Vigorous Root Research Articles

Reprogramming of Fundamental miRNA and Gene Expression during the Barley-Piriformospora indica Interaction.

The interactions between plants and microorganisms, which are widely present in the microbial-dominated rhizosphere, have been studied. This association is highly beneficial to the organisms involved, as plants benefit soil microorganisms by providing them with metabolites, while microorganisms promote plant growth and development by promoting nutrient uptake and/or protecting the plant from biotic and abiotic stresses. Piriformospora indica, an endophytic fungus of Sebacinales, colonizes the roots of a wide range of host plants and establishes various benefits for the plants. In this work, an interaction between barley and the P. indica was established to elucidate microRNA (miRNA)-based regulatory changes in miRNA profiles and gene expression that occurred during the symbiosis. Growth promotion and vigorous root development were confirmed in barley colonized by P. indica. The genome-wide expression profile analysis of miRNAs in barley root showed that 7,798,928, 6,418,039 and 7,136,192 clean reads were obtained from the libraries of mock, 3 dai and 7 dai roots, respectively. Sequencing of the barley genome yielded in 81 novel miRNA and 450 differently expressed genes (DEGs). Additionally, 11, 24, 6 differentially expressed microRNAs (DEMs) in barley were found in the three comparison groups, including 3 dai vs. mock, 7 dai vs. mock and 7 dai vs. 3 dai, respectively. The predicted target genes of these miRNAs are mainly involved in transcription, cell division, auxin signal perception and transduction, photosynthesis and hormone stimulus. Transcriptome analysis of P. indica identified 667 and 594 differentially expressed genes (DEG) at 3 dai and 7 dai. Annotation and GO (Gene Ontology) analysis indicated that the DEGs with the greatest changes were concentrated in oxidoreductase activity, ion transmembrane transporter activity. It implies that reprogramming of fundamental miRNA and gene expression occurs both in barley and P. indica. Analysis of global changes in miRNA profiles of barley colonized with P. indica revealed that several putative endogenous barley miRNAs expressed upon colonization belonging to known micro RNA families involved in growth and developmental regulation.

The Responses of Four Typical Annual Desert Species to Drought and Mixed Growth

Soil desiccation is increasingly threatening the growth of vegetation in artificial forests at the margins of arid desert oases, where a variety of annual herbaceous plants coexist. It is important to understand the response of annual desert plants to droughts and mixed growth and the resulting patterns of change in photosynthetic and physiological properties. Our results showed that annual plants were primarily affected by drought stress, and the effect of interspecific competition was significant only under severe drought stress. In the sprouting stage, moderate drought increased seed germination rates, whereas severe drought stress decreased the germination rates. In the growth phase, the aboveground and belowground parts of annual herbaceous plants showed a synergistic response to drought. Under mild and moderate drought stress, annual herbaceous plants promoted photosynthesis by increasing chlorophyll content, thereby promoting plant stem growth. Following moderate and high drought, root vigor increased to maintain basic metabolic activities and annual herbaceous plants used the “shadow and avoid” response by increasing stem and root length to increase competitive ability. Under severe drought stress, planted seedling chlorophyll levels decreased, resulting in a simultaneous reduction in photosynthetic ability. The root growth of annual herbaceous plants depends on their photosynthesis ability but the decrease in biomass led to a decrease in root growth. The mixed habitat reduced the inhibition of seedling stem growth by drought stress and promoted plant growth.

Growth patterns and environmental adaptions of the tree species planted for ecological remediation in typhoon-disturbed areas—A case study in Zhuhai, China

Typhoon frequently results in various mechanical damages to urban forest ecosystems. Imperative forest remediation projects were launched to restore the environmental conditions in cities, in which massive trees were newly planted. However, it was rarely answered whether the newly planted trees could acclimate to typhoon circumstances and enhance the wind resistance of the local ecosystem. Therefore, it was necessary to achieve information on the physical growth and windy environmental adaption of newly planted trees, which could promote a profound understanding of the efficiency of post-typhoon ecological remediation. In this study, we selected Zhuhai's urban-forest remediation district as our research area that suffered severely from Typhoon Hato (2017). The six newly-planted tree species for the ecological remediation were measured for their above- and below-ground processes from June 2018 to December 2019, including their development of tree height, ground diameter, crown size, and fine root biomass. Additionally, the variations of the soil's physical and chemical properties were also measured to assess the impact of plantation on soil conditions. Our results showed that the six surveyed tree species had different above- and below-ground growth patterns. With robust root development at horizontal and vertical levels combined with relatively short and thick above-ground profiles, Sterculia lanceolata Cav. and Cinnamomum camphora (Linn) were likely to cope well with typhoon disturbances. Ilex rotunda Thunb. and Schima superba Gardn. et Champ. exhibited moderate acclimation to windy environment, while Elaeocarpus sylvestris (Lour.) Poir. and Elaeocarpus apiculatus Mast. were not recommended to be planted in typhoon-disturbed areas concerning their unstable root development. In addition, the ecological remediation did improve the soil properties, specifically for the chemical characteristics including available nitrogen, available potassium, and soil organic matter. To improve the effectiveness of forest remediation in the future, it was better to choose those tree species with vigorous root development and steady values of root:shoot ratios, which might be advantageous for coping with typhoon disturbances. The tree species with prosperous above-ground growth were not suitable for areas facing strong winds directly but could be planted in leeward regions to amplify their landscape functions.

Response of Durum Wheat (Triticum durum L.) Genotypes to Drought stress at Early Growth Stage

Early drought is a great threat limiting wheat production in semi-arid region resulted in poor emergence and weak seedlings. This research experiment attempts to evaluate the drought-tolerance potential of four local Triticum durum L. genotypes at germination stage. Hawler-1, Akassad, Semito and Barcelona subjected to drought stress of about 25 % of the soil water holding capacity (SWHC) and compared to their control 100 % SWHC in a factorial experiment designed in a complete randomization. Under stressed condition Semito genotype showed the significantly highest final germination percentage 54.66 %. Lowest MGT was 12 recorded by Semito and Aksaad. The heaviest roots, shoot dry weight and root: shoot ratio were observed in Akassad; 4.09 and 3.95 g and 1.28 respectively. The longest shoot averaged over all treatments was observed in Semito (23.05 cm). The highest leaves relative water content (LRWC) and membrane stability index (MSI) were 56.39 and 62.05 recorded by Semito. Akassad had the highest content of chlorophyll a, b and total; 2.40, 1.51 and 3.91 mg/ g fresh weight. Highest significant proline content was 0.548 mg/ g fresh and sugar content was 2.94 mg g dry weight accumulated in Semito leaves. Genotypes with a fast germination, more vigorous root system and highest root: shoot ratio are very desirable for the rapid establishment of seedlings and could have best physiological response as well as accumulate more osmoticum in their cytosol. Thus, Akassd and Semito had best potential adaptability to drought stress at early growth stage.

Assessing the Effect of a Major Quantitative Locus for Phosphorus Uptake (Pup1) in Rice (O. sativa L.) Grown under a Temperate Region

Water and phosphorus (P) fertilizer are two of the most critical inputs in rice cultivation. Irrigation and chemical fertilizers are becoming limiting factors under climate change and urbanization, which is leading to significant losses in yield. The Pup1 quantitative trait locus (QTL) confers tolerance to P starvation through enhanced early-stage root vigor and P uptake in indica rice grown in the tropics. Whether the QTL works in temperate rice genetic backgrounds grown in temperate regions remains to be elucidated. To address this question, we introgressed the Pup1 QTL into three temperate rice varieties—MS11, TR22183, and Dasanbyeo—using marker-assisted backcrossing and high-density genotyping. The selected lines all harbored the full Pup1 QTL with recurrent parent genome recovery rates ranging from 66.5% to 99.8%. Under the rainfed and P non-supplied conditions, Pup1 introgression lines did not show clear advantages over the recurrent parents in terms of vegetative growth and grain yield per plant, but exhibited enhanced yield responses to P application, except in Dasanbyeo, which a temperate rice that is genetically similar to indica. Our results suggest that Pup1 confers enhanced P uptake in temperate rice and that the efficacy of Pup1 might depend on the subspecific genomic background of the rice, whether it is japonica or indica.

Calcium peroxide alleviates the waterlogging stress of rapeseed by improving root growth status in a rice-rape rotation field.

Waterlogging stress has a negative influence on agricultural production, particularly for rapeseed yield in a rice-rape rotation field. To alleviate the profound impacts of waterlogging stress on rapeseed production, a new fertilization with calcium peroxide (CaO2) was proposed. In this field experiment, with the conventional rape (Brassica napus L.) variety fengyou958 (FY958) and early maturing rape variety xiangyou420 (XY420) as materials, waterlogging was imposed from the bud to flowering stage, and three supplies of CaO2 (0, C1 for the 594kg hm-2 and C2 for the 864kg hm-2) were added as basal fertilizer. The results showed that CaO2 significantly reduced the accumulation of fermentation products in roots and alleviated the peroxidation of leaves. The reduced waterlogging stress promoted the root vigor and agronomic characters, such as branches, plant height and stem diameter, accelerated dry matter and nutrients accumulation, and resulting in 22.7% (C1) to 232.8% (C2) higher grain yields in XY420, and 112.4% (C1) to 291.8% (C2) higher grain yields in FY958, respectively. In conclusion, 594kg hm-2 to 864kg hm-2 CaO2 application restored the growth of waterlogged rapeseed leaves, and reduced the anaerobic intensity of root, which enhanced the resistance of plants to waterlogging, and improved crop productivity. In a certain range, the higher CaO2 application, the more the yield. This study provides a valid method to prevent damage from flooding in crop fields.

Optimizing the spatial distribution of roots by supplemental irrigation to improve grain yield and water use efficiency of wheat in the North China Plain

Soil moisture affects the yield and water use efficiency (WUE) of winter wheat (Triticum aestivum L.) by regulating the spatial distribution of roots. Therefore, appropriate supplemental irrigation (SI) schemes are essential to achieve high yield and high WUE of wheat by constructing a reasonable root structure. In this study, field experiments were conducted the North China Plain (NCP) from 2018 to 2020. Based on the soil moisture management at sowing on a consistent basis, four SI regimes were set up: no irrigation after seedling emergence (W0), SI at jointing (W1), SI at jointing and anthesis (W2), and SI at regreening, jointing, and anthesis (W3). The results showed that although the grain yield of wheat increased with the SI frequency, the WUE decreased with increasing SI amount. SI at jointing and anthesis significantly increased WUE without reducing or slightly reducing the grain yield. The grain yield and WUE in 2018–2019 were significantly higher than those of the corresponding treatments in 2019–2020, and the yield of Bainong 4199 was higher than that of Zhoumai 18. The grain yield and WUE in 2018–2019 were significantly higher than those of the corresponding treatments in 2019–2020. The root length density (RLD) in the 0–20-cm soil layer increased with increasing SI frequency, but the proportion of RLD in the 40–60-cm soil layer decreased. The average RLD in the 0–60-cm soil layer and grain yield of Bainong 4199 were significantly greater than that of Zhoumai 18. Correlation analysis showed that the grain yield and WUE was positively correlated with the RLD in the 0–20-cm soil layer, and reached a very significant level with RLD in the 0–20-cm soil layer between rows. W2 and W3 in terms of root vigor and the grain filling rate 30 days after anthesis were significantly higher than W1 and W0 and also increased the contribution of post-anthesis dry matter to grain, resulting in an increase in grain weight. These results demonstrated that SI at jointing and anthesis could optimize the spatial distribution of roots, maintain higher root activity and filling rate at the late stage, increase accumulation and translocation of post-anthesis dry matter, and finally improve the yield and WUE. Therefore, we propose that Bainong 4199 was the preferred cultivars for this experiment，under sufficient soil moisture conditions before sowing, SI at jointing and anthesis is the optimal irrigation scheme for wheat on the NCP.

QTL mapping for early root and shoot vigor of upland rice (Oryza sativa L.) under P deficient field conditions in Japan and Madagascar.

Upland rice production is limited by the low phosphorus (P) availability of many highly weathered tropical soils and P deficiency is likely to become increasingly limiting in future drier climates because P mobility decreases sharply with soil moisture. Good seedling root development will be crucial to cope with the combined effects of low P and water availability. Upland rice genebank accession DJ123 was used as a donor for P efficiency and root vigor traits in a cross with inefficient local variety Nerica4 and a set of backcross lines were used to characterize the seedling stage response of upland rice to low P availability and to identify associated QTL in field trials in Japan and Madagascar. Ten QTL were detected for crown root number, root, shoot and total dry weight per plant in a highly P deficient field in Japan using the BC1F3 generation. Of these, qPef9 on chromosome 9 affected multiple traits, increasing root number, root weight and total biomass, whereas a neighboring QTL on chromosome 9 (qPef9-2) increased shoot biomass. Field trials with derived BC1F5 lines in a low-P field in Madagascar confirmed a highly influential region on chromosome 9. However, qPef9-2 appeared more influential than qPef9, as the shoot and root biomass contrast between lines carrying DJ123 or Nerica4 alleles at qPef9-2 was +23.8% and +13.5% compared to +19.2% and +14.4% at qPef9. This advantage increased further during the growing season, leading to 46% higher shoot biomass at the late vegetative stage. Results suggest an introgression between 8.0 and 12.9 Mb on chromosome 9 from P efficient donor DJ123 can improve plant performance under P-limited conditions. The QTL identified here have practical relevance because they were confirmed in the target genetic background of the local variety Nerica4 and can therefore be applied directly to improve its performance.

Straw and nitrogen amendments improve soil, rice yield, and roots in a saline sodic soil

Straw return can improve the physical properties and nutrient status of the soil. However, there are few studies on straw return coupled with nitrogen (N) fertilizer for rice planting in saline sodic areas. Therefore, we conducted a two-year field experiment to evaluate the effects of straw management (retention or removal) with N fertilizer (0, 90, 180, 270 and 360 kg N ha−1) on soil properties, root characteristics, rice yield and N use efficiency in a saline sodic rice growing area. The results showed that straw return significantly reduced soil bulk density, pH, soil electrical conductivity of saturated paste extraction (ECe), exchangeable sodium (ENa+), exchangeable sodium percentage (ESP), and also significantly increased soil organic matter and cation exchange capacity (CEC). Compared with straw removal, straw return reduced soil pH, ECe, ENa+, and ESP by 2.97%, 10.90%, 8.95%, and 13.78%, respectively. At the same N level, straw retention reduced rice root morphology and root vigor at mid-tillering and panicle initiation, but N fertilizer was able to alleviate root inhibition by straw return. Straw return improved root morphology and root vigor in mid and late rice growth and promoted nutrient uptake. Compared with straw removal, the agronomic efficiency nitrogen and partial factor productivity were significantly increased by 13.97% and 4.59%, respectively, in the straw return treatment. With or without straw retention, rice yield increased and then decreased with increasing N fertilizer application rate, and was maximum at 270 kg N ha−1. Compared to straw removal, rice yield was significantly increased by 4.37% (2020) and 7.17% (2021) for straw return treatments, respectively. Meanwhile, straw return can reduce mineral N fertilizer inputs by about 36–43% without affecting rice yield. Under straw return conditions, soil characteristics, root characteristics, and rice yield were optimal at 270 kg N ha−1. Our results suggest that straw return combined with nitrogen fertilization may be a promising management practice to reduce mineral N application without loss of rice yield in saline sodic soils. Among them, straw return combined with 270 kg N ha−1 was most effective in the early stages of straw return in saline sodic rice growing areas.

Plastic film mulching does not increase the seedcotton yield due to the accelerated late-season leaf senescence of short-season cotton compared with non-mulching

Plastic film mulching has been widely applied to improve crop productivity of full-season cotton (Gossypium hirsutum L.). However, in a previous study, plastic mulching did not increase seed cotton yield of short-season cotton compared with non-mulching. The aim of this study was to determine why plastic mulching fails to increase seed cotton yield of short-season cotton. A short-season cultivar Lumian 532 was planted with or without plastic mulching at an experimental station in Linqing in the Yellow River valley of China in 2020 and 2021. Yield, yield components, leaf senescence, photoassimilate accumulation and partitioning, photohormone contents, expression of senescence-related genes, and root traits were examined each year. Seed cotton yield produced with plastic mulching was not significantly different from that produced with non-mulching in short-season cotton. Although number and size of early- and mid-season bolls were significantly greater with plastic mulching than with non-mulching, plastic mulching decreased number and size of late-season bolls by 34.0% and 8.8%, respectively. At the initial boll opening stage, photosynthetic rate and chlorophyll content in main-stem functional leaves were 36.2% and 24.1% lower, respectively, with plastic mulching than with non-mulching, but malondialdehyde content was 34.2% higher, suggesting that plastic mulching accelerated late-season leaf senescence. Canopy photosynthesis and photoassimilate partitioning to reproductive organs at the initial boll-opening stage were 68.1% and 9.4% lower, respectively, with plastic mulching than with non-mulching. Compared with non-mulching, plastic mulching increased abscisic acid and methyl jasmonate contents but decreased those of cytokinins content because of differential expression of hormone metabolism-related genes in late-season main-stem leaves. Plastic mulching also increased root distribution in the shallow soil layer and lowered root vigor in the late season, compared with non-mulching. Overall, plastic mulching negatively affected root distribution and function and altered expression of senescence-related genes and hormone metabolism-related genes to affect hormone balance, which led to accelerated late-season leaf senescence. Because of late-season leaf senescence, canopy photosynthesis and photoassimilate partitioning to cotton bolls were suppressed with plastic mulching, which led to fewer and smaller late-season bolls than those with non-mulching. Thus, plastic mulching failed to improve the seed cotton yield. This study provides a clear explanation of how plastic mulching causes late-season leaf senescence and further demonstrates that plastic film mulching is not required for planting short-season cotton in the Yellow River valley of China or in other cotton growing areas with similar ecology.

Peanut Root Exudates Suppress Fusarium solani and Modulate the Microbial Community Structure of Rhizosphere in Grape Replant Soil

Replant disease significantly hinders the development of the grape industry, and the imbalance of the rhizosphere microecological environment is one of the fundamental reasons hindering grape replants. Peanut is a common intercropping crop, and whether the root exudates of peanut can alleviate grape replant obstacles is still unknown. In this study, the effects of exogenous peanut root exudates on replanting grapevine growth, and the microbial community structure of grapevine replant soils were studied. The results showed that peanut root exudates could promote the growth of replanting grapevine seedlings; enhance root vigor and SOD activity, increasing 55.18% and 95.71%, respectively; and reduce the MDA content of root, decreasing 31.10%. After peanut exudate treatment, the growth of Fusarium solanum, an important harmful fungus that is an obstacle to grape replant, was inhibited. The relative abundances of Gaiella in bacteria and Cystobasidium and Mortierella in fungi increased, and the potential pathogen fungi Fusicolla decreased. Peanut root exudates also modified the soil bacterial and fungal community in a certain range and increased the interaction among the bacteria of grapevine rhizosphere soil. However, they loosened the interaction among fungi. There are extensive mutualistic interactions among bacteria or fungi in grape rhizosphere assemblages after peanut exudates treatment. Therefore, peanut root exudates might be helpful in changing the soil microbial environment and alleviating the grape replanting obstacle.

Crossbreeding Rootstocks Improve Nitrogen Efficiency of Grafted Watermelon by Inducing Leaf Physiological and Root Morphological Responses

This is the first hydroponic study that evaluated the role of the heterotic plant characters of crossbreeding progenies and accessions which were used as rootstock for watermelon (scion) to improve the nitrogen (N) efficiency of this crop by grafting. The target of the research was to evaluate if grafting could enhance the nitrogen efficiency of watermelon through examining the responses of heterotic plant characters of crossbreeding rootstocks in the shoot development at the agronomical stage, root developments at the morphological stage, and leaf growth at various physiological stages. A hydroponic experiment was conducted by using an aerated deep-water culture (DWC) system in a well-equipped growth chamber of Erciyes University’s Plant Physiology Laboratory located at Kayseri, Türkiye. A watermelon cultivar Crimson Tide (CT) was grafted onto watermelon cultivars of Calhoun Gray (CG), Charleston Gray (Cha. G), and accessions of PI 296341 and PI 271769, the crossbreed progenies of Calhoun Gray × PI 296341, Calhoun Gray × PI 271769, and Charleston Gray × PI 296341. Plants were grown in 8 L plastic containers filled continuously with aired stock nutrient solution under two nitrogen (N) doses (low dose N: 0.3 mM unit N, and high dose N: 3.0 mM unit N) in a completely randomized block design (RBD) which was replicated three times, for six weeks. The grafted plants usually showed a higher crop growth performance than the self-grafted control plants, illustrating that nitrogen efficiency was significantly enhanced with respect to rootstocks of crossbreed progenies under a low N dose and high N dose. The N efficiency of grafted watermelon (CT) was improved by the high manifestation of heterosis in some root morphological characters (vigor root development and active root mechanism) of some of the crossbreeding rootstocks (Calhoun Gray × PI 271769) particularly in low-N conditions. Additionally, some of the crossbreeding rootstocks (Charleston Gray × PI 296341) exhibited high heterosis, which led to improving the N efficiency of grafted watermelon (CT) by inducing leaf physiological responses under high N supply. This clearly indicated that heterosis plays a crucial role in exploiting the genetic diversity in the N efficiency of watermelon. Therefore, these heterotic plant traits may be vital for the selection and breeding of nitrogen-efficient rootstocks for both small-scale and large-scale commercial farming in the nearby future.

Proper irrigation amount for eggplant cultivation in a solar greenhouse improved plant growth, fruit quality and yield by influencing the soil microbial community and rhizosphere environment.

Water scarcity is a worldwide problem, and in order to obtain plenty of production, agricultural irrigation water accounts for a large portion. Many studies have shown that the interaction of root microorganisms and soil can promote crop growth. Developing ways to reduce irrigation to maintain soil fertility and ensure crop yield by regulating the root microenvironment is an important research goal. Here, we developed a reasonable irrigation plan for eggplant cultivation in a solar greenhouse. The maximum theoretical amount of water demand during eggplant planting obtained from a previous study was used as the control (CK), and the irrigation in the treatments was reduced by 10, 20 and 30% relative to this amount. The 10% irrigation reduction treatment (T1) significantly improved soil nutrients and increased soil catalase, urease and alkaline phosphatase activities (p < 0.05). Further analysis of rhizosphere microorganisms revealed the highest richness and diversity of the microbial community under the T1 treatment, with Bacilli as the most abundant bacteria and Aspergillaceae as the most abundant fungi and lower relative abundances of Chloroflexi and Acidobacteria (p < 0.05). Changes in microbial community structure under the influence of different irrigation treatments resulted in improvements in rhizosphere N cycling and nutrient catabolism. The plant–microbe interactions led to significant increases in eggplant plant height, root vigour, root surface area, leaf chlorophyll a, leaf net photosynthetic rate, water use efficiency, transpiration rate, and stomatal conductance under the T1 treatment compared to the CK treatment; soluble sugar, soluble protein and free amino acid contents in eggplant fruit increased by 10.8, 12.3 and 6.7%, respectively; and yield increased by 3.9%. Our research proved that the 10% irrigation reduction treatment (T1) could improve microbial community richness and fruit yield, which would improve irrigation efficiency and cost reduction in agriculture.

Regulation of rhizospheric microbial network to enhance plant growth and resist pollutants: Unignorable weak electric field

The union of Plant Growth-Promoting Bacteria (PGPB) and rhizosphere confers a series of functions beneficial to plant. However, the lack of an opearable in situ method limits the further understanding on the mechanism. In this study, a weak electric field was designed to regulate rhizospheric microflora in a constructed root-splitting reactor. Compared with the control, the aboveground and underground biomass of rice seedling increased by 17 % and 18 % (p < 0.05) respectively under the exist of weak electric field of 0.14 V/cm. The joint action of rhizosphere and PGPB displayed the detoxification ability in the condition of soluble petroleum hydrocarbons, where the height, stem diameter, biomass and root vigor of the plant was increased by 58 %, 32 %, 43 % and 48 % respectively than the control. The selective reproduction of endophytes and ectophytes (denitrifying, auxin-producing, hydrocarbon-degrading and electroactive bacteria) was observed under applied weak electric field, which enhanced the nitrogen utilization, cellular metabolic activity and resistance to toxic organics of plant. This was further confirmed by the up-regulated OTUs related to the hydrocarbon degradation function, tryptophan metabolism and metabolism of nicotinate and nicotinamide. Moreover, the weak electric field also enhanced the transfer ability of partial endophytes grown in the root to improve plant stress resistance. The results in this work inspired an exercisable method for in situ enrichment of PGPB in the rhizosphere to cope with food crisis and provided a new way to deal with sudden environmental events.

Differing responses of root morphology and physiology to nitrogen application rates and their relationships with grain yield in rice

Root morphology and physiology influence aboveground growth and yield formation in rice. However, root morphological and physiological differences among rice varieties with differing nitrogen (N) sensitivities and their relationship with grain yield are still unclear. In this study, rice varieties differing in N sensitivity over many years of experiments were used. A field experiment with multiple N rates (0, 90, 180, 270, and 360 kg ha−1) was conducted to elucidate the effects of N application on root morphology, root physiology, and grain yield. A pot experiment with root excision and exogenous application of 6-benzyladenine (6-BA) at heading stage was used to further verify the above effects. The findings revealed that (1) under the same N application rate, N-insensitive varieties (NIV) had relatively large root biomass (root dry weight, length, and number). Grain yield was associated with root biomass in NIV. The oxidation activity and zeatin (Z) + zeatin riboside (ZR) contents in roots obviously and positively correlated with grain yield in N-sensitive varieties (NSV), and accounted for its higher grain yield than that of NIV at lower N application rates (90 and 180 kg ha−1). (2) The root dry weight required for equal grain yield of NIV was greater than that of NSV. Excision of 1/10 and 1/8 of roots at heading stage had no discernible effect on the yield of Liangyoupeijiu (NIV), and it significantly reduced yield by 11.5% and 21.3% in Tianyouhuazhan (NSV), respectively, compared to the treatment without root excision. The decrease of filled kernels and grain weight after root excision was the primary cause for the yield reduction. Root excision and exogenous 6-BA application after root excision had little influence on the root activity of NIV. The oxidation activity and Z + ZR contents in roots of NSV decreased under root excision, and the increase in the proportion of excised roots aggravated these effects. The application of exogenous 6-BA increased the root activity of NSV and increased filled kernels and grain weight, thereby reducing yield loss after root excision. Thus, the root biomass of NIV was large, and there may be a phenomenon of “root growth redundancy.” Vigorous root activity was an essential feature of NSV. Selecting rice varieties with high root activity or increasing root activity by cultivation measures could lead to higher grain yield under lower N application rates.

Effects of different peanut-cotton intercropping modes on physiological characteristics and yield of peanut in late growth stage

Using peanut cultivar Huayu 25 and cotton cultivar Liaomian 19 as experimental material, we examined the effects of different intercropping patterns on physiological characteristics of peanut in later growth stage, yield and economic benefit, based on an experiment with five treatments, including intercropping modes of 4 rows peanut and 4 rows cotton (H4M4), 6 rows peanut and 4 rows cotton (H6M4), 4 rows peanut and 4 rows cotton (H4M2), sole peanut (DH) and sole cotton (DM). The results showed that intercropping mode increased the length of main stem and branches of peanut, but decreased green leaves number of main steam, leaf area index, and total dry matter accumulation. Among the intercropping modes, chlorophyll content, chlorophyll fluorescence parameters, root vigor, nitrate reductase activity under H6M4 and H4M2 were significantly higher than that under H4M4, as well as higher superoxide dismutase, peroxidase, catalase activity and decreased malondialdehyde content. Intercropping significantly reduced peanut and cotton yields, but enhanced the gross economic output value. The yield reduction of H6M4 was the lowest and the economic output was the highest among all the intercropping modes. In addition, the land equivalent ratio of H6M4 was greater than 1, indicating the obvious advantage of intercropping. Our results indicated that appropriate reduction of the ratio of cotton under the peanut-cotton intercropping systems could strengthen root vigor and increased nitrate reductase activity, promote nutrient absorption capacity, reduce senescence, and increase the economic output.

Kernel quality, germination rate and seedling performance of eight wheat varieties produced under three different irrigation regimes

The effects of three different irrigation treatments were tested on kernel quality (i.e. kernel size), germination rate and seedling performance of eight wheat varieties. The irrigation treatments used were as follows: (i) rainfed treatment with 262.8mm annual rainfall received during the growing season, (ii) partial irrigation (PSI) treatment receiving 482.8 mm of water (262.8mm rainfall + 220mm irrigation at anthesis) and (iii) continuous supplementary irrigation (CSI) receiving 640 mm water (262.8 mm rainfall + 377.2 mm supplementary irrigation at 2-3 weeks interval). Seven durum wheat varieties (Sham1, Omqais, Acsad65, Bani Suef6, Bani Suef4, Horani Nawawi, Dairalla6) and one bread wheat variety (Ammon) were included in this study. Split-plot design was used with three replications. The main plots were the irrigation treatments, while the sub-plots were varieties nested within irrigation treatments. Kernels weight was recorded under different irrigation treatments in addition to the germination rate parameters (mean germination time and the time to attain 10% and 50% of complete germination percentage) and seedling attributes (shoot length, maximum seminal root length, coleoptile length, shoot fresh weight and seminal root fresh weight). The thousand kernel weight (TKW) was maximum under PSI (46.21g), followed by CSI (43.20g) and rainfed treatment (41.70g). TKW was maximum in Cham1 (45.37g) and BaniSuef6 (45.22g), while the minimum TKW was recorded in Ammon bread wheat variety (39.19g). Smaller wheat kernels released under rainfed condition were notoriously faster to germinate as compared with kernels released under CSI and PSI, and consequently smaller kernels would be desirable to accelerate the time required from sowing to seedling emergence. Hourani Nawawi and DairAlla 6 gave a more vigorous seedling with longer seminal roots and larger seedling biomass, which might indicate their high adaptability to early drought. In conclusion, smaller kernels were faster in germination, which minimize the time required from germination to emergence for a good stand establishment, while heavy kernels would have seedlings with a more vigorous root system which may help the crop to withstand early drought

Effect of vegetable residues incorporation on soil fertility, rhizosphere microbial community structure, and plant growth of continuously cropped cucumber in a solar greenhouse

PurposeIncorporating crop residues into the soil is considered a sustainable and valuable method to alleviate soil deterioration caused by continuous monoculture in greenhouse production. However, the effect of vegetable residues retention on soil amendments is poorly understood. In the present study, we investigated the impacts of sweet pepper, tomato, and cucumber plant residues on soil microbial communities and plant growth of continuously cropped cucumber in a solar greenhouse.MethodsThe 16S rRNA and ITS1 rRNA genes were amplified, and high-throughput sequencing was performed to explore the impacts of vegetable residues incorporation on soil microbial communities. Additionally, soil chemical properties, cucumber root vigor, and fruit yield were measured to assess the impacts of vegetable residues incorporation on continuously cropped soil and cucumber growth.ResultsThe results showed that incorporating vegetable residues could improve soil buffering capacity, increase the content of soil organic matter and available nutrients, and increased the diversity of soil microorganisms and improved community structure; vegetable residues increased the abundance of beneficial bacteria such as Actinobacteria, Firmicutes, Proteobacteria, and Chloroflexi, while reducing the quantity of soil-borne pathogens such as Bacillariophyta and Acidobacteria. Similar results were observed for the fungal communities: the relative abundance of Ascomycota was decreased to varying degrees, while the relative abundance of Rozellomycota and Basidiomycota was raised. The results demonstrated that vegetable residues incorporation significantly increased cucumber root vigor and enhanced fruit yield. The effects of different types of residues on improving soil properties were ordered sweet pepper plant residues > cucumber plant residues > tomato plant residues, and 20% of sweet pepper plant residues incorporation had the most significant effect on crop yield.ConclusionIn summary, returning vegetable residues alleviated soil continuous cropping obstacles by improving the soil fertility and the diversity and community structure of soil microorganisms, and consequently promoting the growth and yield of greenhouse-grown cucumbers. The findings demonstrated that returning vegetable residues was an effective and sustainable measure for soil amendment during continuous cropping in greenhouse production.

Transcriptomic and metabolomic analyses reveal that exogenous strigolactones alleviate the response of melon root to cadmium stress

Strigolactones (SLs) are classified into plant hormones, playing a key role as a mediator of plant growth in response to several abiotic stresses. Cadmium (Cd), a common heavy metal and soil pollutant, can suppress plant growth and development. In this work, we explored the effects of exogenous SLs on root formation in response to Cd stress using melon seeds subjected to seven germination treatments: CK (control), Cd (300 μmol·L-1 CdCl2), and SL1–SL5 (CdCl2-stressed seeds pretreated with 0.1, 0.5, 1, 2, and 3 μmol·L-1 GR24 solutions). The results indicated that SLs increased the antioxidant enzyme activities and root vigor and decreased the malondialdehyde (MDA) contents in the roots of Cd-stressed melon seedlings. Then we used transcriptomic and metabolomic analyses to explore the mechanisms by which exogenous SLs protect against Cd stress. There were 242 significant differentially expressed genes (DEGs) (78 upregulated, 164 downregulated) and 247 significantly differentially expressed metabolites (DEMs) (222 upregulated, 25 downregulated) between the Cd and SL3 treatments. SLs altered the expression of genes related to redox formation processes, including peroxidase (POD), lipoxygenase (LOX), glutamate dehydrogenase (GDH), and glutathione S-transferase (GST). In addition, we found that SLs regulated the expression of the MYB, AP2/ERF, bHLH, and WRKY transcription factor families. The combined transcriptomic and metabolomic analyses revealed that the DEGs and DEMs involved in Cd stress alleviation were mainly related to the gene expression of jasmonic acid (JA) and flavonoid biosynthesis. SLs might induce LOX-related genes to regulate JA biosynthesis. Moreover, SLs might promote flavonoid biosynthesis by regulating eleven flavonoid-related genes and eight metabolites. The results provide a new perspective for studying the adaptation of plants to Cd stress.

Superior Haplotypes for Early Root Vigor Traits in Rice Under Dry Direct Seeded Low Nitrogen Condition Through Genome Wide Association Mapping.

Water and land resources have been aggressively exploited in the recent decades to meet the growing demands for food. The changing climate has prompted rice scientists and farmers of the tropics and subtropics to adopt the direct seeded rice (DSR) system. DSR system of rice cultivation significantly reduces freshwater consumption and labor requirements, while increasing system productivity, resource use efficiency, and reducing greenhouse gas emissions. Early root vigor is an essential trait required in an ideal DSR system of rice cultivation to ensure a good crop stand, adequate uptake of water, nutrients and compete with weeds. The aus subpopulation which is adapted for DSR was evaluated to understand the biology of early root growth under limited nitrogen conditions over two seasons under two-time points (14 and 28 days). The correlation study identified a positive association between shoot dry weight and root dry weight. The genome-wide association study was conducted on root traits of 14 and 28 days with 2 million single-nucleotide polymorphisms (SNPs) using an efficient mixed model. QTLs over a significant threshold of p < 0.0001 and a 10% false discovery rate were selected to identify genes involved in root growth related to root architecture and nutrient acquisition from 97 QTLs. Candidate genes under these QTLs were explored. On chromosome 4, around 30 Mbp are two important peptide transporters (PTR5 and PTR6) involved in mobilizing nitrogen in the root during the early vegetative stage. In addition, several P transporters and expansin genes with superior haplotypes are discussed. A novel QTL from 21.12 to 21.46 Mb on chromosome 7 with two linkage disequilibrium (LD) blocks governing root length at 14 days were identified. The QTLs/candidate genes with superior haplotype for early root vigor reported here could be explored further to develop genotypes for DSR conditions.