Deepwater Rice Research Articles

Using remote sensing technologies to enhance resource conservation and agricultural productivity in underutilized lands of South Asia

Satisfying the food demands of an ever-increasing population, preserving the natural resource base, and improving livelihoods are major challenges for South Asia. A large area of land in the Middle and Lower Gangetic Plains of South Asia remains either uncultivated or underused following the rice harvest in the kharif (wet) season. The area includes “rice-fallow,” estimated at 6.7 million ha, flood-prone riversides (“ diara lands,” 2.4 million ha), waterlogged areas (4.9 million ha), and salt-affected soils (2.3 million ha). Bringing these lands under production could substantially improve the food supply and enhance livelihoods in the region. This paper describes a methodological case study that targeted resource-conserving technologies in underused lands of the Ballia District of eastern Uttar Pradesh (India) using multispectral remote-sensing images. Classification of temporal satellite data IRS-P6 in combination with Spot VGT 2 permitted the identification of all major categories of underused land during the post-rainy rabi/winter season, with an average accuracy of 89%. Based on three-year averages of field demonstrations, farmers gained an additional income of $63 ha −1 by introducing raised beds in salt-affected soils; $140 and $800 ha −1 by introducing deepwater rice varieties (monsoon) and boro rice (winter) in waterlogged areas; and $581 ha −1 by introducing zero-till lentil (winter) in rain-fed fallow lowland. Timely wheat planting through zero-tillage implies an additional income of $147 ha −1 and could increase wheat production by 35,000–65,000 tons in the district. The methodologies and technologies suggested in the study are applicable to more than 15 million ha of underutilized lands of the Indo-Gangetic Plains of South Asia. If the technologies are precisely applied, they can result in more than 3000 million US $ of additional income every year to these poverty prone areas.

Effects of planting date and variety on flooded rice production in the deepwater area of Thailand

Crop management plays an important role in the transition from a deepwater rice to a flooded rice production system but information about optimum management strategies are currently lacking. The goal of this study was to determine the effect of planting date and variety on flooded rice production in the deepwater area of Thailand. Two experiments were conducted at the Bang Taen His Majesty Private Development Project in 2009 and 2010 to represent conditions prior to flooding (early rainy season) and after flooding (dry season). The early rainy season crop covered the period from May to October 2009, while the dry season crop covered the period from November 2009 to April 2010. The experimental design was a split plot with four main plots and three sub plots replicated four times. The treatments for the main plot were various planting dates, while the treatments for the sub plots were rice varieties. The dates of the critical developmental phases of rice were recorded and biomass was sampled during the growing period. The collected data were statistically analyzed using ANOVA and treatment means were compared to identify the appropriate plating date and the best variety for the area. The highest average yield was obtained for variety PSL2 across transplanting dates from June 19 to July 23, with an average yield of 3898 kg ha −1. The dry season crop showed that both biomass and yield were affected by the interaction between planting date and variety. The highest yield was obtained for variety PTT1 transplanted on November 9. The research showed that the variety PSL2 is the most suitable variety for early rainy season production with a transplanting date ranging from June 19 to July 23, while the variety PTT1 planted on November 9 was the best management practice for the dry season crop. However, a high yielding flooded rice variety that has a short growth duration is still needed for this area.

QTL mapping of sheath blight resistance in a deep-water rice cultivar

Sheath blight, caused by the pathogen Rhizoctonia solani Kuhn, is one of the most serious diseases of rice and leads to severe yield loss worldwide. A recombinant inbred line (RIL) population consisting of 121 lines was constructed from a cross between HH1B and RSB03, the latter of which is a deep-water rice variety. Five traits were used to evaluate sheath blight resistance, namely disease rating (DR), lesion length (LL), lesion height (LH), relative lesion length [RLL, the ratio of LL to plant height (PH)], and relative LH (RLH, the ratio of LH to PH). Using the RIL population and 123 molecular markers, we identified 28 quantitative trait loci (QTLs) for the five traits in two environments. These QTLs are located on nine chromosomes and most of them are environment specific. A major QTL for DR (qSBR1) on chromosome 1 was identified with contributions of 12.7% at Shanghai and 42.6% at Hainan, and it collocated with a QTL for PH. The allele at this locus from RSB03 enhances sheath blight resistance and increases PH. Another QTL for DR on chromosome 7 was adjacent to QTLs for heading date (HD) and four other disease traits. RSB03 also carries the resistant allele at this locus and shortens HD. The susceptible parent, HH1B, provides the resistance allele at the locus qSBR8, where QTLs for four other disease traits were identified. QTL mapping results showed that most QTLs for LL, LH, RLL, and RLH are collocated with QTLs for DR. Three QTLs for DR are independent from HD, PH, and four other disease traits, while four QTLs are closely related to HD and PH. Four QTLs for LL, LH, RLL, and RLH are independent from DR, HD, and PH, while there is only one region harboring QTLs for these four traits and HD. Correlation analysis and QTL mapping results indicated that LL, LH, RLL, and RLH might be important indices, like DR, for evaluating the level of resistance to rice sheath blight.

Vacuolar Proton Pumps and Aquaporins Involved in Rapid Internode Elongation of Deepwater Rice

Rapid growth of the submerged shoots of deepwater rice is essential for survival during the rainy season. We investigated changes in the expression of vacuolar H(+)-ATPase (V-ATPase), H(+)-pyrophosphatase (V-PPase), and aquaporins under submerged conditions. The amounts of vacuolar proton pumps, which support the active transport of ions into the vacuoles, were maintained on a membrane protein basis in the developing vacuoles. Among the six isogenes of V-PPase, OsVHP1;3 was markedly enhanced by submersion. The gene expression of efficient water channels, OsTIP1;1, OsTIP2;2, OsPIP1;1, OsPIP2;1, and OsPIP2;2, was markedly enhanced by submersion. The increase in aquaporin expression might support quick elongation of internodes. The mRNA levels of OsNIP2;2 and OsNIP3;1, which transport silicic and boric acids respectively, clearly decreased. The present study indicates that internodes of deepwater rice upregulate vacuolar proton pumps and water channel aquaporins and downregulate aquaporins that allow permeation of the substrates that suppress internode growth.

Ecology of terrace wet rice-fish environment and role of periphyton

The waterlogged terrace wet rice-fields of Apatani Plateau located at an altitude of 1500msl in Arunachal Pradesh of the north eastern India are stocked with fish Common carp (Cyprinus carpio L) for several decades. The fishes are not fed with supplementary feeds because of the rich organic nature of the rice-fields. The study on water and soil of these fields revealed a strong co-relation to such organic nature. The wet rice-fish integrated fields exhibited the characters of shallow wet ecosystems. The water canals traversed through the rice fields were found inundated with water up to 50m showing the nature of Deep Water Rice fields (DWR) at least for one month. Significant (p<0.001) variations of water were observed for dissolved oxygen (DO) and carbon dioxide (CO2) to diurnal and seasonal changes. Alkalinity of the fields intends to play a role towards its productivity which is otherwise played by DO in other aquatic systems. Soil nitrogen reflected a gradual increasing trend of organic nature. Role of periphyton may not be ignored to the high phosphorus level of the soil at later flood phases in these fields. Key words: Rice-fish; aquatic ecosystem; organic practice; plankton; periphyton DOI: 10.3126/jowe.v4i0.2585Journal of Wetlands Ecology, (2010) Vol. 4, pp 102-111

Phenotypic diversity of panicle and nutritional traits of some widely cultivated indigenous deep-water rice (Oryza sativa L.) cultivars of Dhemaji district, Assam (India)

Deep-water rice shows some morphological and nutritional peculiarities. To evaluate the phenotypic diversity in panicle and nutritional traits, ten widely cultivated indigenous deepwater rice cultivars (viz. Panikakuwa , Kakuwa , Miabao , Dalbao , Maguribao , Negheribao , Panidhan , Bhubao , Amana and Happybao ) collected from different paddy growing fields of Dhemaji district, Assam, have been taken into study. Kernel colour of the cultivars varies from white to dark-purple. Six cultivars have been identified as high protein cultivars (>10%). Amylose content of the selected cultivars ranges from 18.73% to 34.51%. Dalbao has shown the highest total carbohydrate (88.4%), starch (83.25%) and protein (13.37%) content along with highest length of the panicle (33.6 cm), whereas cultivar Bhubao shows highest amylose content (34.51). Dalbao has also been found to possess several characters of rice with ideal panicle type. Protein content shows negative correlation with amylose content (–0.5011). Dalbao , having superior nutritional quality and panicle traits may be considered for inclusion in deep-water rice breeding programmes.

Submergence Tolerant Rice: SUB1’s Journey from Landrace to Modern Cultivar

Rice landraces tolerant of up to 2 weeks of complete submergence were collected from farmers’ fields in the 1950s. Success in fine mapping of SUBMERGENCE 1 (SUB1), a robust quantitative trait locus from the submergence tolerant FR13A landrace, has enabled marker-assisted breeding of high-yielding rice capable of enduring transient complete submergence. At the molecular level, SUB1 is a variable polygenic locus encoding two or three ethylene responsive factor (ERF) DNA binding proteins. All Oryza sativa accessions encode SUB1B and SUB1C at this locus. An additional ERF, SUB1A, is present at SUB1 in FR13A and other tolerant accessions. The induction of SUB1A expression by ethylene during submergence disrupts the elongation escape strategy typical of lowland and deepwater rice, by limiting ethylene-induced gibberellic acid-promoted elongation. Microarray and metabolite studies confirm that SUB1A orchestrates its effects on metabolism and growth in a submergence-dependent manner. Due to the conditional activity of SUB1A, new “Sub1” mega-varieties effectively provide submergence tolerance without apparent ill effect on development, productivity, or grain quality.

Performance evaluation of concurrent rice-fish-prawn culture with and without cull harvesting

This study was carried out in farmers' fields for three experimental culture cycles to evaluate the performance of rice–fish–prawn culture. The treatments carried out were deepwater rice mono-cropping (R), and rice–fish–prawn culture with cull harvesting (R–FC) and without cull harvesting (R–F). Water pH and total alkalinity were significantly higher (P<0.05) in R–FC than in R–F, while the concentrations of total suspended solids, plankton and chlorophyll a were higher in R–F. Cull harvesting in R–FC had no marked influence on the concentrations of dissolved oxygen, NH4+, nitrite, nitrate and phosphate compared with the R–F treatment. The significantly higher fish and prawn yields (P<0.05) and species-wise faster individual growth performance in R–FC than in R–F were probably due to periodic cull harvesting, which minimized the competition for food and space as well as physiological stress at reduced density. The paddy yield and percentage increase in paddy yield over rice mono-crop was significantly higher (P<0.05) in R–FC (25%), followed by R–F (16.9%), probably due to lower chlorophyll a (36.7 mg m−3) and plankton density (1.4 × 104 L−1), which minimized the competition for nutrients with rice plants. The highest rice equivalent yield (38.5), output value–cultivation cost ratio (1.56) and enhanced net return (28%) in deepwater rice–fish culture were recorded when cull harvesting was practiced.

ACO1, a gene for aminocyclopropane‐1‐carboxylate oxidase: effects on internode elongation at the heading stage in rice

Although reports on a gene for 1-amino-cyclopropane-1-carboxylate (ACC) oxidase (ACO1) in rice (Oryza sativa L.) suggest that high levels of its transcript are associated with internode elongation of deep-water rice during submergence, the role of ACO1 in rice development is largely unknown. The tissue-specificity of ACO1 expression indicated that its transcript significantly accumulated in lower parts of elongating internodes at the heading stage. Histochemical analysis and in situ hybridization showed that the ACO1 expression was localized in the basal parts of leaf sheaths immediately above nodes or the lower parts of elongating internodes. To further examine the role of ACO1, ACO1-deficient (aco1) and overexpressing (ACO1-OX) mutants were characterized. The total length of the elongated internodes of aco1 mutants was slightly shorter than that of wild-type plants and that of ACO1-OX mutants was longer. Interestingly, expression of the ACC synthase gene ACS1 and ethylene signalling gene OsEIN2 was up-regulated in the aco1 mutants. This study suggests that the ACO1 has a little effect on internode elongation at the heading stage, and that up-regulation of the ACS1 and OsEIN2 expression may attenuate inhibition of internode elongation.

Stunt or elongate? Two opposite strategies by which rice adapts to floods

Expansion of habitat is important for the perpetuation of species. In particular, plants which are sedentary must evolve specialized functions to adapt itself to new environment. Deepwater rice is cultivated mainly in the lowland areas of South and Southeast Asia that are flooded during the rainy season. The internodes of deepwater rice elongates in response to increasing water level to keep its leaves above the water surface and avoid anoxia. This elongation is stimulated by ethylene-regulated genes, Snorkel1 and Snorkel2. In contrast, when a flash flood occurs at the seedling stage, submergence-tolerant rice, which carries Submergence-1A, remains stunted and survives in water for a few weeks to avoid the energy consumption associated with plant elongation, and restarts its growth using its conserved energy after the water recedes. Interestingly, both Snorkel genes and Submergence-1A encode ethylene-responsive factor-type transcription factor and are connected to gibberellin biosynthesis or signal transduction. However, deepwater and submergence-tolerant rice seem to have opposite flooding response; namely, escape by elongation or remain stunted under water until flood recedes.

Comparison of Some Ecological Characteristics between African Deepwater Rice (Oryza glaberrima STEUD.) Varieties and Asian Deepwater Rice (O. sativa L.) Varieties

Comparison of Some Ecological Characteristics between African Deepwater Rice (Oryza glaberrima STEUD.) Varieties and Asian Deepwater Rice (O. sativa L.) Varieties

Preliminary Studies on Some Ecological Characteristics of African Deep Water Rice (Oryza glaberrima Steud.)

Preliminary Studies on Some Ecological Characteristics of African Deep Water Rice (Oryza glaberrima Steud.)

Grain Shedding of Bangladesh Deepwater Rice

Grain Shedding of Bangladesh Deepwater Rice

Elongation Ability of Deepwater Rice Varieties from Different Land Levels of Bangladesh

Elongation Ability of Deepwater Rice Varieties from Different Land Levels of Bangladesh

Character Association among Isozymic Genotype, Grain Type and Phenol Reaction of Grains in Bangladesh Floating Rice Varieties

Character Association among Isozymic Genotype, Grain Type and Phenol Reaction of Grains in Bangladesh Floating Rice Varieties

Involvement of Acid-induced Growth and Expansin Action in the Internodal Elongation of Submerged Floating Rice

Involvement of Acid-induced Growth and Expansin Action in the Internodal Elongation of Submerged Floating Rice

ACO1, a gene for aminocyclopropane-1-carboxylate oxidase: effects on internode elongation at the heading stage in rice

Although reports on a gene for 1-amino-cyclopropane-1-carboxylate (ACC) oxidase (ACO1) in rice (Oryza sativa L.) suggest that high levels of its transcript are associated with internode elongation of deep-water rice during submergence, the role of ACO1 in rice development is largely unknown. The tissue-specificity of ACO1 expression indicated that its transcript significantly accumulated in lower parts of elongating internodes at the heading stage. Histochemical analysis and in situ hybridization showed that the ACO1 expression was localized in the basal parts of leaf sheaths immediately above nodes or the lower parts of elongating internodes. To further examine the role of ACO1, ACO1-deficient (aco1) and overexpressing (ACO1-OX) mutants were characterized. The total length of the elongated internodes of aco1 mutants was slightly shorter than that of wild-type plants and that of ACO1-OX mutants was longer. Interestingly, expression of the ACC synthase gene ACS1 and ethylene signalling gene OsEIN2 was up-regulated in the aco1 mutants. This study suggests that the ACO1 has a little effect on internode elongation at the heading stage, and that up-regulation of the ACS1 and OsEIN2 expression may attenuate inhibition of internode elongation.

Nature—Carbon Sinks and Rising Rice: Climate Change and Our Biosphere

In recognition of Earth Day 2010, this installment of Reports from Other Journals: Nature summarizes articles on the contribution of China’s vegetation to the global carbon sink, the effects of global warming on carbon sinks, and the promise of deepwater rice to expand cultivation of this important grain.

Impact of high-density stocking and selective harvesting on yield and water productivity of deepwater rice–fish systems

We examine the productivity of deepwater rice�fish systems and management strategies that include high-density initial stocking and selective harvesting. All species of fish and prawns grow faster after 120 days of rearing, probably due to periodic selective harvesting that minimizes the competition for food and space, as well as physiological stress at reduced density. We observe a higher survival rate, a lower apparent feed conversion ratio (1.77) and higher fish yield (14.1%) in rice�fish culture with selective harvesting (T1) than in rice�fish culture without selective harvesting (T2). The highest paddy yield was recorded in T1, primarily due to the higher number of panicles per m2 (139.5) and the number of filled grains per panicle (111.5). The increase in paddy yield over rice mono-cropping was higher in T1 (25%) than T2 (16.9%). The smaller number of panicles (122.2/m2) and filled grains (98.5 per panicle) in rice mono-cropping was probably due to the absence of fish and prawns in the field as fish and prawns improve soil fertility, recover lost energy, and adjust energy flow by consuming plankton, weeds, insects and bacteria that compete with rice for nutrients. The highest rice equivalent yield (38.5 t ha-1), the output value-cultivation cost ratio (1.56) and net water productivity (Rs. 7.30/m3) in deepwater rice�fish culture was recorded when selective harvesting was practiced. This eco-friendly dual production system (rice and fish) and on-dyke horticulture, which generate near-term lucrative returns and generates employment opportunities, can be adopted and expanded in lowlands and waterlogged areas

The ethylene response factors SNORKEL1 and SNORKEL2 allow rice to adapt to deep water

Living organisms must acquire new biological functions to adapt to changing and hostile environments. Deepwater rice has evolved and adapted to flooding by acquiring the ability to significantly elongate its internodes, which have hollow structures and function as snorkels to allow gas exchange with the atmosphere, and thus prevent drowning. Many physiological studies have shown that the phytohormones ethylene, gibberellin and abscisic acid are involved in this response, but the gene(s) responsible for this trait has not been identified. Here we show the molecular mechanism of deepwater response through the identification of the genes SNORKEL1 and SNORKEL2, which trigger deepwater response by encoding ethylene response factors involved in ethylene signalling. Under deepwater conditions, ethylene accumulates in the plant and induces expression of these two genes. The products of SNORKEL1 and SNORKEL2 then trigger remarkable internode elongation via gibberellin. We also demonstrate that the introduction of three quantitative trait loci from deepwater rice into non-deepwater rice enabled the latter to become deepwater rice. This discovery will contribute to rice breeding in lowland areas that are frequently flooded during the rainy season.