Paulo Geraldo Berger

Elaboração e validação de escala diagramática para quantificação da mancha de ramularia do algodoeiro

This study aimed to elaborate and validate a diagrammatic scale to assess areolate mildew on cotton leaves. The proposed scale showed disease levels of 0.05, 0.50, 1.0, 2.0, 4.0, 8.0, 16.0, 32.0 and 67.20%. The scale showed to be adequate to evaluate areolate mildew due to an increase in accuracy, precision, and reproductibility during disease evaluations.

Características agronômicas e o estado nutricional de cultivares de girassol irrigado

This work aimed to assess nutritional status, agronomic characteristics, and productivity of sunflower cultivars under irrigation. Embrapa 122 V-2000, Helio 250, Helio 251, Helio 253, Helio 358, Helio 360, IAC Iarama, and Dow Agroscience M 734 and MG 02 cultivars were sown in randomized block design with four replications. The number of leaves per plant in full bloom was higher in hybrid Helio 250, Helio 251, Helio 253, Helio 358, Helio 360 and Dow Agroscience MG 734 and M 02 related to open-pollinated cultivars Embrapa 122 V-2000 and IAC Iarama. Foliar contents of N, P, K, Ca, Mg, and S were 40.91, 3.51, 35.91, 33.91, 6.23, and 7.88 g kg-1, respectively. Embrapa 122 V-2000 and IAC-Iarama cultivars showed an average content of P in the index leaf lower than the other cultivars. Foliar contents of Zn, Cu, Fe, and Mn were 75.15, 24.11, 98.39, and 348.10 mg kg-1, respectively. Mean content of B in index leaf of hybrid and open-pollinated varieties was 119.25 and 140.35 mg kg-1, respectively. Helio 250, Helio 251, Helio 253, Helio 358, Helio 360, and Dow Agroscience M 734 and MG 02 cultivars had higher productivity than Embrapa 122 V-2000 and IAC Iarama.

Aplicação do fósforo e da irrigação na absorção e exportação de nutrientes pelo algodoeiro

This work aimed to evaluate the effect of phosphorus application in rainfed and irrigated crop on shoot dry matter, the absorption and nutrient exportation, and yield of cotton crop. The experiment was carried out in a Psament in the northeren part of Minas Gerais State, Brazil. The experimental design was in randomized blocks with four replications in a factorial arrangement of two doses of P2O5 x two cropping systems. Two additional treatments in each system without phosphorus application completed six studied treatments. Accumulation of dry biomass, absorption and exportation of nutrients, and yield of seed cotton were evaluated. Phosphorus levels did not influence the accumulation of shoot dry biomass. P supply increased the exportation of P, Ca, Mg, S, and Mn under irrigated and of N, K, and Fe regardless of the cropping system. Irrigation increased the dry biomass of leaves, stems, and shoots at 80 days after emergency, and the absorption of N, P, K, Ca, Mg, S, Cu, Fe, Mn, Zn, and B, as well as their exportation by the crop. There was an increase in the number of bolls per plant, fiber yield and productivity through the irrigation use. Increasing productivity with P application was conditioned to irrigation.

Influence of Boron on Sunflower Yield and Nutritional Status

ABSTRACT Sunflower has been mentioned in the literature as a plant that requires large amounts of boron (B) to achieve a successful crop. This study aimed at evaluating the influence of sunflower fertilization with boron on the soil nutrient concentration, index leaf, seed yield, fatty acids’ composition of sunflower oil, and oil content. Cultivar M734 was selected for boron fertilization at 0, 3, 6, 9, and 12 kg ha−1 rates. The maximum economic return was obtained with 3.13 kg ha−1. Neither oil content nor fatty acid composition was affected by boron. With proper irrigation, the M734 cultivar was able to absorb boron in the 0 − 40-cm layer, ultimately producing about 3000 kg ha−1 of seeds in soils with only 0.30 mg kg−1 of boron. Based on these results, it is suggested that the boron fertilization program be expanded to include the soil strata at 0−20 cm and 20−40 cm.

Mecanismos bioquímicos da defesa do algodoeiro à mancha de ramulária mediados pelo silício

of leaf area, lesion size (LS), foliar Si concentration and the activities of defense enzymes peroxidases (POX), polyphenoloxidases (PPO), chitinases (CHI), s-1,3-glucanases (GLU), and phenylalanine ammonia-lyases (PAL) were evaluated. Data from severity were used to calculate the area under ramularia leaf spot progress curve (AURLSPC). Leaf Si concentration increased by 64% on plants supplied with Si compared to plants not supplied with this element. There were increases of 10 and 14.7% for IP and LP 60 , respectively, on plants supplied with Si. Reductions of 38.6 and 62.4% for NL and 17.2 and 26.6% for LS occurred, respectively, for plants from NuOpal and BRS Buriti cvs supplied with Si. AURLSPC was re- duced by 35% for the +Si treatment compared to the -Si treatment. The concentration of total soluble phenolic compounds on plants of both cv. supplied with Si increased during the progress of ramularia, but the lowest values occurred for the -Si treatment until 18 days after inoculation (dai). The increase on the concentration of lignin derivatives was significant only for plants of cv. BRS Buriti infected by R. areola and supplied with Si. POX activity was higher on plants from the two cultivars supplied with Si compared to plants not supplied with this element. For plants of cv. NuOpal supplied with Si, PPO, CHI, GLU, and PAL activities increased until 18 dai, but the activities of PAL and PPO on plants of cv. BRS Buriti were not potentiated by Si. On plants from cv. BRS Buriti supplied with Si, there was increase on CHI and GLU activities at 21 dai compared to plants not supplied with Si. It can be concluded that cotton resistance to ramularia leaf spot was biochemically enhanced by Si, especially for plants of cv. NuOpal considered susceptible to ramularia leaf spot.

Parcelamento do fertilizante fosfatado no algodoeiro em sistema de cultivo irrigado e de sequeiro

The objective was to evaluate the application of phosphorus doses in parcels in the cotton crop in the systems of cultivation under irrigation and rainfed, being aimed the higher efficiency of phosphate fertilization, in comparison to the traditional application, only at sowing. The experiment was carried out in Quartzanic Neossoil, in the North region of Minas Gerais. The adopted design was randomized blocks, with three replicates. The treatments were the doses of 50 and 120 kg ha-1 of P2O5 applied in four ways: PS, P1, P2 and P3 [100/0; 75/25; 50/50; 25/75% of the dose of phosphate fertilizer applied, respectively at the sowing and at 35 days after the emergence (DAE)], in the irrigated and rainfed crops. Two additional treatments, without P, in the crop without and with irrigation, completed the eighteen studied treatments. The increase of the P doses increased the dry mass of aerial part and the number of reproductive structures at 80 DAE, the relative efficiency of the phosphate fertilization and the productivity of cotton in bull. The response to P doses occurred only under irrigation. The parceled application of the phosphate fertilizer did not increase the efficiency of the fertilization in the cotton farm in Quartzanic Neossoil.

Parcelamento de fósforo em algodoeiro irrigado

Most regions where cotton is cultivated in Brazil present low soil fertility, especially concerning the available phosphorus (P). This study aimed to evaluate the phosphorus split application on irrigated cotton, for reaching a higher phosphate fertilization efficiency, in comparison to the traditional application at sowing. The experiment was conducted in Quartzarenic Neosol with 22 mg dm -3 of P (medium availability), in the north region of the Minas Gerais State, Brazil. The design used was randomized blocks, in a (4x3) + 3 factorial scheme, with three replications. Treatments consisted of P 2 O 5 doses (0 kg ha -1 , 30 kg ha -1 , 60 kg ha -1 , 120 kg ha -1 , and 180 kg ha -1 ) and three split applications (80% and 20%; 60% and 40%; 40% and 60% of the P dose applied respectively at sowing and at 35 days after emergence (DAE)), plus the application of 0 kg ha -1 , 60 kg ha -1 , and 120 kg ha -1 of P 2 O 5 at sowing. The P source was the granulated triple superphosphate, and the P content in the shoots increased according to the doses applied. Nutrient contents in the index leaf, except for P, were not influenced by P levels and split applications. The P content in the index leaf and the number of cotton bolls per plant increased with the increment of P doses, but were not affected by the phosphate fertilizer split application. The application of 40% of the P dose at sowing and the remaining amount split at 35 DAE decreased the cotton boll yield, with no significant effect for the other split applications.

Performance of the Natural Mortality Factors of Aphis gossypii (Hemiptera: Aphididae) as a Function of Cotton Plant Variety and Phenology

Abstract Natural mortality factors are responsible for regulating pest populations in the field. However, plant attributes such as the variety and phenological stage can influence the performance of these factors. Therefore, we investigated the performance of the natural mortality factors of Aphis gossypii (Glover; Hemiptera: Aphididae) as a function of the plant variety and phenology. To investigate the performance of these factors, we evaluated the mortality of A. gossypii caused by natural mortality factors for 2 yr in field conditions in transgenic (Bacillus thuringiensis/Roundup Ready) and non-transgenic cotton crops during vegetative, flowering, and fruiting stages. The natural mortality factors were affected similarly between the transgenic and non-transgenic plants; however, differences were observed in their performance, depending on the phenological stage of the cotton plant. Compared with other stages, predation was higher in the flowering stage, whereas the mortality caused by rainfall was higher in the vegetative stage. Coccinellid beetles were primarily responsible for the predation on A. gossypii. These findings highlight that the performance of the natural mortality factors of A. gossypii varied more as a function of the phenological stage of cotton than of the variety.

Infection process of Phakopsora gossypii in cotton leaves

Tropical rust caused by the biotrophic fungus Phakopsora gossypii is an emerging disease in cotton that has caused significant yield losses of crop/cotton cultivated in Brazil. Considering the current importance of tropical rust and the need to obtain additional basic information about its causal agent to better control this disease, the present study aimed to determine the infection process of P. gossypii in cotton leaves using scanning electron microscopy (SEM). Thirty-day-old plants were inoculated with a suspension of P. gossypii uredospores, and leaf fragments were collected 42 h after inoculation (hai) as well as 20, 25 and 35 days after inoculation (dai) for SEM observations. By 42 hai, the uredospores of P. gossypii had germinated and produced a germ tube and an appressorium that may directly penetrate the leaf cuticle. At 20 dai, closed uredia containing uredospores were observed on the abaxial leaf surface. At 25 dai, the uredia started to open and became fully open by 35 dai and contained many uredospores. By 25 dai, fungal hyphae were growing abundantly in the mesophyll next to the uredia that formed in the leaf fragments with total or partial removal of the epidermis. The results of the present study provide novel information regarding the infection process of P. gossypii in cotton leaves, which might be useful for the development of new and more effective strategies for tropical rust control.