Rice Tillering Research Articles

Discovery of aphid-transmitted Rice tiller inhibition virus from native plants through metagenomic sequencing.

A major threat to rice production is the disease epidemics caused by insect-borne viruses that emerge and re-emerge with undefined origins. It is well known that some human viruses have zoonotic origins from wild animals. However, it remains unknown whether native plants host uncharacterized endemic viruses with spillover potential to rice (Oryza sativa) as emerging pathogens. Here, we discovered rice tiller inhibition virus (RTIV), a novel RNA virus species, from colonies of Asian wild rice (O. rufipogon) in a genetic reserve by metagenomic sequencing. We identified the specific aphid vector that is able to transmit RTIV and found that RTIV would cause low-tillering disease in rice cultivar after transmission. We further demonstrated that an infectious molecular clone of RTIV initiated systemic infection and causes low-tillering disease in an elite rice variety after Agrobacterium-mediated inoculation or stable plant transformation, and RTIV can also be transmitted from transgenic rice plant through its aphid vector to cause disease. Finally, global transcriptome analysis indicated that RTIV may disturb defense and tillering pathway to cause low tillering disease in rice cultivar. Thus, our results show that new rice viral pathogens can emerge from native habitats, and RTIV, a rare aphid-transmitted rice viral pathogen from native wild rice, can threaten the production of rice cultivar after spillover.

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.

Prohexadione-calcium alleviates the leaf and root damage caused by salt stress in rice (Oryza sativa L.) at the tillering stage.

Salt stress, as a principal abiotic stress, harms the growth and metabolism of rice, thus affecting its yield and quality. The tillering stage is the key growth period that controls rice yield. Prohexadione-calcium (Pro-Ca) can increase the lodging resistance of plants by reducing plant height, but its effects on rice leaves and roots at the tillering stage under salt stress are still unclear. This study aimed to evaluate the ability of foliar spraying of Pro-Ca to regulate growth quality at the rice tillering stage under salt stress. The results showed that salt stress reduced the tillering ability of the rice and the antioxidant enzyme activity in the roots. Salt stress also reduced the net photosynthetic rate (Pn), stomatal conductance (Gs) and intercellular CO2 concentration (Ci) of the rice leaves and increased the contents of osmotic regulatory substances in the leaves and roots. The application of exogenous Pro-Ca onto the leaves increased the tiller number of the rice under salt stress and significantly increased the photosynthetic capacity of the leaves. Additionally, it increased the activities of antioxidant enzymes and the AsA content. The contents of an osmotic regulation substance, malondialdehyde (MDA), and H2O2 in the leaves and roots also decreased. These results suggested that Pro-Ca can increase the tillering ability, photosynthetic capacity, osmotic adjustment substance content levels and antioxidant enzyme activity levels in rice and reduce membrane lipid peroxidation, thus improving the salt tolerance of rice at the tillering stage.

OsPIN2 is involved in OsSPL14/17-inhibited tiller bud outgrowth in response to phosphate deficiency in rice

Phosphorus (P) is an essential nutrient for food crops. P-deficiency inhibits tiller development of rice; thus, an understanding of the P-modulated tiller development mechanism is crucial for grain yield. Auxin and strigolactones (SLs) have been implicated as regulators of tiller formation in rice. However, the relationships between the two in P-modulated tiller development are unclear. Here we found that low-P (LP) inhibited rice tiller formation and tiller bud elongation, with higher levels of SLs. The strong interaction between D53 (SL signaling repressor) and SPL14 and 17 (SPL14/17) inhibited their transcriptional activities under normal P (NP) condition, and mutations of SPL14/17 eliminated their inhibitory effects on tiller formation under LP condition, showing SPL14/17 act downstream of SLs signaling to inhibit tiller formation under P-deficiency in rice. Meanwhile, the expression levels of PIN2 were down-regulated under conditions of either LP and NP treated with GR24 when compared with NP condition, demonstrating SLs negative regulation of PIN2 transcription under LP condition. Further study showed that SPL14/17 inhibited the transcription expression of PIN2, and the knockout of PIN2 reduced tiller development by LP condition. Therefore, we presented that, under NP condition, bindings of D53 to SPL14/17 repress their transcriptional inhibition, reversing SPL14/17-inhibited PIN2 transcription and promoting tiller development. Proteasomal degradation of D53 releases SPL14/17, thus repressing PIN2 transcription and preventing production of tillering under LP condition.

Analysis of the Dynamics and Characteristics of Rice Stem Tillers via Water Level Management

Based on theoretical analysis and numerical calculations, this study systematically investigated the changes in rice tillering dynamics and the simulation of stem tiller growth during the tillering stage using the farm water level as a regulation index for rice irrigation and drainage. Based on pit testing, the results of this study show that both flooding and drought in the tillering stage suppress the tiller output of rice and have a certain compensating effect following rehydration. Heavy drought during the tillering period reduced the effective tiller rate, while flooding and light drought had little effect on the effective tiller rate. Flooding and maintaining a high infiltration rate also increased the effective tiller rate. The primary kinetic model of tiller elongation (DMOR) was a good fit for the tiller elongation process (coefficients of determination of 0.99 or higher). In addition, the growth and extinction rates of the stem tiller extinction curves were fitted. The maximum growth rate of the stem tiller growth segment was ranked as CK > L1 > H1 > L2 > H2, and the maximum extinction rate of the stem tiller extinction segment was ranked as CK > H2 > H1 > L2 > L1, indicating that both flooding and drought during the tillering stage could reduce the growth and extinction rates of the stem tiller. This shows that both flooding and drought can reduce the growth and extinction rates of tillers.

Insect Herbivory on Main Stem Enhances Induced Defense of Primary Tillers in Rice (Oryza sativa L.).

Clonal plants are interconnected to form clonal plant networks with physiological integration, enabling the reassignment as well as sharing of resources among the members. The systemic induction of antiherbivore resistance via clonal integration may frequently operate in the networks. Here, we used an important food crop rice (Oryza sativa), and its destructive pest rice leaffolder (LF; Cnaphalocrocis medinalis) as a model to examine defense communication between the main stem and clonal tillers. LF infestation and MeJA pretreatment on the main stem for two days reduced the weight gain of LF larvae fed on the corresponding primary tillers by 44.5% and 29.0%, respectively. LF infestation and MeJA pretreatment on the main stem also enhanced antiherbivore defense responses in primary tillers: increased levels of a trypsin protease inhibitor, putative defensive enzymes, and jasmonic acid (JA), a key signaling compound involved in antiherbivore induced defenses; strong induction of genes encoding JA biosynthesis and perception; and rapid activation of JA pathway. However, in a JA perception OsCOI RNAi line, LF infestation on main stem showed no or minor effects on antiherbivore defense responses in primary tillers. Our work demonstrates that systemic antiherbivore defense operate in the clonal network of rice plants and JA signaling plays a crucial role in mediating defense communication between main stem and tillers in rice plants. Our findings provide a theoretical basis for the ecological control of pests by using the systemic resistance of cloned plants themselves.

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.

LAZY3 interacts with LAZY2 to regulate tiller angle by modulating shoot gravity perception in rice.

Starch biosynthesis in gravity-sensing tissues of rice shoot determines the magnitude of rice shoot gravitropism and thus tiller angle. However, the molecular mechanism underlying starch biosynthesis in rice gravity-sensing tissues is still unclear. We characterized a novel tiller angle gene LAZY3 (LA3) in rice through map-based cloning. Biochemical, molecular and genetic studies further demonstrated the essential roles of LA3 in gravity perception of rice shoot and tiller angle control. The shoot gravitropism and lateral auxin transport were defective in la3 mutant upon gravistimulation. We showed that LA3 encodes a chloroplast-localized tryptophan-rich protein associated with starch granules via Tryptophan-rich region (TRR) domain. Moreover, LA3 could interact with the starch biosynthesis regulator LA2, determining starch granule formation in shoot gravity-sensing tissues. LA3 and LA2 negatively regulate tiller angle in the same pathway acting upstream of LA1 to mediate asymmetric distribution of auxin. Our study defined LA3 as an indispensable factor of starch biosynthesis in rice gravity-sensing tissues that greatly broadens current understanding in the molecular mechanisms underlying the starch granule formation in gravity-sensing tissues, and provides new insights into the regulatory mechanism of shoot gravitropism and rice tiller angle.

Improving the value of CO2 and biogas slurry in agricultural applications: A rice cultivation case

To cope with the global warming caused by CO2 concentration rising, it should be considered to supply CO2 into plants through other suitable forms for encouraging more CO2 uptake by plants. In this study, the physiological toxicity of CO2-stored biogas slurry to crops and its application prospects were investigated using biogas slurry as a carrier to convert CO2 into HCO3- for plant planting. The results showed that the physiological toxicity of biogas slurry after CO2 absorption (i.e., CO2-rich biogas slurry, CRBS) to rice diminishes. Compared with the biogas slurry without storing CO2, the pH values of CRBS and the CO2-rich 5-times concentrated biogas slurry (CR5BS) decrease significantly by 14.5% and 18.5% respectively, and the EC values increase significantly by 49.1% and 19.0%, respectively. The rice cultivated with CRBS and CR5BS have the higher root activities by 86.9% and 29.0% than the rice cultivated with biogas slurry without CO2-storage, respectively. When using CRBS and CR5BS, the physiological toxicity of HCO3- to rice decreases, offering a favorable rhizosphere environment for rice growth. Adopting CRBS and CR5BS can promote the tillering of rice and shorten the tillering stage of rice, when compared to irrigate the biogas slurry without CO2-storage. Similarly, compared with the rice cultivated with biogas slurry without CO2-storage, the accumulation of nitrogen and ferrum by rice cultivated in CRBS increases by 78.2% and 26.1%, respectively. The corresponding values increase by 72.3% and 29.8% for the case adopting CR5BS.

Overexpression of gibberellin 2-oxidase 4 from tall fescue affected plant height, tillering and drought tolerance in rice

Gibberellin (GA) is an important phytohormone that regulates plant growth and development. GA-2-oxidases (GA2oxs) have been found to affect plant height, tillering and stress tolerance by inactivating endogenous bioactive GAs. The present study aimed to isolate GA2oxs genes from tall fescue (Festuca arundinacea), analyze their expression level under abiotic stresses (10% PEG6000 induced drought stress, 150 mM NaCl induced salt stress, heat stress at 38 °C, and cold stress at 4 °C) and search for valuable genes for improving stress tolerance. Among eight FaGA2ox genes, FaGA2ox4 was found to represent a highest expression level at 24 h of PEG-induced drought stress and was chosen for further analysis. Compared with wildtype plants, transgenic rice plants overexpressing FaGA2ox4 exhibited a dwarf and high-tillering phenotype and the dwarf phenotype was partially compensated by foliar application of 10 μM GA3. In addition, transgenic plants showed improved drought stress tolerance, as manifested by higher leaf relative water content and lower electrolyte leakage than wildtype. Further qRT-PCR analysis demonstrated that the enhanced drought stress tolerance may be associated with decreased expression levels of genes involved in chlorophyll degradation (OsSGRL) and GA synthesis (OsGA3ox1) as well as increased expression of ABA-synthesizing gene (OsNCED3) in transgenic plants overexpressing FaGA2ox4.

Winter crop rotation intensification to increase rice yield, soil carbon, and microbial diversity

Crop rotation has widely contributed to increasing farmland biodiversity as well as to improving soil carbon pools and microbial diversity. However, there is a weak understanding of the suitability of winter crop rotation intensification in double rice fields, especially rotation with various winter crops. For this task, a long-term field experiment based on one from 2012 was conducted with five winter crop systems for double rice: winter fallow (T0), winter milk vetch (T1), winter rape (T2), winter garlic (T3), winter rotation intensification with potato, milk vetch, and rape (T4). Parameters such as crop yield, soil carbon, nitrogen, and soil microorganism were measured. It was found that compared to winter fallow, winter milk vetch, rape, garlic, and crop rotation intensification practices increased the late rice yield by 2.5%, 2.3%, 4.5%, and 3.7%, respectively; winter garlic and crop rotation intensification also increased the early rice yield by 4.6% and 3.5%, respectively. This is associated with the promotion of rice tillering. At the same time, for winter crop rotation, compared to winter fallow, the soil organic carbon increased by 21%. With the input of diversified crop residues, winter crops were effective in soil carbon sequestration, improving soil microbial structure, and increasing soil microbial diversity. The Shannon diversity index of winter crops ranged from 9.75 to 9.91, while winter fallow was 9.38. The Simpson’s diversity index of winter crops ranged from 0.997 to 0.998, while winter fallow was 0.996. In conclusion, winter crop practices, especially winter crop rotation intensification, can enhance soil health and sustainability in double rice fields through its positive feedback on crop yield, soil carbon sequestration, and microorganisms.

Effect of rice/cassava rotation on agronomic parameters of rice and cassava grown on Ferralsol in western Côte d'Ivoire

The rice/cassava rotation is one of the dominant rice-based cropping systems in western Côte d'Ivoire due to the inaccessibility of chemical fertilisers. The low productivity of this cropping system makes it necessary to think about improving agronomic performance. The objective of this study is to determine the effect of the rice/cassava rotation on the agronomic parameters of these crops. To achieve this objective, an agronomic trial was set up at the CNRA Research Station in Man on a Ferralsol. Five cropping sequences were compared in a Fischer block design with 5 treatments and 4 replications: 2 intensive monocultures of rice (0.20 m × 0.20 m) and cassava (1 m × 1 m) and 3 alternations of rice and cassava (R/M/R, M/R/M and R/R/M (farmer control)). The parameters measured were height, tillering, and yield of rice and cassava, as well as soil chemical parameters. The results showed that rice in rotation with cassava had a significant effect on cassava production, while cassava had no significant effect on rice grain yield. The rice-cassava rotation harmed soil chemical parameters. Except for the improvement of nitrogen and phosphorus contents due to biochemical reactions in the rhizosphere and the mobility of nutrients along the fertility gradient. Finally, R/M/R was found to be the best cropping sequence in a rice-based cropping system.

PROG1 acts upstream of LAZY1 to regulate rice tiller angle as a repressor

Rice tiller angle, as a component of plant architecture, affects rice grain yield via plant density. However, the molecular mechanism underlying rice tiller angle remains elusive. We report that the key domestication gene PROSTRATE GROWTH 1 (PROG1) controls rice tiller angle by regulating shoot gravitropism and LAZY1 (LA1)-mediated asymmetric distribution of auxin. Acting as a transcriptional repressor, PROG1 negatively regulates the expression of LA1 in light-grown rice seedlings. Overexpression of LA1 partially rescued the larger tiller angle of the PROG1 complementation transgenic plant (prog1-D). Double-mutant analysis showed that PROG1 acts upstream of LA1 to regulate shoot gravitropism and tiller angle. Mutation of Suppressors of lazy1 (SOL1), encoding DWARF3 (D3) acting in the strigolactone signal pathway, suppressed the large tiller angle of prog1-D by rescuing the transcription of LA1. The discovery of a light-sensitive PROG1-LA1 transcription regulatory module controlling rice shoot gravitropism and tiller angle sheds light on the genetic control of rice tiller angle.

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.

Research on Precise Fertilization Method of Rice Tillering Stage Based on UAV Hyperspectral Remote Sensing Prescription Map

Tillering fertilization is an important part of field management in rice production. As the first peak fertilizer requirement period of rice, tillering fertilization directly affects the number of tillers and the growth of rice in the middle and late stages. In order to investigate a method of constructing an accurate fertilizer prescription map in the tillering stage using an unmanned aerial vehicle (UAV) remote sensing nitrogen demand diagnosis and reduce the amount of chemical fertilizer while ensuring the rice yield, this study realized the diagnosis of the rice nitrogen nutrient demand using UAV hyperspectral remote sensing during the tilling stage fertilization window. The results showed that the fertilizer amount was determined using the characteristic waveband and remote sensing. The results showed that five rice hyperspectral variables were extracted in the range of 450–950 nm by the feature band selection and feature extraction for the inversion of rice nitrogen content, and the inversion model of rice nitrogen content constructed by the whale-optimized extreme learning machine (WOA-ELM) was better than that constructed by the whale-optimized extreme learning machine (ELM). The model coefficient of determination was 0.899 and the prescription map variable fertilizer application method based on the nitrogen content inversion results reduced the nitrogen fertilizer by 23.21%. The results of the study can provide data and a model basis for precise variable fertilizer tracking by agricultural drones in the cold rice tillering stage.

Canonical strigolactones are not the major determinant of tillering but important rhizospheric signals in rice.

Strigolactones (SLs) are a plant hormone inhibiting shoot branching/tillering and a rhizospheric, chemical signal that triggers seed germination of the noxious root parasitic plant Striga and mediates symbiosis with beneficial arbuscular mycorrhizal fungi. Identifying specific roles of canonical and noncanonical SLs, the two SL subfamilies, is important for developing Striga-resistant cereals and for engineering plant architecture. Here, we report that rice mutants lacking canonical SLs do not show the shoot phenotypes known for SL-deficient plants, exhibiting only a delay in establishing arbuscular mycorrhizal symbiosis, but release exudates with a significantly decreased Striga seed-germinating activity. Blocking the biosynthesis of canonical SLs by TIS108, a specific enzyme inhibitor, significantly lowered Striga infestation without affecting rice growth. These results indicate that canonical SLs are not the determinant of shoot architecture and pave the way for increasing crop resistance by gene editing or chemical treatment.

Temporal dynamics of total and active root-associated diazotrophic communities in field-grown rice

Plant-associated nitrogen-fixing microorganisms (diazotrophs) are essential to host nutrient acquisition, productivity and health, but how host growth affects the succession characteristics of crop diazotrophic communities is still poorly understood. Here, Illumina sequencing of DNA- and RNA-derived nifH genes was employed to investigate the dynamics of total and active diazotrophic communities across rhizosphere soil and rice roots under four fertilization regimes during three growth periods (tillering, heading and mature stages) of rice in 2015 and 2016. Our results indicated that 71.9–77.2% of the operational taxonomic units (OTUs) were both detected at the DNA and RNA levels. According to the nonmetric multidimensional scaling ordinations of Bray–Curtis distances, the variations in community composition of active rhizosphere diazotrophs were greater than those of total rhizosphere diazotrophs. The community composition (β-diversity) of total and active root-associated diazotrophs was shaped predominantly by microhabitat (niche; R2 ≥ 0.959, p < 0.001), followed by growth period (R2 ≥ 0.15, p < 0.001). The growth period had a stronger effect on endophytic diazotrophs than on rhizosphere diazotrophs. From the tillering stage to the heading stage, the α-diversity indices (Chao1, Shannon and phylogenetic diversity) and network topological parameters (edge numbers, average clustering coefficient and average degree values) of total endophytic diazotrophic communities increased. The proportions of OTUs shared by the total rhizosphere and endophytic diazotrophs in rhizosphere diazotrophs gradually increased during rice growth. Moreover, total diazotrophic α-diversity and network complexity decreased from rhizosphere soil to roots. Collectively, compared with total diazotrophic communities, active diazotrophic communities were better indicators of biological response to environmental changes. The host microhabitat profoundly drove the temporal dynamics of total and active root-associated diazotrophic communities, followed by the plant growth period.

Absence of 4’ methyl on the d-ring of strigolactone does not prevent inhibition of tillering in rice through activation of the strigolactone signaling pathway

Absence of 4’ methyl on the d-ring of strigolactone does not prevent inhibition of tillering in rice through activation of the strigolactone signaling pathway

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.

Image-Based Phenotyping for Non-Destructive In Situ Rice (Oryza sativa L.) Tiller Counting Using Proximal Sensing.

The increase in the number of tillers of rice significantly affects grain yield. However, this is measured only by the manual counting of emerging tillers, where the most common method is to count by hand touching. This study develops an efficient, non-destructive method for estimating the number of tillers during the vegetative and reproductive stages under flooded conditions. Unlike popular deep-learning-based approaches requiring training data and computational resources, we propose a simple image-processing pipeline following the empirical principles of synchronously emerging leaves and tillers in rice morphogenesis. Field images were taken by an unmanned aerial vehicle at a very low flying height for UAV imaging—1.5 to 3 m above the rice canopy. Subsequently, the proposed image-processing pipeline was used, which includes binarization, skeletonization, and leaf-tip detection, to count the number of long-growing leaves. The tiller number was estimated from the number of long-growing leaves. The estimated tiller number in a 1.1 m × 1.1 m area is significantly correlated with the actual number of tillers, with 60% of hills having an error of less than ±3 tillers. This study demonstrates the potential of the proposed image-sensing-based tiller-counting method to help agronomists with efficient, non-destructive field phenotyping.