Yellow Mottle Research Articles

Molecular characterization and infectivity analysis of tomato leaf curl New Delhi virus isolates infecting potato.

The online version contains supplementary material available at 10.1007/s13205-021-02752-5.

Challenges for Small Scale Rice Farmers- A Case Study from Tanzania

The present study was conducted in the Lake Zone of Tanzania, with a sample size of 265 rice farmers has been selected. The objective was to find out the constraints faced by rice farmers to propose Government’s policies regulating to overcome the constraints of rice production promotion and marketing in Tanzania. The study found that the agro-ecological constraints faced by farmers, ranked from more to less serious, were related to production and marketing problems; the major production challenge was drought faced 89.81 % of rice farmers from attaining the high rice production potential in the Lake Zone, followed by pests 34.34 %, shortage of inputs 31.32 % and diseases were the other major challenge encountered by the 25.29 %. The major diseases were the Yellow Mottle Virus and rice blast. Further, it shows that the low price of rice was a major marketing challenge faced by 38.95 %, followed by price fluctuations of 17.90%, and improper measurement scale was observed to be a challenge faced by 14.90 % of rice farmers.

Viral diagnosis in cultivars of Ipomoea batatas (L.) Lam.

Ipomoea batatas (L.) Lam. commonly known as sweet potato, is an important staple food worldwide, mainly due to its high nutritional value and yield. However, vegetative reproduction of sweet potato makes it more susceptible to viral infections, which threatens its productivity, quality, and difficult long-term preservation in germplasm banks. Also, it can act as a virus reservoir infecting the rest of the plant accessions in the bank collections. Hence, this work aimed to screen Begomovirus, Potyvirus, and Carlavirus infections in 16 traditional sweet potato cultivars from the germplasm collection of the ISOPlexis Germplasm Bank, Madeira, Portugal. The infection prevalence by these viruses among cultivars was 81.25%, 25.00%, and 6.25%, respectively; being ISOP1011 the only accession coinfected by Potyvirus and Carlavirus. The accessions ISOP1006, ISOP1010, and ISOP1047 were also coinfected by Begomovirus and Potyvirus, highlighting their vulnerability to viral infections. The ISOP1005 and ISOP1027 accessions were the only ones not infected by any of these viruses. The analysis of the partial sequence obtained from the Carlavirus detected in the accession ISOP1011, revealed the existence of an ORF that encodes for 93 amino acids of the catalytic domain of an RNA-directed RNA polymerase related to the Tymovirus protein family, as could be confirmed by comparison with proteins stored in UniProtKB. Multiple sequence alignment with these proteins showed that Motifs A and B of the catalytic domain were conserved. The search for sequence similarity with sequences deposited in GenBank reported a high sequence identity with Sweet potato yellow mottle virus (SPYMV) and Sweet potato chlorotic fleck virus (SPCFV). However, the 9-11% discrepancy in nucleotide sequence identity and a phylogenetic analysis carried out using the maximum probability method suggests the virus isolated from ISOP1011 is a new divergent strain of the SPCFV species.

Complete genome sequence of artemisia virus B, a new polerovirus infecting Artemisia princeps in South Korea.

The complete genome sequence of a new polerovirus found naturally infecting Artemisia princeps, artemisia virus B (ArtVB), was determined using high-throughput sequencing. The ArtVB genome comprises 6,141 nucleotides and contains six putative open reading frames (ORF0 to ORF5) with a genome structure typical of poleroviruses. A multiple sequence alignment showed that the complete ArtVB genome shares 50.98% nucleotide sequence identity with ixeridium yellow mottle virus 1 (IxYMaV-1, GenBank accession no. KT868949). ArtVB shares the highest amino acid sequence identity in P0 and P3-P5 (21.54%-51.69%) with other known poleroviruses. Phylogenetic analysis indicated that ArtVB should be considered a member of a new species within the genus Polerovirus, family Luteoviridae.

Occurrence and characterization of virus species associated with black pepper (piper nigrum l.) virus diseases in Hainan province, China

AbstractBlack pepper (Piper nigrum L.) is one of the most ancient spice crops in the world. Hainan Province is the largest black pepper‐producing region in China. Viral disease is one of the main factors affecting black pepper. However, there are rarely studies on black pepper viral disease in China. We performed a survey in five major black pepper‐growing counties (Qionghai, Wenchang, Wanning, Haikou and Ding'an) of Hainan Province and collected 589 samples, with virus‐like symptoms from 2014 to 2019. Various viruses were identified including cucumber mosaic virus (CMV), piper yellow mottle virus (PYMoV), Piper DNA virus 1 (PDV‐1) and Piper DNA virus 2 (PDV‐2) using small RNA deep sequencing. The RT‐PCR screening of field samples indicated three types of infection: CMV alone (5.56%), PYMoV + PDV‐1 + PDV‐2 (25.00%) and PYMoV + CMV +PDV‐1 + PDV‐2 (69.44%). The data suggested that PYMoV might be the main pathogen causing virus diseases of black pepper. Two complete genome sequences of PYMoV were obtained. Phylogenetic analysis showed that PYMoV isolates from China were placed in a branch distinct from PYMoV isolates from India. To our knowledge, this is the first report of PYMoV, PDV‐1 and PDV‐2 naturally infecting black pepper, and the first genome sequence of PYMoV in China.

Variation among Tanzania Rice Germplasm Collections Based on Agronomic Traits and Resistance to Rice Yellow Mottle Virus

Rice (Oryza species) is a commercial crop worldwide. Across Africa, the potential yield and quality of rice is diminished by a lack of high performance, locally adapted varieties, and the impact of rice yellow mottle virus (RYMV). The objective of this study was to assess the performance of a diverse collection of rice germplasm for RYMV resistance and agronomic traits, and to select promising lines for breeding for Tanzanian conditions. Fifty-four rice genotypes were field evaluated in two important rice production sites (Ifakara and Mkindo) in Tanzania, which are recognized as RYMV hotspots, using a 6 × 9 alpha lattice design with two replications. There was significant (p < 0.05) genotypic variation for agronomic traits and RYMV susceptibility in the tested germplasm. Seven genotypes with moderate to high RYMV resistance were identified, including Salama M-57, SSD1, IRAT 256, Salama M-55, Mwangaza, Lunyuki, and Salama M-19, which were identified as new sources of resistance genes. Positive and significant correlations were detected between grain yield and number of panicles per plant (NPP), panicle length (PL), number of grains per panicle (NGP), percentage-filled grains (PFG), and thousand-grain weight (TGW), which are useful traits for simultaneous selection for rice yield improvement. A principal component analysis allocated five principal components, accounting for 79.88% of the total variation present in the assessed germplasm collection. Traits that contributed most to variability included NPP, number of tillers/plant (NT), PL, grain yield (GY), and days to 50% flowering (DFL). The genotypes Rangimbili, Gigante, and SARO possess complementary agronomic traits and RYMV resistance, and can be recommended for further evaluation, genetic analysis, and breeding.

Systemic infection and symptom development of agro-inoculated cDNA clone of cherry rusty mottle-associated virus in sweet cherry (Prunus avium)

Cherry rusty mottle-associated virus (CRMaV), which belongs the genus Robigovirus of the family Betaflexiviridae, is strongly associated with cherry rusty mottle disease of sweet cherry, Prunus avium. Here, we report on the successful development of an Agrobacterium-based inoculation system for a cloned CRMaV cDNA construct. Agro-inoculation of virus-free cherry rootstock ‘Krymsk6’ [P. cerasus x (P. cerasus x P. maackii)] resulted in the development of chlorotic yellow mottle symptoms on systemic leaves beginning at 50 days post inoculation. The presence of CRMaV in ‘Krymsk6’ agro-inoculated plants was confirmed by RT-PCR and ELISA. Subsequently, CRMaV from agro-inoculated ‘Krymsk6’ was graft-transmissible onto virus-free sweet cherry rootstock P. avium ‘Mazzard’ as evidenced by the production of typical cherry rusty mottle symptoms beginning at 35 days post grafting, and further confirmed by western blotting and RT-PCR. These results showed conclusively that CRMaV is the causal agent of cherry rusty mottle disease in sweet cherry. The reverse genetic system presented in this study can be used as a tool to investigate the molecular biology of CRMaV and also a template for infectious clone development for other viruses in the genus Robigovirus.

Comparison of sensitivity and rapidness of PCR, recombinase polymerase amplification, and RNA-specific amplification for detection of Rice yellow mottle virus

Comparison of sensitivity and rapidness of PCR, recombinase polymerase amplification, and RNA-specific amplification for detection of Rice yellow mottle virus

Determining the Combining Ability and Gene Action for Rice Yellow Mottle Virus Disease Resistance and Agronomic Traits in Rice (Oryza sativa L.)

Selecting genetically diverse and complementary parental lines and superior crosses are pre-requisites in developing improved cultivars. The objectives of this study were to determine the combining ability effects and gene action conditioning rice yellow mottle virus disease (RYMVD) resistance and agronomic traits in rice (Oryza sativa L.). Ten parental lines and their 45 F2 progenies were field evaluated in three locations using a 5 × 11 alpha lattice design with two replications. The genotype × site interaction effects were significant (p < 0.05) for the number of tillers (NT), number of panicles per plant (NPP), number of grains per panicle (NGP), percentage of filled grains (PFG), thousand grain weight (TGW), RYMVD resistance and grain yield (GY). The analysis of general and specific combining ability (GCA and SCA) indicated involvement of both additive and non-additive gene action governing inheritance of traits. High GCA/SCA ratio estimate revealed additive genetic effect was predominant. Parental lines Mwangaza, Lunyuki, Salama M-57, Salama M-19, IRAT 256 and Salama M-55, which had negative GCA effects for RYMVD, and families such as SARO 5 × Salama M-55, IRAT 245 × Rangimbili, Rangimbili × Gigante and Rangimbili × Mwangaza, which had negative SCA effects for RYMVD, were selected for RYMV resistance breeding. The crosses Rangimbili × Gigante, Gigante × Salama M-19 and Rangimbili × Salama M-55 were selected due to their desirable SCA effects for GY. The predominance of additive gene effects for agronomic traits and RYMVD resistance in the present breeding populations suggested that rice improvement could be achieved through gene introgression using recurrent selection.

Some important elements of soil-water relationship in managing oil palms planted on acid sulfate soils

Oil palms (Elaeis guineensis) are generally able to grow economically and feasibly on various soil types, mostly in tropical countries. However, oil palms planted on acid sulfate soils were producing lesser Fresh Fruit Bunches (FFB) as compared to those on non-acid sulfate soils. The poor performance of oil palms planted on acid sulfate was mainly attributed to the presence of excess sulfates, which limits the FFB yields and vegetative growth.1 Generally, acid sulfate soils have significant amounts of free and absorbed sulfate. Jarosite generally occurs as pale yellow mottles along old root channels and on ped faces in acid sulfate soils. pH in these horizon is less than 4.0.2,3 These soils often are also high in Aluminium (Al), Al saturation and often with phosphorus (P) fixation capacity. These acid sulfate soils are known for having poor values for organic matter, bases, cation exchange capacity, water retention, water holding capacity and microbial activity, which contributes towards their low soil fertility and hence limitations in soil productivity. Of these limitations, Al toxicity and excess sulfates are two major constraints to FFB yields in oil palms. The important relationship of soil and water for managing a sustainable productivity of oil palms on acid sulfate soil are discussed in details in this paper.

Disease Pandemics and Major Epidemics Arising from New Encounters between Indigenous Viruses and Introduced Crops.

Virus disease pandemics and epidemics that occur in the world’s staple food crops pose a major threat to global food security, especially in developing countries with tropical or subtropical climates. Moreover, this threat is escalating rapidly due to increasing difficulties in controlling virus diseases as climate change accelerates and the need to feed the burgeoning global population escalates. One of the main causes of these pandemics and epidemics is the introduction to a new continent of food crops domesticated elsewhere, and their subsequent invasion by damaging virus diseases they never encountered before. This review focusses on providing historical and up-to-date information about pandemics and major epidemics initiated by spillover of indigenous viruses from infected alternative hosts into introduced crops. This spillover requires new encounters at the managed and natural vegetation interface. The principal virus disease pandemic examples described are two (cassava mosaic, cassava brown streak) that threaten food security in sub-Saharan Africa (SSA), and one (tomato yellow leaf curl) doing so globally. A further example describes a virus disease pandemic threatening a major plantation crop producing a vital food export for West Africa (cacao swollen shoot). Also described are two examples of major virus disease epidemics that threaten SSA’s food security (rice yellow mottle, groundnut rosette). In addition, brief accounts are provided of two major maize virus disease epidemics (maize streak in SSA, maize rough dwarf in Mediterranean and Middle Eastern regions), a major rice disease epidemic (rice hoja blanca in the Americas), and damaging tomato tospovirus and begomovirus disease epidemics of tomato that impair food security in different world regions. For each pandemic or major epidemic, the factors involved in driving its initial emergence, and its subsequent increase in importance and geographical distribution, are explained. Finally, clarification is provided over what needs to be done globally to achieve effective management of severe virus disease pandemics and epidemics initiated by spillover events.

Tobamoviruses of two new species trigger resistance in pepper plants harbouring functional L alleles.

Tobamoviruses are often referred to as the most notorious viral pathogens of pepper crops. These viruses are not transmitted by invertebrate vectors, but rather by physical contact and seeds. In this study, pepper plants displaying mild mottle and mosaic symptoms were sampled in four different regions of Peru. Upon double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) tests, seven samples cross-reacted weakly with antibodies against pepper mild mottle virus (PMMoV), suggesting the presence of tobamoviruses. When employing RT-PCR, conserved primers amplified cDNA fragments of viruses from two putative new tobamovirus species in the samples. The complete genome of two representative isolates were, therefore, sequenced and analysed in silico. These viruses, which were tentatively named yellow pepper mild mottle virus (YPMMoV) and chilli pepper mild mottle virus (CPMMoV), shared highest nucleotide genome sequence identities of 83 and 85 % with bell pepper mottle virus (BpeMV), respectively. Mechanical inoculation of indicator plants with YPMMoV and CPMMoV isolates did not show any obvious differences in host ranges. These viruses were also inoculated mechanically on pepper plants harbouring different resistance L alleles to determine their pathotypes. Pepper plants carrying unfunctional L alleles (L0) to tobamoviruses were infected by all isolates and presented differential symptomatology for YPMMoV and CPMMoV. On the other hand, pepper plants carrying L1, L2, L3 and L4 alleles were resistant to all isolates, indicating that these viruses belong to pathotype P0.

Farmers’ Knowledge and Management of Rice Diseases in Uganda

Rice in the recent past has picked up as a food security and income generating crop among farming households in Uganda. Even though, the crop is playing a significant role in reducing food insecurity and poverty within the country, its productivity has remained constant and low at about 1.5 metric tonnes per hectare. Using cross-sectional data collected from rice farmers in Northern (Lira, Dokolo, Otuke and Alebtong Districts); Eastern (Iganga, Bugiri and Kamuli Districts) and Central (Kayunga District) regions of the country, this paper establishes farmers’ knowledge and management of rice diseases from a total of 224 farmers, as a baseline for research initiatives focusing on improving rice productivity within the country. Farmers ranked diseases as the second most important constraint in rice production, after insect pests. Moreover, farmers ranked rice yellow mottle virus (RYMV) as the most important disease in rice production, followed by leaf blast (LB), brown spot (BS), sheath rot (ShR), panicle blast (PB) and bacterial leaf blight (BLB). However, 60% of farmers identified RYMV while less than 30% could clearly diagnose the symptoms of each of the other diseases. Surprisingly, only about 18% of farmers employed management options against RYMV, whereas less than 6% practiced some form of management for each of the other major diseases. The predominant disease control measure was uprooting diseased plants followed by insecticide application. About 10% of farmers reported sedges (Cyperus spp.), goat weed (Ageratum conyzoides), black jack (Bidens pilosa), and cut grass (Leersia spp.) as alternative host plants for rice diseases. An integrated disease management approach, whose development and implementation recognizes farmers as the key players in the rice production chain, is required to achieve improved and sustainable rice productivity.

Assessment of Korean rice lines for their reaction to rice yellow mottle virus in Ghana

Rice yellow mottle virus (RYMV) is the most damaging viral disease of rice in Africa and can cause yield losses of up to 100%. The objective of this study was to characterize newly introduced rice lines from Korea into Ghana for their reaction to RYMV infection. One hundred and seventy-two rice lines from Korea were screened for their level of resistance RYMV in a screen house at Fumesua, Ghana. Four checks consisting of two highly resistant lines (Tog7291 and Gigante with rymv1-2 (resistant gene1-allele2) and rymv2 (resistant gene2) respectively), a moderately resistant line (CRI-Amankwatia) and a susceptible cultivar Jasmine 85 were used. The experiment was carried out in a 4 x 44 lattice design with four replicates. Screening for RYMV resistance was conducted by visual symptom scoring and virus-assessment through serology using enzyme linked immunosorbent assay (ELISA) test. Disease incidence and severity were assessed from 2 to 42 dpi. Data for disease severity and incidence were transformed (Log x+1) for ANOVA.Five lines (8261112, 8261119, 8261133, 8261588, and 8261634) were identified to be highly resistant to the disease just like Tog7291 and Gigante. The study also revealed 24 lines that were resistant but not grouping with Tog7291 and Gigante, whereas 100 moderately resistant lines clustered with the moderately resistance check CRI-Amankwatia in a distinct group. Forty-three (43) susceptible lines were identified with the susceptible check Jasmine 85 falling in this group. No highly susceptible line was identified. The newly idenfied resistant genotypes can be used by breeders to develop RYMV resistant varieties.

Genome Wide Association Study Pinpoints Key Agronomic QTLs in African Rice Oryza glaberrima

BackgroundAfrican rice, Oryza glaberrima, is an invaluable resource for rice cultivation and for the improvement of biotic and abiotic resistance properties. Since its domestication in the inner Niger delta ca. 2500 years BP, African rice has colonized a variety of ecologically and climatically diverse regions. However, little is known about the genetic basis of quantitative traits and adaptive variation of agricultural interest for this species.ResultsUsing a reference set of 163 fully re-sequenced accessions, we report the results of a Genome Wide Association Study carried out for African rice. We investigated a diverse panel of traits, including flowering date, panicle architecture and resistance to Rice yellow mottle virus. For this, we devised a pipeline using complementary statistical association methods. First, using flowering time as a target trait, we found several association peaks, one of which co-localised with a well described gene in the Asian rice flowering pathway, OsGi, and identified new genomic regions that would deserve more study. Then we applied our pipeline to panicle- and resistance-related traits, highlighting some interesting genomic regions and candidate genes. Lastly, using a high-resolution climate database, we performed an association analysis based on climatic variables, searching for genomic regions that might be involved in adaptation to climatic variations.ConclusionOur results collectively provide insights into the extent to which adaptive variation is governed by sequence diversity within the O. glaberrima genome, paving the way for in-depth studies of the genetic basis of traits of interest that might be useful to the rice breeding community.

First Report of Soybean Yellow Mottle Mosaic Virus Infecting Soybean in China

First Report of Soybean Yellow Mottle Mosaic Virus Infecting Soybean in China

English

In Mali, the economy is mainly based on agriculture. Rice contributes about 5% of the GDP and constitutes a strategic sector with enormous potential. Despite its strategic importance, rice cultivation faces multiple biotic constraints among which rice yellow mottle virus disease is the most important one with an incidence varying from 60 to 100%. To reduce yield loses due to this disease, we determined the mode of action of two rice yellow Mottle virus (RYMV) pathotypes previously isolated in rice fields in Mali, and identified by Reverse transcription polymerase chain reaction (RT-PCR). Both types significantly decrease rice height with a more pronounced effect with the type A, which showed more aggressivity even on the SK20-28 genotype recognized as RYMV disease-tolerant variety. Root dry weight, grain production and tiller number were the most affected by the disease. Except for tiller number, the virus type A was always more virulent than the type B. Significant positive correlation was found between disease severity and % reduction in tiller number, percentage reduction in plant height, and grain production. The data presented root inhibition as a mode of action of the two RYMV pathotypes isolated in Mali. This information should be used in order to improve the management strategies for these pathogens on field rice in Mali. Key words: Rice yellow mottle virus, root inhibition, rice, Mali.

English

Rice is an important staple food in Nigeria, affected by several diseases especially viruses. This study was carried out to evaluate the incidence and severity of two important viruses on rice plants and to identify associated insects in the Federal Capital Territory (F.C.T), Abuja in 2019. Field experiment was carried out from June to October, 2019 at the Teaching and Research Farm of the Faculty of Agriculture, University of Abuja, Nigeria, where ten rice varieties were assessed for incidence and severity. The seed and leaf samples were collected for serological indexing. Data collected was subjected to statistical analysis using SPSS and mean separation was done with Duncan Multiple Range Test. Of the 210 leaf samples collected, FARO 61 and 44 had the lowest incidence (19%), while FARO 65 recorded the highest (25.3%). FARO 52 recorded the highest severity (46%) while FARO 61 and FARO 60 had the lowest severity (30.1%) for rice yellow mottle sobemo-virus (RYMV) and maize streak geminivirus (MSV). Insects such as Spittle bug (Locris rubens and Poophilus costalis), Ladybird beetle (Cheilomenes sulphurea) and Groundhopper (Paratettix sp) were trapped on the field. All rice seed and leaf samples collected did not test positive to RYMV and MSV using Enzyme-Linked immunosorbent assay (ELISA). This study provides the first research work on rice viruses in the FCT and further studies are recommended.   Key words: Nigeria, rice, rice yellow mottle sobemo-virus (RYMV), maize streak geminivirus (MSV), incidence, severity, virus symptoms, enzyme linked immuno sorbent assay (ELISA).

Effect of temperature on systemic infection and symptom expression induced by Soybean yellow mottle mosaic virus in leguminous hosts

Temperature is one of the key factors influencing the viral disease development in plants. In this study effect of temperature on SYMMV accumulation and systemic movement was studied in French bean, mungbean and soybean cultivars by keeping them at temperatures range 22-25 °C, 26-29 °C and 30-33 °C. The proliferation of the virus under these conditions was confirmed through symptomatology, DAC-ELISA, RT-PCR with coat protein specific primers and RT-qPCR. French bean plants displayed symptoms by 12dpi at low temperature (22-25 °C) and by 3dpi at medium temperatures (26-29 °C) with continuous increase in viral accumulation from 0 to 24dpi. At high temperatures (30-33 °C), French bean did not show symptoms up to 12dpi but the virus accumulated and moved systemically. However, there was a decline in viral copy number after 12dpi. Mungbean plants showed mottling, mosaic and puckering symptoms at 22-25 °C and 26-29 °C and necrotic symptoms at 30-33 °C. Irrespective of temperature there was an increase in viral accumulation in mungbean from 0 days to 24dpi. Soybean plants showed veinal mild mottling at low and medium temperatures where as no peculiar symptom expression observed at high temperatures. Soybean also showed the reduction of viral copy number from 12 days to 24dpi at low and medium temperatures and from 6 days to 24dpi at high temperatures. These results indicate that temperature played an important role in SYMMV accumulation, movement and symptom expression in these three leguminous plant species. This study also demonstrates that SYMMV can replicate and spread in mungbean plants irrespective of the temperature.

Farmers’ perceptions, production constraints and variety preferences of rice in Tanzania

ABSTRACT Rice (Oryza sativa L.) is a major food and cash crop cultivated under diverse farming systems in Tanzania. The objective of this study was to assess farmers’ perceptions, production constraints, variety preferences and breeding priorities of rice in selected agro-ecologies in Tanzania to guide variety development and release. A participatory rural appraisal study was conducted involving 180 participants using a structured survey. Focus group discussions were held with 90 discussants in the Mvomero, Kilombero and Kyela districts of Tanzania. Survey results indicated that rice was the most important food and cash crop, followed by maize (Zea mays L.), cassava (Manihot esculenta Crantz), sweetpotato (Ipomoea batatas [L.] Lam.), sugarcane (Saccharum officinarum L.), pigeonpea (Cajanus cajan L.), cowpea (Vigna unguiculata [L.] Walp), simsim (Sesamum indicum L.), beans (Phaseolus vulgaris L.), cocoa (Theobroma cacao L.), banana (Musa acuminate L.), groundnuts (Arachis hypogaea L.), and palm (Elaeis guineensis Jacq.). Majority of respondents used saved seed from previous harvest. Major constraints limiting rice production and productivity in all studied areas were disease, insect pests, recurrent drought, non-availability and high cost of fertilizers, a lack of improved cultivars, poor soil fertility and bird damage. The farmers preferred rice varieties with high yield, disease resistance, drought tolerance, high market value, early maturity, aroma, and local adaptation. A systematic rice breeding program, aimed at improving yellow mottle virus resistance and incorporating farmers’ preferred traits, should be designed and implemented to increase productivity and adoption of new cultivars by the farmers across rice-growing areas of Tanzania.