Differential Responses of Soil Organic Carbon Fractions and Carbon Turnover Related Enzyme Activities to Wheat Straw Incorporation in Subtropical China

Soil organic carbon (SOC) fractions and C turnover related enzyme activities are essential for nutrient cycling. This is because they are regarded as important indicators of soil fertility and quality. We measured the effects of wheat straw incorporation on SOC fractions and C turnover related enzyme activities in a paddy field in subtropical China. Soil samples were collected from 0–10 cm and 10–20 cm depths after rice harvesting. The total SOC concentrations were higher in the high rate of wheat straw incorporation treatment (NPKS2) than in the not fertilized control (CK) (P < 0.05). The concentrations of labile C fractions [i.e., water soluble organic C (WSOC), hot-water soluble organic C (HWSOC), microbial biomass C (MBC), and easily oxidizable C (EOC)], were higher in the moderate NPKS1 and NPKS2 treatments than in CK and the fertilized treatment without straw (NPK) (P < 0.05). The geometric means of labile C (GMC) and C pool management index (CPMI) values were highest in NPKS2 (P < 0.05). The SOC concentrations correlated positively with the labile C fractions (P < 0.05). Soil cellulase activity and the geometric mean of enzyme activities (GMea) were higher in NPKS2 than in CK in all soil layers (P < 0.05), and the invertase activity was higher in NPKS2 than in CK in the 0–10 cm layer (P < 0.05). Stepwise multiple linear regression indicated that the formation of the SOC, WSOC, HWSOC, MBC, and EOC was mostly enhanced by the cellulase and invertase activities (P < 0.05). Therefore, the high rate of wheat straw incorporation may be recommended to increase soil C pool levels and soil fertility in subtropical paddy soils.     

Discovering Candidate Chromosomal Regions Linked to Kernel Size-Related Traits via QTL Mapping and Bulked Sample Analysis in Maize

Kernel size-related traits, including kernel length, kernel width, and kernel thickness, are critical components in determining yield and kernel quality in maize (Zea mays L.). Dissecting the phenotypic characteristics of these traits, and discovering the candidate chromosomal regions for these traits, are of potential importance for maize yield and quality improvement. In this study, a total of 139 F2:3 family lines derived from EHel and B73, a distinct line with extremely low ear height (EHel), was used for phenotyping and QTL mapping of three kernel size-related traits, including 10-kernel length (KL), 10-kernel width (KWid), and 10-kernel thickness (KT). The results showed that only one QTL for KWid, i.e., qKWid9 on Chr9, with a phenotypic variation explained (PVE) of 13.4% was detected between SNPs of AX-86298371 and AX-86298372, while no QTLs were detected for KL and KT across all 10 chromosomes. Four bulked groups of family lines, i.e., Groups I to IV, were constructed with F2:3 family lines according to the phenotypic comparisons of KWid between EHel and B73. Among these four groups, Group I possessed a significantly lower KWid than EHel (P = 0.0455), Group II was similar to EHel (P = 0.34), while both Group III and Group IV were statistically higher than EHel (P < 0.05). Besides, except Group IV exhibited a similar KWid to B73 (P = 0.11), KWid of Groups I to III were statistically lower than B73 (P < 0.00). By comparing the bulked genotypes of the four groups to EHel and B73, a stable chromosomal region on Chr9 between SNPs of AX-86298372 to AX-86263154, entirely covered by qKWid9, was identified to link KWid with the positive allele of increasing phenotypic effect to KWid from B73, similar to that of qKWid9. A large amount of enzyme activity and macromolecule binding-related genes were annotated within this chromosomal region, suggesting qKWid9 as a potential QTL for KWid in maize.     

The Effect of Bamboo Charcoal Application on Soil Nutrients and Heavy Metals in Rice

Soil heavy metal pollution is becoming more and more serious. Biomass charcoal application can play an important role in alleviating the toxicity of heavy metals in soils. Compared with other biochar, bamboo charcoal has more unique properties and may have a unique effect on heavy metal pollution. Zhejiang Province of Southeastern China is rich in bamboo resources. However, few studies related to bamboo charcoal application for heavy metal remediation in farmland were reported. In this study, four treatments with different amounts of bamboo charcoal application were set up through a field experiment, namely BC0 (no bamboo charcoal application), BC1 (2500 kg⋅ha⁻¹), BC2 (5000 kg⋅ha⁻¹), and BC3 (10000 kg⋅ha⁻¹), and each treatment was replicated three times. The results showed that (1) The application of bamboo charcoal significantly increased the soil pH and organic matter content. Compared with BC0, the pH and organic content of BC3 increased by 7.4% and 17.4% (P < 0.05) respectively. (2) The HCl-extractable Cd content of paddy soil in the BC1 treatment was significantly lower than other treatments (P < 0.05), and decreased by 15.3%, compared with BC0. The soil HCl-extractable Zn and Cu content did not differ significantly between treatments (P > 0.05). (3) With the increase of bamboo charcoal application, the Cd content in rice gradually decreased, the BC3 treatment significantly decreased by 39.0% (P < 0.05), and the Zn and Cu contents in rice did not differ significantly between treatments (P > 0.05), compared with BC0. (4) Soil pH, organic matter and Cd in rice seeds were significantly negatively correlated (P < 0.01). The heavy metal content in rice does not change with the change of heavy metal content with HCl-extractable state in soil. It means bamboo charcoal does not reduce heavy metal content in rice by simply declining the heavy metal content with HCl-extractable state. The mechanism of action is relatively complicated, and further study is needed.     

Development and field performance of nitrogen use efficient rice lines for Africa

Nitrogen (N) fertilizers are a major input cost in rice production, and its excess application leads to major environmental pollution. Development of rice varieties with improved nitrogen use efficiency (NUE) is essential for sustainable agriculture. Here, we report the results of field evaluations of marker‐free transgenic NERICA4 (New Rice for Africa 4) rice lines overexpressing barley alanine amino transferase (HvAlaAT) under the control of a rice stress‐inducible promoter (pOsAnt1). Field evaluations over three growing seasons and two rice growing ecologies (lowland and upland) revealed that grain yield of pOsAnt1:HvAlaAT transgenic events was significantly higher than sibling nulls and wild‐type controls under different N application rates. Our field results clearly demonstrated that this genetic modification can significantly increase the dry biomass and grain yield compared to controls under limited N supply. Increased yield in transgenic events was correlated with increased tiller and panicle number in the field, and evidence of early establishment of a vigorous root system in hydroponic growth. Our results suggest that expression of the HvAlaAT gene can improve NUE in rice without causing undesirable growth phenotypes. The NUE technology described in this article has the potential to significantly reduce the need for N fertilizer and simultaneously improve food security, augment farm economics and mitigate greenhouse gas emissions from the rice ecosystem.     

Influence of Biochar on Nitrogen Use Efficiency and Root Morphology of Rice-Seedling in Two Contrasting Paddy Soils

Biochar may affect the root morphology and nitrogen (N) use efficiency (NUE) of rice at seedling stage, which has not been clearly verified until now. To clarify it, we conducted a pot experiment regarding to two soil types (Hydragric Anthrosol and Haplic Acrisol), two biochar application rates (0.5 wt% and 1.5 wt %) and two rice varieties (common rice var. Xiushui134 and hybrid super rice var. Zhongkejiayou12-6) meanwhile. Seedling NUE of common rice Xiuhui134 was significantly increased (p < 0.05) by 78.2% in Hydragric Anthrosol and by 91.4% in Haplic Acrisol following biochar addition with 1.5 wt%. However, biochar addition exerted no influence on seedling NUE of super rice Zhongkejiayou12-6 in both soils. Overall, 0.09–0.10 units higher soil pH and 105– 116% higher soil NH₄⁺ -N were observed in Xiushui134 growing two soils with 1.5 wt% biochar. In addition, improved root morphology (including longer root length, larger root surface area, bigger root volume, and more root tips) contributed to the higher seedling NUE of Xiushui134 in two soils. The soil pH and NH₄⁺ -N content, also the root morphology were influenced by biochar, which though could not thoroughly explained the NUE of Zhongkejiayou12-6. In conclusion, biochar application to paddy soil changed soil pH and NH₄⁺ -N content, root growth, and the consequent seedling NUE of rice, which effects are relative with rice cultivar, biochar addition rate, and soil type.     

Influence of Rapeseed Cake on Heavy Metal Uptake by a Subsequent Rice Crop After Phytoextraction Using Sedum plumbizincicola

A glasshouse pot experiment was conducted to study the effects of phytoextraction by Sedum plumbizincicola and application of rapeseed cake (RSC) on heavy metal accumulation by a subsequent rice (Oryza sativa L.) crop in a contaminated paddy soil collected from east China. After phytoextraction by S. plumbizincicola the soil and brown rice Cd concentrations effectively declined. After phytoextraction, RSC application reduced brown rice Cd concentrations in the subsequent rice crop to 0.23–0.28 mg kg^?1, almost down to the standard limit (0.2 mg kg^?1). After phytoextraction and then application of RSC, the soil solution pH, dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) concentrations increased during early stages of rice growth resulting directly and indirectly in lowering the bioavailability of the heavy metals. Thus the grain yield of the subsequent rice crop increased and the heavy metals in the brown rice declined significantly. In this contaminated acid soil, growing the hyperaccumulator S. plumbizincicola and rice in rotation together with RSC application may therefore be regarded as a viable strategy for safe grain production and bioremediation.     

Optimization of Organic Mulches Thickness Improves Soil Moisture Retention under Controlled Conditions

Organic mulch can improve the moisture, chemical composition, dust, and dust suppression of soil, and beautify the environment. In view of the rapid evaporation rate and serious loss of soil water in tropical areas, this paper explored the effect of organic mulch materials with different thickness on the increase of soil water retention rate and the improvement of soil water loss caused by evaporation. Rubberwood sawdust (RWS), rubberwood bark (RWB), coconut fiber (CF), and Mulch (MC) were selected as the mulching materials. Field experiment and laboratory experiment were performed, and soil-moisture content and temperature were continuously monitored. However, from the daily measurement of water content at constant conditions (29°C ± 0.2°C, 74% ± 1% air RH) in the laboratory experiment, the results of variance analysis (ANOVA) showed that there was no significant difference between the soil-water content of covered samples and bare soil (P > 0.05). In the field experiments, the analysis of variance indicated significant differences in the soil-moisture content owing to the effect of the covering material (P < 0.01). Mulching increased the soil-moisture content with smaller fluctuations in the deep soil compared with bare soil. The most stable soil-moisture content were achieved by RWS, RWB, CF, and MC, with thicknesses of 5, 3, 7, and 5 cm, respectively, compared with bare soil, and the average water contents of the 0–40 cm soil layer was 0.58%, 0.01%, 0.82%, and 0.93%, respectively. Vertically, the intensity of the change in soil moisture decreased gradually with increasing depth, and was more stable than that of bare soil and other treatments. Among them, the difference in water content between the adjacent gradient soil layers (the soil layers are graded every 10 cm in depth) M_3–7 (0.011 ± 0.004) was the smallest. It can be concluded that CF mulching materials with a thickness of 7 cm would be preferable when selecting mulching materials for controlling soil moisture in tropical cities.     

Effects of Rhodobacter capsulatus inoculation in combination with graded levels of nitrogen fertilizer on growth and yield of rice in pots and lysimeter experiments

A pot and a lysimeter experiment were carried out to study the effects of inoculation of the roots of rice seedlings with R. capsulatus in combination with graded levels of nitrogen (N) fertilizer on growth and yield of the rice variety Giza 176. Inoculation increased all the measured growth parameters and yield attributes, but the statistically significant differences at all N levels tested were only those for plant dry weight, number of productive tillers, grain and straw yields. The absolute increases in grain yield of the pot experiment due to inoculation were 0.63, 0.93 and 1.22 ton ha^–1 at 0, 47.6 and 95.2 kg N ha^–1, respectively. The results suggest that inoculation along with 47.6 kg N ha^–1 can save 50% of the nitrogen fertilizer needed for optimum G176 rice crop. However, inoculation along with 95.2 kg N ha^–1 can increase grain yield by about 1.2 ton ha^–1. This is probably the first reported evidence of a beneficial effect of phototrophic purple nonsulphur bacteria on rice growth and yield under flooded soil conditions.     

Recovery of 15N-labeled urea and soil nitrogen dynamics as affected by irrigation management and nitrogen application rate in a double rice cropping system

A sophisticated soil microcosm system and ¹⁵N-labeled urea were used to investigate nitrogen (N) use efficiency and soil N dynamics in a rice monoculture system in two successive seasons. Topsoil (0 cm?C20 cm) and subsoil (20 cm?C50 cm) samples were collected from a traditional double rice cropping field in the Jiangxi Province, China, and these soil samples were derived from Quaternary red clay. Treatments were randomly assigned with two irrigation regimes and three N application rates (no application control, 80% traditional rate and 100% traditional rate noted as N0, N1 and N2, respectively). The levels of ¹⁵N recovery of plants, ¹⁵N and N remaining in soil were determined. Moreover, the N dynamic of soil solution from different layers of the soil profile was surveyed. The results showed that the effects of irrigation management and N application rate varied in different rice growing seasons. Irrigation regimes had remarkable effects on grain yield and chemical ¹⁵N fertilizers (CF-¹⁵N) uptake. When compared to flood irrigation (FI), the shallow water depth with wetting and drying (WD) increased grain yield up to 5.7%?C20%. Although the highest grain yield was obtained with reduced N application level, both N apparent recovery (NAR) and ¹⁵N use efficiency (the percentage of plant N uptake derived from applied N, %Ndfan) significantly decreased with increasing N inputs. However, the interaction between irrigation management and N application rate on grain yield and N use efficiency (NUE) of CF-¹⁵N were not significant. A survey of soil solutions every 5 days indicated that NH ₄ ⁺ -N was the main residual form of N, and high NH ₄ ⁺ -N leaching was observed. When compared to FI, WD decreased vertical NH ₄ ⁺ -N and TN leaching, especially at 10?C50 cm depths of soil profile in the second season. NH ₄ ⁺ -N was the main N residual form in the soil profile. Therefore, in this study, the WD irrigation regime and reduced rate (N1) was the optimal irrigation and fertilizer management strategy to increase the NUE of CF-N, increase the after effects of CF-¹⁵N, decrease leaching loss of CF-¹⁵N and minimize the shallow groundwater pollution risk, which were all beneficial for the ecological environment.     

Genetic variation in eggplant for Nitrogen Use Efficiency under contrasting NO3‐ supply

Eggplant (Solanum melongena L.) yield is highly sensitive to N fertilization, the excessive use of which is responsible for environmental and human health damage. Lowering N input together with the selection of improved Nitrogen‐Use‐Efficiency (NUE) genotypes, more able to uptake, utilize, and remobilize N available in soils, can be challenging to maintain high crop yields in a sustainable agriculture. The aim of this study was to explore the natural variation among eggplant accessions from different origins, in response to Low (LN) and High (HN) Nitrate (NO₃^‐) supply, to identify NUE‐contrasting genotypes and their NUE‐related traits, in hydroponic and greenhouse pot experiments. Two eggplants, AM222 and AM22, were identified as N‐use efficient and inefficient, respectively, in hydroponic, and these results were confirmed in a pot experiment, when crop yield was also evaluated. Overall, our results indicated the key role of N‐utilization component (NUtE) to confer high NUE. The remobilization of N from leaves to fruits may be a strategy to enhance NUtE, suggesting glutamate synthase as a key enzyme. Further, omics technologies will be used for focusing on C‐N metabolism interacting networks. The availability of RILs from two other selected NUE‐contrasting genotypes will allow us to detect major genes/quantitative trait loci related to NUE.     

Concurrent activation of OsAMT1;2 and OsGOGAT1 in rice leads to enhanced nitrogen use efficiency under nitrogen limitation

Nitrogen (N) is a major factor for plant development and productivity. However, the application of nitrogenous fertilizers generates environmental and economic problems. To cope with the increasing global food demand, the development of rice varieties with high nitrogen use efficiency (NUE) is indispensable for reducing environmental issues and achieving sustainable agriculture. Here, we report that the concomitant activation of the rice (Oryza sativa) Ammonium transporter 1;2 (OsAMT1;2) and Glutamate synthetase 1 (OsGOGAT1) genes leads to increased tolerance to nitrogen limitation and to better ammonium uptake and N remobilization at the whole plant level. We show that the double activation of OsAMT1;2 and OsGOGAT1 increases plant performance in agriculture, providing better N grain filling without yield penalty under paddy field conditions, as well as better grain yield and N content when plants are grown under N llimitations in field conditions. Combining OsAMT1;2 and OsGOGAT1 activation provides a good breeding strategy for improving plant growth, nitrogen use efficiency and grain productivity, especially under nitrogen limitation, through the enhancement of both nitrogen uptake and assimilation.     

Blocking amino acid transporter OsAAP3 improves grain yield by promoting outgrowth buds and increasing tiller number in rice

Amino acid transporters (AATs) play indispensable roles in nutrient allocation during plant development. In this study, we demonstrated that inhibiting expression of the rice amino acid transporter OsAAP3 increased grain yield due to a formation of larger numbers of tillers as a result of increased bud outgrowth. Elevated expression of OsAAP3 in transgenic plants resulted in significantly higher amino acid concentrations of Lys, Arg, His, Asp, Ala, Gln, Gly, Thr and Tyr, and inhibited bud outgrowth and rice tillering. However, RNAi of OsAAP3 decreased significantly Arg, Lys, Asp and Thr concentrations to a small extent, and thus promoted bud outgrowth, increased significantly tiller numbers and effective panicle numbers per plant, and further enhanced significantly grain yield and nitrogen use efficiency (NUE). The promoter sequences of OsAAP3 showed some divergence between Japonica and Indica rice, and expression of the gene was higher in Japonica, which produced fewer tillers than Indica. We generated knockout lines of OsAAP3 on Japonica ZH11 and KY131 using CRISPR technology and found that grain yield could be increased significantly. These results suggest that manipulation of OsAAP3 expression could be used to increase grain yield in rice.     

Adjusting Nitrogen Application in Accordance with Soil Water Availability Enhances Yield and Water Use by Regulating Physiological Traits of Maize under Drip Fertigation

Knowledge of the interactive effects of water and nitrogen (N) on physio-chemical traits of maize (Zea mays L.) helps to optimize water and N management and improve productivity. A split-plot experiment was conducted with three soil water conditions (severe drought, moderate drought, and fully water supply referring to 45%–55%, 65%–75%, and 85%–95% field capacity, respectively) and four N application rates (N₀, N₁₅₀, N₂₄₀, and N₃₃₀ referring to 0, 150, 240, 330 kg N ha^–1 respectively) under drip fertigation in 2014 and 2015 in the Huang-Huai-Hai Plain of China. The results indicated that drought stress inhibited physiological activity of plants (leaf relative water content, root bleeding sap, and net photosynthetic rate), resulting in low dry matter accumulation after silking, yield, and N uptake, whereas increased WUE and NUE. N application rates over than 150 kg ha^–1 aggravated the inhibition of physiological activity under severe drought condition, while it was offset under moderate drought condition. High N application rates (N₃₃₀) still revealed negative effects under moderate drought condition, as it did not consistently enhance plant physiological activity and significantly reduced N uptake as compared to the N₂₄₀ treatment. With fully water supply, increasing N application rates synergistically enhanced physiological activity, promoted dry matter accumulation after silking, and increased yield, WUE, and N uptake. Although the N₂₄₀ treatment reduced yield by 5.4% in average, it saved 27.3% N under full water supply condition as compared with N₃₃₀ treatment. The results indicated that N regulated growth of maize in aspects of physiological traits, dry matter accumulation, and yield as well as water and N use was depended on soil water status. The appropriate N application rates for maize production was 150 kg ha^–1 under moderate drought or 240 kg ha^–1 under fully water supply under drip fertigation, and high N supply (>150 kg ha^–1) should be avoided under severe drought condition.     

Integrated Nutrient Management Improves Productivity and Quality of Sugarcane (<i>Saccharum Officinarum</i> L.)

Sugarcane is one of the major important sugar yielding crops in Bangladesh. As an exhaustive crop, sugarcane removes a huge amount of plant nutrients from the soil. However, the combined use of organic and inorganic fertilizers can be a good approach to deal with nutrient depletion and promote sustainable crop production as well as improve soil health. Therefore, an attempt was made to identify the most fruitful and profitable integrated nutrient management on the aspects of growth, yield and quality of sugarcane in two consecutive growing seasons. Seven treatments: T₁=Control, T₂=165:55:120:30:10:2.5:4 kg N:P:K:S:Mg:Zn:B ha⁻¹, T₃=Poultry Litter (PL) at 5 t ha⁻¹+95:51:87:9:10:2.5:4 kg N:P:K:S:Mg:Zn:B ha⁻¹, T₄=Cow Dung (CD) at 15 t ha⁻¹+ 36:52:60:17:10:2.5:4 kg N:P:K:S:Mg:Zn:B ha⁻¹, T₅=Press Mud (PM) at 15 t ha⁻¹+10:50:43:0:10:2.5:4 kg N:P:K:S:Mg:Zn:B ha⁻¹, T₆=Mustard Oil Cake (MOC) at 0.5 t ha⁻¹+140:54:115:25:10:2.5:4 kg N:P:K:S:Mg:Zn:B ha⁻¹ and T₇=GM (Green Manure) at 5 t ha⁻¹+140:53:100:28:10:2.5:4 kg N:P:K:S:Mg:Zn:B ha⁻¹ were used in this experiment. Two years data showed that treatment T₃ produced the maximum amount of tillers, total dry matter yield, millable sugarcane, cane yield and sugar yield, followed by the T₄ treatment. The highest stalk heights were recorded in the T₃ treatment, which was statistically similar to all other treatments except T₁ and T₂. The juice quality parameters viz., brix and pol in cane were found significant in treatment T₃ while the highest purity was obtained in the T₇ treatment. All the data of Jaggery (goor) quality parameters, the highest sucrose content, color transmittance, Jaggery (goor) recovery and the lowest ash content of Jaggery (goor) were observed in the T₃ treatment, which was statistically similar to the T₄ treatment in both seasons. The highest cost of production was obtained from the T₆ treatment while the highest gross return, net return and BCR were recorded in the T₃ treatment. No significant changes were found in one cycle of sugarcane in initial and post-harvest soil characteristics viz., pH, organic carbon, total N, and available P, K and S contents due to integrated use of different fertilizer packages. From the experimental findings, it was concluded that treatment T₃ followed by T₄ treatment would be the better productive and profitable integrated nutrient management technology for ensuring higher yields and quality of sugarcane without soil fertility degradation in the High Ganges River Floodplain soils.     

Enhanced OsNLP4‐OsNiR cascade confers nitrogen use efficiency by promoting tiller number in rice

Increased use of nitrogen fertilizers has deleterious impact on the environment. Increase in yield potential at low nitrogen supply is regarded as a cereal breeding goal for future agricultural sustainability. Although natural variations of nitrogen transporters have been investigated, key genes associated with assimilation remain largely unexplored for nitrogen use efficiency (NUE) enhancement. Here, we identified a NIN‐like protein NLP4 associated with NUE through a GWAS in rice. We found that OsNLP4 transactivated OsNiR encoding nitrite reductase that was critical in nitrogen assimilation in rice. We further constructed quadrupling NREs (Nitrate‐responsive cis‐elements) in the promoter of OsNiR (p4xNRE:OsNiR) and enhanced nitrogen assimilation significantly. We demonstrated that OsNLP4‐OsNiR increased tiller number and yield through enhancing nitrogen assimilation and NUE. Our discovery highlights the genetic modulation of OsNLP4‐OsNiR signalling cascade as a strategy for high NUE and yield breeding in rice.     

Arsenic uptake and accumulation in rice (Oryza sativa L.) irrigated with contaminated water

Long-term use of arsenic contaminated groundwater to irrigate crops, especially paddy rice (Oryza sativaL.) has resulted in elevated soil arsenic levels in Bangladesh. There is, therefore, concern regarding accumulation of arsenic in rice grown on these soils. A greenhouse pot experiment was conducted to evaluate the impact of arsenic-contaminated irrigation water on the growth and uptake of arsenic into rice grain, husk, straw and root. There were altogether 10 treatments which were a combination of five arsenate irrigation water concentrations (0–8 mg As l^–1) and two soil phosphate amendments. Use of arsenate containing irrigation water reduced plant height, decreased rice yield and affected development of root growth. Arsenic concentrations in all plant parts increased with increasing arsenate concentration in irrigation water. However, arsenic concentration in rice grain did not exceed the maximum permissible limit of 1.0 mg As kg^–1. Arsenic accumulation in rice straw at very high levels indicates that feeding cattle with such contaminated straw could be a direct threat for their health and also, indirectly, to human health via presumably contaminated bovine meat and milk. Phosphate application neither showed any significant difference in plant growth and development, nor in As concentrations in plant parts.     

Enhancement of Yield,Grain Quality Characters, 2-Acetyl-1-Pyrroline Content,and Photosynthesis of Fragrant Rice Cultivars by Foliar Application of Paclobutrazol

Paclobutrazol is a well-known plant growth regulator. However, the application of paclobutrazol in fragrant rice production has not been reported. The present study conducted a field experiment with two cropping seasons and three fragrant rice cultivars to investigate the effects of paclobutrazol application on yield formation, grain quality, 2-acetyl-1-pyrroline (2-AP, key component of fragrant rice aroma) biosynthesis, and photosynthesis of fragrant rice. At the initial heading stage, paclobutrazol solutions at 0 (control), 30, 60, 100, and 120 mg L^?1 were foliar applied to fragrant rice plants, respectively. Compared with control, paclobutrazol treatments significantly (P?<?0.05) increased grain yield and seed-setting rate of fragrant rice cultivars by 6.77–22.82% and 5.09–25.66%, respectively. Increased contents of photosynthetic pigments (chlorophyll a, chlorophyll b, and carotenoid) and the improved net photosynthetic rate at the grain-filling stage were observed due to paclobutrazol treatments. The paclobutrazol application increased head rice rate and grain 2-AP content by 3.94–8.94% and 6.47–18.80%, respectively. Lower chalky rice rate and chalkiness were recorded in paclobutrazol treatment than in control. Moreover, foliar application of paclobutrazol increased proline and Δ1-pyrroline contents in fragrant rice by 7.90–32.12% and 13.21–34.90%. Overall, foliar application of paclobutrazol could enhance productivity, improve grain quality, and increase the 2-AP content of fragrant rice, and 100–120 mg L^?1 was considered the suggested concentration of paclobutrazol application in fragrant rice production.

     

Effects of Chemical Products on Fire Blight Suppression,and Fruit Production and Quality in Apple (<i>Malus domestica</i> Borkh.) cv. Golden Glory

Antibiotics are widely used in fire blight management programs, yet there are no studies that demonstrate the evaluation of their efficacy in Mexico. Therefore, the present study was conducted to investigate the effects of the active ingredients in five commercial products (Kasumin^® 2L, Agrygent Plus^®, Agricultural Terramycin^®, Agrimicin^® 100, and Actigard^®) on fire blight suppression, and fruit yield and quality of apple (Malus domestica Borkh.) cv. Golden Glory. The experiment was conducted in a commercial orchard using a completely randomized block design, with six treatments: (1) Oxytetracycline [Ox], 110 mg L⁻¹; (2) Kasugamycin [Kas], 4.7 mL L⁻¹; (3) Oxytetracycline + Gentamicin [Ox + Gen], 48 mg L⁻¹+12 mg L⁻¹; (4) Streptomycin + Oxytetracycline [Str + Ox], 90 mg L⁻¹+9 mg L⁻¹; (5) Acibenzolar-S-methyl [ASM], 70 mg L⁻¹; and (6) Control, only water, with four replications, and three 11-year-old trees as an experimental unit. Variables of infection including flowers, shoots and fruits, yield and fruit quality were evaluated. All treatments suppressed infection in flowers, shoots, and fruits. ASM provided the highest levels of reduction of flower and shoot infection, while Kas had the least effect on the reduction of infection in these variables. The Ox + Gen treatment had the greatest suppression of fruit infection, and the best results on fruit yield and quality, followed by Ox and ASM. This is the first study conducted to evaluate the efficacy of the active ingredients of five commercial products used for the management of fire blight in apple trees in Mexico.