Rice Tiller Number Research Articles

The chloroplast pentatricopeptide repeat protein RCN22 regulates tiller number in rice by affecting sugar levels via the TB1–RCN22–RbcL module

As an important yield component, rice tiller number controls panicle number and determines grain yield. Regulation of rice tiller number by chloroplast pentatricopeptide repeat (PPR) proteins has not been reported previously. Here, we report the rice reduced culm number22 (rcn22) mutant, which produces few tillers owing to suppressed tiller bud elongation. Map-based cloning revealed that RCN22 encodes a chloroplast-localized P-type PPR protein. We found that RCN22 specifically binds to the 5′ UTR of RbcL mRNA (encoding the large subunit of Rubisco) and enhances its stability. The reduced abundance of RbcL mRNA in rcn22 leads to a lower photosynthetic rate and decreased sugar levels. Consequently, transcript levels of DWARF3 (D3) and TEOSINTE BRANCHED1 (TB1) (which encode negative regulators of tiller bud elongation) are increased, whereas protein levels of the positive regulator DWARF53 (D53) are decreased. Furthermore, high concentrations of sucrose can rescue the tiller bud growth defect of the rcn22 mutant. On the other hand, TB1 directly binds to the RCN22 promoter and downregulates its expression. The tb1/rcn22 double mutant shows a tillering phenotype similar to that of rcn22. Our results suggest that the TB1–RCN22–RbcL module plays a vital role in rice tiller bud elongation by affecting sugar levels.

A centromere map based on super pan-genome highlights the structure and function of rice centromeres.

Rice (Oryza sativa) is a significant crop worldwide with a genome shaped by various evolutionary factors. Rice centromeres are crucial for chromosome segregation, and contain some unreported genes. Due to the diverse and complex centromere region, a comprehensive understanding of rice centromere structure and function at the population level is needed. We constructed a high-quality centromere map based on the rice super pan-genome consisting of a 251-accession panel comprising both cultivated and wild species of Asian and African rice. We showed that rice centromeres have diverse satellite repeat CentO, which vary across chromosomes and subpopulations, reflecting their distinct evolutionary patterns. We also revealed that long terminal repeats (LTRs), especially young Gypsy-type LTRs, are abundant in the peripheral CentO-enriched regions and drive rice centromere expansion and evolution. Furthermore, high-quality genome assembly and complete telomere-to-telomere (T2T) reference genome enable us to obtain more centromeric genome information despite mapping and cloning of centromere genes being challenging. We investigated the association between structural variations and gene expression in the rice centromere. A centromere gene, OsMAB, which positively regulates rice tiller number, was further confirmed by expression quantitative trait loci, haplotype analysis and clustered regularly interspaced palindromic repeats (CRISPR)/CRISPR-associated protein 9 methods. By revealing the new insights into the evolutionary patterns and biological roles of rice centromeres, our finding will facilitate future research on centromere biology and crop improvement.

Knockout of the sugar transporter OsSTP15 enhances grain yield by improving tiller number due to increased sugar content in the shoot base of rice (Oryza sativa L.).

Sugar transporter proteins (STPs) play critical roles in regulating plant stress tolerance, growth, and development. However, the role of STPs in regulating crop yield is poorly understood. This study elucidates the mechanism by which knockout of the sugar transporter OsSTP15 enhances grain yield via increasing the tiller number in rice. We found that OsSTP15 is specifically expressed in the shoot base and vascular bundle sheath of seedlings and encodes a plasma membrane-localized high-affinity glucose efflux transporter. OsSTP15 knockout enhanced sucrose and trehalose-6-phosphate (Tre6P) synthesis in leaves and improved sucrose transport to the shoot base by inducing the expression of sucrose transporters. Higher glucose, sucrose, and Tre6P contents were observed at the shoot base of stp15 plants. Transcriptome and metabolome analyses of the shoot base demonstrated that OsSTP15 knockout upregulated the expression of cytokinin (CK) synthesis- and signaling pathway-related genes and increased CK levels. These findings suggest that OsSTP15 knockout represses glucose export from the cytoplasm and simultaneously enhances sugar transport from source leaves to the shoot base by promoting the synthesis of sucrose and Tre6P in leaves. Subsequent accumulation of glucose, sucrose, and Tre6P in the shoot base promotes tillering by stimulating the CK signaling pathway.

Propyrisulfuron plus cyhalofop butyl as one-shot herbicides provide high weed control efficiency and net economic performance in mechanically transplanted rice.

Propyrisulfuron is a novel pyrimidinylsulfonylurea herbicide with good activity for controlling annual weed in rice fields. To evaluate the economic performance of propyrisulfuron, a field study was conducted in 2021 and 2022 on a farm of the Jiangsu Academy of Agricultural Sciences, China. Eight different herbicide treatments were employed, including CB (cyhalofop butyl), Py (propyrisulfuron), CBPy (cyhalofop butyl plus propyrisulfuron), PrBe 3, PrBe 10, and PrBe 3+PrBe 10 (pretilachlor plus bensulfuron applied at different times [at 3 (PrBe 3) and 10 (PrBe 10) d] or sequentially, respectively), 2PrBe+PeCBBz (pretilachlor plus bensulfuron [applied sequentially] followed by penoxsulam plus cyhalofop butyl plus bentazone), 2PrBe+MeCBBz (pretilachlor plus bensulfuron [applied sequentially] followed by metamifop plus cyhalofop butyl plus bentazone), along with weed-free and nontreated weedy check treatments. Herbicide treatments did not cause visual phytotoxicity to rice, and bending and leaf rolling were not observed. Only the two propyrisulfuron treatments had temporary negative effects on rice height, but rice recovered quickly. Compared with the weed-free treatment, CBPy did not affect rice tiller number or dry matter accumulation. Compared with the nontreated weedy check, herbicide treatments reduced total weed density by 29.4% to 99.1% and dry biomass by 32.2% to 98.7%. The CBPy treatment provided the best weed control, reducing weed density and biomass by 96.7% and 95.9% in 2021 and 97.4% and 95.6% in 2022, respectively. Rice grain yield was not significantly different between CBPy and the weed-free treatment in either year. Economic analysis showed that CBPy provided the highest net profit, followed by that in 2PrBe+PeCBBz and 2PrBe+MeCBBz, with the lowest net profit in the nontreated weedy check. Thus, CBPy provides good weed control and could be promoted in mechanically transplanted rice fields in China.

OsMDH12: A Peroxisomal Malate Dehydrogenase Regulating Tiller Number and Salt Tolerance in Rice.

Salinity is an important environmental factor influencing crop growth and yield. Malate dehydrogenase (MDH) catalyses the reversible conversion of oxaloacetate (OAA) to malate. While many MDHs have been identified in various plants, the biochemical function of MDH in rice remains uncharacterised, and its role in growth and salt stress response is largely unexplored. In this study, the biochemical function of OsMDH12 was determined, revealing its involvement in regulating tiller number and salt tolerance in rice. OsMDH12 localises in the peroxisome and is expressed across various organs. In vitro analysis confirmed that OsMDH12 converts OAA to malate. Seedlings of OsMDH12-overexpressing (OE) plants had shorter shoot lengths and lower fresh weights than wild-type (WT) plants, while osmdh12 mutants displayed the opposite. At maturity, OsMDH12-OE plants had fewer tillers than WT, whereas osmdh12 mutants had more, suggesting OsMDH12's role in tiller number regulation. Moreover, OsMDH12-OE plants were sensitive to salt stress, but osmdh12 mutants showed enhanced salt tolerance. The Na+/K+ content ratio increased in OsMDH12-OE plants and decreased in osmdh12 mutants, suggesting that OsMDH12 might negatively affect salt tolerance through influencing the Na+/K+ balance. These findings hint at OsMDH12's potential as a genetic tool to enhance rice growth and salt tolerance.

Low phosphorus promotes NSP1–NSP2 heterodimerization to enhance strigolactone biosynthesis and regulate shoot and root architecture in rice

Phosphorus is an essential macronutrient for plant development and metabolism, and plants have evolved ingenious mechanisms to overcome phosphate (Pi) starvation. However, the molecular mechanisms underlying the regulation of shoot and root architecture by low phosphorus conditions and the coordinated utilization of Pi and nitrogen remain largely unclear. Here, we show that Nodulation Signaling Pathway 1 (NSP1) and NSP2 regulate rice tiller number by promoting the biosynthesis of strigolactones (SLs), a class of phytohormones with fundamental effects on plant architecture and environmental responses. We found that NSP1 and NSP2 are induced by Oryza sativa PHOSPHATE STARVATION RESPONSE2 (OsPHR2) in response to low-Pi stress and form a complex to directly bind the promoters of SL biosynthesis genes, thus markedly increasing SL biosynthesis in rice. Interestingly, the NSP1/2–SL signaling module represses the expression of CROWN ROOTLESS 1 (CRL1), a newly identified early SL-responsive gene in roots, to restrain lateral root density under Pi deficiency. We also demonstrated that GR244DO treatment under normal conditions inhibits the expression of OsNRTs and OsAMTs to suppress nitrogen absorption but enhances the expression of OsPTs to promote Pi absorption, thus facilitating the balance between nitrogen and phosphorus uptake in rice. Importantly, we found that NSP1p:NSP1 and NSP2p:NSP2 transgenic plants show improved agronomic traits and grain yield under low- and medium-phosphorus conditions. Taken together, these results revealed a novel regulatory mechanism of SL biosynthesis and signaling in response to Pi starvation, providing genetic resources for improving plant architecture and nutrient-use efficiency in low-Pi environments.

Exploitation of Allelic Variation and Superior Haplotypes for OsMIT3 Regulating Tiller Number in Rice

Rice (Oryza sativa L.) is the staple food for more than 60 % of the population globally and it is consumed in various forms. Increased crop yield under variable climatic circumstances is necessary in light of the world population's rapid growth, yield plateaus, resource depletion, and climate change. In order to overcome these obstacles, novel genes and alleles in the rice gene pool must be found, and unique features like C4 photosynthesis must be modified. The negative effects of climate change, stagnated yields, and diminishing agricultural resources are major obstacles. Tillering is one of the important traits to be considered for increased rice crop production and productivity. The target gene OsMIT3 phenotypically shows higher tillering and is caused by strigolactone deficiency that directly linked to carotenoid biosynthesis pathway, signaling strigolactone genes towards rice tillering. In this study, 100 diverse accessions from Rice 3K-RG panel were selected and analyzed, which shows three significant SNPs and grouped into four haplotypes group with allelic combinations of TAT(H1), ACA(H2), TAA(H3) and ACT(H4). Among the four haplo-group, H3 shows higher mean value for both total number of tillers and productive tillers, which can be further considered as a source of breeding strategy for crop yield.

QTL Mapping of Tiller Number in Korean Japonica Rice Varieties.

Tiller number is an important trait associated with yield in rice. Tiller number in Korean japonica rice was analyzed under greenhouse conditions in 160 recombinant inbred lines (RILs) derived from a cross between the temperate japonica varieties Odae and Unbong40 to identify quantitative trait loci (QTLs). A genetic map comprising 239 kompetitive allele-specific PCR (KASP) and 57 cleaved amplified polymorphic sequence markers was constructed. qTN3, a major QTL for tiller number, was identified at 132.4 cm on chromosome 3. This QTL was also detected under field conditions in a backcross population; thus, qTN3 was stable across generations and environments. qTN3 co-located with QTLs associated with panicle number per plant and culm diameter, indicating it had pleiotropic effects. The qTN3 regions of Odae and Unbong40 differed in a known functional variant (4 bp TGTG insertion/deletion) in the 5' UTR of OsTB1, a gene underlying variation in tiller number and culm strength. Investigation of variation in genotype and tiller number revealed that varieties with the insertion genotype had lower tiller numbers than those with the reference genotype. A high-resolution melting marker was developed to enable efficient marker-assisted selection. The QTL qTN3 will therefore be useful in breeding programs developing japonica varieties with optimal tiller numbers for increased yield.

Fertilization controls tiller numbers via transcriptional regulation of a MAX1-like gene in rice cultivation

Fertilization controls various aspects of cereal growth such as tiller number, leaf size, and panicle size. However, despite such benefits, global chemical fertilizer use must be reduced to achieve sustainable agriculture. Here, based on field transcriptome data from leaf samples collected during rice cultivation, we identify fertilizer responsive genes and focus on Os1900, a gene orthologous to Arabidopsis thaliana MAX1, which is involved in strigolactone biosynthesis. Elaborate genetic and biochemical analyses using CRISPR/Cas9 mutants reveal that Os1900 together with another MAX1-like gene, Os5100, play a critical role in controlling the conversion of carlactone into carlactonoic acid during strigolactone biosynthesis and tillering in rice. Detailed analyses of a series of Os1900 promoter deletion mutations suggest that fertilization controls tiller number in rice through transcriptional regulation of Os1900, and that a few promoter mutations alone can increase tiller numbers and grain yields even under minor-fertilizer conditions, whereas a single defective os1900 mutation does not increase tillers under normal fertilizer condition. Such Os1900 promoter mutations have potential uses in breeding programs for sustainable rice production.

Chloroplastic Sec14-like proteins modulate growth and phosphate deficiency responses in Arabidopsis and rice.

Phosphorus is an essential nutrient acquired from soil as phosphate (Pi), and its deficiency severely reduces plant growth and crop yield. Here, we show that single nucleotide polymorphisms (SNPs) at the PHOSPHATIDYLINOSITOL TRANSFER PROTEIN7 (AtPITP7) locus, which encodes a chloroplastic Sec14-like protein, are associated with genetic diversity regarding Pi uptake activity in Arabidopsis (Arabidopsis thaliana). Inactivation of AtPITP7 and its rice (Oryza sativa) homolog (OsPITP6) through T-DNA insertion and CRISPR/Cas9-mediated gene editing, respectively, decreased Pi uptake and plant growth, regardless of Pi availability. By contrast, overexpression of AtPITP7 and OsPITP6 enhanced Pi uptake and plant growth, especially under limited Pi supply. Importantly, overexpression of OsPITP6 increased tiller number and grain yield in rice. Targeted metabolome analysis of glycerolipids in leaves and chloroplasts revealed that inactivation of OsPITP6 alters phospholipid contents, independent of Pi availability, diminishing the reduction in phospholipid content and increase in glycolipid content induced by Pi deficiency; meanwhile, overexpression of OsPITP6 enhanced Pi deficiency induced metabolic alterations. Together with transcriptome analysis of ospitp6 rice plants and phenotypic analysis of grafted Arabidopsis chimeras, these results suggest that chloroplastic Sec14-like proteins play an essential role in growth modulations in response to changes in Pi availability, although their function is critical for plant growth under any Pi condition. The superior traits of OsPITP6-overexpressing rice plants also highlight the potential of OsPITP6 and its homologs in other crops as additional tools for improving Pi uptake and plant growth in low Pi environments.

Elevated CO2 Priming as a Sustainable Approach to Increasing Rice Tiller Number and Yield Potential

Tillering and yield are linked in rice, with significant efforts being invested to understand the genetic basis of this phenomenon. However, in addition to genetic factors, tillering is also influenced by the environment. Exploiting experiments in which seedlings were first grown in elevated CO2 (eCO2) before transfer and further growth under ambient CO2 (aCO2) levels, we found that even moderate exposure times to eCO2 were sufficient to induce tillering in seedlings, which was maintained in plants grown to maturity plants in controlled environment chambers. We then explored whether brief exposure to eCO2 (eCO2 priming) could be implemented to regulate tiller number and yield in the field. We designed a cost-effective growth system, using yeast to increase the CO2 level for the first 24 days of growth, and grew these seedlings to maturity in semi-field conditions in Malaysia. The increased growth caused by eCO2 priming translated into larger mature plants with increased tillering, panicle number, and improved grain filling and 1000 grain weight. In order to make the process more appealing to conventional rice farmers, we then developed a system in which fungal mycelium was used to generate the eCO2 via respiration of sugars derived by growing the fungus on lignocellulosic waste. Not only does this provide a sustainable source of CO2, it also has the added financial benefit to farmers of generating economically valuable oyster mushrooms as an end-product of mycelium growth. Our experiments show that the system is capable of generating sufficient CO2 to induce increased tillering in rice seedlings, leading eventually to 18% more tillers and panicles in mature paddy-grown crop. We discuss the potential of eCO2 priming as a rapidly implementable, broadly applicable and sustainable system to increase tillering, and thus yield potential in rice.

Natural variation in Tiller Number 1 affects its interaction with TIF1 to regulate tillering in rice.

Tiller number per plant-a cardinal component of ideal plant architecture-affects grain yield potential. Thus, alleles positively affecting tillering must be mined to promote genetic improvement. Here, we report a Tiller Number 1 (TN1) protein harbouring a bromo-adjacent homology domain and RNA recognition motifs, identified through genome-wide association study of tiller numbers. Natural variation in TN1 affects its interaction with TIF1 (TN1 interaction factor 1) to affect DWARF14 expression and negatively regulate tiller number in rice. Further analysis of variations in TN1 among indica genotypes according to geographical distribution revealed that low-tillering varieties with TN1-hapL are concentrated in Southeast Asia and East Asia, whereas high-tillering varieties with TN1-hapH are concentrated in South Asia. Taken together, these results indicate that TN1 is a tillering regulatory factor whose alleles present apparent preferential utilization across geographical regions. Our findings advance the molecular understanding of tiller development.

Identification of superior haplotypes for CCD8 regulating tiller number and grain yield in rice

Rice is one of the major food crops of the world. In the present day of increasing population there is an urgent need to increase the rice grain production. Yield is a complex trait and is mainly orchestrated by plant architecture. In the present study, a diverse set of 100 accessions from the 3K RG panel were evaluated for Carotenoid cleavage dioxygenase 8 (CCD8) loci which plays a role in altering tiller number which ultimately governs the crop yield. A normal phenotypic distribution for total tiller numbers and number of productive tillers was observed for the set of 100 accessions used in the study. Five non synonymous SNPs were present for CCD8 loci for the 100 rice 3K accessions in this study. Haplotype analysis was carried out using five non synonymous SNPs to understand the genetic diversity of the population and of which two significant SNPs in the positions 31223371 and 31223383 grouped the accessions into two haplotype H1 and H2 with the allelic combination of GC and AT respectively. Haplotype group H1 with 89 accessions and H2 with 8 accessions were formed. Among the two haplotype groups, H2 had the maximum mean value for both tiller number and productive tiller number indicating the superiority of the H2 allelic combination over H1. Hence H2 is considered as a superior haplotype that can be potentially explored for allele mining and can be used in future crop improvement programs. Keywords: CCD8, tiller number, genetic diversity, haplotype.

Designing an Interactively Cognitive Humanoid Field-Phenotyping Robot for In-Field Rice Tiller Counting

Field phenotyping is a crucial process in crop breeding, and traditional manual phenotyping is labor-intensive and time-consuming. Therefore, many automatic high-throughput phenotyping platforms (HTPPs) have been studied. However, existing automatic phenotyping methods encounter occlusion problems in fields. This paper presents a new in-field interactive cognition phenotyping paradigm. An active interactive cognition method is proposed to remove occlusion and overlap for better detectable quasi-structured environment construction with a field phenotyping robot. First, a humanoid robot equipped with image acquiring sensory devices is designed to contain an intuitive remote control for field phenotyping manipulations. Second, a bio-inspired solution is introduced to allow the phenotyping robot to mimic the manual phenotyping operations. In this way, automatic high-throughput phenotyping of the full growth period is realized and a large volume of tiller counting data is availed. Third, an attentional residual network (AtResNet) is proposed for rice tiller number recognition. The in-field experiment shows that the proposed method achieves approximately 95% recognition accuracy with the interactive cognition phenotyping platform. This paper opens new possibilities to solve the common technical problems of occlusion and observation pose in field phenotyping.

Dynamic Effect of Organic Fertilizer Application on Rice Growth, Soil Physicochemical Properties and Cd Activity Exposed to Excess Cd.

To investigate the dynamic effects of organic fertilizer application on the agronomic traits of rice (Oryza sativa L.), soil physicochemical properties and soil Cd activity under excess cadmium (Cd) exposure, this study was conducted to simulate a paddy system under different organic fertilizer application rates using exogenous spiked Cd soil as the test soil and conducting a rice pot experiment. The obtained results showed that the application of organic fertilizer increased the number of rice tillers, rice plant height, total grain number and total grain weight at maturity in all treated soils, while it decreased the concentration of Cd in brown rice. The application of organic fertilizer increased the organic matter (OM), redox potential and electrical conductivity of all treated soils but decreased the pH and TCLP-extractable Cd of all treated soils. There was a significant or highly significant negative correlation (p < 0.05 or p < 0.01) between soil TCLP-extractable Cd and soil OM throughout the experimental period, implying that soil OM may be an important factor influencing the changes in Cd activity in soil. In addition, our experiment also examined in detail the dynamic change process of the abovementioned indicators throughout the experimental period and observed that the dynamic change process of soil Cd activity could be described as a trend of first decreasing and then gradually increasing throughout the rice reproductive period.

Using nitrogen-loaded biochar for soil improvement to decrease applied nitrogen and stabilize rice yield under alternate wet-dry irrigation

Nitrogen (N) loss from paddy fields is an important cause of eutrophication and yield decrease. In order to minimize the negative impact of N loss, biochar was used as a medium for the sorption of ammonia from simulated wastewater and subsequently as a N releaser in the cultivation of rice plants under the N deficiency environment during two years. The experiment was conducted in a completely randomized block design, with a conventional fertilization treatment (N1C0), 10 t/hm2 or 20 t/hm2 N-loaded biochar and 25% less N fertilizer (N3/4C1, N3/4C2), and 10 t/hm2 or 20 t/hm2 N-loaded biochar and 50% less N fertilizer (N1/2C1, N1/2C2). The NH4+-N and NO3--N concentrations in surface water, the number of rice tillers, dry matter weight, and N uptake were measured. Results showed that the adsorption efficiency of the prepared N-loaded biochar to NH4+-N was 30.8%; reducing the amount of N fertilizer coupled with N-loaded biochar application reduced the average surface water concentration of NH4+-N by 15.44–43.62% within one week after rice transplantation; it also reduced the average surface water concentration of NO3--N during the whole growth period by 18.76–25.19%. In the late rice growth stage, the average concentration of NH4+-N in surface water was shown in descending order: N3/4C2 ＞N3/4C1 ＞ N1C0＞ N1/2C2 ＞ N1/2C1. Compared with N1C0, N3/4C2 did not clearly impacted the rice tiller numbers, the dry matter weight and N uptake of rice stems, leaves and panicles. In sum, under alternate wet-dry irrigation, 20 t/hm2 N-loaded biochar purified the eutrophic water in the irrigation area and permitted N fertilizer input to be reduced by 25%, which stabilized rice yield and was conductive to improving a spatial balance of “misplaced” N resource.

ADAPTATION TEST OF THE CONSORTIUM OF PHYLLOSPHERE MICROBES FM48 AND RIZOSPHERE MICROBES R15 TO STIMULATE GROWTH RICE PLANT IN PADDY FIELDS

Previous research has succeeded in obtaining a consortium of Phyllosphere microbes Fm48 anda consortium of rhizosphere microbes R15 which are the most effective in increasing the growth and yieldof rice plants in experimental pots. The consortium of microbes of Phyllosphere Fm48 and R15 microbesof rhizosphere have the ability to fix N2 from the air, dissolve P and secrete growth hormones. This studyaims to examine the effectiveness of the consortium of Phyllosphere microbes and rhizosphere microbes inadapting to the rice field environment and their ability to stimulate the growth of rice plants in paddy fields.The research was conducted in nurseries and transplanted plantings, using a completely randomized designconsisting of four treatments, namely: control, giving the consortia of Phyllosphere microbe Fm48, givingconsortium of rhizosphere microbesR15 and the combination of consortium s of Phyllosphere microbeFm48 and consortium of rhizosphere microbesR15. The data obtained were processed by analysis ofvariance and if there was a significant difference, it was continued with the Honest Significant Difference(HSD) test at the 1% level. The consortium of phyllosphere microbes Fm48 and consortium of rhizospheremicrobes R15 had no effect on rice growth in nurseries, but they were able to adapt to the rice fieldenvironment and stimulate rice plant growth even though its process was slow. The consortium ofphyllosphere microbes Fm48 and consortium of rhizosphere microbes R15 and their combination stimulatedthe growth of the number of leaves and the number of rice tillers.

Plant Distance Effect on Rice Cultivation System of Rice Intensification (SRI) Method on Tillers and Yield Numbers in East Sumba Regency

SRI is known as a set of methods to increase the productivity of paddy fields by changing the management of yields, soil, and fertilizers/nutrients. The main components of using the SRI method include: transferring young seedlings, planting one seed per hole, wide spacing, keeping the soil moist and not stagnant, controlling weeds by manual weeding, and adding soil organic matter. The study aims to determine the number of SRI rice tillers based on different spacing treatments and their effect on yield productivity. The results of the two treatments of plant spacing, namely 30 x 30 cm (A) and 20 x 10 cm (B) based on statistical tests using the T-Test, showed no significant difference between the two treatments on the number of tillers produced. While the yield showed that treatment A produced 4.27 tons/ha and treatment B was 4.7 tons/ha, so it concludes that spacing (A) had higher crops than spacing (B).

Establishment of a Rice Tiller Number Prediction Model Using Soil Compaction and Days after Transplanting

Soil compaction has a real effect on rice growth in the Mekong Delta. The correlation between soil compaction and rice growth (tiller number and plant height) in a paddy field in An Giang province was evaluated in the 2020 Winter-Spring and Summer-Autumn crops using the Pearson's correlation test. The research results show that soil compaction 0-20 cm from the soil surface has a positive correlation with rice tiller number, while the effect on plant height is non-significant. Therefore, a prediction model for rice tiller numbers is constructed using the Curve Fitting application in Matlab software. The obtained prediction models can effectively predict the number of rice tillers from the value of the 0-20 cm soil layer compaction at times under 40 DAT in the two studied crops. This study provides the optimal value of soil compaction (about 229.8 and 337.6 kPa in these crops), which can aid in the utilization of soil tillage for paddy rice cultivation by farmers.

Selenium Effect Threshold for Soil Nematodes Under Rice Biofortification.

Crop biofortification with inorganic selenium (Se) fertilizer is a feasible strategy to improve the health of residents in Se-deficient areas. For eco-friendly crop Se biofortification, a comprehensive understanding of the effects of Se on crop and soil nematodes is vital. In this study, a rice pot experiment was carried out to test how selenite supply (untreated control (0), 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 100, or 200 mg Se kg−1) in soil affected rice growth, rice Se accumulation, and soil nematode abundance and composition. The results showed that selenite supply (5–200 mg kg−1) generally increased the number of rice tillers, rice yield, and Se concentrations in rice grains. In soil under 10 mg kg−1 Se treatment, the genus composition of nematodes changed significantly compared with that in the control soil. With increased Se level (> 10 mg kg−1), soil nematode abundance decreased significantly. Correlation analysis also demonstrated the positive relationships between soil Se concentrations (total Se and bioavailable Se) with rice plant parameters (number of rice tillers, rice yield, and grain Se concentration) and negative relationships between soil Se concentrations (total Se and bioavailable Se) with soil nematode indexes (nematode abundance and relative abundance of Tobrilus). This study provides insight into balancing Se biofortification of rice and soil nematode community protection and suggests the effective concentrations for total Se (1.45 mg kg−1) and bioavailable Se (0.21 mg kg−1) to soil nematode abundances at 20% level (EC20) as soil Se thresholds. At Se concentrations below these thresholds, rice plant growth and Se accumulation in the grain will still be promoted, but the disturbance of the soil nematodes would be negligible.