CA farming and the drip irrigation systems for both irrigated vegetables (garlic, onion, cabbage, potato) and rainfed maize production. The water productivity of garlic, cabbage, potato, and maize was increased by 256%, 43%, 53%, and 9%, respectively, under CA as compared to conventional tillage (CT) even under overhead irrigation. Thus, farmers can obtain a significant water-saving benefit from CA regardless of water application systems. However, water and crop productivity could be further improved in the combined use of MajiPump with CA and drip irrigation (i.e., 38% and 33% water productivity and 43% and 36% crop productivity improvements were observed for potato and onion, respectively). Similarly, compared to CT, the use of CA significantly increased garlic, cabbage, potato, and maize yield by 170%, 42%, 43%, and 15%, respectively under the MajiPump water-lifting system. Overall, the solar-powered drip irrigation and CA farming system were found to be efficient to expand small-scale irrigation and improve productivity and livelihoods of smallholder farmers in Ethiopia.

Postemergence grass weed control continues to be a major challenge in grain sorghum [Sorghum bicolor(L.) Moench], primarily due to lack of herbicide options registered for use in this crop. The development of herbicide-resistant sorghum technology to facilitate broad-spectrum postemergence weed control can be an economical and viable solution. The 4-hydroxyphenylpyruvate dioxygenase-inhibitor herbicides (e.g., mesotrione or tembotrione) can control a broad spectrum of weeds including grasses, which, however, are not registered for postemergence application in sorghum due to crop injury. In this study, we identified two tembotrione-resistant sorghum genotypes (G-200, G-350) and one susceptible genotype (S-1) by screening 317 sorghum lines from a sorghum association panel (SAP). These tembotrione-resistant and tembotrione-susceptible genotypes were evaluated in a tembotrione dose–response [0, 5.75, 11.5, 23, 46, 92 (label recommended dose), 184, 368, and 736 g ai ha–1] assay. Compared with S-1, the genotypes G-200 and G-350 exhibited 10- and seven fold more resistance to tembotrione, respectively. To understand the inheritance of tembotrione-resistant trait, crosses were performed using S-1 and G-200 or G-350 to generate F1and F2progeny. The F1and F2progeny were assessed for their response to tembotrione treatment. Genetic analyses of the F1and F2progeny demonstrated that the tembotrione resistance in G-200 and G-350 is a partially dominant polygenic trait. Furthermore, cytochrome P450 (CYP)-inhibitor assay using malathion and piperonyl butoxide suggested possible CYP-mediated metabolism of tembotrione in G-200 and G-350. Genotype-by-sequencing based quantitative trait loci (QTL) mapping revealed QTLs associated with tembotrione resistance in G-200 and G-350 genotypes. Overall, the genotypes G-200 and G-350 confer a high level of metabolic resistance to tembotrione and controlled by a polygenic trait. There is an enormous potential to introgress the tembotrione resistance into breeding lines to develop agronomically desirable sorghum hybrids.

Weather, tillage, and fertilization are the major factors affecting the grain yield of field peas (Pisum sativum L.). However, the impact of tillage and fertilization on yield is not well understood. Therefore, this experiment was initiated in 1999. In this manuscript, we report the data recorded during the period of 2011&ndash, 2015 to quantify the impacts on yield. Field peas were planted in seedbeds prepared through conventional tillage (CT)&mdash, moldboard ploughing to the depth of 0.22 m, and minimum tillage (MT)&mdash, disking to the depth of 0.12 m. The crop received three fertilization treatments, including zero fertilization (control), nitrogen, phosphorus and potassium (NPK) mineral fertilization treatment, and NPK mineral fertilization plus the incorporation of pre-crop biomass. Five years&rsquo, average data indicated the highest yield on fertilized treatments (2.85&ndash, 2.98 t ha&minus, 1 vs. 2.66 t ha&minus, 1) regardless of the tillage. When comparing the yield of fertilized treatments, the yield under CT (2.98 t ha&minus, 1) was significantly higher than that of MT (2.85 t ha&minus, 1). However, on non-fertilized treatments (less fertile plots), a higher yield was recorded under MT (2.71 t ha&minus, 1) compared with CT (2.40 t ha&minus, 1). Overall, the results of this study suggest that fertilizer application together with incorporation of the above-ground biomass of the previous crop may help sustain pea grain yield.

Humic substances (HS) and humic acids (HA) are proven to enhance nutrient uptake and growth in plants. Foliar application of urea combined with HS and HA offers an alternative strategy to increase nitrogen use efficiency (NUE). The objective of this study was to understand the effects of foliar application of HA and HS along with urea on NUE and response of different biometric, biochemical and physiological traits of sugarcane with respect to cultivar, mode of foliar application, geographic location and intervals of foliar application. To study this, two different independent Experiments were conducted in green house facilities at two different agro-climatic zones (USA and Brazil) using two different predominant varieties, modes and intervals of foliar applications. The three different foliar applications used in this study were (1) urea (U), (2) mixture of urea and HS (U+HS) and (3) HA (U+HA). In both Experiments, 15N (nitrogen isotope) recovery or NUE was higher in U+HS followed by U+HA. However, magnitude of NUE changed according to the differences in two Experiments. Results showed that foliar application of U+HS and U+HA was rapidly absorbed and stored in the form of protein and starch. Also induced changes in photosynthesis, intrinsic water use efficiency, protein, total soluble sugars and starch signifying a synergistic effect of U+HS and U+HA on carbon and nitrogen metabolism. These results showed promising use of HS and HA with urea to improve NUE in sugarcane compared to using the urea alone. Simultaneously, mode, quantity, and interval of foliar application should be standardized based on the geographic locations and varieties to optimize the NUE., Sugarcane; Urea; Humic substance; Humic acid; Nitrogen use efficiency; Agricultural water management; Agronomy; Crop biomass; Crop breeding; Crop production; Crop protection; Crop quality; Crop yields; Field crops; Agriculture, Plant biology.

Rapid increases in minimum night temperature than in maximum day temperature is predicted to continue, posing significant challenges to crop productivity. Rice and wheat are two major staples that are sensitive to high night-temperature (HNT) stress. This review aims to (i) systematically compare the grain yield responses of rice and wheat exposed to HNT stress across scales, and (ii) understand the physiological and biochemical responses that affect grain yield and quality. To achieve this, we combined a synthesis of current literature on HNT effects on rice and wheat with information from a series of independent experiments we conducted across scales, using a common set of genetic materials to avoid confounding our findings with differences in genetic background. In addition, we explored HNT-induced alterations in physiological mechanisms including carbon balance, source-sink metabolite changes and reactive oxygen species. Impacts of HNT on grain developmental dynamics focused on grain-filling duration, post-flowering senescence, changes in grain starch and protein composition, starch metabolism enzymes and chalk formation in rice grains are summarized. Finally, we highlight the need for high-throughput field-based phenotyping facilities for improved assessment of large-diversity panels and mapping populations to aid breeding for increased resilience to HNT in crops.

Postemergence grass weed control continues to be a big challenge in grain sorghum (Sorghum bicolor L. Moench), primarily due to a lack of herbicide options registered for use in this crop. The development of herbicide-resistant sorghum technology to facilitate broad-spectrum postemergence weed control is an economical and viable solution. The 4-hydroxyphenylpyruvate dioxygenase-inhibitor herbicides (e.g. mesotrione or tembotrione) can control broad-spectrum of weeds including grasses, which, however, is not registered for postemergence application in sorghum due to crop injury. In this study we identified two tembotrione-resistant sorghum genotypes (G-200, G-350) and one highly susceptible genotype (S-1) through screening 317 sorghum lines from the sorghum association panel (SAP). Compared to S-1, G-200 and G-350 exhibited 10- and 7-fold more resistance to tembotrione, respectively. Genetic analyses of the F1 and F2 progeny generated from a cross between tembotrione-resistant and -susceptible genotypes demonstrated that the resistance is a semi-dominant polygenic trait. Furthermore, cytochrome P450 (CYP)-inhibitor assay using malathion and piperonyl butoxide suggested possible CYP-mediated metabolism of tembotrione in G-200 and G-350. Genotype-by-sequencing based quantitative trait loci (QTL) mapping revealed eight QTLs associated with tembotrione resistance in grain sorghum. Sorghum genotypes G-200 and G-350 confer a high level of metabolic resistance to tembotrione and controlled by a polygenic trait. There is an enormous potential to introgress the tembotrione resistance into breeding lines to develop agronomically desirable sorghum hybrids.One-sentence summaryThis research focuses on characterization, genetic analyses, identification of QTLs-linked to metabolic resistance to tembotrione in Sorghum bicolor, for improved weed control and increased yield

Smallholder agriculture constitutes the main source of livelihood for the Ethiopian rural community. However, soil degradation and uneven distribution of rainfall have threatened agriculture at present. This study is aimed at investigating the impacts of conservation agriculture on irrigation water use, nutrient availability in the root zone, and crop yield under supplementary irrigation. In this study, conservation agriculture (CA), which includes minimum soil disturbance, grass mulch cover, and crop rotation, was practiced and compared with conventional tillage (CT). We used two years&rsquo, (2018 and 2019) experimental data under paired-t design in the production of a local variety green pepper (Capsicum annuum L.). The results showed that CA practices significantly (&alpha, = 0.05) reduced irrigation water use (13% to 29%) and runoff (29% to 51%) while it increased percolated water in the root zone (27% to 50%) when compared with CT practices under the supplementary irrigation phase. In addition, CA significantly decreased NO3-N in the leachate (14% to 44%) and in the runoff (about 100%), while PO4-P significantly decreased in the leachate (33% to 50%) and in the runoff (16%) when compared with CT. Similarly, CA decreased the NO3-N load in the leachate and in the runoff, while the PO4-P load increased in the leachate but decreased in the runoff. The yield return that was achieved under CA treatment was 30% higher in 2018 and 10% higher in 2019 when compared with the CT. This research improves our understanding of water and nutrient dynamics in green pepper grown under CA and CT. Use of CA provides opportunities to optimize water use by decreasing irrigation water requirements and optimize nutrient use by decreasing nutrient losses through the runoff and leaching.

Wheat (Triticum aestivum L.) grain yield response to plant density is inconsistent, and the mechanisms driving this response are unclear. A better understanding of the factors governing this relationship could improve plant density recommendations according to specific environmental and genetics characteristics. Therefore, the aims of this paper were to: i) execute a synthesis-analysis of existing literature related to yield-plant density relationship to provide an indication of the need for different agronomic optimum plant density (AOPD) in different yield environments (YEs), and ii) explore a data set of field research studies conducted in Kansas (USA) on yield response to plant density to determine the AOPD at different YEs, evaluate the effect of tillering potential (TP) on the AOPD, and explain changes in AOPD via variations in wheat yield components. Major findings of this study are: i) the synthesis-analysis portrayed new insights of differences in AOPD at varying YEs, reducing the AOPD as the attainable yield increases (with AOPD moving from 397 pl m-2 for the low YE to 191 pl m-2 for the high YE); ii) the field dataset confirmed the trend observed in the synthesis-analysis but expanded on the physiological mechanisms underpinning the yield response to plant density for wheat, mainly highlighting the following points: a) high TP reduces the AOPD mainly in high and low YEs, b) at canopy-scale, both final number of heads and kernels per square meter were the main factors improving yield response to plant density under high TP, c) under varying YEs, at per-plant-scale, a compensation between heads per plant and kernels per head was the main factor contributing to yield with different TP.

Author(s): Godoy, J; Gizaw, S; Chao, S; Blake, N; Carter, A; Cuthbert, R; Dubcovsky, J; Hucl, P; Kephart, K; Pozniak, C; Prasad, PVV; Pumphrey, M; Talbert, L | Abstract: Inbred cultivars and advanced breeding lines have been subjected to numerous recombination cycles, have strong allelic selection for desired traits, and share important attributes for adaptation and agronomic performance. Genetic variation in elite gene pools captured using molecular markers is immediately useful for cultivar development. The primary goal of this study was to implement a genome-wide association study for 17 agronomic traits using elite inbred lines. A panel consisting of 237 elite hard red spring wheat (Triticum aestivum L.) lines from different wheat breeding institutions in North America were evaluated in 11 locations over 2 yr. A total of 19,192 polymorphic single-nucleotide polymorphism (SNP) markers from the Illumina 90K SNP array and markers linked to major genes controlling plant height, photoperiod sensitivity, and vernalization were used to assay the population. Linkage disequilibrium was observed to decay within a map distance of ~3 cM in the A and B genomes and 7 cM in the D genome. A total of 226 marker-trait associations were identified. Potentially novel associations were detected for grain yield on chromosome 2B and kernels per spike on 1B and 7D, whereas others colocalized with well-known adaptation loci for photoperiod response, vernalization, and plant height. The frequency of positive alleles for specific marker-trait associations differed among the programs, suggesting targets for introgression by the respective breeding programs.

Nitrogen (N) metabolism is a major research target for increasing productivity in crop plants. In maize (Zea mays L.), yield gain over the last few decades has been associated with increased N absorption and utilization efficiency (i.e. grain biomass per unit of N absorbed). However, a dynamical framework is still needed to unravel the role of internal processes such as uptake, allocation, and translocation of N in these adaptations. This study aimed to 1) characterize how genetic enhancement in N efficiency conceals changes in allocation and translocation of N, and 2) quantify internal fluxes behind grain N sources in two historical genotypes under high and low N supply. The genotypes 3394 and P1197, landmark hybrids representing key eras of genetic improvement (1990s and 2010s), were grown under high and low N supply in a two-year field study. Using stable isotope 15N labelling, post-silking nitrogen fluxes were modeled through Bayesian estimation by considering the external N (exogenous-N) and the pre-existing N (endogenous-N) supply across plant organs. Regardless of N availability, P1197 exhibited greater exogenous-N accumulated in leaves and cob-husks. This response was translated to a larger amount of N mobilized to grains (as endogenous-N) during grain-filling in this genotype. Furthermore, the enhanced N supply to leaves in P1197 was associated with increased post-silking carbon accumulation. The overall findings suggest that increased N utilization efficiency over time in maize genotypes was associated with an increased allocation of N to leaves and subsequent translocation to the grains.

Due to the increase in greenhouse gases from burning fossil fuels, there is increased attention on renewable energy sources from specialized crops. These crops should not compete with food security, and it is important to select plant resources which can produce methane-rich biogas efficiently. The most commonly used energy crops are planted and managed intensively with high inputs in productive land, and this negatively affects land use and sustainable use of resources. The main purposes of this study are to: (a) determine the best cropping system for optimal biogas and methane production from sole crops of winter pea, triticale and out and their mixtures at two different maturity stages (first stage: full-flowering stage of winter pea and beginning of milky stage of cereals, second stage: emergence of firsts pods for pea and milky/waxy stage of cereals), and (b) to develop and use a surface model to determine the best combinations of various mixtures that result in highest biogas and methane. The used pure or mixtures of pea, oat and triticale in two seed weight ratios (50%:50% and 75%:25%) produced different green mass, dry matter, solids, biogas and methane yields. The experiments showed that maximum green mass was produced by the mixture of pea and oat at the seed ratio 75%:25% and when crop was harvested at the full-flowering stage of winter pea and beginning of the milky stage of cereals. After quadratic model analyses, the combination ratios of the oat and triticale were, respectively, 30% and 8%, with a maximum green biomass yield of 61.48 t ha−1, while the corresponding values were 28% and 38%, with maximum solids yields of 25.64 t ha−1. As the model was set at 100 for all three independent variables (oat, triticale and pea), the pea should be at 62% (100-30-8) and 34% (100-28-38), respectively, for green mass and organic solids yields. The results of surface analysis and multivariate analysis of variance showed that the mixture of oat and triticale had great potentiality for biogas and methane yields. The optimal mixture of oat with triticale was 27~35% with 73~65% for producing biogas and (or) methane.

Rice is highly sensitive to temperature stress (cold and heat), particularly during the reproductive and grain-filling stages. In this review, we discuss the effects of low- and high-temperature sensitivity in rice at various reproductive stages (from meiosis to grain development) and propose strategies for improving the tolerance of rice to terminal thermal stress. Cold stress impacts reproductive development through (i) delayed heading, due to its effect on anther respiration, which increases sucrose accumulation, protein denaturation and asparagine levels, and decreases proline accumulation, (ii) pollen sterility owing to tapetal hypertrophy and related nutrient imbalances, (iii) reduced activity of cell wall bound invertase in the tapetum of rice anthers, (iv) impaired fertilization due to inhibited anther dehiscence, stigma receptivity and ability of the pollen tube to germinate through the style towards the ovary, and (v) floret sterility, which increases grain abortion, restricts grain size, and thus reduces grain yield. Heat stress affects grain formation and development through (i) poor anther dehiscence due to restricted closure of the locules, leading to reduced pollen dispersal and fewer pollen on the stigma, (ii) changes in pollen proteins resulting in significant reductions in pollen viability and pollen tube growth, leading to spikelet sterility, (iii) delay in heading, (iv) reduced starch biosynthesis in developing grain, which reduces starch accumulation, (v) increased chalkiness of grain with irregular and round-shaped starch granules, and (vi) a shortened grain-filling period resulting in low grain weight. However, physiological and biotechnological tools, along with integrated management and adaptation options, as well as conventional breeding, can help to develop new rice genotypes possessing better grain yield under thermal stress during reproductive and grain-filling phases.

Three sorghum backgrounds [Atlas, Early Hegari (EH), and Kansas Collier (KC)] and two bmr mutants (bmr6 and bmr12) of each line were evaluated and compared for grain and biomass yield, biomass composition, and 2,3-butanediol production from biomass. The data showed that the bmr6 mutation in EH background led to a significant decrease in stover yield and increase in grain yield, whereas the stover yield was increased by 64% without affecting grain yield in KC background. The bmr mutants had 10 to 25% and 2 to 9% less lignin and structural carbohydrate contents, respectively, and 24 to 93% more non-structural sugars than their parents in all sorghum lines, except EH bmr12. The total fermentable sugars released were 22 to 36% more in bmr mutants than in parents for Atlas and KC, but not for EH. The bmr6 mutation in KC background produced the most promising feedstock, among the evaluated bmr mutants, for 2,3-butanediol production without affecting grain yield, followed by KC bmr12 and Atlas bmr6, but the bmr mutation had an adverse effect in EH background. This indicated that the genetic background of the parent line and type of bmr mutation significantly affect the biomass quality as a feedstock for biochemical production.

Sorghum is an important coarse cereal grown in the arid and semiarid regions of the world for food and nutritional security. The resilience of sorghum crop to changes in climate can be improved through a better understanding of the physiological basis of abiotic stress tolerance or susceptibility. Among the various abiotic stresses that limit sorghum production, drought and temperature stress are of foremost importance. Apart from this, flooding, low-temperature, and salinity stress also affect sorghum productivity. Severity of stress is greater if these stresses occur during critical stages of crop growth and development. The primary effects of drought stress are decrease in tissue water content. Similarly, for salinity stress, the major effect is an alteration in tissue water content and ionic imbalance. The membranes are the primary site of action for temperature extremes. Among the various growth stages, reproductive stages, namely, gametes development and flowering, are most sensitive to drought, flooding, high-temperature, and low-temperature stress. Seedling emergence, early vegetative stages, and flowering are sensitive to salinity stress. Abiotic stress decreases photosynthesis and yields through decreases in green leaf area duration, radiation capture, decreased carbon partitioning, lower seed-set and grain numbers, and decreased individual grain weight. The decreased seed-set percentage is associated with loss of gametes (pollen and ovule) viability, embryo abortion, and embryo growth. The decrease in rate and duration of grain filling is responsible for lower individual grain weight. A better understanding of impacts on physiological processes, mechanisms, and traits associated with tolerance or susceptibility along with improved agronomic management practices will help in improving sorghum abiotic stress tolerance and management.

Among various abiotic stresses, heat stress is one of the most damaging, threatening plant productivity and survival all over the world. Warmer temperatures due to climatic anomalies above optimum growing temperatures have detrimental impacts on crop yield potential as well as plant distribution patterns. Heat stress affects overall plant metabolism in terms of physiology, biochemistry, and gene expression. Membrane damage, protein degradation, enzyme inactivation, and the accumulation of reactive oxygen species are some of the harmful effects of heat stress that cause injury to various cellular compartments. Although plants are equipped with various defense strategies to counteract these adversities, their defensive means are not sufficient to defend against the ever-rising temperatures. Hence, substantial yield losses have been observed in all crop species under heat stress. Here, we describe the involvement of various plant growth-regulators (PGRs) (hormones, polyamines, osmoprotectants, antioxidants, and other signaling molecules) in thermotolerance, through diverse cellular mechanisms that protect cells under heat stress. Several studies involving the exogenous application of PGRs to heat-stressed plants have demonstrated their role in imparting tolerance, suggesting the strong potential of these molecules in improving the performance of food crops grown under high temperature.

Increasing irrigated wheat yields is important to the overall profitability of limited-irrigation cropping systems in western Kansas. A simulation study was conducted to (1) validate APSIM‘s (Agricultural Production Systems sIMulator) ability to simulate wheat growth and yield in Kansas, and (2) apply the model to assess the response of wheat yield, biomass, and water productivity to irrigation allocation based on growth stage. The methodology involved combining short-term experimental data, long-term historical weather data (1950-2013), and mechanistic crop growth simulation to determine optimum irrigation management strategies. The model adequately simulated measured soil water in the profile. The goodness-of-fit test between the observed and simulated values for phenology, yield, biomass, and ET of the experimental cultivar in 2008-2009 in our study site agreed well with the ‘Batten winter‘ wheat cultivar in APSIM. Results indicated that, on average, an irrigation allocation of 100 mm increased wheat yield by 14% to 46% compared to rainfed (dryland) production. Application of an additional 100 mm of irrigation did not improve wheat yield substantially (on average -1 ). Higher water productivity for grain yield was obtained when irrigation was applied at booting and heading. Overall, irrigation water use efficiency for grain decreased with an increase in irrigation allocation. The highest irrigation water use efficiency was simulated for wheat grown with a limited irrigation allocation of 100 mm applied at booting and heading. This study demonstrates that limited irrigation targeted at sensitive growth stages could enhance wheat yields and improve water productivity of water-limited cropping systems.

The United States southern and central High Plains including western Kansas are experiencing declining ground water supplies from the Ogallala as a result of withdrawals for irrigation exceeding annual recharge, this situation will be exacerbated by future climate change. The purpose of this simulation based study was to 1) assess the impact of future climate change on maize (Zea mays L.) yield in western Kansas; and 2) evaluate and understand the possible impacts of climate change on maize irrigation water productivity, transpiration, evapotranspiration and days to maturity. The Crop Estimation through Resource and Environment Synthesis (CERES-Maize) crop model within the Decision Support System for Agrotechnology Transfer Cropping Systems Model (DSSAT-CSM) was used in combination with multiple Global Climate Models under two Representative Concentration Pathways (RCPs), and two irrigation scenarios [full (450 mm) and deficit (300)] under three planting dates [early (20th April), normal (5th May) and late (15th May)]. Results showed that maize yield during the mid-21st century will decline relative to the present on average by 18–33% under RCP4.5 and 37–46% under RCP8.5. The yield decline might be caused mainly by shortening of the growing period (9–18% decline in days to maturity), attributed to elevated temperatures. The reduction in transpiration relative to the baseline reached 15% for RCP8.5 under deficit irrigation whereas the reduction was minimal (1–7%) under full irrigation. Indicating that significant yield reductions might occur due to combined effects of deficit irrigation and shortening of the maturity period. Yield increase due to elevated CO2 concentration [CO2] might be masked by the increased temperatures. The current study showed large disparity in simulated yield among the various GCMs. Planting date did not substantially improve yield but there was less simulation variability among GCMs with early planting compared to normal and late planting. There was no substantial difference among the planting dates for water productivity, however, there was a slight tendency of improvement in irrigation water productivity for deficit irrigation under early planting compared to normal and late planting. Under all planting dates and RCPs, the irrigation water productivity of maize under deficit irrigation was slightly higher than that under full irrigation. The difference in irrigation water productivity of maize between the deficit and full irrigation was larger for early compared to normal and late planting. These differences justify that early planting may be suitable under future climate compared to late planting even though the simulated yield with early planting under similar RCPs and irrigation levels are not significantly different from late planting.

Predicted increase in temperature variability can result in short duration of heat stress episodes coinciding with vulnerable reproductive processes leading to significant reduction in floret-fertility in crops. Recent knowledge on alternations in the pollen and stigmatic morphology, pollen biochemical and lipid composition, variable sensitivity of floral reproductive organs and differential temperature thresholds across crops advances the knowledge on heat stress induced reduction in seed-set and harvest index. Rapid increase in night-time temperature, leading to narrowing diurnal temperature amplitude is a major emerging threat to sustain crop productivity. Interestingly, wild wheat (Aegilops spp.) with higher heat-tolerance and wild rice (Oryza officinalis) escaping damage by completing flowering during early morning hours, are examples of novel opportunities to breed field crops resilient to heat stress. Information on mechanisms leading to heat stress induced sterility is biased towards rice, wheat and sorghum, while the same across other field crops is limited. Hence, increasing research efforts in this direction is critical and timely.

Water is the major factor limiting crop production in western Kansas due to declining groundwater levels in the Ogallala aquifer resulting from withdrawals for irrigation exceeding recharge rates coupled with erratic semi-arid rainfall. Study objectives were to assess yield and water productivity of water limited cropping systems in western Kansas using DSSAT-CSM (Decision Support System for Agrotechnology Transfer Cropping Systems Model). The cropping systems evaluated included continuous (corn, wheat, and grain sorghum) and rotation (corn-wheat, corn-wheat-grain sorghum, and corn-wheat-grain sorghum-corn). Results showed that the model adequately reproduced measured days to flowering and maturity as well as yield and aboveground biomass of all three crops. Crop rotation improved water productivity of corn. Under deficit irrigation, corn in rotation produced higher yields, crop water productivity, and irrigation water use efficiency compared to continuous corn, implying that crop rotation is a better option under limited well capacities. Under full irrigation, yield and water productivity of continuous wheat were lower than wheat in rotation. In contrast, continuous wheat yields under deficit irrigation were better than under crop rotation. Deficit irrigation substantially improved irrigation water use efficiency of grain sorghum under both continuous and crop rotations. Long–term average grain sorghum yields under rotation were higher than those of continuous grain sorghum. Indicating grain sorghum should be grown in rotation under deficit irrigation. This research did not simulate the impacts of pests, weeds and diseases, hail and freeze damage on crop yield. However, the study identifies cropping systems that are more likely to produce highest water productivity under semi-arid climate similar to that in western Kansas.

Molecular breeding can complement traditional breeding approaches to achieve genetic gains in a more efficient way. In the present study, genetic mapping was conducted in a sorghum recombinant inbred line (RIL) population developed from Tx436 (a non-stay-green high food quality inbred) × 00MN7645 (a stay-green high yield inbred) and evaluated in eight environments (location and year combination) in a hybrid background of Tx3042 (a non-stay-green A-line). Phenotyping was conducted for agronomic traits (grain yield and flowering time), physiological traits of stay-green (chlorophyll content [SPAD] and chlorophyll fluorescence [Fᵥ/Fₘ] measured on the leaves), and green leaf area visual score (GLAVS). This population was genotyped with genotyping-by-sequencing (GBS) technology. Data processing resulted in 7144 high quality single nucleotide polymorphisms (SNPs) that were used in a genome-wide single marker scan with physical distance. A selected subset of 1414 SNPs was used for composite interval mapping (CIM) with genetic distance. These complementary methods revealed fifteen QTLs for the traits studied. In addition, QTL mapping for individual environments and year-wise combinations revealed 42 QTLs. A consistent QTL for grain yield under normal and stressed conditions was identified in chromosome 1 that explained 8 to 16% of the phenotypic variation. QTLs for flowering time were identified in chromosomes 2, 6, and 9 that explained 6 to 11% of the phenotypic variation. Stay-green QTLs in chromosomes 3 and 4 explained 8 to 24% of the phenotypic variation. These identified QTLs with flanking SNPs of known genomic positions could be used to improve grain yield, flowering time, and stay-green in sorghum molecular breeding programs.

Diversifying and intensifying the rice-based cropping systems in the southern coastal zone of Bangladesh is a government priority to meet the food, feed, and fiber demand of an increasing population and changing climate. This study was conducted for three years (2016–2019) in Polder 30 located in southwest coastal zone of Bangladesh with five cropping systems [improved varieties of rice-maize (R-M); rice-mungbean (R-MB); rice-sunflower (R-S); traditional varieties of rice-mungbean (RTrad-MBTrad); and rice-fallow (RTrad-F)]. The objectives were to quantify yield gaps and spatiotemporal variability in rice production, evaluate various rice-based cropping systems for yield and profitability, and investigate individual crop and system-based stability and resilience in the coastal zone. Averaged over three years, results indicated an approximate 30% attainable yield gap on average within improved varieties and a 56% yield difference between traditional and improved rice varieties. Spatial autocorrelation analysis of both systems was positive and significant, suggesting crop yields in spatially closer locations were similar than those that were far apart. Lower spatial autocorrelation for the improved variety of rice compared to traditional varieties, indicates greater spatial dependence in addition to a narrow yield range for traditional rice. Overall, the improved rice-maize and rice-sunflower systems were the highest yielding and productive cropping systems, followed by the improved rice-mungbean. The traditional rice-fallow system was the least productive. In a high climate-risk year, however, rice was the only crop with positive net income, and the traditional systems had a relatively higher income than the improved systems. In an average opportune year, maize had the highest net income, and all improved rice-based cropping systems had a relatively higher income than traditional systems.

Leguminous cover crop systems have been envisaged as a critical component of sustainable agriculture because of their potential to increase soil productivity by cycling C and N in agricultural systems. Our objectives were to: (i) determine the effects of including summer cover crops and N rates in the cropping system on the growth and yield of the succeeding grain sorghum [Sorghum bicolor (L.) Moench] crop, (ii) calculate the N fertilizer replacement value (NFRV) and evaluate economic returns, and (iii) determine the most cost-effective cropping system. Field experiments were conducted for two seasons in Kansas. Leguminous summer cover crops and double-cropped soybean [Glycine max (L.) Merr.] residues improved soil N availability; N was subsequently used by the succeeding crop. Across years and cropping systems, the mean increases in grain yield as a result of including cowpea [Vigna unguiculata (L.) Walp.], pigeonpea [Cajanus cajan (L.) Millsp.], sunn hemp (Crotalaria juncea L.), double-cropped soybean, and double-cropped grain sorghum in the rotation compared with a fallow system with 0 kg N ha–1 were 56, 62, 43, 32, and 3%, respectively, and NFRVs across the years were 53, 64, 36, 27, and –3 kg N ha–1, respectively. Across years, grain sorghum in a double-cropped soybean system and a fallow system with 90 kg N ha–1 gave profitable economic net returns. We conclude that including leguminous cover crops in a cropping system has the potential to reduce N requirements and improve the N availability and grain yield of the succeeding grain sorghum crop.

Big bluestem (Andropogon gerardii) is an ecologically dominant warm-season (C4) perennial native grass that comprises as much as 80% of the plant biomass in prairies in the grasslands of the North American Midwest. Ranchers adopted the species as a forage crop long ago, but its high cellulosic content and low agricultural input requirements recently have made big bluestem a promising feedstock for ethanol production and bio-oil. The objective of this paper is to review big bluestem׳s potential as a bioenergy crop with respect to both biology and conversion. Biology includes distribution and adaptation of big bluestem, ecotypes and varieties currently studied, production management, and disease and pest control. Conversion includes discussion of the conversion of big bluestem biomass to bio-ethanol and bio-oil. Estimated ethanol yield of big bluestem is about 1886 L/ha, which is comparable to previously reported herbaceous biomasses. Various constraints and potential applications of big bluestem as an energy crop are analyzed in the final section of this paper. Plant breeding research that focuses on modifying big bluestem composition to minimize recalcitrance to bioconversion and increasing biomass yields is imperative.

High temperature (heat) stress is a major constraint for the productivity of crops worldwide. Wheat (Triticum spp.) is particularly vulnerable to high temperature stress compared to other crops. The principal way to mitigate heat damage is to develop heat-tolerant varieties by identifying heat-tolerant germplasm and employing the tolerant lines in breeding programs. The objectives of this study were to investigate the genetic variation for heat tolerance in primitive cultivated subspecies of tetraploid wheat Triticum turgidum L. (AABB genome) and to identify heat-tolerant genotypes. Thirty-eight tetraploid wheat accessions belonging to five subspecies collected from 19 countries were studied for heat tolerance in day/night temperatures of 36/30°C beginning at anthesis. Several lines were classified as heat-tolerant based on small reductions in seed number, single-kernel weight, and total grain weight, as well as slow chlorophyll degradation under heat stress. T. turgidum subsp. polonicum IG110572 from Alg...

A limited-transpiration (TR lim ) trait has been identified in many crop species, including sorghum ( Sorghum bicolor (L.) Moench), that results in restricted transpiration rate under high vapor pressure deficits (VPD). The benefit of TR lim is that under high midday-VPD conditions crop water loss is limited so that there is water conservation and positions the crop to better withstand later-season drought. Previous studies performed at 31 °C found that TR lim was commonly expressed among sorghum genotypes. It was also found that those lines with low VPD breakpoints for expression of the TR lim trait exhibited insensitivity in transpiration rate to being fed silver ions. However, it is uncertain how applicable these previous results obtained at 31 °C might be at higher temperature that may exist at midday in regions where sorghum is commonly grown. The current study tested for the expression of TR lim at 37 °C in 16 sorghum genotypes previously found to express the trait at the lower temperature. Only three of the genotypes sustained expression of TR lim at 37 °C. These results indicate that for environments where temperature may commonly reach or exceed 37 °C, sorghum genotypes have been favored that acclimate to the high temperature by losing the TR lim trait. In conditions in which very high temperatures threaten crop heat stress, those genotypes that lose the TR lim trait at high temperature may be more desirable since increasing transpiration rates at these temperatures can result in leaf cooling. The silver test failed to discriminate genotypes for expression of the TR lim trait at high temperature.

Multiple entry selections of big bluestems and three native C4 grass species, including switchgrass, miscanthus, and Conservation Reserve Program (CRP) mixture grass, were evaluated for their chemical composition and ethanol yields via diluted sulfuric acid pretreatment following simultaneous saccharification and fermentation (SSF). Big bluestem and switchgrass had a similar glucan content that was significantly higher than miscanthus and CRP grass. Big bluestem had the highest average mass recovery (55.56%) after acid pretreatment, and miscanthus had the lowest mass recovery (46.3%). A positive correlation was observed between glucan recovery and mass recovery. No significant difference in average efficiency of SSF was observed among four native grasses, but ethanol yields from big bluestem entries, which averaged 26.2%, were consistently greater than the other three grasses. The highest ethanol yield among the 10 entries was from big bluestem cultivar KAW (27.7%). Approximately 0.26 kg ethanol with 9.4 g/L concentration can be produced from 1 kg of big bluestem biomass under current processing conditions. A negative relationship exists between lignin content and the efficiency of SSF with R = −0.80, and a positive relationship exists between ethanol yield and glucan content with R = 0.71.

To study the cytoplasmic effects on heat tolerance, the nuclear genomes of ten alloplasmic lines were substituted by four or five backcrosses using ‘Karl 92’, ‘Ventnor’, ‘U1275’ and ‘Jagger’ as the recurrent parent. During the final backcross, reciprocal crosses were made to develop cytoplasmic near isogenic lines. Sixty-eight BC5F1/BC4F1 lines and their parents were evaluated in growth chambers for post anthesis heat tolerance. Plants were grown in the greenhouse and subjected to heat stress in growth chambers 10 days after anthesis for 14 days. Growth chambers were maintained at 35/30 °C for heat stress treatment. To create an optimum temperature treatment, the greenhouse was maintained at 20/15 °C. Effects of high temperature on chlorophyll content and Fv/Fm (photosystem II measuring parameter) were significantly affected by different cytoplasms. Seven cytoplasms showed improved tolerance to heat with at least one recurrent parent. These results indicate that cytoplasmic variations can contribute to an increase in chlorophyll content and quantum efficiency of photosystem II of wheat during heat stress, and also highlight the importance of the interaction between cytoplasmic and nuclear genes. The role of cytoplasm may be considered in wheat breeding programs aimed at improving heat tolerance, but the nature of the interaction between cytoplasm and nuclear gene content warrants further investigation.

In the Southern High Plains, dairies are expanding to take advantage of favorable climatic conditions. Currently, corn (Zea mays L.) and forage sorghum [Sorghum bicolor (L.) Moench] are the two major crops grown in the region to meet silage demands for the expanding dairy industry, but they have relatively large water requirements of about 840 and 690 mm, respectively, to achieve desirable results. With rising energy costs and declining water levels in the underlying Ogallala Aquifer, crops that use less water, like finger millet (Eleusine coracana (L.) Gaertn) could become alternate forage crops for dairies to corn or forage silage. In this study, we evaluated the adaptability of five finger millet accessions to the Southern High Plains and compared nutritional quality of their forage to that of corn and sorghum. Results indicated that finger millet can be grown in the Southern High Plains. Comparison of nutrient composition has shown that the quality of finger millet is relatively higher than that of corn and sorghum in terms of calcium, potassium, and phosphorus levels in their forage. However, potential forage yield of most commonly grown corn and sorghum in the region is higher than that of finger millet. Therefore, finger millet may provide a unique opportunity to improve the dairy-fed silage quality by mixing it with corn or sorghum silage while meeting the growing regional forage demand. Further field research is needed to measure its water requirements in the Southern High Plains.