Losses In Rice Production Research Articles

Occurrence of Entomopathogenic Fungi from Natural Ecosystems in Phetchabun, Thailand and Their Virulence Against Brown Planthopper

Brown planthopper (BPH), Nilaparvata lugens Stål, is a serious insect pest of rice. The invasion of BPH causes heavy losses in rice production, both quality and quantity. The objective of this research was to search for Metarhizium spp., a genus of entomopathogenic fungi in the Clavicipitaceae family, from forest soil in three districts of Phetchabun Province, Thailand: Khao Kho, Lom Kao and Nam Nao to control BPH. Metarhizium spp. fungi were isolated by soil dilution plate technique and determined their efficacy using conidia suspension at the concentration of 1X108 conidia/mL on BPH at the 2-3th instar nymph fed on seedlings of susceptible rice cultivars, Taichung Native 1 (TN1). The most effective Metarhizium sp. isolate was identified using the ITS region of 18S rDNA sequencing, Basic Local Alignment Search Tool (BLAST) and evolutionary history. The result showed that 126 isolates of Metarhizium spp. were found and coded as PB-01 to PB-126. All isolates infected BPH nymph with 26.7 to 100% mortality within 6 days after contacting conidia suspension. The isolate of PB-75 showed the highest efficacy (100% BPH mortality) with the lethal times of 50% mortality (LT50) within 2.9 days. The species identification showed that the DNA sequence of Metarhizium sp. isolate, PB-75, was 98.6% similar to M. anisopliae Genbank ID JQ889704.1. Evolutionary history based on phylogenetic analysis using neighbor-joining and maximum parsimony methods confirmed that PB-75 formed the same phylogenetic clade with M. anisopliae Genbank ID JQ889704.1 and M. anisopliae var. anisopliae.

The small brown planthopper (Laodelphax striatellus) as a vector of the rice stripe virus.

The small brown planthopper, Laodelphax striatellus, is a destructive pest insect found in rice fields. L. striatellus not only directly feeds on the phloem sap of rice but also transmits various viruses, such as rice stripe virus (RSV) and rice black-streaked dwarf virus, resulting in serious loss of rice production. RSV is a rice-infecting virus that is found mainly in Korea, China, and Japan. To develop novel strategies to control L. striatellus and L. striatellus-transmitted viruses, various studies have been conducted, based on vector biology, interactions between vectors and pathogens, and omics, including transcriptomics, proteomics, and metabolomics. In this review, we discuss the roles of saliva proteins during phloem sap-sucking and virus transmission, the diversity and role of the microbial community in L. striatellus, the profile and molecular mechanisms of insecticide resistance, classification of L. striatellus-transmitted RSV, its host range and symptoms, its genome composition and roles of virus-derived proteins, its distribution, interactions with L. striatellus, and resistance and control, to suggest future directions for integrated pest management to control L. striatellus and L. striatellus-transmitted viruses.

Voltage-dependent anion channel 2 (VDAC2) facilitates the accumulation of rice stripe virus in the vector Laodelphax striatellus

Rice stripe virus (RSV) causes enormous losses in rice production and is transmitted by the small brown planthopper, Laodelphax striatellus, in a persistent-propagative manner. RSV accumulation within the gut lumen of the vector is indispensable for the successful transmission to rice and insects. In this study, we obtained a 1464 bp full-length cDNA of a voltage-dependent anion channel 2 from L. striatellus (LsVDAC2), which encodes a 283 amino acid protein. RSV infection increased the expression of LsVDAC2 in the midguts and ovaries of L. striatellus by 260% and 228%, respectively. Silencing of LsVDAC2 resulted in a 88% reduction of RSV loads at 24 h after RNAi, indicating that LsVDAC2 facilitates RSV accumulation in the vector. Yeast two-hybrid and GST pulldown assays demonstrated that LsVDAC2 interacted with RSV RNA-dependent RNA polymerase, RdRp. Furthermore, experiments in vivo and in vitro showed that LsVDAC2 induced the apoptotic response in RSV-infected insects and tissues. Silencing of LsVDAC2 via RNAi significantly reduced the expression of genes for apoptosis-related caspases 1a and 1c by 62% and 78%, respectively, in RSV-infected vectors. Whether LsVDAC2-induced RSV accumulation is related to RSV RdRp and LsVDAC2-induced cell apoptosis deserves further investigation.

Can the advisory system Nutrient Expert® balance productivity, profitability and sustainability for rice production systems in China?

CONTEXTTo avoid excessive chemical-fertilizer application and improve agricultural productivity in rice, a fertilizer recommendation system called Nutrient Expert® (NE) was designed. However, the ability of NE to balance yield, profitability and environmental sustainability in rice production needs to be further evaluated, as it is still difficult for farmers to assess the proper nitrogen (N) application rate. OBJECTIVEThe objective of this study was to demonstrate the advantages of the NE system in balancing yield, profitability and N loss in rice production, and recommend proper N application rates for different cropping seasons of rice. METHODSThis study describes results from field experiments conducted in five main rice cropping provinces from 2017 to 2020 in China, to investigate any advantages of NE compared with local farmers' practice (FP), and to determine the proper N application rates for different cropping seasons of rice. RESULTS AND CONCLUSIONSCompared with FP, NE had 12.1% lower N-fertilizer application, but increased rice grain yield by 4.3% and net profit by 7.4%, and decreased yield-scaled N loss by 20.7%. We showed how yield, profitability and N loss were affected by N balance (i.e., N applied to the field minus N removed from the field by the harvested crop biomass), and quantified relationships between N balance and N application rate, and between N output and input. Based on relationships between N balance and N application rate, we recommend N application rates in a range from 122 to 214 kg ha−1, depending on cropping seasons of rice. We demonstrated that NE can simultaneously improve yield, profitability and environmental sustainability. SIGNIFICANCEOur study provided quantitative support for NE-based recommendations on the N application rate for smallholders farming in different rice cropping systems, and these recommendations can serve as a reference for avoiding excessive N application rate in paddy fields in other regions with similar eco-environment.

Reduced Toxicities of Insecticides Against Brown Planthopper (Nilaparvata lugens Stål) Collected from Rice Fields in Bangladesh

The brown planthopper, Nilaparvata lugens (Stål), caused severe yield losses in rice production in many Asian countries. Chemical control is the key component of the integrated pest management tool to control rice brown planthopper (BPH). However, reduced toxicity of insecticides against this pest has been reported. We investigated the BPH mortality rate and the evolution of insecticide resistance in BPH collected from Bangladesh to commonly used insecticides by the rice-stem dipping method. Both the BPH laboratory strain and field populations were used in this study. The mortality rate of the Gazipur field population ranges from 15% to 80%, after exposure to imidacloprid in different concentrations. The highest mortality was found in response to dinotefuran followed by chlorpyrifos and etofenprox. The mortality rate increased after the time of exposure in relation to the increased concentrations of the insecticides. Additionally, the selected BPH strain shows a higher level of resistance to imidacloprid (resistance ratio = 179.45-fold), while other field populations show low to moderate levels of resistance. Increased detoxification enzyme activity, cytochrome P450 monooxygenase, was found in imidacloprid-resistant BPH. This study provides important information regarding the reduced toxicities of frequently used insecticides to control BPH.

Genome-wide and molecular characterization of the DNA replication helicase 2 (DNA2) gene family in rice under drought and salt stress.

Rice plants experience various biotic (such as insect and pest attack) and abiotic (such as drought, salt, heat, and cold etc.) stresses during the growing season, resulting in DNA damage and the subsequent losses in rice production. DNA Replication Helicase/Nuclease2 (DNA2) is known to be involved in DNA replication and repair. In animals and yeast DNA2 are well characterized because it has the abilities of both helicase and nuclease, it plays a crucial role in DNA replication in the nucleus and mitochondrial genomes. However; they are not fully examined in plants due to less focused on plants damage repair. To fill this research gap, the current study focused on the genome-wide identification and characterization of OsDNA2 genes, along with analyses of their transcriptional expression, duplication, and phylogeny in rice. Overall, 17 OsDNA2 members were reported to be found on eight different chromosomes (2, 3, 4, 6, 7, 9, 10, and 11). Among these chromosomes (Chr), Chr4 contained a maximum of six OsDNA2 genes. Based on phylogenetic analysis, the OsDNA2 gene members were clustered into three different groups. Furthermore, the conserved domains, gene structures, and cis-regulatory elements were systematically investigated. Gene duplication analysis revealed that OsDNA2_2 had an evolutionary relationship with OsDNA2_14, OsDNA2_5 with OsDNA2_6, and OsDNA2_1 with OsDNA2_8. Moreover, results showed that the conserved domain (AAA_11 superfamily) were present in the OsDNA2 genes, which belongs to the DEAD-like helicase superfamily. In addition, to understand the post-transcriptional modification of OsDNA2 genes, miRNAs were predicted, where 653 miRNAs were reported to target 17 OsDNA2 genes. The results indicated that at the maximum, OsDNA2_1 and OsDNA2_4 were targeted by 74 miRNAs each, and OsDNA2_9 was less targeted (20 miRNAs). The three-dimensional (3D) structures of 17 OsDNA2 proteins were also predicted. Expression of OsDNA2 members was also carried out under drought and salt stresses, and conclusively their induction indicated the possible involvement of OsDNA2 in DNA repair under stress when compared with the control. Further studies are recommended to confirm where this study will offer valuable basic data on the functioning of DNA2 genes in rice and other crop plants.

Identification of two QTLs, BPH41 and BPH42, and their respective gene candidates for brown planthopper resistance in rice

The brown planthopper (BPH) is the leading cause of insect damage to rice plants and BPH infestations have caused profound losses in rice production since the 1970’s. There is an urgent need to discover new BPH resistance genes to ensure the successful production of rice. Here, a new BPH resistance source provided by SeedWorks International Pvt. Ltd., SWD10, was used for this purpose. QTL mapping using 232 F2 progenies and 216 polymorphic markers revealed two dominant BPH resistance QTLs, BPH41 and BPH42, located on chromosome 4. BPH resistance mechanism test revealed that antibiosis and antixenosis mechanisms both play a role in BPH resistance conferred by these two QTLs. The QTLs were delimited between markers SWRm_01617 and SWRm_01522 for BPH41, and SWRm_01695 and SWRm_00328 for BPH42. Additionally, using RNA-seq data of lines containing the resistant QTLs, we shortlisted four and three gene candidates for BPH41 and BPH42, respectively. Differential gene expression analysis of lines containing the QTLs suggested that SWD10 BPH resistance is contributed by the plant’s innate immunity and the candidate genes may be part of the rice innate immunity pathway. Currently, the newly identified QTLs are being utilized for breeding BPH resistant rice varieties and hybrids.

The effect of integrated pest management on Scirpophaga innotata population and natural enemies on rice field in South Sulawesi, Indonesia

Abstract. Rahmawasiah, Abadi AL, Mudjiono G, Rizali A. 2022. The effect of integrated pest management on Scirpophaga innotata population and natural enemies on rice field in South Sulawesi, Indonesia. Biodiversitas 23: 4510-4516. White rice stem borer, Scirpophaga innotata, is an important pest on rice plants that needs attention because the population is quite large in Luwu Raya. This pest attacks rice plants at all growth stages and can result in yield losses in rice production. Synthetic insecticides are a common control technique used by farmers to control these pests. The continuous use of pesticides will certainly have a negative impact. Therefore, pursuing effective control strategies and maintaining environmental sustainability is necessary. This study aimed to determine the white rice stem borer population and its natural enemies on rainfed land, and permanent irrigated lands managed conventionally and integrated pest management. The research was carried out using insect sampling techniques and calculating the white rice stem borer population and natural enemies in rice cultivation. In rainfed and irrigated rice fields, rice cultivation was carried out using conventional methods and integrated pest management (in the form of planting refugia and regulating the use of synthetic pesticides). The sampling was carried out on plants from the vegetative phase to the generative phase. The type of insect taken was the white rice stem borer in the form of collecting groups of eggs and larvae. Imago was observed visually and using a farmcop. In addition, the collection of natural enemy insects on the plantation was also carried out. The results showed that the application of the integrated pest management system caused no significant effect on the decline of the white rice stem borer population in both rainfed and permanently irrigated lands in Luwu Raya. The white rice stem borer population was more commonly found in rainfed land than permanently irrigated land. The parasitoids found were Telenomus rowani, Tetrastichus schoenobii and Trichogramma japonicum. The population of Telenomus rowani was more numerous than other types of parasitoids. On average, the parasitoid population was more in the land managed by integrated pest management (IPM) application than the conventionally managed land. The predators found on the land were Oxyopes javanus, Agriocnemis femina, Conocephalus longipennis, Menochilus sexmaculata, Ophionea nigrofasciata, Micraspis lineata, and Paederus fuscipes. Predator populations were more on land managed with the application of IPM than on land managed conventionally.

Proteomic analysis of themeristematic root zone in contrasting genotypes reveals new insights in drought tolerance in rice.

Drought is responsible for major losses in rice production. Root tips contain meristematic and elongation zones that play major roles in determination of root traits and adaptive strategies to drought. In this study we analysed two contrasting genotypes of rice: IR64, a lowland, drought-susceptible, and shallow-rooting genotype; and Azucena, an upland, drought-tolerant, and deep-rooting genotype. Samples were collected of root tips of plants grown under control and water deficit stress conditions. Quantitative proteomics analysis resulted in the identification of 7294 proteins from the root tips of IR64 and 6307 proteins from Azucena. Data are available via ProteomeXchange with identifier PXD033343. Using a Partial Least Square Discriminant Analysis on 4170 differentially abundant proteins, 1138 statistically significant proteins across genotypes and conditions were detected. Twenty two enriched biological processes showing contrasting patterns between two genotypes in response to stress were detected through gene ontology enrichment analysis. This included identification of novel proteins involved in root elongation with specific expression patterns in Azucena, including four Expansins and seven Class III Peroxidases. We also detected an antioxidant network and a metallo-sulfur cluster assembly machinery in Azucena, with roles in reactive oxygen species and iron homeostasis, and positive effects on root cell cycle, growth and elongation.

Mathematical Modeling for Estimating the Risk of Rice Farmers’ Losses Due to Weather Changes

This paper discusses the relationship between weather and rice productivity modeled using the Cobb–Douglas production function principle, with the hypothesis that rice production will increase in line with the increase in average rainfall, wind speed, and temperature every month and then decrease if the weather conditions exceed the threshold. As a result, farmers have the risk of losing rice production. To overcome this problem, we try to estimate the value of the risk. The purpose of this study is to estimate the risk of losses that occurred in rice plants due to weather changes. The method used in this study is risk estimation with the Tail Value at Risk (TVaR) approach. In addition to TVaR, it is estimated simultaneously with Value at Risk (VaR) and Conditional Value at Risk (CVaR). This study uses weather data consisting of rainfall data, wind speed, and air temperature collected from geophysical and meteorological data. Meanwhile, yield data were obtained and processed from the Central Statistics Agency and the West Java Agricultural Service. The data used are data from 2008 to 2021. There are two main parts of the results in this study, namely mathematical analysis and data analysis. The mathematical analysis is a risk model derivation process, which includes TVaR risk measurement. The data analysis process is a simulation of the estimated risk of rice production loss. The results obtained from this study are the value of opportunity risk of loss based on the VaR, CVaR, and TVaR approaches. The conclusion of this study is that the rice plants have a risk of loss in the form of reduced yields caused by weather changes. Farmers can plan to overcome this loss problem, by setting up a reserve fund. Risk of loss can be managed through the rice agricultural insurance program. This is in line with the Indonesian government’s program through the ministry of agriculture. Thus, farmers, insurance companies, and the government can manage the risk of losing rice yields.

Searching of Novel Herbicides for Paddy Field Weed Management—A Case Study with Acetyl-CoA Carboxylase

Weed management is the major biological constraint in paddy (Oryza sativa L.) producing areas. Predominantly, barnyard grass (Echinochloa crus-galli) is a rice-mimicking weed that causes 57% of yield loss in rice production. Conventionally, herbicides are the site-specific weed inhibitors often used to suppress E. crus-galli growth. Acetyl-CoA carboxylase (ACCase) is an important target for developing novel herbicides with remarkable selectivity against gramineous weeds. Notably, fenoxaprop-P-ethyl (FPPE) is a selective ACCase herbicide extensively used in paddy fields to inhibit barnyard grass. However, prolonged use of FPPE herbicide elicits phytotoxicity in cultivated rice and herbicide resistance in weeds. Recently, phytotoxins are emerging as an alternative to commercial herbicides with safer environmental profiles. Nevertheless, discovering natural herbicides through in vivo and in vitro techniques is time-consuming and expensive. Therefore, high-end computational screening strategies including Tanimoto similarity, docking, binding free energy, and herbicide-likeness were used to pinpoint the lead molecule. Finally, molecular dynamics and MM/PBSA calculations were employed to validate the binding kinetics of the hit compound. Indeed, sinigrin was identified as a promising phytotoxic inhibitor against the ACCase enzyme. The findings of our study were well correlated with the existing experimental results. Overall, the current work will aid in the development of commercializing phytotoxin herbicides in foreseeable future.

Effect of unseasonal rainfall on rice production in Nepal during the year 2021: A case study

Our study explicit the information regarding the status losses and the compensation amount We browsed the website of Ministry of Agriculture and Livestock Development (MoALD) and visited Agriculture Knowledge Centre to obtain the information. Rice is a major cereal crop, contributing around 25% of GDP and majority of working population are engaged in rice production for at least half year. Increasing population and pernicious natural hazards had declined the rice production leading to increment in import of rice from neighboring countries. Nepal received 15% more rain than average monsoon in year 2021. Flooding in various areas of Nepal occurred, causing huge loss of rice production along with destruction of lives and property indirectly leading to food insecurity. The onset of heavy unseasonal monsoon, occurred at the period when rice crops were ready to harvest or ready to thresh, undermined the labor, time and money invested by the farmers. The total rice production has been reduced to 5.13 million tons in 2021 from 5.55 million tons in 2020 at the rate of 8.74%. Lumbini Province faced the highest loss, followed by Sudarpaschim Province of Nepal. Climate change was the major factor responsible for this, hampering the agricultural productivity. Government of Nepal had decided to provide compensation to them based on three categories: small farmers having holdings of up to 10 katthas received compensation of 65% of their cost of production , medium farmers having land holdings from 11 to 40 katthas received 30% of their cost of production ,the large farmers having land holdings more than 40 katthas received compensation 20% of their cost of production. Also, the partially affected farmers received compensation 20% of their cost of production.

Upaya Pengendalian Wereng Batang Coklat Melalui Penataan Kelembagaan Kelompok Tani

The problem of loss of rice production due to brown planthopper (BP) attacks every year always appears and is felt to be completely unresolved. Many factors cause the lack of success of BP control, one of which is the understanding of farmers on the characteristics of BP, monitoring and control technology is still lacking and the existing farmer group institutions are not yet well established. The purpose of this study is to build a model/pilot of institutional arrangement for farmer groups in solving the problem of yield loss caused by brown planthoppers. The methodology used begins with extracting information on existing technology through focus group discussions, implementing a pilot BP control technology in the form of a 5 ha field laboratory, implementing a field school for 6 meetings, empowering farmer institutions through the formation of pest observer teams and advocacy for pesticide store. The study was conducted in Pamarayan Village, Suka Tani IV Farmer Group, Pamarayan Village, Pamarayan District, Serang Regency, Banten Province in January-December 2019. Data collection was carried out through field observations and filling out questionnaires in the form of pre/post test. The data obtained were analyzed descriptively. The results of the study showed that there was an increase in the knowledge and skills of cooperative farmers in rice cultivation and WBC control technology by 26.53-70.71% and an increase in knowledge and skills of the pest observer team by 79.49-96.77%. The technological and institutional performance of farmer groups succeeded in increasing rice production by 55.63% in MK I and 97.5% in MK II compared to before the program was implemented. It is hoped that this WBC control model can be replicated in other WBC endemic areas.

Climate Change and Its Impact on Agriculture with Special Reference to Production System in India

Agriculture production is directly dependent on climate change and weather. Climate change can bring positive and negative effects on Indian agriculture, India’s agriculture is more dependent on monsoon from the ancient periods. Any change in monsoon trend drastically affects agriculture. Even the increasing temperature is affecting the Indian agriculture. The term “weather” refers to the short-term (daily) changes in temperature, wind, and/or rainfall of a region. In the long run, the climatic change could affect agriculture in several ways such as quantity and quality of crops in terms of productivity, growth rates, photosynthesis and transpiration taxes, wetness accessibility etc. Climate change is likely to directly impact food production across the globe. Increase in the mean seasonal temperature can reduce the duration of many crops and hence reduce the yield. In areas where temperatures are already close to the physiological maxima for crops, warming will impact produces more immediately. Motorists of climate change through alterations in atmospheric arrangement can also influence food production directly by its impacts on plant physiology. The consequences of agriculture’s contribution to climate change, and of climate change’s negative impact on agriculture, are severe which is projected to have a great impact on food production and may threaten the food security and hence, need special agricultural measures to struggle with. In the Indo-Gangetic Plain, these pre monsoon changes will primarily affect the wheat crop (>0.5oC increase in time slice 2010-2039). In the states of Jharkhand, Odisha and Chhattisgarh alone, rice production losses during severe deficiencies (about one year in five) average about 40% of total production, with an estimated value of $800 million. The consequence of climate change poses many threats; one of the important significances is bringing about changes in the quality and quantity water resources and agriculture productivity This study focus on study about the climate change how affecting the agriculture production in India different regions. Keywords: Climate Change: Impact: Agriculture Production: Temperature

Development of New Rice (Oryza. sativa L.) Breeding Lines through Marker-Assisted Introgression and Pyramiding of Brown Planthopper, Blast, Bacterial Leaf Blight Resistance, and Aroma Genes

Brown planthopper, blast, and bacterial blight are the main biotic stressors of rice and can cause a massive loss in rice production. Aroma is an important character of rice quality. It is of far-reaching significance to breed resistant and high-quality varieties using germplasms with objective genes. In this study, the introgression and pyramiding of brown planthopper (BPH), blast, and bacterial leaf blight (BLB) resistance genes and aroma genes into elite rice maintainers and restorers were conducted through conventional cross-breeding coupled with the marker-assisted selection (MAS) breeding method. Single-plant selection was performed from F2 onwards to select desirable recombinants possessing alleles of interest with suitable phenotypes. Respective linked markers were used in each generation from intercrossing to the F7 generation for tracking the presence of targeted genes. A total of 74 improved lines (ILs) have been developed which possess a combination of 1 to 4 genes for BPH, blast, and BLB resistance and aroma. These ILs showed moderate to high resistance to multiple biotic stresses (BPH, blast and BLB) or aromatic fragrance without obvious negative effects on agronomic traits. As multiple resistance and aromatic traits have become significant objectives in rice breeding, these resistance and/or aroma gene introgressed or pyramided lines have important application prospects. Core ideas: (1) marker-assisted breeding was used to pyramid multiple genes for an elite breeding line; (2) improved lines with the introgression of 1–4 genes were developed to achieve high resistance against various biotic stresses and aroma; (3) new lines were used as donor parents to introgress multiple genes in other genetic backgrounds.

Climate change favours connectivity between virus-bearing pest and rice cultivations in sub-Saharan Africa, depressing local economies.

AimsRice is a staple food for many countries, being fundamental for a large part of the worlds’ population. In sub-Saharan Africa, its importance is currently high and is likely to become even more relevant, considering that the number of people and the per-capita consumption are both predicted to increase. The flea beetles belonging to the Chaetocnema pulla species group (pulla group), a harmful rice pest, are an important vector of the Rice Yellow Mottle Virus, a disease which leads even to 80–100% yield losses in rice production. We present a continental-scale study aiming at: (1) locating current and future suitable territories for both pulla group and rice; (2) identifying areas where rice cultivations may occur without suffering the presence of pulla group using an Ecological Niche Modelling (ENM) approach; (3) estimating current and future connectivity among pulla group populations and areas predicted to host rice cultivations, based on the most recent land-use estimates for future agricultural trends; (4) proposing a new connectivity index called “Pest Aggression Index” (PAI) to measure the agricultural susceptibility to the potential future invasions of pests and disease; (5) quantifying losses in terms of production when rice cultivations co‐occur with the pulla group and identifying the SSA countries which, in the future inferred scenarios, will potentially suffer the greatest losses.LocationSub-Saharan Africa.MethodsSince the ongoing climate and land-use changes affect species’ distributions, we first assess the impact of these changes through a spatially-jackknifed Maxent-based Ecological Niche Modelling in GIS environment, for both the pulla group and rice, in two climatic/socioeconomic future scenarios (SSP_2.45 and 3.70). We then assess the connectivity potential of the pulla group populations towards rice cultivations, for both current and future predictions, through a circuit theory-based approach (Circuitscape implemented in Julia language). We finally measure the rice production and GPD loss per country through the spatial index named “Pest Aggression Index”, based on the inferred connectivity magnitude.ResultsThe most considerable losses in rice production are observed for Liberia, Sierra Leone and Madagascar in all future scenarios (2030, 2050, 2070). The future economic cost, calculated as USD lost from rice losses/country’s GDP results are high for Central African Republic (−0.6% in SSP_2.45 and −3.0% in SSP_3.70) and Guinea–Bissau (−0.4% in SSP_2.45 and −0.68% in SSP_3.70), with relevant losses also obtained for other countries.Main conclusionsSince our results are spatially explicit and focused on each country, we encourage careful land-use planning. Our findings could support best practices to avoid the future settlement of new cultivations in territories where rice would be attacked by pulla group and the virus, bringing economic and biodiversity losses.

A Histone Deacetylase, Magnaporthe oryzae RPD3, Regulates Reproduction and Pathogenic Development in the Rice Blast Fungus.

ABSTRACTAcetylation and deacetylation of histones are key epigenetic mechanisms for gene regulation in response to environmental stimuli. RPD3 is a well-conserved class I histone deacetylase (HDAC) that is involved in diverse biological processes. Here, we investigated the roles of the Magnaporthe oryzae RPD3 (MoRPD3) gene, an ortholog of Saccharomyces cerevisiae Rpd3, during development and pathogenesis in the model plant-pathogenic fungus Magnaporthe oryzae. We demonstrated that the MoRPD3 gene is able to functionally complement the yeast Rpd3 deletion mutant despite the C-terminal extension of the MoRPD3 protein. MoRPD3 localizes primarily to the nuclei of vegetative hyphae, asexual spores, and invasive hyphae. Deletion of MoRPD3 appears to be lethal. Depletion of MoRPD3 transcripts via gene silencing (MoRPD3kd, where “kd” stands for “knockdown”) has opposing effects on asexual and sexual reproduction. Although conidial germination and appressorium formation rates of the mutants were almost comparable to those of the wild type, in-depth analysis revealed that the appressoria of mutants are smaller than those of the wild type. Furthermore, the MoRPD3kd strain shows a significant reduction in pathogenicity, which can be attributed to the delay in appressorium-mediated penetration and impaired invasive growth. Interestingly, MoRPD3 does not regulate potassium transporters, as shown for Rpd3 of S. cerevisiae. However, it functioned in association with the target of rapamycin (TOR) kinase pathway, resulting in the dependency of appressorium formation on hydrophilic surfaces and on TOR’s inhibition by MoRPD3. Taken together, our results uncovered distinct and evolutionarily conserved roles of MoRPD3 in regulating fungal reproduction, infection-specific development, and virulence.

RNA-Seq and Electrical Penetration Graph Revealed the Role of Grh1-Mediated Activation of Defense Mechanisms towards Green Rice Leafhopper (Nephotettix cincticeps Uhler) Resistance in Rice (Oryza sativa L.).

The green rice leafhopper (GRH, Nephotettix cincticeps Uhler) is one of the most important insect pests causing serious damage to rice production and yield loss in East Asia. Prior to performing RNA-Seq analysis, we conducted an electrical penetration graph (EPG) test to investigate the feeding behavior of GRH on Ilpum (recurrent parent, GRH-susceptible cultivar), a near-isogenic line (NIL carrying Grh1) compared to the Grh1 donor parent (Shingwang). Then, we conducted a transcriptome-wide analysis of GRH-responsive genes in Ilpum and NIL, which was followed by the validation of RNA-Seq data by qPCR. On the one hand, EPG results showed differential feeding behaviors of GRH between Ilpum and NIL. The phloem-like feeding pattern was detected in Ilpum, whereas the EPG test indicated a xylem-like feeding habit of GRH on NIL. In addition, we observed a high death rate of GRH on NIL (92%) compared to Ilpum (28%) 72 h post infestation, attributed to GRH failure to suck the phloem sap of NIL. On the other hand, RNA-Seq data revealed that Ilpum and NIL GRH-treated plants generated 1,766,347 and 3,676,765 counts per million mapped (CPM) reads, respectively. The alignment of reads indicated that more than 75% of reads were mapped to the reference genome, and 8859 genes and 15,815,400 transcripts were obtained. Of this number, 3424 differentially expressed genes (DEGs, 1605 upregulated in Ilpum and downregulated in NIL; 1819 genes upregulated in NIL and downregulated in Ilpum) were identified. According to the quantile normalization of the fragments per kilobase of transcript per million mapped reads (FPKM) values, followed by the Student’s t-test (p < 0.05), we identified 3283 DEGs in Ilpum (1935 upregulated and 1348 downregulated) and 2599 DEGs in NIL (1621 upregulated and 978 downregulated) with at least a log2 (logarithm base 2) twofold change (Log2FC ≥2) in the expression level upon GRH infestation. Upregulated genes in NIL exceeded by 13.3% those recorded in Ilpum. The majority of genes associated with the metabolism of carbohydrates, amino acids, lipids, nucleotides, the activity of coenzymes, the action of phytohormones, protein modification, homeostasis, the transport of solutes, and the uptake of nutrients, among others, were abundantly upregulated in NIL (carrying Grh1). However, a high number of upregulated genes involved in photosynthesis, cellular respiration, secondary metabolism, redox homeostasis, protein biosynthesis, protein translocation, and external stimuli response related genes were found in Ilpum. Therefore, all data suggest that Grh1-mediated resistance against GRH in rice would involve a transcriptome-wide reprogramming, resulting in the activation of bZIP, MYB, NAC, bHLH, WRKY, and GRAS transcription factors, coupled with the induction of the pathogen-pattern triggered immunity (PTI), systemic acquired resistance (SAR), symbiotic signaling pathway, and the activation of genes associated with the response mechanisms against viruses. This comprehensive transcriptome profile of GRH-responsive genes gives new insights into the molecular response mechanisms underlying GRH (insect pest)–rice (plant) interaction.

Optimizing agronomic traits and increasing economic returns of machine-transplanted rice with side-deep fertilization of double-cropping rice system in southern China

• Machine-transplanted rice with side deep fertilization (MRSF) could optimize agronomic traits and yield components. • MRSF increased grain yield by 0.5 %–20.2 % compared with conventional fertilization (CF). • MRSF increased economic return by 9.9 %–31.8 % compared with CF. • MRSF enhanced NPK fertilizer uptake but reduced their application rates. • MRSF combined with decreased nitrogen input by 20–30 % is the appropriate system. Machine-transplanted rice with side-deep fertilization (MRSF) is a recommended strategy to reduce labor cost and nitrogen (N) fertilizer loss in sustainable double-cropping rice production in China. However, the effects of MRSF on double-cropping rice profitability and agronomic traits are unclear. Here, experiments were conducted in two sites at Dongting Lake to determine the yield and economic benefits of MRSF and the optimal N application rate. Six fertilization treatments for early- and late-season rice at various N rates (0/0, 90/99, 105/116, 120/132, 135/149, and 150/165 kg N ha −1 ) were tested. The grain yield of early-season rice (ESR) was the highest (8.7 t ha −1 ) under 70 % deep fertilization (DF), whereas that of late-season rice (LSR) was the highest (6.1 t ha −1 ) under 80 % DF treatment in Miluo. The grain yield of ESR and LSR (7.5 and 7.9 t ha −1 , respectively) were the highest under 80 % DF treatment in Yiyang. Compared with conventional fertilization (CF), MRSF significantly enhanced grain yield by 0.5 %–20.2 % and 5.3 %–15.0 % in Miluo and Yiyang, respectively. The high grain yield under MRSF can be attributed to higher leaf area index, chlorophyll content, nutrient uptake, biomass accumulation, and spikelet number per m 2 . Relative to CF, MRSF increased the panicle bearing tiller rate by 8.4 %–24.6 % (Miluo) and 3.3 %–12.2 % (Yiyang), thereby improving dry matter accumulation and nutrient uptake. Furthermore, the economic benefit under MRSF increased by 9.9 %–31.8 % (Miluo) and 15.0 %–25.7 % (Yiyang) compared with that under CF. N reduction in the MRSF treatments resulted in fewer effective panicles than the 100 % DF treatment. Improved yield and nutrient uptake in double-cropping rice were associated with deep fertilizer placement rather than N application rate. The number of filled grains per panicle had the strongest influence on ESR and LSR grain yield. Overall, MRSF is recommended as an alternative approach to increase grain yield, profitability, and agronomic traits while lowering the N application rate in the double-cropped rice systems near Dongting Lake, southern China.

Fine Mapping of a Novel Major Quantitative Trait Locus, qPAA7, That Controls Panicle Apical Abortion in Rice.

The panicle apical abortion (PAA) causes severe yield losses in rice production, but details about its development and molecular basis remain elusive. Here, we detected PAA quantitative trait loci (QTLs) in three environments using a set of chromosome segment substitution lines (CSSLs) that was constructed with indica Changhui121 as the recurrent parent and japonica Koshihikari as the donor parent. First, we identified a novel major effector quantitative trait locus, qPAA7, and selected a severe PAA line, CSSL176, which had the highest PAA rate among CSSLs having Koshihikari segments at this locus. Next, an F2 population was constructed from a cross between CSS176 and CH121. Using F2 to make recombinantion analysis, qPAA7 was mapped to an 73.8-kb interval in chromosome 7. Among nine candidate genes within this interval, there isn’t any known genes affecting PAA. According to the gene annotation, gene expression profile and alignment of genomic DNA, LOC_Os07g41220 and LOC_Os07g41280 were predicted as putative candidate genes of qPAA7. Our study provides a foundation for cloning and functional characterization of the target gene from this locus.