The epidemiology of malaria in Prábis, Guinea-Bissau

This article reports upon a community survey of malaria in Prábis, Guinea-Bissau. A house to house census of the population was initially carried out from August to December 1991(rainy season). After completing the census of each village, the population was invited to come, a week later, to a central point, where they were medically examined and finger-prick blood samples were collected for epidemiological characterization of the malaria situation in the area. The blood films of the one single village were used to compare the sensitivity and specificity of Polymerase Chain Reaction (PCR) with optical microscopy detection of parasites. In another village, the occurrence of parasitaemia was compared in children with and without fever. During the dry season, from March to June 1992, the population in each village was again invited to come to a central point. Some of the field procedures were repeated. The study revealed Prábis as an administrative Sector of Guinea-Bissau with endemic malaria, mostly due to Plasmodium falciparum, but with a significant rate of mixed infections. Active transmission occurred throughout the year, but it was more intensive during the rainy season and in the northwestern quadrant of the Sector. The level of endemicity of the villages varied from hypo to holoendemic. The factors associated with the differences among villages included village size and predominant economic activity (closeness to rice fields). The transmission paradigm was, most likely, a mixture of malaria of the African wet Savannah and malaria associated with irrigated paddy fields. PCR proved to be a sensitive method with low specificity during the dry season. Pyraexia of 37.4ºC or higher in children aged 2-9 years is not a sensitive indicator of parasitaemia but, it is highly specific and it has a clinically useful predictive value.

The role of urea in the oviposition behaviour of Japanese encephalitis vectors in rice fields of South India

The effect of urea on the oviposition behaviour of culicine vectors of Japanese encephalitis was studied in rice fields. Gravid females had a strong preference for oviposition in urea treated areas in rice fields, while no such preference was exhibited in untreated areas. The egg laying declined in the area where urea treated water surface had a mechanical barrier, which allowed volatile fractions to escape, but prevented contact with the water. Urea was shown to act as an oviposition attractant/stimulant for Culex tritaeniorhynchus, but its role was not clear for Cx. vishnui, as the number of egg rafts obtained for the latter species was low.

From MuSIASEM theory to practice: report and reflections from field research in Kampot province, Cambodia

This document contains a report and summary of the field research activities in a rural community of rice farmers in Kampot province, Cambodia in 2011, which I conducted within the context of my PhD research at ICTA-UAB (Institute of Environmental Science and Technology, Autonomous University of Barcelona, Spain). The purpose of the field research was to gather data for a MuSIASEM analysis (Multi-Scale Integrated Analysis of Societal and Ecosystem Metabolism) at the village and household level, in order to analyze the multidimensional challenges that small farmers may face nowadays within the context of global rural change and declining access to land. While the literature on MuSIASEM offers a great variety of theoretical explanations and practical applications, there is little information available for students regarding the practical steps required for doing a MuSIASEM analysis at the local level. Within this context, this report offers not only a documentation of the field research design and data collection methods, but further provides a general overview on some organizational and preparative aspects, including some personal reflections, that one may face when preparing and conducting field research for MuSIASEM analysis. In summary, this document thus serves three objectives: (i) to assure methodological transparency for the future work, based on the collected data during field research, (ii) to share my personal experience on the preparative and practical steps required for field research and data collection for a MuSIASEM analysis at the local level, and (iii) to make available for the further interested reader some more detailed background information on the case study village.

Thrips species (Thysanoptera, Terebrantia) inhabiting irrigated rice and surrounding habitats in Cachoeirinha, state of Rio Grande do Sul, Brazil

In Brazil, almost nothing is known about the thrips fauna associated with rice crops. This is especially true for Rio Grande do Sul State (RS), the major rice producer in Brazil, where no systematic surveys have been conducted. Thus, this work records preliminarily the species of suborder Terebrantia inhabitanting irrigated rice (RC) and three nearby habitats: the area selected for rice, before cultivation (BR), grassland (GR) and forest border (FB) in Cachoeirinha, RS (50º58'21"W; 29º55'30"S). Eight field trips were carried out between October/2004 and February/2005 to Estação Experimental do Arroz in Cachoeirinha. Thrips specimens were collected with sweeping net and transported to laboratory for identification. A total of 623 adults terebrantians were recorded, belonging to two families and 18 species. Frankliniella rodeos (55.5%), Neohydatothrips cf. paraensis (30.3%) and Frankliniella schultzei (5.6%), were the most abundant, comprising more than 90% of the individuals. FB showed the highest species richness (S=15), followed by GR (S=10), RC (S=9) and BR (S=6). FB presented a low number of individuals (14.0%), contrasting with GR (44.8%) and BR (36.7%). In general, thrips abundance in RC was low at EEA (4.5%), and few species seems to effectively use rice as a host-plant. Two species previously considered of economic importance were found, F. rodeos and F. schultzei, the latter a new record for rice in Brazil. Five species are new records to RS.

Spatial variability of the chemical, physical and biological properties in lowland cultivated with irrigated rice

In the areas where irrigated rice is grown in the south of Brazil, few studies have been carried out to investigate the spatial variability structure of soil properties and to establish new forms of soil management as well as determine soil corrective and fertilizer applications. In this sense, this study had the objective of evaluating the spatial variability of chemical, physical and biological soil properties in a lowland area under irrigated rice cultivation in the conventional till system. For this purpose, a 10 x 10 m grid of 100 points was established, in an experimental field of the Embrapa Clima Temperado, in the County of Capão do Leão, State of Rio Grande do Sul. The spatial variability structure was evaluated by geostatistical tools and the number of subsamples required to represent each soil property in future studies was calculated using classical statistics. Results showed that the spatial variability structure of sand, silt, SMP index, cation exchange capacity (pH 7.0), Al3+ and total N properties could be detected by geostatistical analysis. A pure nugget effect was observed for the nutrients K, S and B, as well as macroporosity, mean weighted diameter of aggregates, and soil water storage. The cross validation procedure, based on linear regression and the determination coefficient, was more efficient to evaluate the quality of the adjusted mathematical model than the degree of spatial dependence. It was also concluded that the combination of classical with geostatistics can in many cases simplify the soil sampling process without losing information quality.

The use of total luminescence spectroscopy in the investigation of the effects of different rice management practices on humic substances of a planosol

In the Earth's carbon cycle, C stocks in the soil are higher than in vegetation and atmosphere. Maintaining and conserving organic C concentrations in the soil by specific management practices can improve soil fertility and productivity. The aim of this study was to evaluate the impact of agricultural management techniques and influence of water regime (flooded or drained) on the structure of humic substances by excitation/emission matrix fluorescence. Six samples of a Planosol (Planossolo by the Brazilian System of Soil Classification) were collected from a rice field. Humic substances (HS) were extracted from flooded and drained soil under different agricultural management techniques: conventional tillage, reduced tillage and grassland. Two peaks at a long emission wavelength were observed in the EEM spectra of HA whereas those of the corresponding FA contained a unique fluorophore at an intermediate excitation/emission wavelength pair (EEWP) value. The fluorescence intensity measured by total luminescence (FI TL) of HA was lower than that of the corresponding FA. A comparison of all samples (i.e., the HA values compared to each other) revealed only slight differences in the EEWP position, but the FI TL values were significantly different. In this soil, anoxic conditions and reduced tillage (little plowing) seem to favor a higher degree of humification of the soil organic matter compared with aerated conditions and conventional tillage.

Attributes of irrigated rice as affected by soil sodicity and potassic fertilizer application

Soils of the coastal plains of Rio Grande do Sul, Brazil, are affected by salinization, which can hamper the establishment and development of crops in general, including rice. The application of high doses of KCl may aggravate the crop damage, due to the high saline content of this fertilizer. This study aimed to evaluate the effect of K fertilizer management on some properties of rice plant, grown in soils with different sodicity levels, and determine which attribute is best related to yield. The field study was conducted in four Albaqualfs with exchangeable Na percentages of 5.6, 9.0, 21 and 32 %. The management of KCl fertilizer consisted of the application of 90 kg ha-1 K2O broadcast, 90 kg ha-1 K2O in the row and 45 kg ha-1 K2O in the row + 45 kg ha-1 K2O at panicle initiation (PI). Plant density, dry matter evolution, height, SPAD (Soil Plant Analysis Development value indicating relative chlorophyll contents) index, tiller mass, 1,000-grain weight, panicle length and grain yield were evaluated. The plant density was damaged by application of K fertilizer in the row, especially at full dose (90 kg ha-1), at three sodicity levels, resulting in loss in biomass accumulation in later stages, affecting the crop yield, even at the lowest level of soil sodicity (5.6 %). All properties were correlated with yield; the highest positive correlation was found with plant density and shoot dry matter at full flowering, and a negative correlation with panicle length.

Iron oxidation on the surface of adventitious roots and its relation to aerenchyma formation in rice genotypes

Establishment of the water layer in an irrigated rice crop leads to consumption of free oxygen in the soil which enters in a chemical reduction process mediated by anaerobic microorganisms, changing the crop environment. To maintain optimal growth in an environment without O2, rice plants develop pore spaces (aerenchyma) that allow O2 transport from air to the roots. Carrying capacity is determined by the rice genome and it may vary among cultivars. Plants that have higher capacity for formation of aerenchyma should theoretically carry more O2 to the roots. However, part of the O2 that reaches the roots is lost due to permeability of the roots and the O2 gradient created between the soil and roots. The O2 that is lost to the outside medium can react with chemically reduced elements present in the soil; one of them is iron, which reacts with oxygen and forms an iron plaque on the outer root surface. Therefore, evaluation of the iron plaque and of the formation of pore spaces on the root can serve as a parameter to differentiate rice cultivars in regard to the volume of O2 transported via aerenchyma. An experiment was thus carried out in a greenhouse with the aim of comparing aerenchyma and iron plaque formation in 13 rice cultivars grown in flooded soils to their formation under growing conditions similar to a normal field, without free oxygen. The results indicated significant differences in the volume of pore spaces in the roots among cultivars and along the root segment in each cultivar, indicating that under flooded conditions the genetic potential of the plant is crucial in induction of cell death and formation of aerenchyma in response to lack of O2. In addition, the amount of Fe accumulated on the root surface was different among genotypes and along the roots. Thus, we concluded that the rice genotypes exhibit different responses for aerenchyma formation, oxygen release by the roots and iron plaque formation, and that there is a direct relationship between porosity and the amount of iron oxidized on the root surface.

Rice husk ash as corrective of soil acidity

Rice husk ash (RHA) is a by-product from the burning of rice husk that can have favorable effects on the soil in terms of acidity correction. The objectives of this study were to determine the effective calcium carbonate equivalent (ECC) of RHA under field conditions, and establish technical criteria as a basis for estimating the overall ECC of RHA. The 12 treatments of the experiment consisted of 10 RHA dosages (0, 10, 20, 30, 40, 60, 80, 100, 120, and 140 Mg ha-1) and two references, one of which was an absolute control (AC) and the other a plot limed and fertilized according to official recommendations (recommended fertilization - RF). The soil was sampled twice (15 and 210 days after incorporating RHA), in the layers 0.00-0.10 and 0.10-0.20 m, to determine the pH(H2O) and base saturation (V%). The ECC and neutralizing value (NV) of RHA were also determined. The results showed that RHA neutralizes soil acidity, in a faster reaction than conventional limestone, despite a low ECC (around 3 %).

Hydro-Physical Properties of a Typic Hapludult under the Effect of Rice Husk Ash

ABSTRACT The combustion of rice husk generates a partially burnt mixture called rice husk ash (RHA) that can be used as a source of nutrients to crops and as a conditioner of soil physical properties. The objective of this study was to evaluate the effect of RHA levels on the hydro-physical properties of a Typic Hapludult. The experimental design was composed of random blocks with four replications, which comprised plots of 24 m2 and treatments with increasing RHA rates: 0, 40, 80 and 120 Mg ha-1. Undisturbed soil samples were collected in the soil layers of 0.00-0.10 and 0.10-0.20 m after nine months of RHA application, using steel cylinders (0.03 m of height and 0.047 m of diameter). These samples were used to determine soil bulk density (Bd), total soil porosity (TP), soil macroporosity (Ma), soil microporosity (Mi) and the available water capacity (AWC). Disturbed soil samples were collected to determine the stability of soil aggregates in water, mean weight diameter of water stable aggregates (MWD), and soil particle size distribution. The results show that, as the RHA rate increased in the soil, Bd values decreased and TP, Ma and MWD values increased. No effect of RHA was found on Mi and AWC values. The effects of RHA on the S parameter (Dexter, 2004), precompression stress and compression index (Dias Junior and Pierce, 1995) values are consistent those shown for density and total porosity. Rice husk ash was shown to be an efficient residue to improve soil physical properties, mainly at rates between 40 and 80 Mg ha-1. Rice husk ash reduces bulk density and increases total porosity, macroporosity and soil aggregation, but does not affect microporosity, field capacity, permanent wilting point, and available water capacity of the soil. The effect of rice husk ash on the S parameter, precompression stress and index compressibility coefficient values are consistent with those observed for the bulk density and total porosity.

Relationship between potassium fertilization and panicle blast severity in upland rice

The influence of K2O (0, 40, 80, 120 kg ha-1) at varying rates of N application (0, 30, 60 kg ha-1) at planting, on panicle blast (Pyricularia grisea (Cooke) Sacc.) was studied in a field experiment conducted during three consecutive years with the upland rice cultivar Douradão. Panicle blast severity decreased with increasing rates of potassium in the absence of nitrogen (N0). The relationship between panicle blast and K rates was quadratic at 30 kg ha-1 of nitrogen. Significant response to K fertilization was not obtained at 60 kg ha-1 of nitrogen in relation to panicle blast severity.

Development of blast resistant somaclones of the upland rice cultivar araguaia

The degree of blast resistance of upland rice (Oryza sativa L.) cultivar Araguaia has decreased over time causing significant yield losses. The major objective of this study was to obtain blast (Pyricularia grisea) resistant somaclones, adapting greenhouse and field selection procedures. Rice blast resistance and agronomic traits were assessed in R2 to R6 generations derived from regenerant plants (R1) from immature panicles of Araguaia. The evaluation and selection procedures include testing of early segregating populations and fixed lines in the advanced generations, under natural field conditions, and artificial inoculations in the greenhouse, with prevalent races IB-1 and IB-9 of P. grisea. Somaclones with both vertical resistance and slow blasting resistance were obtained. Twenty of 31 somaclones developed with a high degree of vertical resistance and fan shaped plant type maintained resistance in field and blast nursery tests in the R6 generation. Greenhouse selection with two specific physiologic races yielded 44 somaclones with slow blasting resistance, similar plant type and yield potential as that of Araguaia.

Carbon isotope discrimination and yield of upland rice as affected by drought at flowering

Field experiments involving upland rice genotypes, sown in various dates in late season, were carried out to assess the relationship of carbon isotope discrimination with grain yield and drought resistance. In each one of the three years, one trial was kept under good water availability, while other suffered water shortage for a period of 18-23 days, encompassing panicle emergence and flowering. Drought stress reduced carbon isotope discrimination measured on soluble sugars (deltas) extracted from stem uppermost internode at the end of the imposition period, but had relatively less effect on bulk dry matter of leaves, sampled at the same period, or that of uppermost internodes and grains, sampled at harvest. The drought-induced reduction in deltas was accompanied of reduced spikelet fertility and grain yield. In the three trials subjected to drought, genotypes with the highest yield and spikelet fertility had the lowest deltas. However, this relationship was weak and it was concluded that deltas is not a sufficiently reliable indicator of rice drought resistance to be useful as a screening test in breeding programs. On the other hand, grain yield and spikelet fertility of genotypes which were the soonest to reach 50% flowering within the drought imposition period, were the least adversely affected by drought. Then, timing of drought in relation to panicle emergence and to flowering appeared to be a more important cause of yield variation among genotypes than variation in deltas.

Defining molecular components of symbiotic phosphate uptake in rice

Phosphate (Pi) acquisition of crops via arbuscular mycorrhizal (AM) symbiosis acquires increasing importance due to the limited rock Pi reserves and the demand for environmentally sustainable agriculture. However, the symbiotic Pi uptake machinery has not been characterized in any monocotyledonous plant species. Among these, rice is the primary staple food for more than half of the human population and thus central for future food security. However, the relevance of the AM symbiosis for rice Pi nutrition is presently unclear. Here, we show that 70% of the overall Pi acquired by rice is delivered via the symbiotic route. To better understand this pathway we combined genetic, molecular and physiological approaches to determine the specific functions of the two rice Pi transporters, PT11 and PT13, which are expressed only during AM symbiosis. The PT11 lineage of proteins is present in mono- and dicotyledons whereas PT13, while found across the Poaceae, is absent from dicotyledons. Surprisingly, mutations in either PT11 or PT13 affected fungal colonization and arbuscule formation demonstrating that both genes are essential for AM symbiosis between rice and Glomus intra.rad.ices. Importantly, for symbiotic Pi uptake, only PT11 is necessary and sufficient. We found that mycorrhizal rice, remarkably, received almost all Pi via the symbiotic route. Such dominating mycorrhizal Pi uptake was found in plants grown under controlled conditions as well as in field soils, suggesting that the AM symbiosis is relevant for the Pi nutrition of field grown rice. Development of smaller arbuscules in PT11 mutants suggested that symbiotic Pi signaling is required for fungal nourishment by the plant. However, co-culture of mutant with wild type nurse plants did not restore normal arbuscule size in mutant roots, indicating that other factors than malnutrition accounted for the altered arbuscule phenotype. Surprisingly, the loss of PT13 did not affect symbiotic Pi uptake although it impacted arbuscule morphology, suggesting that PT13 is involved in signaling during arbuscule development. However, induction of PT13 was not only monitored in arbusculated cells but also in inner cortex cells of non-inoculated roots of plants grown under high Pi fertilization conditions. According to preliminary observations, PT13 localized at the tonoplast in arbusculated and non-arbusculated cells, suggesting that it might be involved in transporting Pi into the vacuole, possibly for maintaining cellular Pi homeostasis. The further investigation showed that fungal colonization level was significantly affected in the crown roots of two ptlS mutant alleles, but not in large lateral roots, implying the possible role of PT13 for maintaining Pi homeostasis in the crown roots. - L'acquisition de phosphate (Pi) par les plantes cultivées s'effectue grâce à une symbiose mycorhizienne arbasculaire (AM). L'étude de cette symbiose devient fondamentale puisque d'une part, les réserves en phosphate minéral sont limitées, et, d'autre part, la demande pour une agriculture écologiquement soutenable se renforce. La machinerie d'absorption symbiotique du phosphate n'est cependant pas encore élucidée chez les plantes monocotylédones. Parmi celles-ci, le riz occupe une place primordiale. Aliment de base pour plus de la moitié de la population mondiale, il revêt de ce fait une dimension essentielle en termes de sécurité alimentaire. Pourtant, l'importance de la symbiose AM chez le riz dans le processus d'acquisition du phosphate n'est, encore de nos jours, que peu comprise. Dans cette étude, nous montrons que 70% du phosphate acquis par le riz est mis à disposition de la plante grâce à la symbiose AM. Afin de mieux comprendre ce mécanisme, nous avons employé des approches physiologiques et génétiques nous permettant de déterminer les fonctions spécifiques de deux transporteurs de Pi, PT11 et PT13, présents chez le riz et exprimés uniquement durant la symbiose AM. La famille de gènes à laquelle appartient PT11 est présente chez les monocotylédones ainsi que chez les dicotylédones tandis que PT13, bien que retrouvé au sein des Poaceae, est absent chez les dicotylédones. Etonnamment, des versions mutées de PT11 ou de PT13 affectent la colonisation par le champignon endo-mycorhizien ainsi que la formation d'arbuscules, démontrant l'importance de ces deux gènes dans la symbiose AM entre le riz et Glomus intraradices. Il est à noter que seul PT11 se révèle nécessaire et suffisant pour l'apport de Pi grâce à la symbiose. Nous avons observé que la presque totalité du phosphate dont dispose le riz lors d'une symbiose AM provient du champignon. De telles proportions ont été observées tant chez des plantes cultivées en conditions contrôlées que chez des plantes cultivées dans les champs. Cela suggère l'importance de la symbiose AM dans le processus d'acquisition du Pi chez le riz cultivé à l'extérieur. Le développement d'arbuscules plus petits chez le mutant PT11 tend à montrer qu'une voie signalétique impliquant le Pi symbiotique est nécessaire pour l'entretien du champignon par la plante. Toutefois, une co-culture du mutant avec des plantes sauvages ne permet pas de restaurer des arbuscules de taille normale dans les racines du mutant. Ce résultat indique le rôle de facteurs autres que la malnutrition aboutissant à la formation d'arbuscules altérés. Si la perte de PT13 n'affecte pas l'acquisition de phosphate symbiotique, la morphologie de l'arbuscule est, quant à elle, modifiée. Ceci suggère un rôle de PT13 durant le développement de l'arbuscule. Or, l'induction de PT13 est non seulement détectée dans des cellules contenant des arbuscules mais également dans des cellules du cortex, ceci chez des plantes cultivées sans champignon mais dans des conditions de fortes concentrations en engrais phosphaté. En accord avec des observations précédentes, PT13 est localisé au niveau du tonoplaste des cellules contenant ou non des arbuscules. Ceci suggère que PT13 pourrait être impliqué dans le transport du Pi vers la vacuole, éventuellement pour maintenir une certaine homéostasie du phosphate. Dans cette étude, nous démontrons également que le niveau de colonisation par le champignon est affecté de manière significative dans les racines principales des deux allèles du mutants ptl3, mais pas dans les grosses racines latérales. Cela impliquerait un rôle possible de PT13 dans le maintien de l'homéostasie du phosphate dans les racines principales. RESUME POUR UN LARGE PUBLIC Le phosphate (Pi), l'un des éléments minéraux essentiel au développement des plantes, se trouve généralement en faible quantité dans le sol, limitant ainsi la croissance des plantes. Le rendement de la production agricole dépend dès lors de l'addition d'engrais contenant du phosphate inorganique (Pi), obtenu à partir de ressources minières riches en phosphate. Or, ces ressources devraient être épuisées d'ici la fin du siècle. Les racines des plantes possèdent des transporteurs de phosphate efficaces leur permettant d'acquérir rapidement le Pi présent dans le sol. Comme le Pi s'avère immobile dans le sol, l'absorption rapide par les racines crée des zones pauvres en Pi autour des systèmes racinaires. Pour surmonter cet obstacle, les plantes ont développé une symbiose avec des champignons endomycorhiziens, la symbiose mycorhizienne arbusculaire (AM). Cette association leur donne accès à d'autres ressources en phosphate puisque le mycélium de ces champignons se développe sur une surface 100 fois supérieure à celle des racines. Cela augmente considérablement la surface de nutrition, dépassant ainsi la zone appauvrie en Pi. Le phosphate, transporté grâce au champignon jusqu'à l'intérieur des racines, est fourni à la plante par le biais de structures établies à l'intérieur des cellules végétales, appelées arbuscules. De leur côté, les plantes possèdent des transporteurs spécifiques afin de recevoir le Pi fourni par les champignons. A l'heure actuelle, la machinerie nécessaire à cette absorption a été uniquement décrite chez des plantes dicotylédones. Or, comprendre l'apport de phosphate par les champignons mycorhiziens s'avère particulièrement pertinent dans le cas des espèces monocotylédones cultivées telles que les céréales. Ces dernières constituent en effet la majeure partie de l'alimentation humaine. Parmi les céréales, le riz demeure l'aliment de base de la population mondiale, d'où son importance en terme de sécurité alimentaire. Durant mon travail de thèse, j'ai identifié et caractérisé le transporteur du riz impliqué dans l'apport de phosphate par ce type de symbiose AM. J'ai également démontré que le riz, lorsqu'il vit en symbiose, bénéficie de la presque totalité du Pi transporté par le champignon. Environ 40% de la production globale de riz est cultivée dans des conditions permettant la symbiose avec des mycorhizes arbusculaires. Les variétés de riz adaptées à ces conditions aérobiques deviennent des alternatives favorables aux cultivars actuels nécessitant une forte irrigation. Elles se révèlent en effet plus tolérantes aux pénuries d'eau et permettent l'utilisation de pratiques agricoles moins intensives. Les données présentées dans cette étude enrichissent nos connaissances concernant l'absorption du phosphate chez le riz grâce à la symbiose AM. Ces connaissances peuvent s'avérer décisives pour le développement de cultivars du riz plus adaptés à une agriculture écologiquement soutenable.

Cultivar response to fungicide application in relation to rice blast control, productivity and sustainability

Four field trials were conducted, from 1995 to 1997, with the objective of studying the response of four upland cultivars to foliar fungicide application in relation to panicle blast control, grain yield and sustainability. Differential disease control and yield response of cultivars to fungicide treatment were obtained. Losses in grain yield of cultivars IAC 202, Caiapó, Rio Paranaíba and Araguaia due to panicle blast were 44.8%, 27.4%, 24.4% and 18.2%, respectively. Two applications of tricyclazole or benomyl controlled panicle blast, as indicated by lower values of disease progress curve and relative panicle blast severity, and increased grain yield of the cultivar IAC 202. The losses in 100 panicle grain weight and grain yield were significantly reduced by 22.3% and 25.1% in IAC 202 and 23.6% and 20.5% in Caiapó, respectively, with two sprays of tricyclazole. Sustainable value index for yield was maximum with two applications of tricyclazole (0.59), followed by one application at booting (0.46) and at heading (0.40) in cultivar IAC 202. Results showed no yield response of the cultivars Rio Paranaíba and Araguaia to fungicide applications for panicle blast control.