Gustavo Malagi

Differentiated Responses of Apple Tree Floral Phenology to Global Warming in Contrasting Climatic Regions

The responses of flowering phenology to temperature increases in temperate fruit trees have rarely been investigated in contrasting climatic regions. This is an appropriate framework for highlighting varying responses to diverse warming contexts, which would potentially combine chill accumulation (CA) declines and heat accumulation (HA) increases. To examine this issue, a data set was constituted in apple tree from flowering dates collected for two phenological stages of three cultivars in seven climate-contrasting temperate regions of Western Europe and in three mild regions, one in Northern Morocco and two in Southern Brazil. Multiple change-point models were applied to flowering date series, as well as to corresponding series of mean temperature during two successive periods, respectively determining for the fulfillment of chill and heat requirements. A new overview in space and time of flowering date changes was provided in apple tree highlighting not only flowering date advances as in previous studies but also stationary flowering date series. At global scale, differentiated flowering time patterns result from varying interactions between contrasting thermal determinisms of flowering dates and contrasting warming contexts. This may explain flowering date advances in most of European regions and in Morocco vs. stationary flowering date series in the Brazilian regions. A notable exception in Europe was found in the French Mediterranean region where the flowering date series was stationary. While the flowering duration series were stationary whatever the region, the flowering durations were far longer in mild regions compared to temperate regions. Our findings suggest a new warming vulnerability in temperate Mediterranean regions, which could shift toward responding more to chill decline and consequently experience late and extended flowering under future warming scenarios.

Escala diagramática para avaliação de severidade da helmintosporiose comum em milho

The Helminthosporium leaf blight, caused by Exserohilum turcicum, is one of the main spots that attacks corn crop in Southern Brazil. This disease causes considerable economic losses on this crop, especially when the attack begins before the flowering period. The aim of this research was to elaborate and validate a diagrammatic scale to evaluate the severity of the Helminthosporium leaf blight in corn. Corn leaves with symptoms of the disease were collected for measuring the real severity and defining the maximum and minimum limits, as well as the intermediate levels and the logarithmic increments, according to Weber-Fechners stimulus-response law. The elaborated scale suggested seven severity levels: 0,5; 1,0; 2,5; 6,5; 15,5; 30,0 and 54,0%. The validation was performed by six persons without previous experience to quantify this disease. The severity of 30 leaves with different levels of symptoms was estimated, with and without the help of the scale. The use of the diagrammatic scale resulted in better accuracy and precision in the estimates, being a tool for quick and easy use, which can be adopted to assist in the severity evaluation of the Helminthosporium leaf blight in corn.

Variability in leaf rust susceptibility among peach cultivars

The aim of this work was to estimate the susceptibility of thirty-six peach cultivars to leaf rust caused by Tranzschelia discolor f. sp. persica. The incidence and severity of the disease as well as defoliation in peach trees of an experimental orchard of Parana Federal University of Technology, Campus Dois Vizinhos were evaluated on the growing seasons 2004/2005 and 2005/2006. Immunity to this disease was not observed in the studied cultivars. There was difference in leaf rust intensity depending on the growing season conditions. Cultivars ‘Pilcha‘, ‘Sinuelo‘, ‘Chirua‘, ‘Sulina‘, ‘Eldorado‘ and ‘Pampeano‘ showed tolerance to leaf rust, whereas cultivars ‘Vila Nova‘, ‘Fla 1372‘, ‘Coral 2‘, ‘Chimarrita‘, ‘Della Nona‘, ‘BR-1‘ and ‘Guaiaca‘ showed high susceptibility.

Differentiated dynamics of bud dormancy and growth in temperate fruit trees relating to bud phenology adaptation, the case of apple and almond trees

Few studies have focused on the characterization of bud dormancy and growth dynamics for temperate fruit species in temperate and mild cropping areas, although this is an appropriate framework to anticipate phenology adaptation facing future warming contexts which would potentially combine chill declines and heat increases. To examine this issue, two experimental approaches and field observations were used for high- and low-chill apple cultivars in temperate climate of southern France and in mild climates of northern Morocco and southern Brazil. Low-chill almond cultivars offered an additional relevant plant material for comparison with apple in northern Morocco. Divergent patterns of dormancy and growth dynamics were clearly found in apple tree between southern France and southern Brazil. Divergences were less pronounced between France and Morocco. A global view outlined main differences in the dormancy chronology and intensity, the transition between endordormancy and ecodormancy and the duration of ecodormancy. A key role of bud rehydration in the transition period was shown. High-chill cultivars would be submitted in mild conditions to heterogeneous rehydration capacities linked to insufficient chill fulfillment and excessive forcing linked to high temperatures. This would favor bud competitions and consequently excessive flowering durations and weak flowering. Low chilling requirements in apple and almond would conversely confer biological capacities to tolerate superficial dormancy and abrupt transition from endordormancy to ecodormancy without important heterogeneous rehydration states within buds. It may also assume that low-chill cultivars can also tolerate high temperatures during ecodormancy as well as extended flowering durations.

Enxertia interespecífica de jabuticabeira: influência do tipo de garfo

This research aimed to evaluate craft success and development of two grafted species of Jabuticaba (Plinia spp.) using different methods of grafting. A Complete randomized experimental design was used with ten replicates, under a factorial scheme of 2x3 (species x diameter of stem cutting), and the experimental unit was composed by one plant. Plinia trunciflora and Plinia cauliflora were the scion species grafted on P. cauliflora by cleft grafting, using herbaceous cuttings (diameters smaller than 3mm), semi-woody cuttings of low caliber (diameter 3-5mm), and semi-woody cuttings of medium caliber (diameter 5-7mm). P. trunciflora presented the higher number of buddings but the length of buddings were 44% lower than P. cauliflora. Budding percentage was not significantly different among studied species. The semi-wood cuttings of low caliber increased significantly the number of buddings and graft success when compared to herbaceous cuttings, not presenting significant difference when compared to semi-woody cuttings of medium caliber herbaceous cuttings.

Non-destructive method for leaf area determination of grapevine 'BRS-Violeta' cultivar

ABSTRACT- The objective of this work was to evaluate combinations between lengths of secondary and main veins of leaves to estimate leaf area from grapevine, ‘BRS-Violeta’ cultivar. Random sampling was made from 200 entire and completely developed leaves, within an area of experimental cultivation. Actual leaf area (AFR) and the lengths of secondary (left-right) and main veins were determined. Three regressions were obtained with the coefficients of determination in order to identify the most accurate relation, consider-ing main vein length (CNP), sum of secondary vein lengths (SCNS) and sum of secondary and main vein lengths (SCNSP), as independent variables. AFR was considered dependent variable in the three regressions. Relation between AFR x SCNS resulted in a higher coefficient of determination (0.87). Leaf area estimated by the equation obtained from AFR x SCNS relation was 87% accurate, according to AFR x AFE (estimated leaf area) relation. Therefore, leaf area from grapevine ‘BRS-Violeta’ cultivar can be estimated by the equa-tion: y = 0.2169 (SCNS)

Modo de reprodução e viabilidade de pólen de três espécies de jabuticabeira

ABSTRACT - The objective of this study was to determine the reproductive mode and the conditions for in vitro pollen viability testing of three jabuticaba tree species (Plinia cauliflora, P. trunciflora and P. jaboticaba). Observed fruit set in bagged and not bagged branches and aspects of floral morphology. Pollen viability was evaluated in culture medium with and without boric acid with pollen collected at different times after anthesis. Pollen germination of six genotypes was quantified before and after storage. P. trunciflora and P. jaboticaba are self-compatible, however the polinizer increase fruiting. The P. cauliflora requires polinizers for fruiting, because it has flowers with greater stigma-anther distance than the other two species, which prevents the passive self-pollination. Boric acid ads in the culture medium improve in vitro germination of jabuticaba tree pollen. The pollen viability is greater six hours after anthesis. It is possible the conservation of pollen for up to 90 days in freezer (-18°C), if it has high initial germination (greater than 80%). These results will help in planning crosses in jabutica tree.Index terms: Plinia sp., pollination, pollen storage, boron.

Morphological variability of Kabatiella zeae isolates and aspect of fungus colonies in culture media

Thirty-five Kabatiella zeae isolates from different corn genetic materials were used to evaluate their morphological characteristics and mycelial growth. The following culture media were used: PSA (potato, sucrose, and agar), MA (malt and agar), OA (oat and agar) and CA (corn meal and agar). Disks (5 mm diameter) were removed from the margins of colonies grown on PSA medium for 10 days and placed at the center of dishes containing the corresponding culture media. The dishes were incubated at 24°C and a 12-hour photoperiod for 10 days. The morphological characteristics of the isolates as well as colony characteristics were evaluated in PSA, while mycelial growth was evaluated in the four media. All isolates showed variability in relation to the culture media. Spore size ranged from 3-4 × 27-33 μm in width and length, respectively. Eighty percent of the isolates had a light (pink) color and a coriaceous and wrinkled aspect; the highest mycelial growth was observed in the PSA medium.