Length Grain Research Articles

Microstructure and tribological properties of in-situ TiC reinforced Ti2AlNb-based coatings by laser cladding

The TiC reinforced Ti2AlNb-based coatings were fabricated on the surface of Ti-6Al-4V using Ti, Al, and Nb powder mixtures with different NbC addition (0, 1.25, 2.5, and 5 wt%) by laser cladding to improve the mechanical behavior of Ti-6Al-4V. The effects of NbC on the morphology, microstructure evolution and mechanical properties of the TiC/Ti2AlNb coatings were studied systematically. Results revealed that the matrix phases of all coatings were mainly composed of lamellar O phase and B2 phase. TiC in situ formed effectively refined grains, in which the length of the B2 grains was reduced from 205.36 μm to 25.31 μm, and the O phase was reduced from 5 μm to <1 μm as the NbC addition increased from 0 wt% to 5 wt%. Mechanical properties illustrated that the coating with the NbC addition of 2.5 wt% had the highest microhardness with 575.6 HV0.2 and the smallest volume loss with 0.66 mm3 due to fine grain strengthening and dispersion strengthening of TiC. Compared to the Ti-6Al-4V substrate, the microhardness was increased by 1.64 times, and the volume loss was reduced to 30 %. Nevertheless, the mechanical properties of the coatings will exhibit a downward trend by adding excessive NbC (5 wt%), and the coarsening of the TiC could be used to explain this slight decrease.

Agronomic and Physiological Indices for Reproductive Stage Heat Stress Tolerance in Green Super Rice

Optimum growing temperature is necessary for maximum yield-potential in any crop. The global atmospheric temperature is changing more rapidly and irregularly every year. High temperature at the flowering/reproductive stage in rice causes partial to complete pollen sterility, resulting in significant reduction in grain yield. Green Super Rice (GSR) is an effort to develop an elite rice type that can withstand multiple environmental stresses and maintain yield in different agro-ecological zones. The current study was performed to assess the effect of heat stress on agronomic and physiological attributes of GSR at flowering stage. Twenty-two GSR lines and four local checks were evaluated under normal and heat-stress conditions for different agro-physiological parameters, including plant height (PH), tillers per plant (TPP), grain yield per plant (GY), straw yield per plant (SY), harvest index (HI), 1000-grain weight (GW), grain length (GL), cell membrane stability (CMS), normalized difference vegetative index (NDVI), and pollen fertility percentage (PFP). Genotypes showed high significant variations for all the studied parameters except NDVI. Association and principal component analysis (PCA) explained the genetic diversity of the genotypes, and relationship between the particular parameters and grain yield. We found that GY, along with other agronomic traits, such as TPP, SY, HI, and CMS, were greatly affected by heat stress in most of the genotypes, while PH, GW, GL, PFP, and NDVI were affected only in a few genotypes. Outperforming NGSR-16 and NGSR-18 in heat stress could be utilized as a parent for the development of heat-tolerant rice. Moreover, these findings will be helpful in the prevention and management of heat stress in rice.

Identification and validation of major QTL for grain size and weight in bread wheat (Triticum aestivum L.)

Grain size and weight are key components of wheat yield. Exploitation of major underlying quantitative trait loci (QTL) can improve yield potential in wheat breeding. A recombinant inbred line (RIL) population was constructed to detect QTL for thousand-grain weight (TGW), grain length (GL) and grain width (GW) across eight environments. Genomic regions associated with grain size and grain weight were identified on chromosomes 4A and 6A using bulked segregant exome sequencing (BSE-Seq) analysis. After constructing genetic maps, six major QTL detected in at least four individual environments and in best linear unbiased estimator (BLUE) datasets, explained 7.50%–23.45% of the phenotypic variation. Except for QGl.cib-4A, the other five QTL were co-located in two regions, namely QTgw/Gw.cib-4A and QTgw/Gw/Gl.cib-6A. Interactions of these QTL were analyzed. Unlike QTgw/Gw/Gl.cib-6A, QTgw/Gw.cib-4A and QGl.cib-4A had no effect on grain number per spike (GNS). The QTL were validated in a second cross using Kompetitive Allele Specific PCR (KASP) markers. Since QTgw/Gw.cib-4A was probably a novel locus, it and the KASP markers reported here can be used in wheat breeding. TraesCS4A03G0191200 was predicted to be potential candidate gene for QTgw/Gw.cib-4A based on the sequence differences, spatiotemporal expression patterns, gene annotation and haplotype analysis. Our findings will be useful for fine mapping and for marker-assisted selection in wheat grain yield improvement.

GL9 from Oryza glumaepatula controls grain size and chalkiness in rice

Grain size is a key factor influencing grain yield and appearance quality in rice. We identified twelve quantitative trait loci (QTL) for grain length (GL), nine for grain width (GW), and nine for 1000-kernel weight (TKW) using GLU-SSSLs, which are single-segment substitution lines with Oryza glumaepatula as donor parent and Huajingxian 74 (HJX74) as recipient parent. Among the QTL, qGL1-2, qGL1-4, qGL9-2, qGW2-2, qGW9-1 and qTKW9-2 contributed to high grain yield. GL9 was identified as a candidate gene for qGL9-2 by map-based cloning and sequencing, and is a novel allele of GS9. The kernel of NIL-gl9 was slenderer and longer than that of HJX74, and the TKW and grain yield per plant of NIL-gl9 were higher than those of HJX74. The proportion of grain chalkiness of NIL-gl9 was much lower than that of HJX74. Thus, gl9 increased grain yield and appearance quality simultaneously. Three pyramid lines, NIL-gs3/gl9, NIL-GW7/gl9 and NIL-gw8/gl9, were developed and the kernel of each was longer than that of the corresponding recipient parent lines. The gl9 allele may be beneficial for breeding rice varieties with high grain yield and good appearance quality.

Effect of Different Seed Rates and Row Spacing on Yield Attributes and Yield of Late Sown Wheat (Triticum aestivum L.)

Background: Wheat (Triticum aestivum L.) is the most important cereal crop throughout India and other parts of the world. In late sowing conditions the variety selection, seed rate and row spacing is an important factor for a better crop yield. Higher seed rate and narrow row spacing are used in late sowing as compared to normal sowing conditions. Methods: The present field experiment was conducted at the Students Research Farm, Khalsa College, Amritsar, Punjab, India during rabi season of 2020-21. A field experiment was laid out in split-plot design with replicated three times comprising four levels of seed rate viz. (100, 110, 120 and 130 kg/ha) and three-row spacing viz. (12, 15 and 18 cm) of wheat cultivar DBW 187 (Karan Vandana). Result: The result showed that the number of tiller per meter, spike length, grains per spike, test weight, grain, straw and biological yield were significantly affected by different seed rates and row spacing. The seed rate 120 kg/ha recorded significantly higher grain yield (50.47 q/ha), effective tiller per meter row length (70) and the number of grain per spike (58), whereas 130 kg/ha gave significantly higher straw yield (73.40 q/ha). The crop sown with row spacing 18 cm showed significantly higher grain yield (49.13 q/ha), straw yield (72.70 q/ha), biological yield (121.83 q/ha), effective tiller per meter row length (68), spike length (12.10 cm) and number of grain per spike (56.16).

Potassium Fertilizer Influences Growth Traits and Yield of Wheat (Triticum aestivum L.) under Saline Regime

Soil salinity is one of major deleterious abiotic stress limiting the yield of wheat crop. Plant growth produce is severely affected by various biotic and environmental and metabolic processes. Application of Potash fertilizer can reduce the harmful effects of saline stress and increase crop yield. This research was carried out to evaluate detrimental effects of salinity stress on wheat produce and to suggest appropriate dose of potash fertilizer to achieve optimum production under saline conditions. There were four K doses as (ck, 50, 3/4th and 100 kilogram K2O/ ha). The results depicted that potash fertilizer application increased wheat crop growth traits and produce substantially under saline regime, significantly. With potassium supplement, height of plant enhanced about 19.23 %, tillers per plant (36.24 %), length of spike (27.33 %) cm, wheat grains (23.5 %), and grain production increased (24.11 %) kg/ha. It was concluded that soil applied potassium fertilizer as K rate at 100 kg K2O yielded in maximum crop growth development and wheat produce at rate of 50 and 75 kg K2O ha-1. Therefore, potash fertilizer at rate of 100 kg K2O ha-1 may be adopted for optimum yield in wheat under saline environment.

Evaluation of improved varieties of rice (Oryza sativa L.) under environmental condition of Namsai, Arunachal Pradesh, India

An experiment was performed for evaluation of improved varieties of rice under environmental conditions occurring at Namsai district of Arunachal Pradesh in Research Farm of Arunachal University. Studies were conducted during Kharif season for identifying the promising variety. Thirteen varieties, namely Deepthi; NPT Cul-1; Red Matta Triveni; Jyothi; Uma; Akhaya; Sapmpada; Aathiva; JS-7; Khamti Lahi; Thailand Lahi; MTU and Bora were assessed in replicated randomized block design with 2 replication. The results revealed that the varieties showed significant variations on growth and yield parameters viz; Plant height at the vegetative stage, Number of productive tillers, Number of days for panicle emergence, Crop duration, Number of grains per panicle, Length of panicle, Length of grain, 1000 grain weight, Yield per plot and Length/Breadth ratio of grains. From the above findings, it is observed that, considering the growth and yield parameters, improved rice varieties Uma and JS-7, exotic variety Thailand Lahi, indigenous variety Bora and Khamti Lahi were found to be promising under the Namsai condition of Arunachal Pradesh.

Identification of qGL3.5, a Novel Locus Controlling Grain Length in Rice Through Bulked Segregant Analysis and Fine Mapping.

Grain length (GL) directly affects the yield and quality of rice. Very few cloned GL-related genes are applied in production because their yield-increasing effects are not obvious, and the overall regulatory networks underlying the associated processes remain poorly understood. DNA samples from two bulk DNA pools (L-pool and S-pool) and their parents (KJ01 and Huaye 3) were subjected to high-throughput sequencing. Using bulked segregant analysis (BSA), qGL3.5 was mapped to a 0.34-Mb “hotspot” region on chromosome 3 that contains 37 genes related to various traits. Then, qGL3.5 was mapped to the genomic interval between the flanking markers M2 and M3 using 2786 BC4F2 individuals. Because the region from B5 to B6 was not the associated region under BSA-seq analysis, qGL3.5 was narrowed down to the interval between B6 and M3, which spanned 24.0-kb. Of all 37 genes with non-synonymous single-nucleotide polymorphisms (SNPs) between KJ01 and Huaye 3 based on BSA-seq analysis, only one complete annotated gene, ORF18 (Gene ID: LOC_Os03g42790.1) was found. ORF18 encodes an IBR-RING zinc-finger-related protein, with one really interesting new gene (RING) and two in between ring finger (IBR) domains. The knockout of ORF18 derived from Huaye 3 using clustered, regularly interspaced, short palindromic repeat (CRISPR)/CRISPR-associated 9 (Cas9) editing technology increased the GL of the mutant by approximately 2.2 mm. The novel locus qGL3.5 negatively regulated GL by promoting elongation of the longitudinal cell of the grain outer glume. These results provide a new genetic resource for rice grain shape breeding and a starting point for the functional characterization of the wild rice GL gene.

Identification and Validation of Quantitative Trait Loci for Grain Size in Bread Wheat (Triticum aestivum L.)

Grain width (GW) and grain length (GL) are crucial components affecting grain weight. Dissection of their genetic control is essential for improving yield potential in wheat breeding. Yangmai 12 (YM12) and Yanzhan 1 (YZ1) are two elite cultivars released in the Middle and Lower Yangtze Valleys Wheat Zone (MLYVWZ) and the Yellow-Huai River Valleys Wheat Zone (YRVWZ), respectively. One biparental population derived from YM12/YZ1 cross was employed to perform QTL mapping based on the data from four environments over two years to detect quantitative trait loci (QTL) for GW and GL. A total of eight QTL were identified on chromosomes 1B, 2D, 3B, 4B, 5A, and 6B. Notably, QGW.yz.2D was co-located with QGL.yz.2D, and QGW.yz.4B was co-located with QGL.yz.4B, respectively. QGW.yz.2D and QGL.yz.2D, with the increasing GW/GL allele from YZ1, explained 12.36–18.27% and 13.69–26.53% of the phenotypic variations for GW and GL, respectively. QGW.yz.4B and QGL.yz.4B, with the increasing GW/GL allele from YM12, explained 10.34–11.95% and 10.35–16.04% of the phenotypic variation for GW and GL, respectively. QGL.yz.5A, with the increasing GL allele from YM12, explained 10.04–12.48% of the phenotypic variation for GL. Moreover, the positive alleles of these three QTL regions could significantly increase thousand-grain weight, and QGW.yz.4B/QGL.yz.4B and QGL.yz.5A did not show significant negative effects on grain number per spike. QGL.yz.2D, QGW.yz.4B/QGL.yz.4B, and QGL.yz.5A have not been reported. These three QTL regions were then further validated using Kompetitive Allele-Specific PCR (KASP) markers in 159 wheat cultivars/lines from MLYVWZ and YRVWZ. Combining the positive alleles of the major QTL significantly increased GW and GL. Eleven candidate genes associated with encoding ethylene-responsive transcription factor, oleosin, osmotin protein, and thaumatin protein were identified. Three major QTL and KASP markers reported here will be helpful in developing new wheat cultivars with high and stable yields.

Study of the intrinsic mechanisms of nickel additive for grain refinement and strength enhancement of laser aided additively manufactured Ti–6Al–4V

It is well-known that grain refiners can tailor the microstructure and enhance the mechanical properties of titanium alloys fabricated by additive manufacturing (AM). However, the intrinsic mechanisms of Ni addition on AM-built Ti–6Al–4V alloy is not well established. This limits its industrial applications. This work systematically investigated the influence of Ni additive on Ti–6Al–4V alloy fabricated by laser aided additive manufacturing (LAAM). The results showed that Ni addition yields three key effects on the microstructural evolution of LAAM-built Ti–6Al–4V alloy. (a) Ni additive remarkably refines the prior-β grains, which is due to the widened solidification range. As the Ni addition increased from 0 to 2.5 wt. %, the major-axis length and aspect ratio of the prior-β grains reduced from over 1500 μm and 7 to 97.7 μm and 1.46, respectively. (b) Ni additive can discernibly induce the formation of globular α phase, which is attributed to the enhanced concentration gradient between the β and α phases. This is the driving force of globularization according to the termination mass transfer theory. The aspect ratio of the α laths decreased from 4.14 to 2.79 as the Ni addition increased from 0 to 2.5 wt. %. (c) Ni as a well-known β-stabilizer and it can remarkably increase the volume fraction of β phase. Room-temperature tensile results demonstrated an increase in mechanical strength and an almost linearly decreasing elongation with increasing Ni addition. A modified mathematical model was used to quantitatively analyze the strengthening mechanism. It was evident from the results that the α lath phase and the solid solutes contribute the most to the overall yield strength of the LAAM-built Ti–6Al–4V–xNi alloys in this work. Furthermore, the decrease in elongation with increasing Ni addition is due to the deterioration in deformability of the β phase caused by a large amount of solid-solution Ni atoms. These findings can accelerate the development of additively manufactured titanium alloys.

The Triticum ispahanicum elongated glume locus P2 maps to chromosome 6A and is associated with the ectopic expression of SVP-A1

Key messageWe propose the MADS-box transcription factor SVP-A1 as a promising candidate gene for the elongated glume locus P2, which maps to chromosome 6A instead of the previously proposed chromosome 7B.In rice and wheat, glume and floral organ length are positively correlated with grain size, making them an important target to increase grain size and potentially yield. The wheat subspecies Triticum ispahanicum is known to develop elongated glumes and floral organs as well as long grains. These multiple phenotypic effects are controlled by the P2 locus, which was previously mapped to wheat chromosome 7B. Using three mapping populations, we show that the long glume locus P2 does not map to chromosome 7B, but instead maps to a 1.68 Mbp interval on chromosome 6A. Within this interval, we identified SVP-A1, a MADS box transcription factor which is the direct ortholog of the maize gene underlying the ‘pod corn’ Tunicate locus and is a paralog to the T. polonicum elongated glume P1 gene. In T. ispahanicum, we identified a unique allele which has a 482-bp deletion in the SVP-A1 promoter and is associated with ectopic and higher expression of SVP-A1 in the elongated glumes and floral organs. We used near-isogenic lines (NILs) to show that P2 has a consistent positive effect on the length of glume, lemma, palea, spike and grain. Based on the mapping data, natural variation, biological function of SVP genes in cereals and expression analyses, we propose the MADS-box transcription factor SVP-A1 as a promising candidate for P2.

High-resolution detection of quantitative trait loci for seven important yield-related traits in wheat (Triticum aestivum L.) using a high-density SLAF-seq genetic map

BackgroundYield-related traits including thousand grain weight (TGW), grain number per spike (GNS), grain width (GW), grain length (GL), plant height (PH), spike length (SL), and spikelet number per spike (SNS) are greatly associated with grain yield of wheat (Triticum aestivum L.). To detect quantitative trait loci (QTL) associated with them, 193 recombinant inbred lines derived from two elite winter wheat varieties Chuanmai42 and Chuanmai39 were employed to perform QTL mapping in six/eight environments.ResultsA total of 30 QTLs on chromosomes 1A, 1B, 1D, 2A, 2B, 2D, 3A, 4A, 5A, 5B, 6A, 6D, 7A, 7B and 7D were identified. Among them, six major QTLs QTgw.cib-6A.1, QTgw.cib-6A.2, QGw.cib-6A, QGl.cib-3A, QGl.cib-6A, and QSl.cib-2D explaining 5.96-23.75% of the phenotypic variance were detected in multi-environments and showed strong and stable effects on corresponding traits. Three QTL clusters on chromosomes 2D and 6A containing 10 QTLs were also detected, which showed significant pleiotropic effects on multiple traits. Additionally, three Kompetitive Allele Specific PCR (KASP) markers linked with five of these major QTLs were developed. Candidate genes of QTgw.cib-6A.1/QGl.cib-6A and QGl.cib-3A were analyzed based on the spatiotemporal expression patterns, gene annotation, and orthologous search.ConclusionsSix major QTLs for TGW, GL, GW and SL were detected. Three KASP markers linked with five of these major QTLs were developed. These QTLs and KASP markers will be useful for elucidating the genetic architecture of grain yield and developing new wheat varieties with high and stable yield in wheat.

PHENOTYPIC PARAMETER EXTRACTION FOR WHEAT EARS BASED ON AN IMPROVED MASK-RCNN ALGORITHM

The acquisition of traditional wheat ear phenotypic parameters is labour intensive and subjective, and some trait parameters are difficult to measure, which greatly limits the progress of wheat ear research. To obtain the phenotypic parameters of wheat ears in batches at a low cost, this paper proposed a convenient and accurate method for extracting phenotypic parameters of wheat ears. First, three improvement directions were proposed based on the Mask Region-Convolutional Neural Network (Mask-RCNN) model. 1) To extract the multiscale features of wheat ears, a hierarchical residual link was constructed in a single residual block of the backbone network ResNet101 to obtain information on different sizes of receptive fields. 2) The feature pyramid network (FPN) was improved to increase the recognition accuracy of wheat ear edges through multiple two-way information flow sampling. 3) The mask evaluation mechanism was improved, specific network blocks were used to learn and predict the quality of the mask, and the detection of wheat ears and grains was performed by precise segmentation; an automatic extraction algorithm was designed for wheat ear phenotypic parameters based on the segmentation results to extract 22 phenotypic parameters. The experiments showed that the improved Mask-RCNN was superior to the existing model in the segmentation accuracy of wheat ears and grains; the parameters of wheat ear length, width, and number of grains extracted by the automatic extraction algorithm were close to the manual measurement values. This research meets the demand for automatic extraction of wheat ear phenotype data for large-scale quality testing and commercial breeding and has strong practicability.

Grain Properties of Indigenous Rice Cultivars from Khagrachari District of Bangladesh

A study was conducted in the Agronomy Laboratory of Agrotechnology Discipline, Khulna University, Khulna, Bangladesh to find out the variations in grain characters of fifteen local rice cultivars collected from Khagrachari district, Bangladesh. Significant variations were observed in all of the investigated parameter. The highest and lowest length of grain was recorded in the cultivar Chonchonbini (7.1 mm) and Mashlajira (4.12 mm), respectively. Grain width of Badia (2.78 mm) was the highest and the lowest width was recorded in Mashlajira (2.13 mm). Grain thickness varied from 1.6 mm to 1.94 mm. The highest L/W ratio (3.11) was observed in Curi. Most of the variety showed medium grain shape. The highest alkali spreading score was found in Moisanguribini (6). All of the varieties showed soft gel consistency. Variation in grain characters observed among the local rice cultivars in the present study and these characters may be used as valuable resources for future breeding programs. South Asian J. Agric., 8(1&amp;2): 51-56

RESPONSE OF THREE WHEAT VARIETIES TO NITROGEN LEVELS, SEEDING RATES AND THEIR COMBINATION; 2: SPIKE CHARACTERS

To achieve larger production per unit area, sciences and farmers face a great defiance in improving cropping practices and elicitation new top yielding wheat varieties and also to establish the effects of these factors on the spike characters. Two years experiment were conducted to evaluate the effect of three nitrogen fertilizer levels (recommend rate 80 kg N/fed and 25% lower and higher than the recommended, i.e. 60 and 100 kg N/ fed, three seeding rates (40, 60 and 80 kg grains/fed) and there varieties (Giza-171, Gemmiza-12 and Shandawil-1), on spike characters of wheat at the Agricultural and experimental Research Station, Faculty of Agriculture, Cairo University, Giza, Egypt during 2018/2019 and 2019/2020 seasons.The experimental design was a split- split plot in randomized complete block arrangement with three replications. Nitrogen levels were allocated to the main plots, while the sub plots were assigned for seeding rates. 2 Wheat varieties were distributed at random in the sub-sub plots.Each sub-sub plots area 4 m (2 x 2m).Generally,results indicated that significant effect on spike length and number of grains/ spike in both seasons and on weight of grains/ spike and 1000-grain weight in one season,where the tallest and heaviest spike as well as the heaviest 1000-grain weight were produced at the 100 kg N/fed in both seasons but the highest number of grains/spike was obtained at 80 kg N/fed in one season. It could be concluded that application nitrogen at the rate of 100 kg/fed proceed the favorable effect on spike characters under the environmental conditions of the experimental site and the similar conditions. Seeding rates caused a significant effect on all studied traits in one season,so the highest values were at 80 kg grains/fed,but this effect on 1000-grain weight was true in both seasons,where the highest value was at 60 kg grains/fed.Moreover,varieties were significantly differed in all spike character in both seasons except number and weight of grains/spike in one season where Giza-12 variety surpassed others.Al studied interactions had significant effect on all studied traits either in one or two season.Planting Giza-171 with 80 kg grains/fed and application of 100 kg N/fed was the pest treatmnt.

Potential lines of black rice crossing with Jeliteng variety and their reciprocals

Climate change causes an increase in rice plant pests, one of them is brown planthopper. The effort through an assembly of black rice potential lines was made by mutation induction of Cempo Ireng black rice, but it’s only able to shorten the age of plant without being able to improve rice resistance to brown planthopper. Jeliteng as a new high yielding variety of black rice that is resistant to brown planthopper biotype 1 makes it worthy of being a potential parent source. Reciprocal crosses needed to be carried out to get offspring that have superior traits from both parents. This research aims to get F1 generation from the potential lines of black rice crossing with the Jeliteng variety and their reciprocals to improve local varieties of black rice. The research was conducted in the experimental field of the village of Gawanan, Sukoharjo Regency from August 2020 to April 2021. The planting materials were the Jeliteng variety as male parents while 6 potential lines of black rice 8, 13, 44, 46, 51, 52, and Cempo Ireng variety as female parents. Crosses were conducted by hand crossing technique on 14 sets. The data were analyzed descriptively and using the Chi-square test. The results showed that the crossing set could be crossed and produced fertile F1 generation. The length of grain, the width of grain, and the weight of a grain of the F1 varied in all sets. The skin colour of the F1 generation in all sets was mostly straw yellow with brown spots.

Genetic variability and multivariate studies on the grain physical properties of rice (Oryza sativa L.) landraces

Thirty rice landraces were evaluated during the 2020 wet season for the estimation of the genetic variability of six grain physical properties, viz. grain length (GL), grain breadth (GB), milled grain length (MGL), milled grain breadth (MGB), milled grain length breadth ratio (MGL/MGB), and 1000-grain weight (TGW), at the Bangladesh Institute of Nuclear Agriculture Substation, Sunamganj, Bangladesh. The relative contribution of these traits to variability was estimated by using principal component analysis (PCA), and the landraces were clustered by using Mahalanobis distance (D2) statistics. The TGW and MGL/MGB ratio exhibited high estimates of the phenotypic coefficient of variation and genotypic coefficient of variation. The high broad-sense heritability and genetic advance of all the traits indicated that the environmental effect had a weak involvement in the expression of these traits. PCA revealed six principal components, among which two were significant and contributed up to 96.9% of the total variance cumulatively. GL, GB, MGL, and TGW contributed to PC1 to create the variation among the landraces, whereas MGL/MGB ratio, GL, and MGL contributed to PC2. The landraces were grouped into six clusters. Cluster analysis revealed that the maximum and minimum intracluster distances were found in cluster III (235.11) and cluster VI (0.00), respectively. The longest intercluster distance was found between clusters IV and VI, and the shortest distance was found between clusters I and III. The maximum mean values for GL and TGW were observed in cluster VI. The mean values for GB and MGB were highest in cluster V, whereas the MGL/MGB ratio and MGL were highest in cluster II. ‘Madhumala’/‘Sada Madhumala’ and ‘Pankhuraj’ could be used in hybridization programs to exploit maximum heterosis for rice grain size and shape and for the direct selection of superior quality traits because these traits are less affected by the environment than other traits.

English

Two low-light sensitive varieties of sweet corn (Zea mays L.), cultivars Xiantian 5, and Huazhen, were subjected to different shading-intensity treatments during the grain-filling stage in a field experiment in order to clarify physiological mechanisms of lowlight effects on the yield, quality, and sucrose-metabolizing enzyme activity of sweet corn. The results showed that under weak light stress (50% light transmittance), the ear length and diameter, fresh ear yield, grains per row and grain weight, weight per ear and sugar content of the grains decreased sharply, while the bald length and water content of the fresh grains increased significantly. The 50% shading decreased the fresh ear yield, max weight per 100 fresh grains, and soluble sugar content of Xiantian 5 by 40.5, 31.3, and 19.5%, respectively, whereas those of Huazhen were decreased by 17.5, 19.8 and 10.1%, respectively. Shading furthermore suppressed the activities of sucrose phosphate synthase (SPS) and sucrose synthetase (SS), and delayed the emergence of peak SPS activity. Key words: Sweet corn, shading condition, yield, quality, sucrose-metabolizing enzyme.

Identifying QTLs for Grain Size in a Colossal Grain Rice (Oryza sativa L.) Line, and Analysis of Additive Effects of QTLs.

Grain size is an important component of quality and harvest traits in the field of rice breeding. Although numerous quantitative trait loci (QTLs) of grain size in rice have been reported, the molecular mechanisms of these QTLs remain poorly understood, and further research on QTL observation and candidate gene identification is warranted. In our research, we developed a suite of F2 intercross populations from a cross of 9311 and CG. These primary populations were used to map QTLs conferring grain size, evaluated across three environments, and then subjected to bulked-segregant analysis-seq (BSA-seq). In total, 4, 11, 12 and 14 QTLs for grain length (GL), grain width (GW), 1000-grain weight (TGW), and length/width ratio (LWR), respectively, were detected on the basis of a single-environment analysis. In particular, over 200 splicing-related sites were identified by whole-genome sequencing, including one splicing-site mutation with G>A at the beginning of intron 4 on Os03g0841800 (qGL3.3), producing a smaller open reading frame, without the third and fourth exons. A previous study revealed that the loss-of-function allele caused by this splicing site can negatively regulate rice grain length. Furthermore, qTGW2.1 and qGW2.3 were new QTLs for grain width. We used the near-isogenic lines (NILs) of these GW QTLs to study their genetic effects on individuals and pyramiding, and found that they have additive effects on GW. In summary, these discoveries provide a valuable genetic resource, which will facilitate further study of the genetic polymorphism of new rice varieties in rice breeding.

A Genetic Resource for Rice Improvement: Introgression Library of Agronomic Traits for All AA Genome Oryza Species.

Rice improvement depends on the availability of genetic variation, and AA genome Oryza species are the natural reservoir of favorable alleles that are useful for rice breeding. To systematically evaluate and utilize potentially valuable traits of new QTLs or genes for the Asian cultivated rice improvement from all AA genome Oryza species, 6,372 agronomic trait introgression lines (ILs) from BC2 to BC6 were screened and raised based on the variations in agronomic traits by crossing 170 accessions of 7 AA genome species and 160 upland rice accessions of O. sativa as the donor parents, with three elite cultivars of O. sativa, Dianjingyou 1 (a japonica variety), Yundao 1 (a japonica variety), and RD23 (an indica variety) as the recurrent parents, respectively. The agronomic traits, such as spreading panicle, erect panicle, dense panicle, lax panicle, awn, prostrate growth, plant height, pericarp color, kernel color, glabrous hull, grain size, 1,000-grain weight, drought resistance and aerobic adaption, and blast resistance, were derived from more than one species. Further, 1,401 agronomic trait ILs in the Dianjingyou 1 background were genotyped using 168 SSR markers distributed on the whole genome. A total of twenty-two novel allelic variations were identified to be highly related to the traits of grain length (GL) and grain width (GW), respectively. In addition, allelic variations for the same locus were detected from the different donor species, which suggest that these QTLs or genes were conserved and the different haplotypes of a QTL (gene) were valuable resources for broadening the genetic basis in Asian cultivated rice. Thus, this agronomic trait introgression library from multiple species and accessions provided a powerful resource for future rice improvement and genetic dissection of agronomic traits.