Direct-seeded Rice Cultivation Research Articles

Relationship between the field history of barnyardgrass infestation and the buried seed population in dry paddy fields under direct-seeded rice cultivation region

Relationship between the field history of barnyardgrass infestation and the buried seed population in dry paddy fields under direct-seeded rice cultivation region

Development and Genetic Characterization of A Novel Herbicide (Imazethapyr) Tolerant Mutant in Rice (Oryza sativa L.)

BackgroundIncreased water and labour scarcity in major rice growing areas warrants a shift towards direct seeded rice cultivation under which management of weeds is a major issue. Use of broad spectrum non-selective herbicides is an efficient means to manage weeds. Availability of rice genotypes with complete tolerance against broad-spectrum non-selective herbicides is a pre-requisite for advocating use of such herbicides. In the present study, we developed an EMS induced rice mutant, ‘HTM-N22‘, exhibiting tolerance to a broad spectrum herbicide, ‘Imazethapyr‘, and identified the mutations imparting tolerance to the herbicide.ResultsWe identified a stable and true breeding rice mutant, HTM-N22 (HTM), tolerant to herbicide, Imazethapyr, from an EMS-mutagenized population of approximately 100,000 M2 plants of an upland rice variety, Nagina 22 (N22). Analysis of inheritance of herbicide tolerance in a cross between Pusa 1656-10-61/HTM showed that this trait is governed by a single dominant gene. To identify the causal gene for Imazethapyr tolerance, bulked segregant analysis (BSA) was followed using microsatellite markers flanking the three putative candidate genes viz., an Acetolactate Synthase (ALS) on chromosome 6 and two Acetohydroxy Acid Synthase (AHAS) genes, one on chromosomes 2 and another on chromosome 4. RM 6844 on chromosome 2 located 0.16 Mbp upstream of AHAS (LOC_Os02g30630) was found to co-segregate with herbicide tolerance. Cloning and sequencing of AHAS (LOC_Os02g30630) from the wild type, N22 and the mutant HTM and their comparison with reference Nipponbare sequence revealed several Single Nucleotide Polymorphisms (SNPs) in the mutant, of which eight resulted in non-synonymous mutations. Three of the eight amino acid substitutions were identical to Nipponbare and hence were not considered as causal changes. Of the five putative candidate SNPs, four were novel (at positions 30, 50, 81 and 152) while the remaining one, S627D was a previously reported mutant, known to result in Imidazolinone tolerance in rice. Of the novel ones, G152E was found to alter the hydrophobicty and abolish an N myristoylation site in the HTM compared to the WT, from reference based modeling and motif prediction studies.ConclusionsA novel mutant tolerant to the herbicide “Imazethapyr” was developed and characterized for genetic, sequence and protein level variations. This is a HTM in rice without any IPR (Intellectual Property Rights) infringements and hence can be used in rice breeding as a novel genetic stock by the public funded organizations in the country and elsewhere.

暖地の農家水田におけるべんモリ被覆種子での代かき同時打ち込み点播による水稲湛水直播の苗立ちと収量および収穫物のモリブデン含有率

水稲湛水直播では苗立ちの確保が重要で，このために過酸化カルシウム粉粒剤 （以下，過酸化Ca剤） による種子被覆が実施されてきた．過酸化Ca剤による被覆は資材費や手間がかかる．これらの負担を軽減するために，新たな種子被覆法としてべんモリ被覆を考案した．この方法は，三酸化モリブデンと酸化鉄とポリビニルアルコールの混合粉末で種子を被覆する．そこで，2013～2015年に，これまで過酸化Ca剤被覆種子で代かき同時打ち込み点播を実施してきた佐賀県上峰地域の農家水田において，過酸化Ca剤被覆種子とべんモリ被覆種子を直播する区を設けた．その結果，苗立ち，生育，収量において，種子被覆の違いによる有意差はなかった．また，収穫期の水稲地上部と玄米，および栽培後の土壌のモリブデン含有率に，種子被覆の違いによる有意差はなかった．さらに，試験水田の周辺の農家水田でべんモリ直播の普及がみられたので，それらの水田の苗立ちと収量を調査したところ，十分な苗立ちが得られ，栽培においてべんモリ直播による不都合はみられなかった．以上から，暖地における代かき同時打ち込み点播では，過酸化Ca剤被覆の代わりにべんモリ被覆での代替が可能であり，これによって資材費が安く，被覆作業も容易になると期待された．

Benmoly Coating of Seeds for Submerged Direct-Seeded Rice Cultivation

Benmoly Coating of Seeds for Submerged Direct-Seeded Rice Cultivation

水田の土壌状態に基づいた プラウ耕鎮圧体系乾田直播栽培の適用性

プラウ耕鎮圧体系乾田直播栽培の適用可能な条件を明らかにするため，5地域20筆の圃場において，鎮圧処理方法の異なる乾田直播栽培を行い，土壌状態，土層の飽和透水係数および減水深を調査した．鎮圧処理として，播種後に鎮圧を1回のみ行う低鎮圧処理，2回以上鎮圧を行う高鎮圧処理，および無鎮圧の圃場を設定して，鎮圧処理による土層の透水性の違いと減水深の関係性を解析した．土層内にグライ層が確認された圃場では，低鎮圧処理においても減水深が適正値である20 mm/d以下となりやすく，乾田直播が容易に適用可能な条件であることが明らかになった．地表下3 cmまたは5 cmから採取した土壌と下層土の飽和透水係数と減水深の関係を考察した結果，下層の透水性が高まり，止水層が存在しない圃場は，2回以上の鎮圧を行い地表付近の透水性を低下させることにより，減水深が低減していることが示された．このように地表付近と下層土の飽和透水係数を横軸と縦軸に配置し，2軸マトリクスで各圃場を分類することで，下層の透水性が高い場合は十分に鎮圧することが必要であることなど，鎮圧の必要性および排水機能の必要性を判断することが可能であり，乾田直播栽培の適用性の判定に有用であると考えられた．

Fertilizer and Weed Management Options for Direct Wet Seeded Rice in Dry Season

Direct seeding of rice is an emerging technology. However, direct seeded rice culture in the main field is hindered by enormous weed infestation and it lacks judicious fertilizer management. So, experiments were conducted during dry seasons of 2010 and 2012 with three fertilizer packages and four weed control measures. Rice seed was sown in the field using drum seeder in wet soil. The results revealed that weed density and weed biomass were strongly influenced by weed control methods and fertilizer rates. Weed density was higher in unweeded plots with 140:36:43 kg NPK ha-1. Among the species Echinichloa crusgalli (L.) P. Beauv. was the dominant species. Three hand weeding controlled maximum weeds. Uses of herbicide for controlling weeds were above 80 and 70% effective. Strong negative correlation was recorded between grain yield and weed density. Herbicide with one hand weeding and BRRI weeder in combination with 160:46:53 kg NPK ha-1 produced about 81- 104% higher grain yield than no weeding. Weed free plot produced 112% higher yield with 160:46:53 kg NPK ha-1. Besides, herbicide with one hand weeding and BRRI weeder treated plot produced similar yield irrespective of fertilizer doses. The strong positive and linear relationship was found in case of yield and yield components. Herbicide with one hand weeding and 120:26:33 kg NPK ha-1 gave higher net return (1145 $/ha). The benefit cost ratio was also higher in herbicide based weed management with reduced rate of fertilizer. Direct seeded culture using herbicide with one hand weeding and 120:26:33 kg NPK ha-1 could be an option for reducing production cost in dry season along with satisfactory grain yield.Bangladesh Rice j. 2016, 20(1): 65-75

Contribution of seedling vigour and anoxia/hypoxia-responsive genes to submergence tolerance in Vietnamese lowland rice (Oryza sativa L.)

ABSTRACTA direct-seeded rice cultivation system has been widely adopted in Asian countries. Optimum germination and vigorous seedling growth under submergence are key traits for the practice of direct seeding. We studied the post-germination seedling vigour in Vietnamese lowland rice accessions based on three bio-parameters, shoot elongation growth under five-day submergence in water-filled test-tubes, seedling recovery rate five days after transferring submerged seedlings to pots with soil and seedling survival rate 21 days after sowing seeds in nursery beds and immediate incubation under submergence. A large diversity was found in seedling vigour thus estimated among the accessions. Significantly high correlations were observed among all three bio-parameters, verifying the contribution of seedling vigour to the manifestation of submergence tolerance at this critical stage of rice development. To examine the roles of anoxia/hypoxia-responsive genes, the expression of 17 candidate genes was studied by reverse transcription polymerase chain reaction (RT-PCR) and compared between selected vigorous and non-vigorous groups of accessions. Transcripts of all but two genes showed marked accumulation in submerged seedlings. No differences, however, were found between the two contrasting groups. The observed common and coordinate expression of anoxia/hypoxia-induced genes suggests that they might assume roles in attaining baseline tolerance against submergence stress. It was also suggested that some unknown genetic factors are operating in determining cultivar/genotype-specific levels of submergence tolerance as assessed by post-germination seedling vigour.

Weed management on direct-seeded rice system - a review

In direct seeded rice (DSR) cultivation systems, rice and weed seedlings emerge simultaneously and there is no standing water to suppress weed emergence and growth at crop emergence. For this reason, weeds are considered one of the major biological constraints in DSR and cause a substantial rice yield loss. Weeds are mainly controlled using herbicides or manually. However, manual weeding is becoming less effective because of labor crisis at critical times and increased labor costs. Herbicides are replacing manual weeding as they are easy to use but there are concerns about the sole use of herbicides, such as evolution of resistance in weeds, shifts in weed populations, cost of weed management to farmers and concerns about the environment. There is a need to integrate different weed management strategies to achieve effective and sustainable weed control in DSR systems. This paper describes different approaches, including preventive and cultural approaches, to manage weeds in DSR culture systems.Progressive Agriculture 27 (1): 1-8, 2016

Direct Seeded Rice: Potential and Constraints in Punjab

Rice production contributes to global climate change through emissions of methane and nitrous oxide gases. Further water table is lowering at an alarming rate in Punjab due to excessive drawing of groundwater for rice cultivation. Water use in rice production, therefore, needs to be decreased by increasing water-use efficiency, decreasing seepage, percolation and evaporation losses. DSR (direct seeded rice) has got the potential to improve water use efficiency, reduce other losses besides significantly reducing the methane production by producing the aerobic conditions. The FLD on DSR were conducted during 2013–14 to 2015–16 in Bathinda district of Punjab to assess prospects and constraints of DSR over NTR (normal transplanted rice). DSR has saved labour worth 5250 per hectare, irrigations to the tune of 40 per cent and has also given 2.61 per cent additional yield worth 3298 per hectare over NTR. A successful transition of rice cultivation from normal transplanting system to DSR culture demands breeding of special rice varieties and developing appropriate management strategies. Despite threats of weed flora, NO2 emissions, lodging, nutrient deficiencies and blast attack the technique, thus, need to be popularized on heavy soils through suitable policy at the state level.

Genetic diversity of Vietnamese lowland rice germplasms as revealed by SSR markers in relation to seedling vigour under submergence

ABSTRACTIn the direct-seeding rice cultivation system, seedling vigour is one of the most important traits for stable stand establishment during early seedling stages, particularly under submergence that is caused by temporal flash flood. We studied the genetic diversity in a set of 40 Vietnamese lowland rice varieties using 30 simple sequence repeat (SSR) markers covering all rice chromosomes. A total of 111 alleles were detected, with a mean of 3.7 alleles per locus. The number of polymorphic alleles detected by each SSR marker ranged from 2 to 6. The fragment size of a given SSR locus varied between 85 and 650 bp and the frequency of a major allele at each locus ranged from 32.5% to 76.9%. Polymorphism information content value varied from 0.355 to 0.774 with an average of 0.594. The genetic similarity calculated between pairs of rice varieties ranged from 0.03 to 0.97 with an average of 0.27. According to a constructed dendrogram of unweighted pair group method with arithmetic mean based on the SSR marker analysis, the tested rice varieties were clustered into two major groups consisting of five subgroups. Significant correlations existed between the mean genetic similarity and the mean seedling vigour estimated by shoot length under submergence among the tested varieties. Our results suggested usefulness of the SSR marker system to assess genetic diversity in Vietnamese rice germplasms in relation to their seedling vigour under submergence.

Synergistic Effects of Ethephon and Gibberellic Acid on the Growth of Rice Seedlings Grown under Field and Environmentally Controlled Conditions

A B S T R A C T Improving early seedling growth is crucial for direct-seeding rice cultivation. In this study, field and laboratory experiments were conducted to determine the effects of Plant Growth Regulators (PGRs) such as gibberellic acid (GA3) and ethephon (ET) on the early growth of direct-seeded rice. Seeds were treated with the PGRs and pre-germinated at 30°C in the dark. For the field experiment, two Flooding Depth (FD) regimes were established during the growth period: 0 cm (drained condition) and 2 cm (flooded condition). Treatment of seeds with ET or GA3 alone promoted the growth of seedling organs compared to that of the control at both the FDs in some cases. However, combined application of ET and GA3 (ET+GA3) synergistically improved the growth of different seedling organs at both the FDs in most cases with slight exception: the coleoptile and mesocotyl plus coleoptile (mesocotyl+coleoptile) length were not different across the PGR treatments under drained condition. Further, the growth of the second node tiller was stimulated by the application of ET alone under drained conditions. The laboratory experiment revealed that ET+GA3 increased the growth rate of mesocotyl+coleoptile and that of the first leaf. These results suggest that the combined application of ET and GA3 might be useful for improving the growth performance of rice seedlings in the direct seeding method.

大区画水稲乾田直播圃場における鎮圧作業による浸透抑制効果

大区画水稲乾田直播圃場における鎮圧作業による浸透抑制効果

Modelling Rice-Weed Competition in Direct-Seeded Rice Cultivation

Two field experiments were conducted to investigate rice-weed competition during direct-seeded rice cultivation. A rectangular hyperbolic equation was used to predict rice yield as a function of weed densities. Economic thresholds (ET) of multi-species weeds were estimated considering the cost of weed control and price of rice yield. The dry matter production and intraspecific competition of weeds were 1.13–3.63 g plant−1 and 0.0375–0.0383, respectively. The competition effect of weeds on rice was significant and the competitivity value ranged from 0.0170 to 0.0126. Therefore, the number of panicles m−2, grains panicle−1 and 1,000-grain weight were significantly reduced by the competition of weed species. Considering the weed competitivity, weed control costs and price of grain, the ET values of weeds were 4.72–9.17 plants m−2. These findings will be useful for weed management in direct-seeded rice cultivation.

Rice responses to rising temperatures--challenges, perspectives and future directions.

Phenotypic plasticity in overcoming heat stress-induced damage across hot tropical rice-growing regions is predominantly governed by relative humidity. Expression of transpiration cooling, an effective heat-avoiding mechanism, will diminish with the transition from fully flooded paddies to water-saving technologies, such as direct-seeded and aerobic rice cultivation, thus further aggravating stress damage. This change can potentially introduce greater sensitivity to previously unaffected developmental stages such as floral meristem (panicle) initiation and spikelet differentiation, and further intensify vulnerability at the known sensitive gametogenesis and flowering stages. More than the mean temperature rise, increased variability and a more rapid increase in nighttime temperature compared with the daytime maximum present a greater challenge. This review addresses (1) the importance of vapour pressure deficit under fully flooded paddies and increased vulnerability of rice production to heat stress or intermittent occurrence of combined heat and drought stress under emerging water-saving rice technologies; (2) the major disconnect with high night temperature response between field and controlled environments in terms of spikelet sterility; (3) highlights the most important mechanisms that affect key grain quality parameters, such as chalk formation under heat stress; and finally (4), we model and estimate heat stress-induced spikelet sterility taking South Asia as a case study.

Nitrogen uptake and ammonium-N content of flooded soil in direct-seeded rice cultivation in Hokkaido

Nitrogen uptake and ammonium-N content of flooded soil in direct-seeded rice cultivation in Hokkaido

Rice Adaptation to Aerobic Soils: Physiological Considerations and Implications for Agronomy

Aerobic culture is a water-saving technique for direct-seeded rice cultivation. Growing rice under continuously unsaturated soil conditions can maximize water-use efficiency and minimize both labor requirements and greenhouse-gas emissions. Under a temperate climate, aerobic culture can produce a rice yield greater than 9 t ha–1 especially in central Japan (11.4 t ha–1). Aerobic culture using large-scale center-pivot sprinklers is being established in the central United States, where yields can surpass 10 t ha–1. However, yields remain at less than 8 t ha–1 in the tropics. The high yield of Japanese aerobic culture is mainly attributed to vigorous nitrogen uptake during the reproductive stage, which allows rice plants to produce more spikelets and biomass. Fertilizer management for aerobic culture must satisfy both the nitrogen demand and control spikelet density to achieve an appropriate sink–source balance. Unfortunately, the poor development of the root system in rice limits its water uptake from unsaturated soil. Adaptive responses such as adventitious root emergence, lateral root branching, and deep root penetration would protect the plants against dehydration stress in aerobic culture. Intermediate plant height with a few large tillers rather than semi-dwarf stature with profuse tillering should be a suitable plant type for aerobic culture, and plants should show leaf expansion despite fluctuations of soil moisture. The development and identification of suitable genotypes and crop management options are underway worldwide for more resource-use efficient and productive aerobic rice culture.

Benzobicyclon 혼합제의 제형 및 처리시기가 제초활성 및 벼 생육에 미치는 영향

This study was conducted to evaluate the efficacy of two different formulations and application timings of benzobicyclon+penoxsulam+pyrzaosulfuron-ethyl (BPP) in rice field. BPP granule (GR) and tablet (TB) controlled more than 90% of four weed species 10 and 15 days after sowing in direct seeding when compared with untreated control. BPP TB was highly effective to control herbicide resistant Scirpus juncoides and Monochoria vaginalis both 10 and 15 days after transplanting (DAT). BPP GR controlled 94.0 and 96.5% of S. juncoides and M. vaginalis, respectively 10 DAT, but its efficacy decreased to 88.5 and 49.8% respectively 15 DAT. When compared with untreated control, no visual injuries were detected at 255 and 510 g a.i./ha of BPP. The yield of rice increased in both BPP GR and TB in transplanting and direct seeding rice cultivation when compared with untreated control. Based on these data, early application (10 DAT) of BPP GR and TB can be applied to provide effective weed control, especially in the field infested with herbicide resistant weed species.

벼 담수직파재배시 Iprobenfos-metconazole(IPM) 처리에 따른 생육과 도복경감효과

본 연구는 벼 담수직파재배에서 식물생장억제제인 IPM(Iprobenfos-metconazole)을 벼의 출수기 전에 처리함으로 써 벼의 생육과 도복경감효과를 구명하기 위하여 수행하였다. 1. 출수기에 간장은 식물생장억제제를 처리한 구에서 무처리구보다 간장이 단축되는 결과를 보였으며, 출수전 30일에 처리하였을 때 가장 단축효과가 컸고, 하위 4절간의 단축율이 가장 높았다. 2. 출수후 20일에 지엽의 엽색도를 조사한 결과 IPM 처리구는 무처리구에 비하여 높았고, 엽중 질소 농도는 IPM 처리구가 무처리구에 낮았으나 규산 함량은 무처리구에 비하여 높았고, 규산/질소 비율이 증가하였다. 3. 하위 절간(3~4)의 좌절중은 무처리구에 비하여 IPM 처리구가 유의하게 높았으며, 도복지수는 무처리구에 비하여 낮아지는 것으로 조사되었고 포장도복도 크게 경감되었다. 4. 수량 및 수량구성요소를 조사한 결과 IPM 처리구는 무처리구에 비하여 도복이 되지 않아서 등숙률과 천립중이 높아짐으로서 수량 증수 효과가 있었다. Lodging in the direct seeded rice cultivation on flooded paddy is being severe problem due to the lower production and grain quality at ripening stage. This study was conducted to examine the effect of Iprobenfos-metconazole (IPM) treated 50, 40 and 30 days before heading respectively as a plant regulator to reduce the lodging at ripening stage of direct seeding rice cultivation. The culm length treated with IPM, especially the 4th culm internode, was shortened more than with untreated plot, and the most effective time was at 30 days before heading. At 20 days after heading the flag leaves colour showed more greening than in the untreated leaves and the plot with IPM treatment was to be maintained longer compared to the control plot. The Nitrogen concentration of leaves with IPM was lower than in the control plot, and <TEX>$SiO_2$</TEX> contents were higher than in the untreated plot and <TEX>$SiO_2/N$</TEX> ratio was increased more in the IPM plot than in the control plot. The breaking strength of 3rd and 4th culm internode with IPM treatment was higher than in the untreated plot, and the lodging index was reduced in the IPM plot significantly and the field lodging also was reduced. As the results the rice production in the IPM plot was increased more due to be higher ripening ratio and seed grain weight compared to the untreated plot to be occurred the field lodging.

QTL mapping and confirmation for tolerance of anaerobic conditions during germination derived from the rice landrace Ma-Zhan Red

Wide adoption of direct-seeded rice practices has been hindered by poorly leveled fields, heavy rainfall and poor drainage, which cause accumulation of water in the fields shortly after sowing, leading to poor crop establishment. This is due to the inability of most rice varieties to germinate and reach the water surface under complete submergence. Hence, tolerance of anaerobic conditions during germination is an essential trait for direct-seeded rice cultivation in both rainfed and irrigated ecosystems. A QTL study was conducted to unravel the genetic basis of tolerance of anaerobic conditions during germination using a population derived from a cross between IR42, a susceptible variety, and Ma-Zhan Red, a tolerant landrace from China. Phenotypic data was collected based on the survival rates of the seedlings at 21days after sowing of dry seeds under 10cm of water. QTL analysis of the mapping population consisting of 175 F2:3 families genotyped with 118 SSR markers identified six significant QTLs on chromosomes 2, 5, 6, and 7, and in all cases the tolerant alleles were contributed by Ma-Zhan Red. The largest QTL on chromosome 7, having a LOD score of 14.5 and an R (2) of 31.7%, was confirmed using a BC2F3 population. The QTLs detected in this study provide promising targets for further genetic characterization and for use in marker-assisted selection to rapidly develop varieties with improved tolerance to anaerobic condition during germination. Ultimately, this trait can be combined with other abiotic stress tolerance QTLs to provide resilient varieties for direct-seeded systems.

Mapping of quantitative trait loci controlling seedling vigor in rice (Oryza sativa L.) under submergence

Submergence-induced suppression of seedling vigor is a serious constraint particularly in the direct seeding rice cultivation system. To identify quantitative trait loci (QTLs) associated with seedling vigor in rice under submergence, a mapping population of 98 Backcross Inbred Lines derived from a cross of Nipponbare/Kasalath//Nipponbare was used. Phenotypic evaluation of seedling vigor under submergence was based on shoot length (SHL), root length (RTL) and shoot fresh weight (SFW) using a test tube bioassay method. Thirty-two putative QTLs were detected among which 7 were for SHL, 11 for RTL and 14 for SFW. Phenotypic evaluation was also made of the parental lines and a set of 54 chromosome segment substitution lines in which Nipponbare segments were substituted for by their homologous Kasalath segments covering the entire rice genome. Two QTLs with more than 10 % contribution to the total phenotypic variance were verified for SHL, and at least one for RTL and six for SFW on chromosomes 1, 3, 4, 6 and 7 at the 1 % significance level. Among these, all but two showed reductions in one, two or all three traits. Our present and previous results suggest that the Nipponbare genome has a potential to improve seedling vigor under submergence and that japonica germplasms can be used to breed for this important trait in indica rice.