Hudson Teixeira

White Mold Management in Common Bean by Increasing Within-Row Distance Between Plants

White mold of common bean (Phaseolus vulgaris), caused by Sclerotinia sclerotiorum, is a major yield-limiting disease during the fall-winter season in Brazil. This study was conducted to evaluate the efficacy of decreasing within-row densities for an indeterminate growth habit (type IIIa) cultivar, keeping constant the between-row spacing of 0.5 m, to manage the disease. A modification of within-row plant distributions was also attempted in order to reduce white mold intensity. The study was conducted with sprinkler irrigation in two growing seasons (2000 and 2001) in Viçosa, State of Minas Gerais, Brazil, in an area naturally infested with sclerotia. In 2000, treatments were arranged as 3 × 2 × 2 factorial combination of within-row densities (15, 7.5, or 5 plants/m), within-row plant distributions (single and equidistant plants or equidistant groups of three plants), and fluazinam treatments (with or without). In 2001, 16, 12, 8, or 4 plants/m were combined with fluazinam treatments. Fluazinam was applied at both flowering onset and 10 or 13 days later. Average incidence was 92.6% in 2000 and 77.8% in 2001; severity index was 69.8% in 2000 and 40.2% in 2001; and yield was 1,656 kg/ha in 2000 and 2,542 kg/ha in 2001. White mold decreased and yield increased as within-row densities were reduced, regardless of fluazinam treatments. A distribution of equidistant groups of three plants was ineffective in reducing disease. The use of 4 equidistant plants/m in infested irrigated areas was an effective strategy in white mold management.

Transmissibility and effect of Acremonium strictum in maize seeds

Acremonium strictum is pathogenic to seeds, stalk and seedlings of maize. It is a fungus that can interfere in the vigor, stand and final productivity of plants. In addition, it can be disseminated and transmitted through seeds to the progeny, although the real proportions of that are not well known. This study reports the effects of A. strictum on maize seeds and seedlings quality (germination, vigor, healthness), some vegetative growth parameters and also sanity (infection and transmission rates) of young maize plants. The transmission rate of the fungus was evaluated using the water restriction technique. The fungus formulation was cultivated on malt extract agar medium amended with mannitol to a water potential of -1,4 MPa. The maize seeds germination was reduced by seeds exposition to A. strictum for periods longer than 72 hours. The potentials vigor and viability were not affected by A. strictum. Theincidence of this fungus reduced the vegetative growth of maize plants measured 28 days after sowing. The fungus originating from inoculated seeds was transmitted to young maize plants.

Management of white mold in type III common bean with plant spacing and fungicide

White mold is a yield-limiting disease during the fall-winter season in southeastern Brazil when irrigated type III common beans are generally sown 0.5 m apart with 10 to 12 plants per meter. The aim of this study was to evaluate the efficacy of combining increased row width (RW) and reduced planting density (PD), with or without fungicide, for white mold management. Treatments were arranged as a 23 factorial: RW (0.50 or 0.75 m), PD (6 or 12 plants per meter), and fungicide (sprayed or unsprayed). Two trials were conducted in Vicosa, State of Minas Gerais. In 2002, the average incidence of white mold was 43.2%, the severity index, 31.1%, and the yield, 2513 kg ha-1. In 2003, the values of these variables were 48.0%, 22.6%, and 2159 kg ha-1, respectively. Interactions involving both RW and PD were not significant for either disease intensity or yield in the combined analysis across years. Increasing RW led to reduction in white mold intensity in 2002. The lower PD reduced disease incidence in 2002 and did not affect yield in the combined analysis. In fungicide sprayed plots, wide RW decreased yield in 2002, but RW did not affect yield in 2003. In unsprayed plots, RW did not affect yield in both years. We conclude that increasing RW to 0.75 m combined with low PD is a promising strategy for white mold management when fungicide is not applied. When fungicide is applied, the current row width (0.50 m) combined with low PD maximize the yield.

Foliar application of calcium chloride and calcium silicate decreases white mold intensity on dry beans

White mold (Sclerotinia sclerotiorum) is the most important common bean disease during the fall-winter season in Brazil. Different control strategies are necessary to control this disease and increase bean yield in infested areas. The aim of this research was to evaluate the effect of application of calcium chloride (CaCl 2 ) and calcium silicate (CaSiO 3 ) on white mold control on common bean. The experiment was carried out during the 2006 fall-winter season in Vicosa MG, Brazil, in a field naturally infested with sclerotia . Both CaCl 2 and CaSiO 3 were applied at 45 days after emergence (DAE) (early bloom) over the plants with a hand sprayer (800 L ha -1 ) at the rates of 100, 200, 300 and 400 mg L -1 or at 45 and 55 DAE at 300 mg L -1 . Two additional treatments were used: water (untreated control) and the fungicide fluazinam (0.5 L ha -1 ) applied at 45 and 55 DAE. Both incidence and severity of white mold were significantly reduced with application of CaCl 2 and CaSiO 3 , but there was no effect on yield. Fluazinam reduced significantly the disease incidence and severity by 52% and 73%, respectively, and increased the yield by 31%.

BRSMG Madrepérola: common bean cultivar with late-darkening Carioca grain

The cultivar BRSMG Madreperola, recommended for cultivation in Minas Gerais, has the feature of maintaining a light grain color for a longer period than other Carioca grain cultivars. The yield potential is high and the resistance level good to the major anthracnose races in the region.

Adaptation and Resistance to Diseases in Brazil of Putative Sources of Common Bean Resistance to White Mold

Common bean breeding programs for white mold (WM) resistance are in their initial stages in Brazil. Sources of partial resistance to WM are available abroad but their performance in Brazil is unknown. In two greenhouse (straw test) and three field experiments conducted in three districts in the state of Minas Gerais, Brazil, we evaluated a total of 23 lines with putative WM resistance with the objective to select lines with resistance to WM and other diseases associated with high yield potential. Two field-resistant local lines, two susceptible local cultivars, and two susceptible international lines were also included in the study. In the greenhouse, Cornell 605, A 195, and G122 were among the lines with the highest partial resistance to WM. In the field, these three lines were highly resistant to WM and had intermediate resistance or were resistant to anthracnose, angular leaf spot, rust, and Fusarium wilt. Cornell 605 and A 195 had high-yield potential but G122 yielded 47% less than the local lines under WM pressure. Our results suggest that Cornell 605 and A 195 are the most useful sources of resistance to WM for use in common bean breeding programs in Brazil.

Resistance of advanced common bean lines to Fusarium root rot

Fusarium root rot (FRR) is a distributed disease of common beans in Brazil. Our main aim was to verify if there are genotypes, mainly advanced lines from the common bean breeding program with levels of resistance to FRR similar to those of the line A-300. We also compared three developmental stages for FRR assessment. Genotypes of six classes were evaluated in greenhouse and field experiments. In greenhouse, substrate was infested with chlamydospores. In field, genotypes were screened in area infested with Fusarium solani f. sp. phaseoli. Plants were rated for disease at V3, R5 and R7 stages. Correlation among area under the disease progress curve (AUDPC) in greenhouse and in the field experiments was significant. Genotypes were ranked into four groups based on AUDPC. Sixteen advanced lines were as resistant to FRR as A-300. Correlation between the disease rating at R5 stages and AUDPC was higher than those among AUDPC and either disease rating at V3 or R7 in all experiments. Our results indicate that there are advanced lines with levels of FRR resistance similar to those of A-300 and that the FRR assessment at the R5 stage is more appropriated than at either V3 or R7.

Técnica de restrição hídrica: efeito sobre Acremonium strictum, protrusão de sementes e obtenção de sementes de milho infetadas

Water restriction technique: effect on Acremonium strictum, seeds protusion and obtaining of maize seeds infected This work was carried out to obtain maize (Zea mays) seeds with Acremonium strictum, by means of an adapted water restriction technique, in order to use them in pathogen-host studies. An evaluation was made of the effects of mannitol, NaCl and KCl at potentials of -0.48; -0.6; -0.8; -1.0; -1.2 and -1.4 MPa in malt extract agar medium (MEA) on the colony morphology and sporulation of A. strictum, and on radicle protrusion of maize seeds. Also evaluated was the correlation between different exposition periods of the seeds to the fungal colony and its incidence on disinfested and non-disinfested seeds with NaClO 1% (2 min). The micelial growth of A. strictum was stimulated in MEA + mannitol medium at potentials of -0.6 to -1.4 MPa. The morphology of A. strictum colonies in MEA medium for all the solutes used differed from the colonies in the control treatment (-0.48 MPa). Fungal sporulation was stimulated by mannitol on potentials –0.8 to –1.4 MPa in MEA. The lowest percentages of radicle protrusion in maize seeds were observed in cases when seeds were exposed to water restriction induced by MEA + mannitol at potential of -1,4 MPa; MEA + NaCl at -1,2 and -1,4 MPa. The NaCl, however, was verified to cause toxic effects in seed germination. This work shows that it is possible to obtain A. strictum infection in 36% of maize seeds infected by means of water restriction. Additional keywords: fungus, seed, inoculation, infection, protrusion in maize seeds.

Limitations in controlling white mold on common beans with Trichoderma spp. at the fall-winter season

We studied the effectiveness of application of Trichoderma spp. in controlling white mold on common beans at the fall-winter crop in the Zona da Mata region of the State of Minas Gerais, Brazil. There was no effect of the antagonist in reducing the disease severity, which could be explained by the low temperatures and the high inoculum pressure in the field. We concluded that Trichoderma applications are not recommended for control of white mold on common beans at the fall-winter season in regions with average temperature bellow 20 °C, since this condition favor more the pathogen than the antagonist.

Trichoderma spp. decrease Fusarium root rot in common bean

The effectiveness of six Trichoderma-based commercial products (TCP) in controlling Fusarium root rot (FRR) in common bean was assessed under field conditions. Three TCP, used for seed treatment or applied in the furrow, increased seedling emergence as much as the fungicide fludioxonil. FRR incidence was not affected, but all TCP and fludioxonil reduced the disease severity, compared to control. Application of Trichoderma-based products was as effective as that of fludioxonil in FRR management.