Extreme nighttime air temperatures in 2010 impact rice chalkiness and milling quality

Research shows that elevated nighttime air temperatures (NTATs) contribute to increased chalk formation and reduced milling quality in rice. Arkansas rice-growing regions experienced exceptionally warm weather conditions during the summer of 2010, providing an opportunity to test this hypothesis under extreme conditions. Data from a previous study, conducted in years 2007-2009 (Ambardekar et al., 2011), was extended to include 2010 data, and analyzed to evaluate the correlations of 95th percentiles of NTAT frequencies (NT₉₅) occurring during reproductive (R) stages of six rice cultivars with chalk and peak head rice yields (pHRYs). Long-grain cultivars produced chalk values that were positively correlated to NT₉₅, and pHRYs that were inversely correlated, during the R5 through R8 stages. Medium-grain cultivars, Bengal and Jupiter, which in the original study showed little or no response to elevated NTATs during all R-stages, showed significant positive correlations between chalk, and negative correlations between pHRY, and NT₉₅, during the R7 and R8 stages. The 2007-2009 analyses indicated quadratic relationships of chalk with NT₉₅ and linear relationships of pHRY with NT₉₅. However, addition of the 2010 data indicated that both of these relationships were quadratic in nature. The extreme temperatures observed in 2010 also verified that while cultivars vary in their level of resistance to NTAT effects, all of the rice cultivars analyzed throughout the four-year study exhibited some degree of susceptibility to extreme NTAT temperatures occurring during critical grain-filling stages.     

Effect of soaking temperature on commingled rice properties

Parboiling involves soaking, steaming, and drying, and soaking is important in achieving desired parboiled rice properties. This study investigated the effects of soaking temperature and commingling on rice properties prior to steaming. Rough rice of four cultivars (Taggart, CL151, XL753, and CL XL745) and their combinations at 1:1 wt ratio were soaked at 65, 70 or 75 °C for 3 h, and dried. Both soaking temperature and difference in onset gelatinization temperature (T_o) of individual cultivars in commingled rice affected milling and physicochemical properties. The head brown rice yield was greater when the soaking temperature was below but close to the T_o for individual rice cultivars, but became difficult to predict for commingled rice. Commingled rice consisting of high T_o rice cultivars required higher soaking temperatures to reduce chalkiness during soaking. The color attributes of commingled rice was predominately affected by the cultivar that exhibited the most change. The gelatinization properties were governed by the low-T_o cultivar, whereas the pasting properties were more influenced by the high-T_o cultivar for the commingled rice. Therefore, using commingled rice with a wide range of gelatinization temperature as a feedstock may lead to inconsistent quality of parboiled rice.     

Effects of cultivar resistance and single fungicide application on rice sheath blight, yield, and quality

The increased number of sheath blight (Rhizoctonia solani)-resistant rice (Oryza sativa) cultivars available will allow producers to use less fungicide and avoid significant reductions in grain and milling yields. Among cultivars currently in cultivation in the southern United States, sheath blight resistance levels range from very susceptible to moderately resistant. A study was conducted to determine the response of cultivars, with different levels of susceptibility, to sheath blight inoculations and fungicide application and to determine the impact of sheath blight disease development on rice yield and quality. Sheath blight epidemics in field plots were initiated by inoculation at the panicle differentiation growth stage in 2006 and 2007. Azoxystrobin at 0.17 kg a.i. ha⁻¹ was applied at mid-boot. Inoculation significantly increased sheath blight severity and incidence and caused yield losses of 8% in moderately resistant cv. Jupiter to 40% in very susceptible cv. Trenasse. Milling yields were affected to a lesser extent. Fungicide treatments reduced sheath blight incidence and severity, regardless of cultivar except in Jupiter. Single azoxystrobin applications were effective in minimizing yield loss due to sheath blight in all cultivars.     

Influence of high daytime temperature during the grain filling stage on fissure formation in rice

High daytime temperatures during the grain filling stage in rice have negative impacts on milling quality traits. In this study, we used growth chambers to evaluate the influence of high daytime temperature (33 °C) during grain filling, together with grain moisture content at harvest (26%, 18% and 15%), on grain fissure formation. Varietal susceptibility to fissure formation was also evaluated by exposing grains to high temperature at different grain filling stages (milky, dough, maturing). Two fissure resistant varieties: Cypress (long-grain) and Reiziq (medium-grain) and susceptible varieties: YC53-00-7 (long-grain) and Baru (medium-grain) were compared. The average head rice yield (HRY) of Cypress declined from 62.7% at 25 °C to 53.5% at 33 °C, while Reiziq declined from 56.2% (25 °C) to 47.4% (33 °C). Both were significantly higher than the HRY of YC53-00-7 (39.2% and 24.9%) and Baru (39.3% and 31.7%) at 25 °C and 33 °C, respectively. When grains were drier at harvest (15% cf. 26%) there was a greater reduction in HRY. When the four varieties were exposed to high temperature, the highest average reduction of HRY was recorded at 21 days after heading. It is important to choose an optimal sowing date to avoid coincidence of the final grainfilling stage with high temperatures, in order to minimize milling quality losses.     

Effect of elevated carbon dioxide (CO2) on phenolic acids,flavonoids, tocopherols,tocotrienols, γ-oryzanol and antioxidant capacities of rice (Oryza sativa L.)

There have been no studies conducted with the objective of investigating the effect of elevated CO₂ concentrations ([CO₂]) on antioxidants in grains. Therefore, a two-year field experiment was conducted using open-top chambers with two levels of atmospheric CO₂ (375 and 550 μmol/mol) to evaluate their effects on rice grain antioxidants. Following exposure to high [CO₂], the total phenolic content of all rice milling fractions decreased (3%–18%), with the highest reduction in the brown rice for sinapic acid (167%), and in the white rice for p-hydroxybenzoic acid (100%). The total flavonoid content also decreased under elevated [CO₂] in all rice milling fractions (8%–14%), with apigenin (25%) being highly affected in the white rice, and tricin (12%) in the bran. The same trend was found for γ-oryzanol, with decreases of 35%, 32%, 25%, and 2% in the white rice, brown rice, husk, and bran, respectively. In the white and brown rices, tocopherols and tocotrienols were all lower under elevated [CO₂], with reductions larger for α-tocotrienol (69%), γ-tocotrienol (46%), and α-tocopherol (38%). Good correlations between antioxidant contents and DPPH radical scavenging capacities indicated that these decreases may be meaningful in the preventive ability of rice against free radical-mediated degenerative diseases.     

Temporal Dynamics of Antioxidant Defence System in Relation to Polyamine Catabolism in Rice under Direct-Seeded and Transplanted Conditions

Six rice cultivars viz. PR120, PR116, Feng Ai Zan, PR115, PAU201 and Punjab Mehak 1 under the direct-seeded and transplanted conditions were used to investigate the involvement of antioxidative defence system in relation to polyamine catabolism in temporal regulation of developing grains. Activities of ascorbate peroxidase(APx), guaiacol peroxidase(GPx), catalase(CAT), superoxide dismutase(SOD), polyamine oxidases(PAO) and contents of ascorbate, α-tocopherol, proline and polyamines increased gradually until mid-milky stage and then declined towards maturity stage under both planting conditions. The transplanted condition led to higher activities of antioxidative enzymes(APx, GPx and CAT) and contents of ascorbate, α-tocopherol and proline whereas the direct-seeded condition had elevated levels of PAO and SOD activities and contents of polyamines, lipid peroxide and hydrogen peroxide. Cultivars Feng Ai Zan and PR120 exhibited superior tolerance over other cultivars by accumulating higher contents of ascorbate, α-tocopherol and proline with increasing level of PAO and SOD activities under the direct-seeded condition. However, under the transplanted condition PR116 and PAU201 showed higher activities of antioxidative enzymes with decreasing content of lipid peroxide. Therefore, we concluded that under the direct-seeded condition, enhancements of polyamines content and PAO activity enabled rice cultivars more tolerant to oxidative stress, while under the transplanted condition, antioxidative defence with decreasing of lipid peroxide content was closely associated with the protection of grains by maintaining membrane integrity during rice grain filling. The results indicated that temporal dynamics of H2O2 metabolic machinery was strongly up-regulated especially at the mid-milky stage.     

转bar基因水稻除草剂抗性遗传研究及其应用

试验用３个恢复系－测６４,明恢６３和特青作母本分别与３个抗除草剂转ｂａｒ基因水稻品种－Ｂｅｎｇａｌ－Ｈｕ１０,Ｃｙｐｒｅｓｓ ＰＢ－６和Ｇｕｌｆｍｏｎｔ杂交,对其后代（Ｆ１,Ｆ２和ＢＣ１）进行遗传分析表明,除草剂的抗性是受一对显性核基因控制,通过杂交可将这种基因转育到恢复系,配出抗除草剂杂交组合,应用这项技术可放宽对不育系完全雄性不育的严格要求,有利于优良不育系的培育及高产、优质,多抗新组合的选配     

Effects of Elevated Atmospheric Carbon Dioxide Concentration on Silica Deposition in Rice (Oryza sativa L.) Panicle

Abstract

The effects of elevated carbon dioxide concentration ([CO₂]) on silica deposition on husk epidermis of rice (Oryza sativa L. cv. Akitakomachi) during the flowering stage were investigated in this study. The study was motivated by the concept that the rice yield maybe affected by global warming as a result of elevated [CO₂] environment since sterility of rice is related to the panicle silica content that influences transpiration, and elevated [CO₂] could affect plant transpiration. Silica deposition analysis was focused on the flowering stage of the rice crop grown hydroponically under two [CO₂] conditions: 350 μmol mol-¹ (ambient) and 700 μmol mol-¹ (elevated). Silica deposition on the husk epidermis from three parts of the panicle at four flowering stages were examined using a scanning electron microscope (SEM) combined with an energy dispersive X-ray microanalyzer (EDX). The results demonstrated that elevated [CO₂] significantly suppressed silica deposition on the husk epidermis at the lower part of the panicle, and at the early flowering stage when 1/3 of the panicle emerged from the leaf sheath. In the transverse section analysis of the husk, silica deposition on the husk epidermis under elevated [CO₂] was less than that under ambient [CO₂] at the late flowering stage. The less silica deposition observed on the husks at the late flowering stage under elevated [CO₂] might be related to the suppressed transpiration from the panicle by elevated [CO₂] found in a previous study.     

几个水稻品种碳素代谢特征的比较

结合饲料稻品种选育,在不同生育期对5个水稻品种（组合）进行了光合作用、呼吸作用、茎鞘非结构碳水化合物的积累和转运以及籽粒充实特性的比较研究。结果表明,不同品种其碳素代谢特性各不相同,杂交组合威优56光合作用、呼吸作用较强,茎鞘非结构碳水化合物在孕穗期积累丰富,到成熟期残留较少,后期籽粒充实速度下降缓慢,是一个碳素代谢十分旺盛的组合。常规稻辐丰早92－124在灌浆后期仍维持较高的光合强度和较强的籽粒充实速度,且成熟期茎鞘内非结构碳水化合物残留最少,也是一个后期碳素代谢较为理想的水稻品种。     

Impact of elevated CO2 concentration on inter-subspecific hybrid rice cultivar Liangyoupeijiu under fully open-air field conditions

Hybrid rice cultivar plays an important role in rice production system due to its high yield potential and resistance to environmental stress. Quantification of its responses to rising CO₂ concentration ([CO₂]) will reduce our uncertainty in predicting future food security and assist in development of adaptation strategies. Using free air CO₂ enrichment (FACE), we measured seasonal changes in growth and nitrogen (N) uptake of an inter-subspecific hybrid rice cultivar Liangyoupeijiu grown under two levels of [CO₂] (ambient and elevated by 200 μmol mol⁻¹) and two levels of N fertilization in 2005–2006. Average across the 2 years, FACE increased crop growth rate similarly by 22%, 24% and 23% in the periods from transplanting to panicle initiation (PI), PI to heading and heading to maturity, which was mainly attributed to an increase in green leaf area index rather than the greater net assimilation rate. Grain yield increased greatly under FACE as a result of similar contributions by panicle number per unit area, grain number per panicle and individual grain yield. Final aboveground N acquisition showed a 10.4% increase under FACE, which resulted from enhanced N uptake at both vegetative and reproductive growth stages. Compared with previous FACE studies on final productivity of two inbred japonica cultivars, inter-subspecific hybrid cultivar appears to profit more from elevated [CO₂], which mainly resulted from its greater enhancement in photosynthetic production during reproductive growth due to a lack of N limitations late in the season.     

高温胁迫下水稻产量的高光谱估测研究

为了定量分析不同生育期冠层反射光谱参数与水稻产量及产量构成要素的相互关系,确定能够准确预测高温胁迫下水稻籽粒产量的敏感光谱参数,通过盆栽试验,测定了孕穗期4种温度胁迫处理后的2个水稻品种不同生育期冠层高光谱反射率以及成熟后的理论产量、实际产量、穗数、每穗粒数、千粒重、穗长、穗干质量和结实率。结果表明,相对于蜡熟期的光谱参数,抽穗期和灌浆期的光谱参数与理论产量、实际产量、穗数、每穗粒数、千粒重、穗长、穗干质量以及结实率的相关性都较高,均达到显著水平。此两个时期可以作为预测水稻产量的关键时期。其中,差值植被指数DVI[810,A(450,560,680)]、垂直植被指数PVI(810,680)、红边幅值Dλred和红边峰值面积可以同时预测成熟水稻的理论产量和实际产量。而差值植被指数DVI(810,450)和DVI(810,560)、垂直植被指数PVI(810,680)和Dλred可以同时预测成熟水稻的穗数、每穗粒数和千粒重。相对于灌浆期的模型,抽穗期的模型能较可靠地监测水稻产量。     

Identification of novel glutelin subunits and a comparison of glutelin composition between japonica and indica rice (Oryza sativa L.)

Glutelin, a major protein in rice grains, is encoded by a multigene family. However, its protein composition is not well characterised. Here, we identified and characterised two novel glutelin subunits, GluBX and GluC. The individual glutelin subunits of japonica cv. Nipponbare and indica cv. 93-11 rice were analysed using 2-dimensional gel electrophoresis, LC–MS/MS, and Western blotting. Comparison of the glutelin profiles between three japonica and three indica cultivars indicated two distinct subunits (GluA-1 and GluA-3 isomers) and a distinction in the subunit composition (notably GluA-3 and Lys-rich GluB-1 components) of these two subspecies. Sequence alignment revealed different nutritional (Lys residues) and functional (Cys residues) characteristics between the type-A and type-B glutelin subfamilies. We also analysed amino acid and total protein contents of the grains in thirty-five cultivars, and we demonstrated that the Lys-rich glutelin composition of indica cultivars is superior to that of japonica cultivars. The Lys-rich and Cys-poor GluBX subunit is a native protein and is a high nutritional protein in grains. Our combined approaches for the identification of glutelin subunits have revealed the nutritional characteristics of individual subunits in rice, and this knowledge will provide new insights for improving grain quality during rice breeding.     

Study of water stress effects in different growth stages on yield and yield components of different rice (Oryza sativa L.) cultivars

A field experiment was conducted during 2001-2003 to evaluate the effect of water stress on the yield and yield components of four rice cultivars commonly grown in Mazandaran province, Iran. In northern Iran irrigated lowland rice usually experiences water deficit during the growing season include of land preparation time, planting, tillering stage, flowering and grain filing period. Recently drought affected 20 of 28 provinces in Iran; with the southeastern, central and eastern parts of the country being most severely affected. The local and improved cultivars used were Tarom, Khazar, Fajr and Nemat. The different water stress conditions were water stress during vegetative, flowering and grain filling stages and well watered was the control. Water stress at vegetative stage significantly reduced plant height of all cultivars. Water stress at flowering stage had a greater grain yield reduction than water stress at other times. The reduction of grain yield largely resulted from the reduction in fertile panicle and filled grain percentage. Water deficit during vegetative, flowering and grain filling stages reduced mean grain yield by 21, 50 and 21% on average in comparison to control respectively. The yield advantage of two semidwarf varieties, Fajr and Nemat, were not maintained under drought stress. Total biomass, harvest index, plant height, filled grain, unfilled grain and 1000 grain weight were reduced under water stress in all cultivars. Water stress at vegetative stage effectively reduced total biomass due to decrease of photosynthesis rate and dry matter accumulation.     

Residues of carbaryl,lindane and monocrotophos on rice treated for control of rice bug, Leptocorisa oratorius (Fab.)

This study investigated the correlation between insect mortality and insecticide residue levels in rice grain during the developing stages and at harvest, and also determined the relative toxicities of three insecticides, monocrotophos (Azodrin 16·8 EC), lindane (Agrocide 26 DP), and carbaryl (Sevin 85 WP) to Leptocorisa oratorius (Fab.), (Hemiptera: Alydidae). The insecticides were applied on field plots at 0·75 kg a.i./ha at the start of the milk stage of the developing grains. Sampling was conducted at 2 hours and 1, 2, 3, 4 and 5 days after spraying, which covered the milk stage to the soft dough stage. Mortality of insects exposed to the treated grain, the residue analysis of the treated grain during development and at harvest, and the LD₅₀s of the insecticides were determined. Monocrotophos was the most effective insecticide against the rice bug; lindane provided control for only one day; carbaryl was ineffective. Maximum residue levels of lindane and carbaryl in the harvested grains were below the established tolerance limits provided by FAO/WHO. There is no established tolerance for monocrotophos in rice.     

Genetic analyses of heading date of Japonica rice cultivars from Northeast China

Northeast regions of China (38–55°N latitude) play an important role in Japonica rice planting. Heading dates of 10 Japonica rice cultivars native to the Northeast of China were investigated and their sensitivities to photoperiod and temperature were analyzed. The results showed that these Japonica rice cultivars were insensitive to photoperiod but strongly sensitive to temperature, i.e. a high temperature can markedly shorten the heading date. Genetic analyses were conducted on these 10 cultivars using a set of heading date tester lines. All these Japonica cultivars carried a dominant early heading gene Ef-1, and most of these cultivars carried the photoperiod insensitivity allele e₁, and two types of alleles were presented at the Se-1 locus, including recessive photoperiod insensitivity gene Se-1^e and dominant strong photoperiod-sensitivity (PS) gene Se-1ⁿ. The PS of these cultivars carrying E₁ or Se-1ⁿ can be repressed or weakened by Ef-1 and the recessive allele hd2 they carried. These results provided a reasonable explanation to the adaptability of Japonica rice to the high latitude environment of the Northeast China, and could be useful for breeding new cultivars well adapted to the high latitude regions and expanding the rice cultivation range.     

Differential Sensitivity of Rice Cultivars to Salinity and Its Relation to Ion Accumulation and Root Tip Structure

Abstract

Effects of NaCl on the growth, ion content, root cap structure and Casparian band development were examined in four rice (Oryza sativa L.) cultivars with different salt resistance (salt-sensitive indica-type IR 24 and japonica-type Nipponbare and salt-resistant indica-type Nona Bokra and Pokkali). Experiments were conducted to find the differences in salinity resistance during early seedling and developed seedling stages among the cultivars. For salinity treatment, sodium chloride (NaCl) was added to nutrient solution at concentrations of 0, 25 and 50 mM for 7 days from germination to the 7th day (early seedling stage) or from the 7th day to 14th day (developed seedling stage). Growth inhibition by salinity was more prominent in the early seedling stage than in the developed seedling stage. Based on the growth, the order of the sensitivity was IR24 > Nipponbare > Nona Bokra > Pokkali. The growth of NaCl-treated rice cultivars relative to control was significantly and negatively correlated with the Na⁺ content and Na⁺/K⁺ ratio in roots and shoots in both stages. Scanning electron microscopic observation revealed that the root cap tissues proliferated and extended to the basal part of the root tip by salinity. The length of root cap was, however, reduced by 50 mM NaCl in sensitive cultivars due to peeling off. An endodermal Casparian band was formed in the basal region of the root tip. Development of the Casparian band was more prominent in sensitive cultivars than in tolerant cultivars. Root cap proliferation might be related to NaCl resistance in rice seedlings, but the Casparian band may not function efficiently in Na⁺ exclusion. Essentially the present results suggest that exclusion of Na⁺ from roots plays a critical role in expression of Na⁺ resistance in rice seedlings and the root cap is important for Na⁺ exclusion.     

Milling characteristics and distribution of phytic acid and zinc in long-, medium- and short-grain rice

Milling and polishing are important operations during the production of white rice. The degree of milling and polishing has a significant effect on the nutritional aspects of white rice, especially on minerals, due to a non-uniform distribution of nutrients in the kernel. Information on the distribution of nutrients in rice will greatly help in understanding the effect of milling and aid in designing procedures that improve technological and sensory properties of rice while retaining its essential nutrients as much as possible. In this study, three kernel shapes (short-, medium- and long-grain) of rice were selected for the study of milling characteristics and distribution of zinc (Zn) and phytic acid using abrasive milling and X-ray fluorescent microscope imaging approaches.Milling characteristics differed with kernel shapes and cultivars. Mass loss (y, %) correlated well with milling duration (x, s) and was fitted using a polynomial equation of y=ax²+bx+c (R²=0.99). Different kernel shapes of rice resulted in different patterns. Breakage in milling increased with longer duration of milling. The relation between breakage (y, %) and milling duration (x, s) fitted the exponential equation y=ae^bx. Levels of phytic acid, as well as Zn, decreased with prolonged milling. Phytic acid decreased at a higher rate than Zn. The analysis of different milling runs showed that the concentration of phytic acid decreased from the surface region inward, whereas X-ray fluorescent images indicated that the highest concentration of phosphorus was at the interface of the embryo and perisperm.Our results help in understanding the milling characteristics of different rice cultivars. Understanding these characteristics offers opportunities to optimize milling procedures for maximum phytate removal at minimum mineral losses and yield loss.     

Performance of diverse upland rice cultivars in low and high soil fertility conditions in West Africa

Traditional tropical japonica (Oryza sativa) and Oryza glaberrima cultivars are typically grown in low-input, subsistence production systems in the uplands of West Africa by resource-poor farmers. In these systems, low soil fertility (LF), which is generally associated with lower organic carbon content, and N and P availability, is one of the major constraints to rice productivity. Thus, cultivars adapted to LF are needed for the food security of farmers, who would otherwise be solely reliant on nutrient inputs to increase productivity. This study evaluated the performance of six diverse cultivars grown in LF and high soil fertility (HF) conditions with supplemental irrigation over two seasons. Average grain yield across all cultivars in LF was 54% of that in HF (156 vs. 340 g m⁻²). Three improved indica rice cultivars and CG 14 (O. glaberrima) out-yielded Morobérékan (traditional tropical japonica) and WAB450-IBP-38-HB (progeny from interspecific hybridization of tropical japonica and O. glaberrima) in LF (181 vs. 105 g m⁻² on average). The high grain yield in LF was the result of large spikelet number m⁻² due to superior tillering ability and high harvest index rather than biomass production. The high-yielding cultivars in LF consistently had lower leaf chlorophyll content and higher specific leaf area during the period from the early vegetative stage through the reproductive stage. Among them, two indica cultivars (B6144F-MR-6-0-0 and IR 55423-01) were also high yielding in HF. The use of improved indica cultivars adapted to LF, but also with input-responsiveness, appears to offer an attractive and economical approach to improving upland rice productivity and widening genetic diversity in this region.     

Cropping calendar options for rice-wheat production systems at high-altitudes

The onset of rains during dry to wet transition fallow periods in rice-wheat production systems in Nepal cause substantial losses of soil nitrogen if the system is improperly managed. To make use of available nutrients and water, this transition period can either be shortened by early rice planting, or be extended by late planting, allowing a third crop to be grown. Shifting planting dates would require rice genotypes adapted to the different environments. Crop duration is influenced by both vegetative and reproductive development, which in turn is influenced by the photo-thermal environment and genotypic responses to it. An experiment was conducted to derive genotypic photo-thermal constants from phenological observations on diverse rice cultivars, which were then applied to the concept of the phenological model RIDEV to design cropping calendar options. Environmental effects on variation of crop duration were determined by planting at different dates. The risk of yield losses to sterility caused by low temperatures was estimated by simulation. Thirty-one different genotypes of rice were planted at 8 dates in 15-day intervals starting 27 April 2004 at the experimental field of the Regional Agriculture Research Station, Lumle, Nepal. The shortest duration to flowering was observed for planting dates in late May and early June. Simulation of flowering dates with RIDEV yielded correct results only for the early planting dates. For later planting dates simulated flowering dates showed an increasing deviation from the observed. In most cultivars, minimum air temperature below 18 °C during booting to heading stages caused near-total spikelet sterility and a specific delay in flowering. However, the chilling tolerant cultivars Chomrong and Machhapuchre-3 cultivated at high altitude showed less than 30% spikelet sterility even at 15 °C. Simulating crop durations with the derived thermal constants allowed evaluating the different calendar options for high altitude systems.     

Silicon fertilization modulates 2-acetyl-1-pyrroline content,yield formation and grain quality of aromatic rice

Present study aimed to assess silicon (Si) mediated yield, grain quality and regulations in 2-acetyl-1-pyrroline accumulation (2-AP) in aromatic rice. Four different levels of Si at 15, 30, 45 and 60 mg kg⁻¹ were applied to two aromatic rice cultivars i.e., Nongxiang 18 and Meixiangzhan 2, while pots without Si were served as control (CK). Results revealed that Si fertilization improved 2-AP, Si and proline contents in leaves and grains as well as activities of proline dehydrogenase (PRODH) and net photosynthetic rates (Pn) (in leaves) while interfered with total N contents in leaves and grains. Moreover, leaves N and proline contents, and net photosynthetic rates (Pn) were decreased with plant age i.e., tillering > flowering > maturity while PRODH activities and Si contents were highest at flowering and maturity stages, respectively and minimum at tillering stage. Furthermore, growth, yield and quality components were also improved by Si application but results were not consistent regarding grain quality for both rice cultivars. Further, Si contents in leaves have significant positive relations (r = 0.3974, P < 0.05) with grain 2-AP contents at flowering stage. Hence, Si proved better for both rice cultivars whereas 2-AP contents were higher for Meixiangzhan 2 than Nongxiang 18.