Plant Type Rice Research Articles

QTL analysis for soil‐surface roots originating from a New Plant Type rice (Oryza sativa L.)

AbstractThe introgression line YTH16 harbouring chromosome segments from the New Plant Type cultivar IR65600–87–2‐2–3 with genetic background of an Indica Group rice IR 64 forms soil‐surface roots. To clarify the genetic mechanism, QTL analysis was performed using hybrid populations derived from a cross between IR 64 and YTH16. A total of eight QTLs were detected in the three introgressed segments on chromosomes 2, 5 and 7. Seven chromosome segment lines (CSLs) combining these three QTL regions were selected from the progenies. The two CSLs harbouring a single region (excluding the CSL with a region on chromosome 5) showed high scores and low means of root angle distribution in comparison with IR 64. Four CSLs harbouring two or three regions showed high scores and low means of root angle distribution in comparison with YTH16 and the CSLs harbouring a single QTL region. These results indicated that the soil‐surface rooting of YTH16 was controlled by the three QTLs’ regions and that chr. 5 particularly played a role in supporting the effect with others.

Optimasi Konsentrasi Asetosiringon dan Higromisin dalam Transformasi Genetik Padi Fatmawati dengan Perantaraan Agrobacterium tumefaciens

Protocols for genetic transformation of rice have been widely developed, however the protocols are not universal and inapplicable for all types of rice plants directly. Transformation protocol on rice cv. Fatmawati needs to be developed to generate transgenic lines. The present research was carried out to optimize genetic transformation protocol in rice cv. Fatmawati mediated by Agrobacterium tumefaciens harboring pCambia1301 construct using immature embryo as an explant. The experiment was arranged in a completely randomized design. Factors influencing efficiency of transformation, i.e., sensitivity of callus to hygromycin antibiotic, acetosyringone concentration used in cultivation medium, hygromycin concentration for transformant selection were optimized. The results showed that genetic transformation of rice cv. Fatmawati mediated by A. tumefaciens using immature embryos have been successfully carried out with several parameters. Addition of 100 µM acetosyringone in co-cultivation medium and 30 mg L-1 hygromycin for transformant callus selection were optimal for genetic transformation of rice cv. Fatmawati mediated by A. tumefaciens. Transformation efficiency was found to be 7.84% based on the lines carrying the hpt gene. This result would be a valuable reference in genetic transformation of rice cv. Fatmawati using target genes.Keywords: immature embryo, Oryza sativa, pCambia1301, transformation efficiency

Evaluation of some new plant type of upland rice (Oryza sativa L.) lines derived from cross breeding for the growth and yield characteristics

Improving rice production through cross breeding is one of the efforts to overcome a major challenge in future need of rice consumers. An experiment was conducted to evaluate different upland rice lines for their growth and yield characteristics. Four rice lines including GS44-2 (V1), GS16-2 (V2), GS44-1 (V3), and GS16-1 (V4) were evaluated in a randomized complete block design (RCBD). The variables observed were vegetative character and generative character including grain yield. Data on various growth and yield characteristics revealed there were growth and yield characteristics different among breeding lines of local upland rice. Plant height at age 84 DAP, GS16-2 line was the tallest (92.71 cm) and GS44-1 line the shortest one (70.07 cm). Breeding line of GS16-2 produced higher leaf area (61.0 cm2), panicle length (30.94 cm), grain number per panicle (230.60), and filled grain number (190.25). The lowest unfilled grain percentage (26.67 %) was also recorded from GS16-2 lines. The highest number of tillers, number of productive tillers, grain dry weight, and grain yield were obtained from GS44-2 lines. Further, grain yield component such as grain dry weight and 1000 grain weight recorded positive and significant correlation with number of productive tillers per hill.

Relative grain zinc loading ability of cereals (rice, wheat, maize) and a grain legume (chickpea)

Data from field experiments conducted at the ICAR-Indian Agricultural Research Institute, New Delhi, India during the last few years on Zn biofortification of the cereals, viz. wheat (Triticum asestivum L.), rice (Oryza sativa L.) and maize (Zea mays L.) and a grain legume (chickpea) were utilized in studying the comparative efficiency of these crops in grain Zn loading. Although Zn uptake per tonne of grain produced was the highest, the grain Zn loading was the lowest in rice. Zn concentration in grain (an intensity factor) was the highest in wheat at 46.8 mg/kg, closely followed by maize at 45.1 mg/kg, chickpea at 41.8 mg/kg and was the least for rice kernels at 21.2 mg/kg. ZnHI (a capacity factor for measuring grain Zn loading) was also the highest for wheat at 51%, followed by chickpea at 39.3%, maize at 35.9% and was the least for rice at 17.9%. Further, rice grain contains husk (about one-third by weight) and only kernel is consumed, for which ZnHI was only 6.3%; a major part of Zn loaded on grain in rice goes to the husk. Thus, from the Zn nutrition point of view rice is the poorest cereal. However, rice deserves utmost attention, because it is the staple food in South, Southeast and East Asia, where about 62.5% of the world’s people live and hunger and malnutrition is rampant. Since most grain Zn loading in rice is from the Zn absorbed by the roots through xylem in contrast to other crops, where it is mostly achieved through mobilization of Zn in the vegetative tissue through phloem, it is suggested that rice plant types using grain Zn loading through phloem be developed. It is necessary, because applied Zn gets fixed or precipitated in soil through several mechanisms and its availability to rice plants gets reduced as it reaches grain filling stage.

Studies of the relationship between rice stem composition and lodging resistance

AbstractPlant height and lodging resistance can affect rice yield significantly, but these traits have always conflicted in crop cultivation and breeding. The current study aimed to establish a rapid and accurate plant type evaluation mechanism to provide a basis for breeding tall but lodging-resistant super rice varieties. A comprehensive approach integrating plant anatomy and histochemistry was used to investigate variations in flexural strength (a material property, defined as the stress in a material just before it yields in a flexure test) of the rice stem and the lodging index of 15 rice accessions at different growth stages to understand trends in these parameters and the potential factors influencing them. Rice stem anatomical structure was observed and the lignin content the cell wall was determined at different developmental stages. Three rice lodging evaluation models were established using correlation analysis, multivariate regression and artificial radial basis function (RBF) neural network analysis, and the results were compared to identify the most suitable model for predicting optimal rice plant types. Among the three evaluation methods, the mean residual and relative prediction errors were lowest using the RBF network, indicating that it was highly accurate and robust and could be used to establish a mathematical model of the morphological characteristics and lodging resistance of rice to identify optimal varieties.

Relationship between Rubisco activase and Rubisco contents in transgenic rice plants with overproduced or decreased Rubisco content

ABSTRACTOverproduction of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco; E.C. 4.1.1.39) in rice did not necessarily improve photosynthesis. The reason for this was that a partial deactivation of Rubisco occurred in RBCS-overexpressed rice plants. Since a negative correlation between the amounts of Rubisco activase (RCA) and Rubisco has been reported for plants with overproduced or decreased RCA, the possibility that RCA content declines in RBCS-overexpressed rice plants was considered. The relationship between RCA and Rubisco contents was examined in RBCS-overexpressed and RBCS-antisense rice plants. Whereas the ratio of RCA to Rubisco contents in RBCS-antisense plants increased three- to fourfold as compared with that of the wild-type levels, this ratio decreased 60–70% of the wild-type levels in RBCS-overexpressed rice plants. Thus, an apparent trade-off between the amounts of RCA and Rubisco was observed in RBCS-transgenic rice plants. However, the amounts of several Calvin–Benson cycle enzymes changed in a similar manner to that of RCA in both types of RBCS-transgenic rice plants. When the relationships between the amounts of these enzymes, including RCA, and those of total leaf-N minus Rubisco-N and trichloroacetic acid (TCA)-soluble N were examined, there were no differences between them irrespective of genotypes. These results indicate that the negative correlation between the amounts of RCA and Rubisco in RBCS-transgenic rice plants is the result of a change in N allocation to Rubisco in transgenic rice plants rather than a trade-off. Such a negative correlation was also found for other Calvin–Benson cycle enzymes. In addition, since the amounts of these Calvin–Benson cycle enzymes and RCA were highly correlated with their mRNA levels irrespective of genotype, it is suggested that changes in the amounts of these proteins are regulated at their transcript levels by a change in N allocation to Rubisco.

Optimization of Nitrogen Fertilization and Seedling Density of A New Rice Type (Oryza sativa L.) “IPB 3S”

The new plant type of rice, or ‘padi tipe baru’ (PTB) in Indonesian, is a new group of rice cultivars with a higher productivity compared to the modern rice varieties (‘varietas unggul baru’ or VUB). This study was conducted to determine the optimum dose of nitrogen fertilization and the seedling density or number of seedlings per hill to increase growth and yield of the new type of rice “IPB 3”. The experiment was conducted in the Bogor Experimental Station in January to June 2015. Nitrogen doses (90, 120, 150, 180 kg N.ha-1) and number of seeds per hill (1, 5, 10, 15 and 20) were tested. The results showed that the increased dose of nitrogen fertilizer reduced the percentage of filled grains, the rate of photosynthesis and the grain yield per hectare. Similarly, an increase in the seedling density up to 15 seeds decreased the dry matter of the crop, the number of grains per panicle, and grain weight per plant, but increased the grain yield per hectare. The optimum yield of “IPB 3S” was achieved with 90 kg N.ha-1 with 15 seeds per hill. The results of this study have provided a guideline for an improved nitrogen management in relation to rice seedling population to increase yield of a new rice type “IPB3S”.Keywords: “IPB 3S”, new plant type, fertilizer, local variety

Non-canonical regulation of SPL transcription factors by a human OTUB1-like deubiquitinase defines a new plant type rice associated with higher grain yield

Achieving increased grain productivity has long been the overriding focus of cereal breeding programs. The ideotype approach has been used to improve rice yield potential at the International Rice Research Institute and in China. However, the genetic basis of yield-related traits in rice remains unclear. Here, we show that a major quantitative trait locus, qNPT1, acts through the determination of a 'new plant type' (NPT) architecture characterized by fewer tillers, sturdier culms and larger panicles, and it encodes a deubiquitinating enzyme with homology to human OTUB1. Downregulation of OsOTUB1 enhances meristematic activity, resulting in reduced tiller number, increased grain number, enhanced grain weight and a consequent increase in grain yield in rice. Unlike human OTUB1, OsOTUB1 can cleave both K48- and K63-linked polyubiquitin. OsOTUB1 interacts with the E2 ubiquitin-conjugating protein OsUBC13 and the squamosa promoter-binding protein-like transcription factor OsSPL14. OsOTUB1 and OsSPL14 share common target genes, and their physical interaction limits K63-linked ubiquitination (K63Ub) of OsSPL14, which in turn promotes K48Ub-dependent proteasomal degradation of OsSPL14. Conversely, loss-of-function of OsOTUB1 is correlated with the accumulation of high levels of OsSPL14, resulting in the NPT architecture. We also demonstrated that pyramiding of high-yielding npt1 and dep1-1 alleles provides a new strategy for increasing rice yield potential above what is currently achievable.

Fine mapping of a quantitative trait locus for spikelet number per panicle in a new plant type rice and evaluation of a near-isogenic line for grain productivity.

Total spikelet number per panicle (TSN) is one of the determinants of grain productivity in rice (Oryza sativa L.). In this study, we attempted to detect quantitative trait loci (QTLs) for TSN in the introgression lines with high TSN, derived from the cross of Indica Group variety IR 64 with new plant type lines. Two QTLs were detected on the long arm of chromosome 12: qTSN12.1 in the BC4F2 population of YTH63/IR 64 and qTSN12.2 in the BC4F3 population of YTH83/IR 64. TSN of the main tiller was significantly higher in near-isogenic lines (NILs) for qTSN12.1 (IR 64-NIL1; 188.6) and for qTSN12.2 (IR 64-NIL12; 199.4) than in IR 64 (141.2), owing to a significant increase in both primary and secondary branch numbers. These results suggest the critical function of these QTLs in the promotion of rachis branching at the panicle formation stage. Fine mapping of qTSN12.2 revealed six candidate genes in a 92-kb region of the Nipponbare reference genome sequence between flanking markers RM28746 and RM28753. Detailed phenotyping of agronomic traits of IR 64-NIL12 carrying qTSN12.2 showed drastic changes in plant architecture: this line had lower panicle number, longer culm, and longer and wider leaves compared with IR 64. Percentage of fertility and 1000-grain weight tended to be greater, and grain yield per square meter was also greater in IR 64-NIL12 than in IR 64. The newly identified QTLs will be useful for genetic improvement of the yield potential of Indica Group varieties. The markers tightly linked to qTSN12.2 are available for marker-assisted breeding.

Fine Mapping and Candidate Gene Analysis of the Tiller Suppression Gene ts1 in Rice.

Tiller number is one of the key factors that influences rice plant type and yield components. In this study, an EMS-induced rice tiller suppression mutant ts1 was characterized. Morphological and histological observations revealed that, in the ts1 plants, the tiller buds were abnormally formed and therefore cannot outgrow into tillers. With an F2 population derived from a cross between ts1 and an indica cultivar Wushansimiao, a major gene, tiller suppression 1 (ts1) was fine-mapped to a 108.5 kb genomic region between markers ID8378 and SSR6884 on the short arm of rice chromosome 2. Candidate gene analysis identified nineteen putative genes. Among them, ORF4 (LOC_Os02g01610) is a PPR gene which harbored a point mutation c.+733/C→T in ts1 mutant plants. A co-dominant SNP marker cd-733C/T was subsequently developed and the SNP assay demonstrated that the point mutation co-segregated with tiller suppression phenotype. Quantitative RT-PCR analysis showed that the expression level of ORF4 in ts1 plants was significantly lower than that in their wild plants, and the expression of rice tillering regulators MOC1 and HTD1 was also significantly decreased in ts1 plants. Our data indicated that ORF4 was a strong candidate gene for ts1 and ts1 might play a role in regulating rice tillering through MOC1 and HTD1 associated pathway. The results above provide a basis for further functional characterization of ts1 and will shed light on molecular mechanism of rice tillering. The informative SNP marker cd-733C/T will facilitate marker-assisted selection of ts1 in rice plant type breeding.

Kultur Antera untuk Percepatan Perakitan Varietas Padi di Indonesia

<p>Rice is a staple<br />food crop in Indonesia, while the need is increasing due to<br />high rice consumption as well as population increase. The<br />problems can be solved through increase of national rice<br />production. Productivity of lowland and upland should be<br />increased intensively and other potential dry area outside<br />Java and Bali Islands should be considered for extending the<br />area of production. Recently, high yielding variety such as<br />semi dwarf variety, hybrid rice, and new plant type of rice<br />were being developed by Indonesian breeders. However,<br />new method is needed to complement conventional<br />breeding method in order to accelerate rice breeding.<br />Anther culture is one of in vitro culture techniques that can<br />be used to accelerate the obtainment of pure lines through<br />doubled-haploids (DHs) regenerated at first generation of<br />culture for less than one year. Thus, application of anther<br />culture in conventional breeding will increase the efficiency<br />of selection process as well as reducing the cost for labour,<br />land and breeder’s time. The obtainment of green plantlets<br />derived from anther culture of indica rice subspecies has<br />been improved by the addition of 1 mM putrescine into<br />induction and regeneration media. Recently, several upland<br />rice lines tolerant to abiotic stresses (i.e. low light intensity<br />and aluminum toxicity) and biotic stresses (i.e. leaf and<br />neck blast), several lowland rice/paddy lines tolerant to<br />biotic stresses (i.e. bacterial leaf blight and blast), and<br />several hybrid parental lines (i.e. male sterile, maintainer<br />and restorer) were obtained in 2-3 years from several rice<br />breeding program involving anther culture. However,<br />potential use anther culture to provide unique genetic<br />material for mapping populations for use in functional<br />genomics and molecular breeding has not been explored.<br />The results indicated that anther culture is a feasible<br />technology that can be used for accelerating rice breeding<br />program in Indonesia.</p>

Joint Mapping and Allele Mining of the Rolled Leaf Trait in Rice (Oryza sativa L.).

The rolled leaf trait, long considered to be a key component of plant architecture, represents an important target trait for improving plant architecture at the population level. We therefore performed linkage mapping using a set of 262 highly variable RILs from two rice cultivars (Minghui 63 and 02428) with minor differences in leaf rolling index (LRI) in conjunction with GWAS mapping of a random subset of the 1127 germplasms from the 3K Rice Genomes Project (3K Rice). A total of seven main-effect loci were found to underlie the transgressive segregation of progenies from parents with minor differences in LRI. Five of these loci were previously identified and two (qRl7b and qRl9b) are newly reported with additional evidence from GWAS mapping for qRl7b. A total of 18 QTLs were identified by GWAS, including four newly identified QTLs. Six QTLs were confirmed by linkage mapping with the above RIL population, and 83.3% were found to be consistent with previously reported loci based on comparative mapping. We also performed allele mining with representative SNPs and identified the elite germplasms for the improvement of rolled leaf trait. Most favorable alleles at the detected loci were contributed by various 3K Rice germplasms. By a re-scanning of the candidate region with more saturated SNP markers, we dissected the region harboring gRl4-2 into three subregions, in which the average effect on LRI was 3.5% with a range from 2.4 to 4.1% in the third subregion, suggesting the presence of a new locus or loci within this region. The representative SNPs for favorable alleles in the reliable QTLs which were consistently identified in both bi-parental mapping and GWAS, such as qRl4, qRl5, qRl6, qRl7a, and qRl7b will be useful for future molecular breeding programs for ideal plant type in rice.

Genetic algorithm based approach to optimize phenotypical traits of virtual rice

How to select and combine good traits of rice to get high-production individuals is one of the key points in developing crop ideotype cultivation technologies. Existing cultivation methods for producing ideal plants, such as field trials and crop modeling, have some limits. In this paper, we propose a method based on a genetic algorithm (GA) and a functional-structural plant model (FSPM) to optimize plant types of virtual rice by dynamically adjusting phenotypical traits. In this algorithm, phenotypical traits such as leaf angles, plant heights, the maximum number of tiller, and the angle of tiller are considered as input parameters of our virtual rice model. We evaluate the photosynthetic output as a function of these parameters, and optimized them using a GA. This method has been implemented on GroIMP using the modeling language XL (eXtended L-System) and RGG (Relational Growth Grammar). A double haploid population of rice is adopted as test material in a case study. Our experimental results show that our method can not only optimize the parameters of rice plant type and increase the amount of light absorption, but can also significantly increase crop yield.

Penampilan Galur Harapan Mutan Dihaploid Padi Tipe Baru di Sulawesi Selatan

<p>ABSTRACT</p><p>South Sulawesi is known as one of national rice production centers. However, average productivity of rice varieties planted in that area (4.43 ton ha-1) is lower than those of rice productivity in Java (5.25 ton ha-1). The aims of this research were to evaluate agronomic characters and adaptation of 7 dihaploid mutant advanced lines of new plant type (DH-NPT) of rice at several locations in South Sulawesi. The research was conducted in 2012 at Maros, Gowa, Barru, and Pangkep. The experiments were conducted in randomized complete block design with 3 replications nested in locations. Treatment consisted of 7 DH-NPT of rice, i.e., BIO-MF115, BIO-MF116, BIO-MF125, BIO-MF130, BIO-MF133, BIO-MF151, BIO-MF153, and control varieties i.e., Fatmawati, Ciherang, and Inpari13. The results indicated that in general the lines had medium height (102.77-110.23 cm), moderate productive tiller (9-16 tiller per hill), moderate days to flower (50%), i.e., 73-76 days after sowing (DAS), earlier days to harvest (103-110 DAS), moderate panicle length (28.35-29.31 cm), large number of grain per panicle (> 250 grains) with moderate panicle fertility (63-70%), moderate 1,000 grain weight, i.e., 26.51-27.75 g, and high yield (7.51-8.09 ton ha-1). Four lines, i.e., BIO-MF116, BIO-MF130, BIO-MF151, and BIO-MF153 were stable and had wide adaptability. Other lines, i.e., BIO-MF125 and BIO-MF133 were sensitive to environmental changes, therefore they were classified as specifically adapted to favorable environment; while BIO-MF115 was not sensitive to environmental changes, and therefore it was adapted to non-favorable environment.</p><p>Keywords: adaptation, agronomic characters, rice mutant</p>

Breeding Strategies for Improving Rice Yield—A Review

An increase in productivity is always one of the main goals of any crop breeding program including rice. However, many goals can be identified for this crop varying in importance from region to region, country to country, and even within a given country. Increase in grain yield potential is the major goal of almost all rice breeders programs. The major impacts are related to the development of new strategies to increase the genetic grain yield potential of the varieties. Rice breeders have been very successful in improving the crop. Some milestones are the contribution to the green revolution with the semi-dwarf varieties, the new rice plant type and hybrid rice. The main breeding method used to improve rice is the pedigree, but development of hybrids and population improvement are added to the breeder’s portfolio. Breeders have been taking advantage of biotechnology tools to enhance their breeding capacity; however, many programs are still struggling on how to integrate them into the breeding programs and how to balance the allocation of resources between conventional and modern tools.

Effect of Planting Density of Mechanically Transplanted Pot Seedlings on Yield, Plant Type and Lodging Resistance in Rice with Different Panicle Types

In order to identify the suitable planting density and high-yielding charcteristices of mechanically transplanted pot seedlings of rice(PS) with different panicle types, and clarify the effect of planting density on plant type and loding resitance, a field experiment was conducted using rice cultivar with three panicle types in 2012 and 2013. By setting high, medium and low planting density treatments and using mechanically transplanted carpet seedling as control(CK), we investigated yield and its components, panicle traits, canopy leaf system configuration, physical properties of culm and lodging resistance. Resluts showed as follows:(1) With decreasing planting density, yield of three density treatments in the large panicle cultivar increased firstly and then reduced which was higher than that of CK;,and yield of three density treatments reduced progressively for the medium and small panicle cultivar. With decreasing planting density, number of panicles in all cultivars reduced significantly, and spikelets per panicle increased markedly, but there was no significant difference in grain-filled percentage and 1000-grain weight.(2) With decreasing planting density, in all cultivars with PS, panicle length, grain density, grain weight per panicle, No. of primary branch, No. of secondary branch, No. of grains of primary branch and No. of grains of secondary branch showed a tendency of increase, and were higher than those in CK, but it showed a decreasing tendency in ratio of No. of primary branch to No. of secondary branch and ratio of No. of grains of primary branch to No. of grains of secondary branch.(3) Leaf length, leaf width, leaf basal angle, drooping angle of top three leaves and specific leaf weight from flag leaf to the 3rd leaf in all cultivars with PS were enhanced with decreasing planting density, and were higher than those in CK except for leaf basal angle and drooping angle.(4) With decreasing planting density, length of basal 1st, 2nd, and 3rd internodes were shortened, and culm diameter, culm wall thickness, dry matter weight per unit internode of basal inernodes, neck internode length, stalk length, plant height and gravity center height were increased.(5) The breaking resistance and bending moment of basal 1st, 2nd and 3rd internodes were increased with decreasing planting density, but lodging index was decreased. Therefore, for increasing yield with PS, the large panicle cultivar should reduce planting density appropriately, and increase grain number per panicle; the medium panicle cultivar should coordinate number of panicles and spikelets per panicle, getting a large amount of the total spikelets; the small panicle cultivar should depend on number of panicles. When the plant density reduced in PS, panicle traits and top three leaves area could be improved, but leaf basal angle and drooping angle could be increased; meanwhile, it was benefical to shorten the length of basal internodes and increase culm diameter, culm wall thickness and dry matter weight per unit internode, resulting in enhanced breaking resistance and reduced lodging index.

Agronomic performance of an IR64 introgression line with large leaves derived from New Plant Type rice in aerobic culture

Aerobic culture is a promising water-saving technology in irrigated rice ecosystems, but the vulnerability of plants to fluctuations in soil moisture constrains leaf expansion and yield. The objective of this study was to examine whether an aboveground architecture with large leaves and reduced tillering is associated with vigorous leaf growth in aerobic rice culture. In a series of field experiments, we evaluated the agronomic performance of an IR64 introgression line, YTH323 (IR84640-11-27-1-9-3-2-4-2-2-2-B), with fewer tillers and larger leaves than IR64, derived from New Plant Type rice, under various water and nitrogen conditions. In flooded culture, YTH323 yielded the same as IR64 and 38% more than IR65564-44-51 (a New Plant Type rice) (9.0 vs. 6.6tha−1). In aerobic culture, in contrast, it yielded 81% more than IR64 in slightly dry soils (5.1 vs. 2.8tha−1). YTH323 had a higher leaf area index than IR64 and IR65564-44-51 under slightly dry soil conditions and under a range of nitrogen conditions. The higher and more stable yield of YTH323 in aerobic culture was attributable to greater early vigor, high specific leaf area, a high ratio of leaf weight to total biomass, and larger leaves, along with the characteristics of high-yield cultivars such as high responsiveness to fertilizers and good grain filling. We conclude that genetic modification of the aboveground architecture of IR64, a typical tropical lowland rice cultivar, to reduce tiller and leaf number improves adaptation to aerobic culture.

Simulation of Canopy Leaf Inclination Angle in Rice

A leaf inclination angle distribution model, which is applicable to simulate leaf inclination angle distribution in six heights of layered canopy at different growth stages, was established by component factors affecting plant type in rice. The accuracy of the simulation results was validated by measured values from a field experiment. The coefficient of determination (R2) and the root mean square error (RMSE) between the simulated and measured values were 0.9472 and 3.93%, respectively. The simulation results showed that the distribution of leaf inclination angles differed among the three plant types. The leaf inclination angles were larger in the compact variety Liangyoupeijiu with erect leaves than in the loose variety Shanyou 63 with droopy leaves and the intermediate variety Liangyou Y06. The leaf inclination angles were distributed in the lower range in Shanyou 63, which matched up with field measurements. The distribution of leaf inclination angles in the same variety changed throughout the seven growth stages. The leaf inclination angles enlarged gradually from transplanting to booting. During the post-booting period, the leaf inclination angle increased in Shanyou 63 and Liangyou Y06, but changed little in Liangyoupeijiu. At every growth stage of each variety, canopy leaf inclination angle distribution on the six heights of canopy layers was variable. As canopy height increased, the layered leaf area index (LAI) decreased in all the three plant types. However, while the leaf inclination angles showed little change in Liangyoupeijiu, they became larger in Shanyou 63 but smaller in Liangyou Y06. The simulation results used in the constructed model were very similar to the actual measurement values. The model provides a method for estimating canopy leaf inclination angle distribution in rice production.

Changes in the Chlorophyll Content and Cytokinin Levels in the Top Three Leaves of New Plant Type Rice During Grain Filling

This paper reports the ways that the differences in leaf senescence are related to grain filling, grain yield, and the dynamics of cytokinins (CKs) in the top three leaves of four field-grown new plant type (NPT) rice, a tropical japonica developed at the International Rice Research Institute, Philippines, to increase the yield potential of rice. The chlorophyll content in leaves decreased from flowering to maturity in all the NPT lines, whereas the grain filling percentage was higher in the fast-senescing NPT line than in slow-senescing NPT line. Grain yield was positively correlated with senescence in the flag leaf. Rapid changes in the CK levels were recorded in the leaves of the fast-senescing line, whereas the CK levels were relatively stable in leaves of the slow-senescing line, suggesting that the dynamics of CKs in the fast-senescing line are vital for fast senescence. There were no significant changes in bioactive CKs, CK O-glucosides (storage CKs), and cis-zeatin derivatives in different leaves of the slow-senescing NPT line between 0 and 3 weeks after flowering, suggesting that the content of these CKs is relatively stable during grain filling. A progressive increase in levels of bioactive CKs was positively correlated with gradual accumulation of CK N-glucosides (inactive CKs) in the top three leaves of the slow-senescing NPT line, whereas the decrease of bioactive CKs in the flag leaf of the fast-senescing line was accompanied by accumulation of CK O-glucosides. These results suggest that there is a higher rate of biosynthesis and/or import of bioactive CKs as well as their turnover which may favor delay of leaf senescence in the slow-senescing NPT line.

ENHANCING WATER AND FERTILIZER SAVING WITHOUT COMPROMISING RICE YIELD THROUGH INTEGRATED CROP MANAGEMENT

<p>Water and fertilizer scarcity amid the increasing need of rice production challenges today’s agriculture. Integrated crop management (ICM) is a combination of water, crop, and nutrient management that optimizes the synergistic interaction of these components aiming at improving resource use efficiency, i.e. high productivity of water, land, and labor. The objectives of the study were to investigate the effects of crop establishment method, organic matter amendment, NPK management, and water management on yield of lowland rice. Five series of experiments were conducted at Sukamandi and Kuningan Experimental Stations, West Java. The first experiment was focused on crop establishment method, i.e. plant spacing and number of seedlings per hill. The second, third, and fourth experiments were directed to study the effect of NPK and organic matter applications on rice yield. The fifth experiments was designed to evaluate the effect of water management on rice yield. Results showed that 20 cm x 20 cm plant spacing resulted in the highest grain yield for the new plant type rice varieties. Organic matter and P fertilizer application did not significantly affect grain yield, but the yield response to P fertilization tended to be stronger with organic matter amendment. Split P application did not significantly increase grain yield. The use of a scale 4 leaf color chart reading resulted in a considerable N fertilizer saving without compromising rice yield. Intermittent irrigation technique saved water up to 55% without affecting yields, resulting in a 2-3 times higher water productivity.</p>