Chalky Kernels Research Articles

Exogenous abscisic acid improves grain filling capacity under heat stress by enhancing antioxidative defense capability in rice

BackgroundHeat stress is a major restrictive factor that causes yield loss in rice. We previously reported the priming effect of abscisic acid (ABA) on rice for enhanced thermotolerance at the germination, seedling and heading stages. In the present study, we aimed to understand the priming effect and mechanism of ABA on grain filling capacity in rice under heat stress.ResultsRice plants were pretreated with distilled water, 50 μM ABA and 10 μM fluridone by leaf spraying at 8 d or 15 d after initial heading (AIH) stage and then were subjected to heat stress conditions of 38 °C day/30 °C night for 7 days, respectively. Exogenous ABA pretreatment significantly super-activated the ABA signaling pathway and improved the SOD, POD, CAT and APX enzyme activity levels, as well as upregulated the ROS-scavenging genes; and decreased the heat stress-induced ROS content (O2– and H2O2) by 15.0–25.5% in rice grain under heat stress. ABA pretreatment also increased starch synthetase activities in rice grain under heat stress. Furthermore, ABA pretreatment significantly improved yield component indices and grain yield by 14.4–16.5% under heat stress. ABA pretreatment improved the milling quality and the quality of appearance and decreased the incidence of chalky kernels and chalkiness in rice grain and improved the rice grain cooking quality by improving starch content and gel consistence and decreasing the amylose percentage under heat stress. The application of paraquat caused overaccumulation of ROS, decreased starch synthetase activities and ultimately decreased starch content and grain yield. Exogenous antioxidants decreased ROS overaccumulation and increased starch content and grain yield under heat stress.ConclusionTaken together, these results suggest that exogenous ABA has a potential priming effect for enhancing rice grain filling capacity under heat stress at grain filling stage mainly by inhibiting ROS overaccumulation and improving starch synthetase activities in rice grain.

Evaluation of commercial rice grains present in the Amman market

Rice is a staple food that contributes to significant energy intake. Jordan relies on importing to provide the market with the required quantities of rice. Different varieties from different sources with various qualities are available in the market. This study aimed to evaluate the quality of rice available in the markets in Amman city-Jordan. Twenty-five brands (three samples from each brand) were collected. Samples were evaluated regarding chemical composition, dimensions before and after cooking, percentage of different defects, pasting profile (pasting temperature, peak viscosity, peak time, trough, and final viscosity), whiteness, transparency, and milling degree. All rice samples tested comply with the Jordanian standard except for chalky kernels (four brands), heat-damaged kernels (one brand), and insect infestation (two brands). All samples that did not fulfil the Jordanian specifications were from the long-grain rice. Medium-grain rice has higher whiteness, transparency, milling degree, moisture, starch, peak viscosity, trough, and final viscosity than long-grain rice. On the other hand, long-grain rice has a higher protein, pasting temperature, and peak time. There were significant differences in pasting and chemical composition parameters within the two groups of grain sizes. The average elongation ratio for all samples was 1.57 ±0.14, with significant differences between different brands. Due to the higher pasting temperature and peak time, long-grain rice requires more energy during cooking than medium-grain rice.

Impact of different levels of zinc and nitrogen on growth, productivity, and quality of aromatic rice cultivated under various irrigation regimes in two districts of Pakistan.

Rice is a staple food for more than 50% of the global population and it is one of the most valuable cereal crops. To fulfill the dietary requirement of the ever-growing world population, an increase in per-unit production of rice is direly required. In Pakistan, it stands as the 2nd in consumption after wheat, which is a staple food. A huge gap is observed between yield potential and actual yield of the aromatic rice cultivars at a farmer-field level. The significant limitations responsible for this gap are shortage of irrigation water, inappropriate application of fertilizers, less plant population, deficiency of micronutrients, and improper and poor plant protection measures. A field study was planned to assess the yield response and quality attributes of aromatic rice to three levels of zinc (Zn) and nitrogen (N) under three irrigation regimes (8-, 12-, and 16-acre inches) in the Sheikhupura and Sargodha districts of Pakistan. Irrigation treatments significantly influenced the growth, yield, and quality attributes; however, maximum improvement was observed by the application of irrigation at 12-acre inches. Among the Zn treatments, application of Zn at 10 kg ha–1 was observed to be more responsive to improving the growth and quality parameters of aromatic rice crops. In the case of N treatments, application of N at 140 kg ha–1 produced the maximum total tillers, as well as productive tillers per hill, spikelets per panicle, leaf area index, leaf area duration, crop growth rate, total dry matter, harvest index, kernel length, kernel width, and 1,000-kernel weight. Application of N at 140 kg ha–1 not only improved the growth attributes but also increased the net assimilation rate, photosynthetically active radiation, and radiation use efficiency, with respect to total dry matter and kernel yield. The maximum percentage of normal kernels and minimum percentage of opaque, abortive, and chalky kernels were also recorded by application of N at 140 kg ha–1. The outcomes of current experiments depicted that application of irrigational water, zinc, and nitrogen at 12-acre inches, 10, and 140 kg ha–1, respectively, are responsible to achieve maximum resource utilization efficiency, along with increased yield and quality of rice.

Effect of steam curing on pasting and textural properties, starch structure and the quality of a local aromatic rice variety

Steam curing is a process that is used to improve the quality of freshly harvested rice in the shortest time. The purpose of this study was to evaluate the effects of initial moisture content (IMC) and steaming time on the marketability of rice. The results indicate positive and more impressive effects of prolonged steaming (30 min) on head rice percentage (HRP), grain hardness, and elongation in the sample with IMC of 20% (w.b) compared with the sample with IMC of 17% (w.b). The results also showed a decreased peak (PV) and breakdown (BD) viscosity in both IMC. The highest decrease was observed in the samples that were steamed for 30 min. The results of scanning electron microscopy (SEM) revealed that the steaming of paddy for 30 min could not create a completely smooth surface in the grain. These observations indicate the inadequacy and uneven distribution of moisture for complete gelatinization even in grains with higher IMC. Practical applications Steam curing at atmospheric pressure is an applicable and effective method to reduce losses during milling process even for short time due to the structural changes. For high quality aromatic rice, short time steaming has positive effect on cooking quality with no significant changes in aroma. In order to produce good quality and marketable product by this method, it is necessary to process paddy with minimal or no chalky kernels.

Estimating Chalkiness in Endosperm of Typical and Bleached Durum Kernels from Transmission Scanned Images

HighlightsDurum wheat kernels were examined using flatbed scanner in transmission mode.Image processing routines were written to determine the %chalkiness per kernel.The distribution of %chalkiness uniquely described market samples.Abstract. The vitreousness of durum samples is regarded by the worldwide wheat industry as an important quality factor for durum shipments. One issue with grading durum occurs on occasional years of unfavorable harvest conditions which result in the kernel outer bran becoming cloudy. Imaging scanners can use either reflective or transmitted lighting. All scanned images of our durum samples were collected using transmissive lighting. Although, “vitreousness” is the usual term applied to durum samples, for this study, “chalkiness” or the inverse property was featured.Both typical and bleached durum kernels were imaged and analyzed. Bleaching seeds has aided grain inspector to visually evaluate the kernels. With computer imaging analysis of bleached kernels, the magnitude of %chalk was significantly attenuated with bleaching verses typical kernels. Still, discrimination of medium and highly chalky kernels was possible with both the typical and bleached seeds.Seed orientation was a source of measurement variability. Seeds were manually and carefully oriented into two distinctly different positions. At the critical lower levels of detection, crease-down orientation may indicate a 100% vitreous seed with the two-dimension view of the scanner, but then 11 of 25 seeds measured some amount of chalkiness when the seed was turned on its side. Furthermore, for seeds with higher amounts of chalkiness, over half of those seeds measured 30% differences.Several durum market samples were provided by Federal Grain Inspection Service and contained levels of non-vitreous seeds for each of three sub-classes of durum: 80%, 65%, 50% vitreous seed. The samples were imaged and analyzed, and chalkiness distributions were plotted. These plots characterize the %chalk for the three classes of wheat. The imaging methods worked satisfactorily for the high and medium levels %chalk per kernel. But the very-low level of chalkiness per kernel proved to be more challenging and was not consistent. Keywords: Grain inspection, HVAC (hard and vitreous kernels of amber color), Image analysis, Vitreousness.

Zinc coated urea enhanced the growth and quality of rice cultivated under aerobic and anaerobic culture

Agricultural systems all over the world are facing extraordinary pressure in term of squeezed natural resources to meet the increasing food demand of fast growing population in recent times. Water being the most useful natural resource has become scare due to climate change and global warming as it is key input of agronomic crops particularly rice. An experiment was carried out to evaluate the impact of nitrogenous fertilizers on rice productivity under aerobic and anaerobic cultures in green house conditions. In aerobic culture, soil was kept aerated by maintaining 80–100% field capacity while flooded conditions were maintained throughout the cultivation period by putting polythene bags in pots regarding anaerobic culture. Nitrogenous fertilizers include urea, neem coated urea and zinc coated urea. All the nitrogenous fertilizers enhanced the growth, yield and quality attributes of rice plant as compared to control treatment but maximum improvement was recorded by application of zinc coated urea. Application of zinc coated urea produced maximum productive tillers, kernel length, 100-kernel weight and kernels per spikelet. Maximum transpiration rate was also observed by application of zinc coated urea. Application of zinc coated urea produced maximum normal kernels while percentage of opaque, abortive and chalky kernels was significantly reduced. Zinc coated urea was found responsible for maximum production of straw and kernel yield. Anaerobic conditions were also recorded more responsive comparatively. Among the nitrogenous fertilizers, zinc coated urea is recommended to enhance the productivity of rice with good quality kernels under anaerobic culture.

Enhancing Rice Yield and Weed Management in Direct Seeded Rice Using Ammonium Sulfate as Adjuvant with Lower Dose of Early Postemergence Herbicides

A field experiment was conducted in 2016 to find out the sequential use of different herbicides with adjuvants (a substance which enhances pesticides efficiency) towards improved rice production and weed management in direct-seeded rice crop. The early postemergence herbicides (Kelion 50 WG, Ryzelan 240 SC, and Nominee 100 SC were applied at full or 75% of the full dose with and without adjuvants i.e. 2% solution of ammonium sulfate (AS) and alkyl ether sulfate (AES) at 14 days after sowing (DAS), followed by late postemergence herbicides i.e. Puma super (7.5 EW) and Sunstar 60 WG at 28 DAS. Application of herbicides with and without adjuvant substantially suppressed weed with weed dry weight at 40 and 60 DAS and improved rice yield attributes over a weedy check. It was found that a combination of 75% of Nominee 100 SC along with adjuvant i.e. AS (2% v/v) resulted in higher biological yield (9.16 t/ha), harvest index (30.65%), more grains per panicle (98.13), 1000 grain weight (21.32 g) with improved seed yield (3.86 t/ha). Also, abortive kernel (5.33), chalky kernels (5.66), opaque kernels (5.00), normal kernel (70.66), water absorptive ratio (4.28), and kernel length (10.13).

Grain chalkiness traits is affected by the synthesis and dynamic accumulation of the storage protein in rice.

Grain chalkiness lowers the market value of rice. Alleviating grain chalkiness is the most challenging issue in many rice-producing areas of the world. Nitrogen (N) metabolism has received increasing attention as a result of its relationship with grain chalkiness, although little information is available on the mechanism of N-induced grain chalk. A highly chalky rice variety OM052 was used to explore the protein synthesis and its accumulation in the grain exposed to N topdressing (N+) at the panicle initiation stage and a control (N-). The results showed that chalky kernels were stimulated by the N+ treatment and more prone to occur on the top and primary rachis. The grain protein content was increased because of the increased average and maximum rates of protein accumulation during grain filling, which was related to the enhanced activities of glutamine synthetase, glutamate synthase, glutamic oxalo-acetic transaminase and glutamate pyruvate transaminase under the N+ treatment. The activities of these enzymes at 15 days after flowering (DAF) were notably positively correlated with grain chalky traits and protein content. N topdressing regulates the synthesis and accumulation of the protein by affecting the key enzymes, especially at 15 DAF, which is attributed to grain chalkiness in rice. © 2021 Society of Chemical Industry.

YIELD POTENTIAL AND GENETIC VARIABILITY OF SEMIEXOTIC MAIZE POPULATIONS AS A BASIS FOR SELECTION

In order to verify the genetic and agronomic value, yield potential and inbreeding depression of synthesized composites, as well as quantifying the population variability and incorporating new sources of semiexotic germplasm in maize genetic improvement programs, four populations, identified as NAP-FA x HG-71 (P1), NAP-FL x HG-49 (P2), NAP-FB x HG-49 (P3), and NAP-DB x HG-49 (P4), with two levels of inbreeding (S0 and S1), were evaluated in three locations. From the P1 and P4 populations, 100 full-sib progenies were evaluated in only one location. Plant and ear height, lodging, breakage, ear length and diameter, resistance to diseases, ears with chalky kernels and grain yield were evaluated. The grain yield of the S0 and S1 populations varied between 5.50 and 6.65 t ha-1 and 3.8 and 4.58 t ha-1, respectively, with an average inbreeding depression between 23.9% and 38.0%. Considering all the locations, the grain yields of the non-inbreeding populations varied between 64.4% and 78.0% in relation to commercial hybrids (witnesses), indicating a good yield potential for start of improvement program. In the P1 and P4 populations, sufficient genetic variability was identified in most of the characters, which accredits them for recurrent selection. Gains of 13.7% and 17.8% for grain yield and 31.64% and 29.9% for ears with chalky kernels were estimated.

Influence of water management techniques on milling recovery, grain quality and mercury uptake in different rice production systems

Reducing water inputs, by maintaining grain yield quality, is important for sustainable production of rice. This study was conducted to investigate the influence of different water management techniques on milling recovery, grain quality, and mercury uptake in rice under dry direct-seeded and transplanted production systems. Two aromatic rice cultivars (Basmati-515 and Chenab Basmati) were planted in conventional puddled-transplanted rice (TPR) and dry direct-seeded rice (DDSR). Three irrigation management systems, based on soil moisture tension (SMT), continuous flooding (> −10 kPa SMT), alternate wetting and drying (AWD) (−20 kPa SMT) and aerobic rice (−40 kPa SMT) were maintained. Rice planting in DDSR system performed comparable to TPR, however, percentage of broken rice, chalky kernels, abortive kernels and opaque kernels were higher (5–8 %, 20 %, 19 % and 25 %, respectively) under DDSR system. However, kernel amylopectin contents and mercury uptake were reduced by 9% and 11 % under DDSR system. In AWD irrigation management, substantial increase in brown head rice (11 %), white head rice (15 %) and kernel protein contents (11 %) were recorded as compared to aerobic irrigation management. However, AWD irrigation reduced the kernel chalkiness (42 %), abortive kernels (51 %) and opaque kernels (62 %) as compared to aerobic irrigation management. Moreover, the AWD irrigation threshold also reduced the kernel amylose contents (15 %), amylopectin contents (6%) and mercury uptake (21 %) in comparison to continuous flooded irrigation threshold. In conclusion, AWD improved the milling recovery as well as grain quality and reduced the mercury uptake under TPR and DDSR in both rice cultivars. Rice cultivation under DDSR in combination with AWD can help to improve the quality traits while reducing the total water inputs and heavy metal accumulation.

Effects of irrigation regimes on yield and quality of upland rice and paddy rice and their interaction with nitrogen rates

The study of water-nitrogen (N) interaction to improve crop drought resistance and reduce environmental pollution has increasingly become a hot topic. However, the response of yield and quality of paddy rice and upland rice to N nutrition under different irrigation regimes is little known. Continuous flooding cultivation (CF, control) and bare-dry cultivation (BD) were used to cultivate paddy rice cultivar Yangjing 687 (japonica) and upland rice cultivar Zhonghan 3 (japonica), and 3 N application rates, 140 (low N, LN), 210 (normal N, NN) and 280 kg ha−1(high N, HN), were set for each irrigation regime. The results showed that under BD and CF irrigation regimes, the yield of paddy rice was the highest at NN, while that of upland rice was the highest at BD with NN and at CF with HN, breakdown viscosity was the highest and setback viscosity was the lowest for paddy rice at LN and for upland rice at NN. Increasing N application, the chalky kernels percentage and the chalkiness of upland rice increased first and then decreased, while that of paddy rice decreased under BD and increased under CF. Compared with CF, BD made the seed setting percentage and 1000-grain weight of upland rice and paddy rice different, and improved the appearance and nutritional quality of upland rice. The correlation between the cooking and nutritional quality and leaf N content of upland rice was lower than that of paddy rice. These results suggest that the yield and cooking quality of upland rice were high under BD with NN, and the paddy rice yield was high under BD with NN or CF with NN.

Optimizing integrative cultivation management improves grain quality while increasing yield and nitrogen use efficiency in rice

A major challenge in rice (Oryza sativa L.) production is to cope with increasing grain yield and fertilizer use efficiency without compromising grain quality. This study was designed to determine if optimizing integrative cultivation management in rice could improve grain quality while increase yield and nitrogen use efficiency (NUE). An indica-japonica hybrid rice cultivar and a japonica rice cultivar were grown in the field, with five cultivation managements including no N application (0 N), local farmer's practice (LFP), and three optimizing integrative cultivation managements, reducing N rate and increasing plant density (ND), ND+alternate wetting and moderate soil drying irrigation (NDW), and NDW+applying rapeseed cake fertilizer (NDWR). The results showed that the optimizing integrative cultivation managements could not only increase grain yield, but also enhance NUE compared to LFP. Compared to LFP, NDWR significantly increased brown, milled, head milled rice rate, ratio of the kernel length to breadth and breakdown value of starch, whereas decreased amylose content, gel consistency, prolamin content, setback value, percentage of chalky kernels, and chalkiness. The three optimizing integrative cultivation managements increased contents of total proteins, albumin and glutelin, activities of the key enzymes involved in the sucrose-starch conversion in grains, root oxidation activity, and malic and succinic acid concentrations in root exudates during the grain-filling period. The results suggested that optimizing integrative cultivation managements could improve grain quality meanwhile increase grain yield and NUE by enhancing physiological activities of rice plants.

Detection of chalk in single kernels of long‐grain milled rice using imaging and visible/near‐infrared instruments

AbstractBackground and objectivesTo maintain the competitiveness of U.S. long‐grain rice in U.S. and foreign markets, having translucent whole milled grain is critical. An objective technique to detect grain chalk, opaque areas in the grain, will provide breeders and industry with an effective tool for developing low‐chalk varieties or agronomic practices that reduce chalk occurrence. Two instruments developed at the Center for Grain and Animal Health Research, U.S. Department of Agriculture‐Agricultural Research Service (USDA‐ARS), a single‐kernel near‐infrared (SKNIR) tube instrument and a silicon‐based light‐emitting diode (SiLED) high‐speed sorter, were compared with two commercially available imaging instruments, WinSEEDLE and SeedCount used for chalk quantification. Three 2‐way chalk classifications were defined for single kernels based on visual inspection: (a) <50% or ≥50% opacity or chalk (modified Grain Inspection, Packers & Stockyards Administration [GIPSA]), (b) <10% or ≥10% opacity (10% cutoff), and (c) 100% opacity or 100% translucent (MaxLevel).FindingsThe SKNIR method provided the best classification for the modified GIPSA definition with an 82.4% average correct classification (CC), that is, 89% and 76% for nonchalky and chalky kernels, respectively. The WinSEEDLE had the best classification for the 10% cutoff definition, with an 84% CC for nonchalky kernels and a 96% CC for chalky kernels. For the MaxLevel definition, average CCs of both the SKNIR and SiLED methods were similar, at 93% and 95%, respectively. The average CCs were lower for both the WinSEEDLE method and the SeedCount method at 14% and 58%, respectively. These low CC values are a result of using a threshold of 100% for chalky or nonchalky kernels, where a single misclassified pixel within the image will cause misclassification. Calibration models developed for both the SKNIR and SiLED methods indicate that their classifications were based mainly on spectral differences near the adsorption bands for starch, protein, and water content.ConclusionsAll of the instruments can be used to classify chalk, but their level of accuracy depends on how chalk is defined.Significance and noveltyThe SiLED has the capability to process seeds at a high rate, and the SKNIR has the potential to measure compositional traits in addition to chalk measurements.

Occurrence of rice blast on and grain quality of irrigated rice fertilized with nitrogen and silicates

Abstract: The objective of this work was to evaluate the effects of fertilization with nitrogen topdressing and silicates, as well as of the use of fungicides, on the occurrence of rice blast on panicles, milling yield, and whole grains, vitreous grains, and chalky kernels in a flood-irrigated rice cultivar sensitive to the disease. Two experiments were conducted in a randomized complete block design, in a 4×4×2 factorial arrangement, with four replicates: in experiment 1, four doses of nitrogen × four doses of calcium and magnesium silicate on soil × with and without fungicides; and, in experiment 2, four doses of nitrogen × four doses of potassium silicate applied on leaves x with and without fungicides. At the doses above 60 kg ha-1 nitrogen without fungicides, there was an increase of rice blast severity on panicles, a decrease in the percentage of whole and vitreous grains, and an increase in chalky kernels and chalky area. The greatest effects of silicates occurred without fungicides. Fungicide use reduced the severity of rice blast on panicles. Milling yield ranged from 60 to 70% in both experiments. The control of rice blast with fungicides maintains high rice grain quality, milling yield, and percentages of whole and vitreous grains.

Relationships among the chalkiness, kernel size and endosperm cell morphology of rice kernels at different spikelet positions within a panicle

ABSTRACTThe occurrence of chalky kernels in rice is causally related to kernel size and endosperm morphology. This study aimed to investigate the occurrence of chalky kernels by analyzing kernel size, and the number and area of endosperm cells. Spikelets were sampled from upper and middle primary branches and lower secondary branches in a panicle, and divided into four categories: upper, middle, and lower perfect (PF) kernels and lower milky-white (MW) kernels. On the lower secondary branches, there was a higher percentage of chalky kernels, with smaller kernel lengths, widths and thicknesses, than the kernels on the upper and middle primary branches. MW kernels were smaller in size than PF kernels even on the same lower secondary branches. Regardless of grain appearance quality traits, the total areas of endosperm cross sections in lower kernels were significantly smaller than in upper kernels owing to the decreased cell area, and there was a significant negative correlation between the number of cells and average cell area. When the numbers and the areas of cells were analyzed using angular 30° intervals from the line connecting the center point and the dorsal vascular bundle, the MW kernels had significantly less cells than PF kernels near the ventral side at 120–180°. Thus, the decrease in the number of cells near the ventral side was a main causal factor in the decrease in MW kernel widths compared with PF kernel widths, and this suggested that cell division in MW kernels was inhibited at the early grain-filling stage.

Effects of wheat straw mulch application and nitrogen management on rice root growth, dry matter accumulation and rice quality in soils of different fertility

The root is the most sensitive part of the plant. This study examined the effects of wheat straw mulch, nitrogen (N) management and soil fertility on rice root morphology, dry matter accumulation, grain yield and rice quality and explored the correlation between root morphology and rice quality indexes. Wheat straw mulch had an obvious inhibitory effect on rice root morphology, especially on the total root length and total root surface area at 20 days after transplanting in the high- and low-fertility soil. The low-fertility soil treatments had higher levels of inhibition. However, straw mulch significantly promoted root growth, increased dry matter accumulation in the subsequent growth periods and improved the grain yield and rice quality, which mainly reduced the percentage of chalky kernels and the chalkiness degree. Increasing the nitrogen fertilizer percentage applied as a basal or tillering fertilizer reduced the inhibition in the early growth period; for balanced rice root growth, dry matter accumulation, grain yield and rice quality, 30% as basal fertilizer, 30% as tillering fertilizer and 40% as panicle fertilizer were the best N management strategy. Correlation analysis showed that the rice quality was extremely significantly positively correlated (r = 0.30–0.59, P < 0.05) with the root morphology indexes of the brown rice and protein contents and was significantly or extremely negatively correlated (r = − 0.73 to − 0.28, P < 0.05) with the length–width ratio, percentage of chalky kernels, chalkiness degree and amylose content.

Soil water tension and rice grain quality

Due to the high water use in rice irrigation at the main producing regions of Brazil, it is necessary to test and develop new water-saving cropping systems. The alternate wetting and drying (AWD) system is promising in terms of maintaining productivity levels and water savings. In addition to grain yield, grain quality should be considered, as it is important for commercialization. This study aimed to evaluate the effect of moderate soil water deficiency at different phenological stages of three rice cultivars, on rice grain quality. The experiment was installed in randomized blocks design, with split‑plots and four replications. Treatments consisted on the following soil water levels (Factor B): (1) flooding; (2) saturated (0 kPa) but no flooding; (3) water tension up to 10 kPa; and (4) water tension up to 40 kPa. The crop developmental stage in which these water levels were applied was subdivided into three stages (Factor A): vegetative; reproductive initial and reproductive final. The whole, broken and streaked grains, chalky kernels and chalkiness were analyzed. There are no negative effects of water deficits up to 40 kPa applied to soil, at any phenological stage of rice, on grain quality of rice cultivar developed for continuous flood irrigation.

Genetic progress of grain quality of flooded-irrigated rice cultivars in the state of Rio Grande do Sul, Brazil

Abstract: The objective of this work was to determine the genetic progress of grain quality attributes of flooded irrigated rice (Oryza sativa) cultivars in the state of Rio Grande do Sul, Brazil, between 1972 and 2016. The genetic estimates followed an approach based on the comparative analysis of 25 cultivars released by Embrapa’s breeding program over this period. The experiment was implemented in four producing regions of the state of Rio Grande do Sul: Sul, Campanha, Planície Costeira Interna, and Planície Costeira Externa. The following significant genetic gains were observed: 0.20% per year, for percentage of whole grains after processing; -1.38% per year, for percentage of chalky kernels and white-core grains; -0.77% per year, for total chalky area; -0.08% per year, for total whiteness; and -0.82% per year, for non-vitreous grain whiteness. Most cultivars released have high amylose content and a low gelatinization temperature. Therefore, the breeding program presented significant annual genetic progresses between 1972 and 2016 for the main attributes of grain quality, and made cultivars available according to the national demand for grain quality in the several segments of the rice production industry.

Milling Yields and Physicochemical Properties of Long-Grain Rice Thickness Fractions

Thickness grading of rice ( L.) can divert thin, chalky kernels to a secondary processing stream, thus improving milling yields of the primary stream. However, the quantity and functionality of the secondary stream may impact processing operations. Rough rice of multiple long-grain cultivar lots was either left unfractioned (Unf) or thickness graded into fractions comprising A ( 2.05 mm). Mass distribution of rough rice; milled rice yield (MRY), and head rice yield (HRY); kernel dimensions of brown rice; crude protein content (CP) and chalkiness of brown and head rice; and paste viscosities of head rice flour were determined for each cultivar lot/fraction. For all cultivar lots, MRY, HRY, and kernel dimensions increased with increasing thickness fraction, while chalkiness and CP decreased. Milling yields were the greatest for the C/D/E fractions. Including the C fraction (C/D/E) with the primary stream resulted in an average 17.4 percentage point mass increase compared to D/E alone; this with minimal impacts to milling yields of the primary stream. Weighted-average MRYs and HRYs of the combined C/D/E fractions increased by up to 6.9 and 12.8 percentage points, respectively, compared to Unf rice. The A/B fractions were generally of greater chalkiness and CP; however, paste viscosities remained relatively consistent with those of the C/D/E fractions. Thickness grading could be justified on the merits of improved milling yields, kernel uniformity, and reduced chalkiness of the primary processing stream. A small change in the thickness grading procedure decreased the quantity of the secondary stream; moreover when milled, the secondary stream retained functionality similar to the primary stream.

Observational studies on amyloplasts with single-starch granule in rice endosperm

Rice is one of the most important cereal crops worldwide. Grain chalkiness has been reported to decrease rice quality and to be associated with starch biosynthesis and accumulation. In order to explore mechanism of chalky starch formation, microscopic and submicroscopic techniques were adopted in this study to observe the amyloplast morphology of rice endosperm cells. These techniques used serial semi-thin sections of rice caryopsis endosperm cells and chalky rice kernels at different development stages after anthesis. Amyloplasts with single-starch granule existed in both developing and mature endosperm cells from their appearance to degradation. In addition, particle size analysis of the chalky and normal starch granules showed that the circularity of the chalky single-starch granule was greater than that of the normal starch granule. Given the loose arrangement of single-starch granule caused by undesirable development, its granule is different from that of the normal endosperm cell. Therefore, the defective development of starch might be related to the chalky formation.