J.A. Noldin

Resistência de Cyperus difformis a herbicidas inibidores da ALS em lavoura de arroz irrigado em Santa Catarina

Herbicide resistance is a worldwide phenomenon of great concern to scientists, technicians and producers. It is characterized as the capacity of a biotype to survive a treatment using herbicide that controls the other individuals of the same population under normal field conditions and at the dose recommended by the manufacturer. The objective of this research was to determine the resistance level of two Cyperus difformis biotypes to ALS-inhibiting herbicides. The herbicide treatments consisted of the application of bispyribac-sodium, pyrazosulfuron-ethyl, (ALS-inhibitors) and bentazon (photosystem II inhibitor) sprayed at seven multiple commercial doses (0,0x; 0.5x; 1x; 2x; 4x; 8x and 16x), on two plant populations of C. difformis, at the stage of four to six leaves. The CYPDI-10 biotype showed a crossed-resistance to the ALS- inhibiting herbicides pyrazosulfuron-ethyl and bispyribac-sodium, while bentazon showed an efficient control of the resistant and susceptible populations. It was concluded that for the correct management of ALS-resistant C. difformis biotypes in flooded rice areas of Santa Catarina, Brazil, the use of herbicides with different action mechanisms should be adopted, as well as other management practices in order to restrict the expansion of resistant populations of C. difformis.

Effect of dose and application site on quinclorac absorption by barnyardgrass biotypes

This work aimed to evaluate the uptake and translocation of quinclorac in function of application sites (shoot or roots) by Echinochloa crusgalli biotypes resistant and susceptible to this herbicide. The treatments consisted of quinclorac doses (0; 0.5; 1; 2; 4; 16 and 64xa0ppm), applied on the shoot or roots of seedlings of barnyardgrass biotypes. The experimental units consisted of plastic cups containing 250 cm3 of sand. The treatments were applied 10 days after emergence, when barnyardgrass plants reached a 2- to 3- leaf growth stage. The barnyardgrass biotypes were irrigated with nutritive solution weekly and maintained for 40 days after emergence, when length, fresh and dry matter of shoot and roots were evaluated. Variance analysis was carried out using the F test at 5% probability, and in case of significance, a non-linear regression analysis was also carried out using a three-parameter logistic model. In the susceptible biotype, quinclorac was more absorbed by the roots than by the shoot. Comparing dry mass production of the different plant parts of the susceptible biotype per application site, it was verified that quinclorac action is higher when applied to the plant roots. However, for the resistant biotype, it was not possible to determine the dose causing 50% reduction in dry mass accumulation (GR50) and in the resistance index (RI) between both biotypes, due to its high resistance to quinclorac (128 times the recommended dosage). The results showed that quinclorac resistance by the evaluated biotype is not due to differences in the absorption site, strongly suggesting that the resistance acquired by the biotype may result from alteration in the target site.

Competitive ability of rice plants with barnyardgrass biotypes resistant or susceptible to quinclorac

The objective of this study was to evaluate the competitive ability of the rice cultivar BRS Pelota with biotypes resistant or susceptible to the herbicide Quinclorac. The experiment was conducted under greenhouse conditions in a completely randomized design with four replications, with the treatments arranged in a 2xa0xxa06 factorial. The experimental units consisted of plastic pots containing 10xa0dm3 of soil, with pH and nutrient level being previously corrected. The treatments consisted of a competition between a rice plant, BRS Pelota cultivar, with populations (0, 1, 2, 3, 4 or 5xa0plantsxa0per pot) of the barnyardgrass biotypes resistant (ECH-13) or susceptible (ECH -12) to the herbicide Quinclorac. The evaluations were performed at 40xa0DAE,including shoot dry weight (MSPA), growth rate (TC), specific leaf area (SLA), leaf mass ratio (LWR), leaf area ratio (LAR) and leaf area index (LAI). The interference in the development of the BRS Pelota rice cultivar was proportionally higher with population increase of both barnyardgrass biotypes. The biotypes showed, in general, similar competitive ability.

Avaliação de germinação e dormência de ecótipos de arroz-vermelho

The objective of this work was to evaluate aspects related to the phenotypic characterization of red rice ecotypes collected in the states of Rio Grande do Sul and Santa Catarina. The ecotypes were studied and compared to the commercial rice cultivars BR-IRGA 409, BR-IRGA 410, IRGA 417, and El Paso L 144. In the laboratory experiment, seed biometry, 1000 seed-weight and seed germination and dormancy 30, 60, 90, 120, and 150 days after harvesting were evaluated. The red rice ecotypes from the rice fields evaluated showed wide variability in seed characteristics and dormancy intensity and duration. Some ecotypes showed dormancy period above 150 days after harvesting. The results of this study confirm that red rice populations infesting rice fields are quite diverse, and appropriate control of red rice is only achieved when growers adopt not only isolated control measures, but also several management practices to reduce red rice yield losses.

Tolerância de trigo (Triticum aestivum) e aveia (Avena sp.) a herbicidas inibidores da enzima acetolactato sintase (ALS)

A caracterizacao de cultivares quanto a tolerância aos herbicidas representa uma ferramenta adicional na identificacao de genes de resistencia no melhoramento genetico de plantas. Os objetivos do presente trabalho foram determinar a variabilidade genetica em genotipos de trigo, aveia-branca e aveia-preta para tolerância a quatro herbicidas inibidores da ALS; identificar herbicidas que nao apresentam efeito fitotoxico nas especies avaliadas; e indicar possiveis genotipos tolerantes para utilizacao em programas de melhoramento. Os resultados demonstraram a existencia de variabilidade genetica em trigo para tolerância aos herbicidas inibidores da ALS. O herbicida penoxsulam nao apresentou efeito sobre a producao de materia seca nos genotipos de trigo e aveia. Os genotipos de trigo ICA 7, BRS 208 e CD 111 e a aveia-branca (Albasul) evidenciaram tolerância aos herbicidas bispyribac-sodium e penoxsulam; a aveia-preta (Agozebu) tambem se mostrou tolerante ao metsulfuron-methyl.

Caracterização morfológica de ecótipos de arroz daninho (Oryza sativa) provenientes de áreas de arroz irrigado

Objetivou-se neste estudo a caracterizacao fenotipica de 16 ecotipos de arroz daninho provenientes de lavouras comerciais dos Estados do Rio Grande do Sul e Santa Catarina, quando comparados aos cultivares BR-IRGA 409, BR-IRGA 410, IRGA 417 e El Paso L 144, em casa de vegetacao. Foram semeados 16 ecotipos de arroz daninho e os quatro cultivares de arroz irrigado. O cultivo foi realizado em vasos plasticos com capacidade para 9 litros, contendo solo, utilizando-se cinco repeticoes por genotipo. Foram avaliadas as seguintes variaveis: coloracao das folhas, pilosidade, afilhamento efetivo, graus-dia biologico para completar o florescimento, degrane, numero de afilhos ferteis, area foliar da folha-bandeira, altura de planta, numero de sementes por panicula e producao por planta. Os resultados obtidos evidenciam grande variabilidade morfologica entre os ecotipos estudados.

Competition between rice plants and Echinochloa spp. biotypes resistant or susceptible to quinclorac

This work aimed to evaluate the interspecific competitiveness of Echinochloa spp. biotypes resistant or susceptible to the herbicide quinclorac. The trial was installed under greenhouse conditions, with the biotypes resistant (ITJ-13) and susceptible (ITJ-17) to quinclorac under competition with the rice plants. The treatments consisted of maintaining one rice plant at the center of the experimental unit, surrounded by 0, 1, 2, 3, 4 or 5 Echinochloa plants, according to the treatment. The trial was arranged in a completely randomized blocks design and factorial scheme 2xa0xxa06, with four replications. Forty days after emergence, fresh dry weights and water content of the shoots were evaluated. There was a significant effect for all the variables when the rice was grown in the presence of R or S.xa0Echinochloa spp. This effect was additive in the proportion of onexa0plant m-2. However, the competitive capacity of R and S to quinclorac Echinochloa spp biotypes against the rice plants showed similar behavior when plant density per area varied.

Competitividade de biótipos de capim-arroz resistente e suscetível ao quinclorac

The objective of this research was to evaluate the competitive potential of two Echinochloa sp. biotypes, resistant and susceptible to quinclorac, collected in rice regions in the state of Santa Catarina. The trial was carried out under controlled environment, and the treatments consisted of plant densities of Echinochloa resistant or susceptible to quinclorac. At the center of the experimental unit, three seeds of the biotype were planted and considered as the treatment. Ten seeds of the opposite biotype were planted on the edges. Ten days after emergence, the number of plants was standardized, with only one plant left at the center of the experimental unit, and a variable number of plants on the edges (0, 1, 2, 3, 4 or 5 plants), according to the treatment. The experimental design consisted of completely randomized blocks in a factorial scheme 2 x 6, with four replications. Forty days after emergence, plant height, number of tillers and leaves, leaf area, fresh and dry weight and water content were evaluated. Data were analyzed by the F-test, using the DMRT test for the increasing density effect, and DMS test to compare the biotypes. All analyses were run at 5% significance level. A correlation matrix was built among the evaluated variables. The Echinochloa sp. biotypes studied, resistant and susceptible to quinclorac, are similar in behavior under high competition levels, with the susceptible ones being superior to the resistant ones in some of the variables studied, at low or moderate competition levels.

Crescimento de biótipos de capim-arroz em condição de competição

The objective of this work was to evaluate the growth of barnyard grass biotypes resistant and susceptible to the herbicide quinclorac, under competition between plants of the same and opposite biotypes. Plants of both biotypes were grown in different proportions in the experimental units. The treatments were arranged in a factorial scheme 2 x 6, with four replications in a completely randomized block design. Forty-five days after emergence, the leaf area and dry mass of the shoots were determined, sorted out into leaves and shoots. Growth rate (TC), specific leaf area (AFE), leaf area index (IAF), leaf weight rate (RPF) and leaf area rate (RAF) were calculated. The variables dry mass, growth rate, leaf area index, leaf weight rate and leaf area rate did not differ between the biotypes, independently of the treatment evaluated. However, the susceptible biotype was superior to the resistant one in relation to the specific leaf area, both isolated or in community. It was concluded that only discrete differences occur between biotypes resistant and susceptible to the herbicide quinclorac in relation to growth potential under competition.