Increased Harvest Index Research Articles

Overexpression of rice lectin receptor-like kinase, OsLec-RLK, confers salinity stress tolerance and increases seed yield in pigeon pea (Cajanus cajan (L.) Millsp.).

OsLec-RLK overexpression enhances cell signalling and salt stress tolerance in pigeon pea, enhancing seed yield and harvest index and thus, enabling marginal lands to increase food and nutritional security. Lectin Receptor-like kinases (Lec-RLKs) are highly effective cell signaling molecules that counteract various stresses, including salt stress. We engineered pigeon pea by overexpressing OsLec-RLK gene for enhancing salt tolerance. The OsLec-RLK overexpression lines demonstrated superior performance under salt stress, from vegetative to reproductive phase, compared to wild types (WT). The overexpression lines had significantly higher K+/Na+ratio than WT exposed to 100mM NaCl. Under salt stress, transgenic lines showed higher levels of chlorophyll, proline, total soluble sugars, relative water content, and peroxidase and catalase activity than WT plants. Membrane injury index and lipid peroxidation were significantly reduced in transgenic lines. Analysis of phenological and yield attributes confirmed that the OsLec-RLK pigeon pea lines maintain plant vigor, with 10.34-fold increase in seed yield (per plant) and 4-5-fold increase in harvest index of overexpression lines, compared to wild type. Meanwhile, the overexpression ofOsLec-RLK up-regulated the expression levels ofhistone deacetylase1, acyl CoA, ascorbate peroxidase, peroxidase, glutathione reductase and catalase, which were involved in the K+/Na+homeostasis pathway. This study showed the potential of OsLec-RLK gene for increasing crop productivity and yields under salt stress and enabling the crops to be grown on marginal lands for increasing food and nutritional security.

Pollination services in the North China Plain measured using buckwheat sentinel plants; is there a deficit?

The transition of food systems for healthy diets and sustainable food systems calls for greater production of fruit and nuts, i.e. pollinated crops. The North China Plain (NCP) is a cereal dominated area that needs to transition to a more sustainable food system with a nutritionally more diverse output. Buckwheat pairs high nutritional quality with low input requirement, but it is pollination dependent. There is little knowledge on the pollinator communities and pollination service in the NCP. We selected Quzhou county as a study region on the NCP, and used potted plants of buckwheat (Fagopyrum esculentum M.) to measure pollination in three treatments: insect exclusion, open pollination, and honeybee supplementation. Measurements were made at 24 sites across the county in 2021 and 2022. At each site, we directly observed the activity of flower-visiting insects and measured the pollination rate, seed set, seed abortion rate and yield-related indicators. Most flower visits were made by hoverflies (Syrphidae) and flies from the families Muscidae, Sarcophagidae, and Calliphoridae. Compared with open pollination, insect exclusion reduced buckwheat pollination rate and seed set by more than 90 %. Without honeybee supplementation, the pollination rate in different experimental sessions was reduced by 12–21 %, and the seed set was reduced by 22–33 %. Honeybee supplementation increased harvest index and seed weight per plant with factors of 1.6 and 2.0, respectively. Hence, a pollination deficit would exist if only natural pollinators were relied upon. Managed honeybees provide an efficient means for enhancing pollination of buckwheat in the North China Plain.

Growth , yield and quality of medicinal plant Chia (Salvia hispanica) as influenced by planting methods and density

An experiment was conducted at Central Research Farm, Gayeshpur, Nadia under BCKV, West Bengal to assess the impact of plant density and planting methods on growth, yield and quality attributes of chia (Salvia hispanica L.) grown during winter (rabi) seasons of 2019–20 and 2020–21. Treatments were distributed in split-plot design, with 2 establishment methods (M1, direct sowing and M2, Transplanting) in main plots and 4 planting density (S1, 60 cm × 50 cm = 33,333 plants/ha; S2, 50 cm × 50 cm = 40,000 plants/ha; S3, 50 cm × 25 cm = 80,000 plants/ha; S4, 50 cm × 20 cm = 1,00,000 plants/ha) in sub-plots. Crop under direct sowing with closer spacing (50 cm × 20 cm) had the greater number of primary branch (15.7/plant), primary branch length (38.4 cm) and main inflorescence length (25.9 cm), thereby reflecting superiority of this treatment combination over others. The same treatment combination produced significantly the highest grain (671.7 kg/ha), stem (1109.4 kg/ha) and husk yield (375.2 kg/ha), which led to increase harvest index (31.2). The greatest economic response in terms of gross return (228.4 × 103 ₹/ha), net return (166.3 × 103 ₹/ha) and B: C ratio (3.67) was recorded in crop under the same treatment combination. Based on quadratic regression equation, the optimum plant density of chia was calculated as 71,428 plants/ha. Thus, direct seed sowing at a density of 71,428 plants/ha (spacing ~ 55 cm × 25 cm) can be done for chia cultivation during rabi season in West Bengal condition.

Enhancing maize grain yield under salt‐affected field conditions using salt‐resistant maize hybrids and higher planting density

AbstractBackgroundIn arid and semiarid countries, grain yield of maize is increasingly impaired by soil salinity. Beside soil amelioration, the development of salt‐resistant cultivars is a possibility to enhance crop yield on salt‐affected soils.AimsThis study aimed at testing yield performance in the field of salt‐resistant maize hybrids on a salt‐affected soil. In addition, planting density was optimized under the saline conditions.MethodsFour salt‐resistant maize hybrids (Zea mays L. SR‐05, SR‐12, SR‐15, and SR‐16) were grown under control (EC = 2.0–2.5 dS m−1) and saline (EC = 10.0–12.0 dS m−1) field conditions and compared to the salt‐sensitive maize cv. Pioneer‐3906. Planting density (5, 8, or 11 plants m−2) was optimized for saline soil conditions for SR‐12 and the local hybrid EV‐78.ResultsYield of Pioneer‐3906 was significantly reduced under salinity because of inhibited kernel setting, whereas the SR hybrids showed no decrease in grain yield. Based on grain yield, the optimum planting density was 8 plants m−2 with no further increase with 11 plants m−2. In contrast to SR‐12, for cv. EV‐78 no increase of harvest index with 8 relative to 5 plants m−2 was observed.ConclusionsVegetative growth of Pioneer‐3906 and the SR hybrids was decreased due to Phase‐I effects but neither due to water deficiency nor ion toxicity. The experiment corroborated the salt resistance of the SR hybrids under field conditions. Under saline conditions, optimum planting density of salt‐resistant cultivars may be higher than under nonsaline conditions when sufficient water supply by artificial irrigation is guaranteed.

White Lupin Drought Tolerance: Genetic Variation, Trait Genetic Architecture, and Genome-Enabled Prediction.

White lupin is a high-protein crop requiring drought tolerance improvement. This study focused on a genetically-broad population of 138 lines to investigate the phenotypic variation and genotype × environment interaction (GEI) for grain yield and other traits across drought-prone and moisture-favourable managed environments, the trait genetic architecture and relevant genomic regions by a GWAS using 9828 mapped SNP markers, and the predictive ability of genomic selection (GS) models. Water treatments across two late cropping months implied max. available soil water content of 60-80% for favourable conditions and from wilting point to 15% for severe drought. Line yield responses across environments featured a genetic correlation of 0.84. Relatively better line yield under drought was associated with an increased harvest index. Two significant QTLs emerged for yield in each condition that differed across conditions. Line yield under stress displayed an inverse linear relationship with the onset of flowering, confirmed genomically by a common major QTL. An adjusted grain yield computed as deviation from phenology-predicted yield acted as an indicator of intrinsic drought tolerance. On the whole, the yield in both conditions and the adjusted yield were polygenic, heritable, and exploitable by GS with a high predictive ability (0.62-0.78). Our results can support selection for climatically different drought-prone regions.

Optimal water and nitrogen management increases cotton yield through improving leaf number and canopy light environment

Recently-published information on cotton agronomic and light energy use responses to nitrogen (N) under varying water availability is limited in Xinjiang, northwest China. A two-year field experiment was conducted to evaluate the effects of two irrigation patterns (I 400 , conventional irrigation; I 267 , limited irrigation) and three N fertilizer rates (N 320 , 320; N 272 , 272; N 224 , 224 kg N ha −1 ) on leaf number (LN), mean inclination angle (MIA) of leaves, light interception rate (LIR), dry matter accumulation, and seed cotton yield. Under the I 400 condition, seed cotton yield for N 272 was comparable to that for N 320 , but 9.6% higher than that for N 224 . Compared with N 320 , N 272 plots exhibited a 4.7% reduction in biological yield and 4.9% increase in harvest index. N 272 I 400 slightly reduced the leaf number and increased the MIA of the top-canopy, and improved the LN and LIR in the middle canopy, canopy photosynthetic rate (CAP), and dry matter accumulation. In contrast, under I 267 conditions, N 320 significantly increased leaf area and achieved the better LIR, dry matter accumulation, and yield than N 272 and N 224 . The LIR induced by the variation in leaf number was strongly associated with CAP and dry matter accumulation. The LN of the middle canopy likely represented the strong link in photosynthetic response to N rate and water supply. Leaf number was strongly associated with leaf area and was negatively correlated with MIA. These results suggest that leaf number is a key regulatory factor for regulating canopy leaf inclination and light interception. We suggest that estimates of light energy utilization should be included along with leaf number estimates in future efforts to scale from leaf physiology to canopy construction in cotton. • The leaf number determines the canopy light environment and yield of cotton. • Optimal leaf number of middle canopy promoted light interception, photosynthesis capacity, and dry matter production. • N-induced changes in leaf number are important factors in regulating the leaf angle and light capture. • Nitrogen rate for high-yield cotton should be adjusted based on water availability.

Balanced below- and above-ground growth improved yield and water productivity by cultivar renewal for winter wheat.

Breeding cultivars that can maintain high production and water productivity (WP) under various growing conditions would be important for mitigating freshwater shortage problems. Experiments were carried out to assess the changes in yield and WP of different cultivars by breeding and traits related to the changes using tubes with 1.05m depth and 19.2cm inner diameter buried in the field located in the North China Plain. Six winter wheat cultivars released from the 1970s to 2010s were assessed under three water levels for three seasons. The results indicated that yield was on average improved by 19.9% and WP by 21.5% under the three water levels for the three seasons for the cultivar released in the 2010s as compared with that released in the 1970s. The performance of the six cultivars was relatively stable across the experimental duration. The improvement in yield was mainly attributed to the maintenance of higher photosynthetic capacity during the reproductive growth stage and greater above-ground biomass accumulation. These improvements were larger under wet conditions than that under dry conditions, indicating that the yield potential was increased by cultivar renewal. Traits related to yield and WP improvements included the increased harvest index and reduced root: shoot ratio. New cultivars reduced the redundancy in root proliferation in the topsoil layer, which did not compromise the efficient utilization of soil moisture but reduced the metabolic input in root growth. Balanced above- and below-ground growth resulted in a significant improvement in root efficiency at grain yield level up to 40% from the cultivars released in the 1970s to those recently released. The results from this study indicated that the improved efficiency in both the above- and below-parts played important roles in enhancing crop production and resource use efficiency.

Genotype-dependent responses to long-term water stress reveal different water-saving strategies in Chenopodium quinoa Willd.

Within the current climate context, freshwater resources have become scarce. Agriculture, especially in rain-fed conditions, should deal with the need of increasing yields to contribute to food security under limiting water availability. Exploring underutilized crops such as Chenopodium quinoa (quinoa) has become a unique opportunity as some of these crops possess the ability to tolerate several abiotic stresses, including drought. In line with this, this work aimed at evaluating the genotype-dependent response to drought by comparing the performance of different European-adapted cultivars (F14, F15, F16, and Titicaca). The results show that the cultivars here evaluated presented different mechanisms to cope with long-term water stress, including changes in phenology, morphology, or physiology. Among them, the cultivar F16 might be the most promising genotype to grow under water-limiting conditions as it presented a reduced foliar total surface (fewer branches and leaves) with higher chlorophyll contents and was able to increase Water Use Efficiency (WUE), reducing the stomatal conductance and keeping CO 2 assimilation rates similar to well-watered conditions. These characteristics lead to F16 maintaining seed yield and increasing harvest index (HI) under water deficit conditions, making it a cultivar tolerant to drought. Furthermore, based on these results, we propose a model in which differences between a water-use efficient and a drought-sensitive genotype are presented. Altogether, we believe that this work will significantly contribute to broadening our understanding of how quinoa responds to long-term water stress highlighting genotype-related differences that will allow the selection of the best-adapted genotypes for water-limiting environments. • Water deficit alters quinoa phenology in a genotype-dependent way accelerating flowering and shortening seed filling stage. • Morphological changes like the reduction of total leaf surface under drought contributes to a reduced water loss in quinoa. • Increments in leaf chlorophyll contents under drought can lead to higher photosynthetic rates. • Chlorophyll fluorescence parameters are developmental stage-dependent but are not sensitive to long-term water deficit. • A reduced water loss and photosynthesis maintenance under water deficit contribute to keep yields in tolerant cultivars.

A Decreased Nitrogen Rate with Increased Planting Density Facilitated Better Palatability of Conventional japonica Rice at High Yield Levels

A decreased nitrogen (N) rate with increased planting density (DNID) is recommended as a feasible method to maintain rice grain yield and N-utilization efficiency. However, it is still unclear whether DNID could improve grain quality, particularly the edible quality of rice. Three high-yield rice with superior palatability (HYSP) and three high-yield rice with inferior palatability (HYIP) were grown under DNID and local cultivation practices (LCP) in the same paddy fields during the 2018 and 2019 rice planting seasons. HYSP exhibited similar grain yields to HYIP under both cultivation treatments. HYSP had more spikelets per m2 through panicles per m2, while having lower spikelets per panicle and 1000-kernel weight than HYIP. DNID increased panicles per m2 and 1000-kernel weight and decreased spikelets per panicle of HYSP and HYIP compared with LCP. HYSP exhibited more biomass accumulation during heading to maturity under NDID and LCP (p < 0.05), which is supported by a higher leaf area index (LAI) and SPAD values after heading. DNID reduced shoot biomass weight and non-structural carbohydrate, while increasing harvest index and NSC remobilization reserve, especially for HYSP (p < 0.05). HYSP had a higher amylopectin content, total starch content, gel consistency, stickiness, and overall palatability (p < 0.05), while it had a lower hardness (p < 0.05) than HYIP. Compared with LCP, DNID increased the amylose content, amylopectin content, total starch content, gel consistency, stickiness, and overall palatability, while it decreased grain protein content and hardness of HYSP and HYIP. HYSP showed consistently higher peak viscosity, breakdown, and gelatinization temperatures (p < 0.05), while it showed lower setback (p < 0.05) than HYIP. For HYSP and HYIP, DNID increased the peak viscosity, breakdown, and gelatinization temperatures (p < 0.05), while it decreased the setback compared with LCP. Generally, the results indicated that coordinated yield components, more post-heading biomass accumulation, lower amylose content, higher peak viscosity and breakdown with lower setback, and higher gelatinization temperatures facilitated high-level grain yield and excellent cooked rice palatability of HYSP. DNID is a feasible method to maintain rice grain yield and enhance the quality of cooked rice for edible properties.

Biofilm forming rhizobacteria affect the physiological and biochemical responses of wheat to drought

Plant growth promoting rhizobacteria (PGPR) can attenuate the adverse effects of water deficit on plant growth. Since drought stress tolerance of bacteria has earlier been associated to biofilm formation, we aimed to investigate the role of bacterial biofilm formation in their PGPR activity upon drought stress. To this end, a biofilm-forming bacterial collection was isolated from the rhizospheres of native arid grassland plants, and characterized by their drought tolerance and evaluated on their plant growth promoting properties. Most bacterial strains formed biofilm in vitro. Most isolates were drought tolerant, produced auxins, showed 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity and solubilized mineral phosphate and potassium, but at considerably different levels. Greenhouse experiments with the most promising isolates, B1, B2 and B3, under three levels of water deficit and two wheat varieties led to an increased relative water content and increased harvest index at both moderate and severe water deficit. However, the bacteria did not affect these plant parameters upon regular watering. In addition, decreased hydrogen peroxide levels and increased glutathione S-transferase activity occurred under water deficit. Based on these results, we conclude that by improving root traits and antioxidant defensive system of wheat, arid grassland rhizospheric biofilm forming bacilli may promote plant growth under water scarcity.

Yield and Resource Utilization Efficiency Gap in Early Maturing Japonica Rice Cultivars under Different Management Strategies—A Different Location Investigation

High input costs and poor management options have resulted in a large rice yield gap. Thus, there is a need to reduce production costs and improve resource-use efficiency by using new cultivation techniques at different locations. The objective of this study was to determine yield and utilization efficiency gaps in early maturing japonica rice under four treatments; no nitrogen application (N0), local farmer practice (FP), high-yield, high-efficiency practice (HYP), and super-high-yield practice (SHY). The average yields under N0, FP, HYP, and SHY were 5012, 7356, 8448, and 9629 kg ha−1, respectively. Differences among treatments were as: N0 to FP (gap 1); FP to HYP (gap 2); and HYP to SHY (gap 3). Yield gaps 1, 2, and 3 were 2337, 1092, and 1181 kg ha−1, respectively. Yield gap was positively associated with panicles per square meter. Yield under HYP and SHY was 14.8% and 30.9% higher than that under FP, respectively. This increase in yield was mainly associated with a higher number of panicles. For resources, gaps 1, 2, and 3 were as follows: water-use efficiency, 0.1706, 0.1513, and 0.1089 kg m−3; radiation-use efficiency, 0.3285%, 0.1780%, and 0.0941%; and heat-use efficiency, 1.8685, 1.0339, and 0.8798 kg °C−1 d−1 ha−1, respectively. The yield was positively correlated with water, radiation, and heat-use efficiencies. The differences in yield and resource-use efficiency were significant between sites. A reduction in yield and efficiency gaps can ensure sufficient panicle per square meter, stabilize grain number per panicle, and increase harvest index and biomass. Overall, HYP is a promising option to increase the yield of early maturing japonica rice yield in cold regions.

Seedling and field assessment of wheat (Triticum aestivum L.) dwarfing genes and their influence on root traits in multiple genetic backgrounds.

Deployment of the Rht-B1b and Rht-D1b dwarfing genes helped facilitate the Green Revolution to increase wheat yields globally. Much is known of the influence of these genes on plant height and agronomic performance, but not of their effects on root architecture. We assessed 29 near-isogenic lines (NILs) representing 11 Green Revolution and alternative dwarfing genes across multiple genetic backgrounds for root architecture characteristics in controlled and field environments. Genetic background did not influence plant height, but had a small and significant (P<0.05) effect on root architecture. All dwarfing gene NILs were significantly (P<0.01) shorter compared with tall controls. The Green Revolution Rht-B1b and Rht-D1b sometimes had longer seedling roots but were not different from their respective tall controls for root depth in the field. The Rht8, Rht12, and Rht18 dwarfing gene NILs produced long seminal roots in seedling pouches, and a greater maximum rooting depth (MRD) and root penetration rate (RPR) in the field. Genotypic increases in MRD and RPR were strongly correlated with increased harvest index and grain yield, particularly in dry environments. Careful root phenotyping highlights the potential of novel dwarfing genes for wheat genetic improvement under water-limited conditions.

Yield and water-use related traits in landrace and new soybean cultivars in arid and semi-arid areas of China

Empirical soybean breeding has improved its yield in arid and semi-arid areas of China. The objective of this study was to identify the important traits found in successful commercial soybean cultivars following the domestication of landraces through breeding in the semi-arid region of North-west China. A further objective was to identify any key traits that can be targeted using trait-based selection to improve yield under drought. Seed yield, phenology, water-use, water-use efficiency and their related traits in soybean landraces and successful cultivars were compared over a four year period in the field and this was supplemented with an outdoor pot experiment. The results in both field and pot experiments showed that successful soybean cultivars have a reduced thermal time to flowering but the thermal time for seed filling has increased. This change in partitioning of phenological time in the commercial cultivars resulted in a lower number of pods, fewer seeds per unit area but an increase in 100-seed weight, harvest index and seed yield. New soybean cultivars with high seed yield also had a lower vegetative biomass and less water use in both field and pot experiments than landraces but the lower water use did not compromise seed yield. The commercial cultivars also had a lower pod wall ratio (ratio of pod wall weight to total pod weight at maturity) which also contributed to yield by improving harvest index. We conclude that the key traits that have been altered as a result of soybean breeding in arid and semi-arid areas of China have been (1) a shortening of the duration between sowing and flowering but an extension of the seed filling period, (2) fewer pods but an increase in seed number per pod and 100-seed weight and also a decreased pod wall ratio, (3) an increased harvest index and (4) a reduced water use, particularly in the deeper soil layers. • Yield improvements in soybean in dry areas were investigated in a study over four years. • Soybean breeding resulted in a shorter thermal time to flower but a longer thermal time for seed filling. • The longer reproductive period resulted in a higher seed number per pod, seed weight and seed yield. • A reduction in the thermal time to flowering reduced leaf fraction and total water-use but did not compromise seed yield. • Newer varieties had lower soil water use at depth but a higher HI than the landraces.

Compatibility of Leucaena leucocephala biomass and cattle manure combination under rainwater harvesting on sorghum (Sorghum bicolor (L.) Moench) productivity in semi-arid region of Zimbabwe

Soil infertility is one of the constraints contributing to poor sorghum production in semi-arid areas across Africa. To increase sorghum production, there is need to address soil fertility issues. Therefore, the objective was to assess the effects of Leucaena/cattle manure combination on grain and stover yields, harvest index and net return of two sorghum varieties (Macia and SV1) under rainwater harvesting techniques. The field experiment was conducted as a randomized complete block design over three cropping seasons in a split-split plot arrangement. Results show significant (P < 0.05) increase in sorghum grain yield with increased applications of Leucaena/cattle manure combination. Macia variety had statistically greater (P < 0.05) grain yield than SV1 variety. Tied contour show considerably higher yield for both varieties across all seasons. Stover yield show significant differences (P < 0.05) as affected by Leucaena/cattle manure and rainwater harvesting techniques. Rainwater harvesting techniques significantly influence (P < 0.05) harvest index, with tied contour and infiltration pits having comparably higher harvest index than standard contour. Application of Leucaena/cattle manure combination show significant increases in harvest index with increased application rates. However, no significant effect was observed at 20 and 30 t ha−1 from SV1 variety across all seasons. Leucaena/cattle manure combination significantly influenced (P < 0.05) sorghum net return across all seasons except at 5 t ha−1 where no significant effect was observed. Macia variety had higher net return than SV1. To increase grain yield and net return, farmers can adopt Macia variety, tied contour and 10 t ha−1 Leucaena/cattle manure combination due to higher incremental yield per tonne.

IMPACT OF SALICYLIC ACID TREATMENTS ON YIELD ATTRIBUTES OF CANOLA AND GROWTH OF Schizaphis Graminum

The present investigation was studied the effect of various trends of salicylic acid on canola yield traits besides, aphid interaction. For this purpose, the research trial was conducted under the semi-natural conditions of the net house of the Plant Pathology Research Institute, Ayub Agriculture Research Institute Faisalabad during November 6, 2019. The canola seeds were planted in the pots following (RCBD) with six treatments (0 ppm, 10 ppm, 20 ppm, 40 ppm, 80 ppm and 160 ppm) and three replications. The maximum plant height (212.41cm), number of pods per plant (675.67), number of seeds per pod (25.29), thousand seed weight (3.85g), biological yield (24817.2 kg-1), seed yield (3666.33 kg-1), seed oil content (47.16%) and protein contents (24.1%) were observed with the application of the high concentration of salicylic acid (160 ppm/pot) over control. A significant increase in harvest index increased (18.8) was recorded with the application of 20 ppm concentration of salicylic acid. The exogenous application of salicylic acid treatments significantly increased the mortality percentage of 1st, 2nd and 3rd instar nymph. The maximum mortality percentage of 1st, 2nd and 3rd instar nymph were recorded 43.67, 76.6 and 83% with the application of high level of salicylic acid concentration (160 ppm/pot) as compared to the control, respectively. The honey drops of aphid and nymph survival percentage were reduced with the foliar application of salicylic acid over control. The minimum honey drops (17.9%), nymph survival (61.8%) and reproductive periods (18%) were recorded with the use of salicylic acid. It was concluded that foliar application of salicylic acid had a significant impact on yield attributes of canola genotypes and biology of canola aphid.

Population structure, allelic variation at Rht-B1 and Ppd-A1 loci and its effects on agronomic traits in Argentinian durum wheat

Exploring the genetic variability in yield and yield-related traits is essential to continue improving genetic gains. Fifty-nine Argentinian durum wheat cultivars were analyzed for important agronomic traits in three field experiments. The collection was genotyped with 3565 genome-wide SNPs and functional markers in order to determine the allelic variation at Rht-B1 and Ppd-A1 genes. Population structure analyses revealed the presence of three main groups, composed by old, modern and genotypes with European or CIMMYT ancestry. The photoperiod sensitivity Ppd-A1b allele showed higher frequency (75%) than the insensitivity one Ppd-A1a (GS105). The semi-dwarfism Rht-B1b and the Ppd-A1a (GS105) alleles were associated with increases in harvest index and decreases in plant height, grain protein content and earlier heading date, although only the varieties carrying the Rht-B1 variants showed differences in grain yield. Out of the two main yield components, grain number per plant was affected by allelic variants at Rht-B1 and Ppd-A1 loci, while no differences were observed in thousand kernel weight. The increases in grain number per spike associated with Rht-B1b were attributed to a higher grain number per spikelet, whereas Ppd-A1a (GS105) was associated with higher grain number per spikelet, but also with lower spikelets per spike.

Yield sustainability of winter wheat under three limited-irrigation schemes based on a 28-year field experiment

Sustainable intensification is an agricultural development direction internationally. However, little is known about the yield sustainability of winter wheat (Triticum aestivum L.) under limited irrigation schemes on the North China Plain (NCP). A 28-year field experiment from 1991 to 2018 at Wuqiao Experimental Station was used to characterize long-term yield, evapotranspiration (ET), and water use efficiency (WUE) trends under three irrigation treatments (W1, irrigation just before sowing; W2, irrigation before sowing and at jointing stage; W3, irrigation before sowing, at jointing stage, and at anthesis). Yield gaps and the effects of genetic improvement, climate change, and climate variables on wheat yield and key phenological stages were estimated using the Agricultural Production Systems Simulator (APSIM) model. Grain yield and WUE of winter wheat increased during the 28 years under the three irrigation treatments, and the upward trend of WUE followed a saturation curve pattern. ET increased slightly. Simulation results showed that genetic improvement dramatically prolonged the phenological stages of vegetative growth period and contributed to yield increase by 0.03%–15.6%. The rapid increase in yield with lower water use was associated mainly with an increase in biomass with genetic improvement and partly with an increase in harvest index. A curvilinear relationship between WUE and yield emphasized the importance of obtaining high yields for high WUE. The yield gaps between potential yield and yield under W1 treatment increased from 1991 to 2018 but were relatively constant for the W2 and W3 treatments. Elevated atmospheric CO2 concentration offset the negative effects of temperature increase on yield, leading to minor (−2.3% to 0.3%) changes in yield under climate change. Thus, genetic improvement played a dominant role in yield increase, and limited-irrigation schemes (W2 and W3) can increase wheat yield and promote sustainability of crop production on the NCP.

Maize genetic progress in the central Pampas of Argentina: effects of contrasting sowing dates

Delayed sowing date of maize (Zea mays L.) has become a broadly adopted practice in the Pampas region of Argentina, because late-sown crops frequently experience a more favorable water balance around flowering and a reduction in the year-to-year yield variation. However, breeding efforts in this region have been focused on early sowing date environments. In addition, there has been no research on genetic progress of grain yield and the underlying attributes under late-sowing conditions. The aim of this study was to compare genetic progress in grain yield and secondary traits for hybrids released between 1980 and 2016 when grown in early- versus late sowing environments in the central Pampas region. Grain yield, its components (kernel number and kernel weight), and its physiological determinants (total shoot biomass and harvest index) were assessed in two contrasting sowing dates during three years. Biomass at silking (BR1) and during the post-silking period (BR1-R6), plant growth rate and source-sink ratios during the critical and the effective kernel-filling periods were also analyzed. Grain yield genetic progress was similar for early (0.9% y-1) relative to late sowing dates (0.8% y-1). Kernel number increase with the year of release (YOR) was more important in early (0.6% y-1) than in late (0.4% y-1) sowings, whereas the opposite trend was documented for kernel weight (0.2% and 0.3% y-1, respectively). Newer hybrids showed greater biomass production in both sowing dates (0.8% y-1 for early, 0.6% y-1 for late) and a slight increase in harvest index in late sowings (0.2% y-1). Breeding effects on shoot biomass production were exclusively attributed to the post-silking period (1.2% y-1 for early and 0.9% y-1 for late), as BR1 remained unchanged with YOR. Assimilate availability per kernel during the effective kernel filling increased with YOR in both sowing dates (1.0% y-1 for early and 0.9% y-1 for late), promoting a longer kernel filling duration. Results demonstrated that breeding efforts focused on early sowings as the main target environment, have also impacted yield gains in late sowings. However, the enhanced importance of kernel weight on grain yield determination among late- than among early sowings will demand future breeding strategies to pay special attention to unfavorable photothermal conditions during kernel filling.

Both biomass accumulation and harvest index drive the yield improvements in soybean at high and low phosphorus in south-west China

Soybean breeding is typically conducted in soils with favourable soil phosphorus yet soil P levels are typically low in sub-tropical regions. This study was conducted to determine yield progress of soybean cultivars released between 1995 and 2016 in sub-tropical parts of south-west China and grown at both low and high P availability. The principal factors that changed indirectly with breeding and that contribute to soybean yield were also determined. Field experiments were conducted in three consecutive years with two different sites each year. A more detailed investigation of traits contributing to soybean yield was investigated in one year at two sites. The rate of genetic gain in seed yield was around 2% per year and this was found at both low P and high P. Thus, breeding under favourable conditions has also resulted in substantial gains in soils with low P. Yield gains were attributed to a longer duration of pod filling but there was no change in the duration from sowing to flowering. The extended pod filling duration increased both above-ground biomass and harvest index (HI) at both P levels and both were important in contributing to yield gains. The increase in HI was also a result of the changed allocation of assimilates away from stems and instead to the pods and growing seeds. The allometric analysis (ratios between log transformations of the leaf, stem and pod dry weight) showed that the stem weight decreased as pod dry weight became heavier whereas leaf weight remained constant as stems became lighter as a result of breeding. Breeding also progressively increased pod number and the total seed number but there was no change in average seed weight. • Soybean breeding conducted under favourable soil P levels has successfully increased seed yield in soils with favourable and unfavourable P levels. • The rate of genetic gain between 1995 and 2016 in south-west China is around 2% per year in both high and low P soils. • Yield gains have been attributed to both an increase in above-ground dry weight and an increase in harvest index. • Breeding has not increased seed weight but seed number has increased.

Improvements in grain yield and nutrient utilization efficiency of japonica inbred rice released since the 1980s in eastern China

The cropping area of japonica inbred rice has expanded rapidly since the 1980 s, which occupies 90% of the total cropping area nowadays in Jiangsu, east China. In this process, information on the genetic improvement in grain yield and nutrient use efficiency of japonica inbred rice is still limited. Fifteen japonica inbred rice released from 1983 to 2014 were tested during the 2018 and 2019 rice-growing seasons. Grain yield increased yearly at 65.1 kg ha −1 (0.65%) in 2018 and 58.1 kg ha −1 (0.59%) in 2019. Panicles per m 2 and filled-kernel percentage decreased (P < 0.01), while spikelets per panicle increased (P < 0.01), with year of release. Pre-heading biomass, post-heading biomass, and total biomass increased (P < 0.01 or P < 0.05) linearly with year of release; while harvest index gradually increased with year of release before 2000, thereafter remaining relatively stable. Leaf area index (LAI) at heading and maturity, plant height, specific leaf weight, and flag leaf photosynthetic rate at heading, and intercepted radiation and radiation use efficiency (RUE) from heading to maturity all increased (P < 0.01) with year of release, which was associated with the increased biomass accumulation during the breeding process. Genetic improvement has increased total N, P, and K accumulation, as well as their use efficiencies. Grain yield and harvest index correlated positively (P < 0.01) with NUEg, PUEg, and KUEg among rice cultivars. Our results suggested the impressive progress in grain yield and nutrient use efficiency of japonica inbred rice since the 1980 s in eastern China. The yield progress was mainly attributed to the increased spikelets per panicle. For rice cultivars released before 2000, an increase in harvest index contributed more to yield improvement than total biomass; while the yield improvement after 2000 resulted from total biomass. The results also indicated possible opportunities for improving use efficiency of N, P, and K through increasing harvest index in rice. • Genetic improvement has progressively increased grain yield of japonica inbred rice since the 1980s in eastern China. • The increased harvest index contributed more to yield gain before 2000, while total biomass for yield gain after 2000. • Genetic selection for rice grain yield has also improved N, P, and K use efficiencies. • Harvest index was positively (P<0.01) correlated with NUEg, PUEg, and KUEg in rice.