Fernando José Hawerroth

Chilling privation during dormancy period and carbohydrate mobilization in Japanese pear trees

The flower bud abortion is one of the main problems that limit commercial pear (Pyrus pyrifolia) production in the southern region of Brazil. Insufficient chilling during the dormancy period is known as the main factor of this problem. One of the hypotheses to explain this problem is that the starch mobilization and carbohydrate fluxes to the buds are impeded when mild temperatures occurred during winter. This study compared the total soluble sugars (TSS) and reducing sugars (RS) concentrations, the cell wall acid invertase (CWAI - EC 3.2.1.26) and sucrose-phosphate synthase (SPS - EC 2.4.1.14) activities in wood of branches and floral buds of Japanese pear trees cv. Housui, grafted on Pyrus calleryana and submitted to chilling conditions during the dormancy period. Treatments were: (i) natural conditions; (ii) continuous artificial chilling; (iii) alternating temperatures, and (iv) total chilling privation. TSS and RS contents, as well as CWAI and SPS activities in tissues of branches that received insufficient chilling were lower than those that received sufficient chilling during winter. The starch concentration was superior in wood tissues of branches kept under chilling privation. The chilling privation disturbs carbohydrate mobilization in pear trees, reducing the sucrose synthesis capacity in wood tissues (source) and sucrose importation by the floral buds (sink).

Avaliação de temperaturas hibernais na brotação de gemas de macieira utilizando ramos enxertados

ABSTRACT - Temperature is the main climate factor related to induction, maintenance and dormancy release in apple ( Malus domestica Borkh.). The inadequate chilling exposure in apples causes budbreak problems, resulting in decrease in yield potential. Thus, the knowledge of physiological principles and environmental factors determining the dormancy phenomenon, especially winter temperature effects, it is necessary for the efficient selection of cultivars in a productive region. In addition, it is indispensable to adapt the orchard management aiming to decrease the problems caused by lack chilling during winter. The objective of this study was to evaluate the influence of different thermal conditions during the dormancy period on budbreak of apple cultivars. One-year-old twigs of ‘Castel Gala’ and ‘Royal Gala’ cultivars, grafted on M7 rootstock, were submitted to temperatures of 5, 10 and 15oC for different exposure periods (168; 336; 672; 1,008 and 1,344 hours). After treatments execution, the plants were kept in a greenhouse at 25oC. Budbreak was quantified when accumulated 3,444; 6,888; 10,332; 13,776; 17,220 and 20,664 GDHoC after temperature treatments. The cultivars responded differently to temperature effect during the winter period. The temperature of 15°C during winter shows a greater effectiveness on ‘Castel Gala’ apple budbreak while in the ‘Royal Gala’ apples the temperatures of 5 and 10oC show better performance. ‘Castel Gala’ cultivar (low chilling requirement) may supply its physiological necessities, may be capable to budburst, even when subjected to higher temperatures in relation to ‘Royal Gala’ apples (high chilling requirement).

CONTROLE DA MATURAÇÃO PRÉ-COLHEITA DE MAÇÃS ‘ROYAL GALA’ PELA INIBIÇÃO DA AÇÃO OU SÍNTESE DO ETILENO

ABSTRACTThe objective of this research was to evaluate the effects of ethylene action inhibition (by sprayable formulation of 1-methylcyclopropene; 1-MCP) and ethylene synthesis inhibition (by aminoethoxyvinylglycine; AVG) on preharvest apple fruit maturation. ‘Royal Gala’ apple trees were sprayed with 1-MCP (at 50 or 100 mg L-1)) seven days before anticipated harvest (DBAH), or with AVG (124 mg L-1)) 28 DBAH. Apple trees not sprayed with 1-MCP and AVG were used as control. Fruit were harvested weekly,along five weeks from the 7th day after 1-MCP spraying, and then analyzed in terms of maturity and quality one day after harvest. Fruit maturity and quality attributes when fruit reached the flesh firmness of 71.1 N were estimated by analysis of regression, for each treatment. 1-MCP (50 and 100 mg L-1)) and AVG delayed fruit maturation, by reducing the ethylene production rates, starch degradation, loss of flesh firmness and acidity, skin yellowing, increase of soluble solids content and skin red color development. 1-MCP (100 mg L-1)) and AVG delayed in 6 and 12 days, respectively, the time required for fruit to reach the flesh firmness of 71.1 N on the tree, in comparison to the control. Fruit treated with 1-MCP or AVG had starch index, ethylene production and acidity values similar or smaller than the control, at the date when all treatments achieved the flesh firmness of 71.1 N. The magnitude of 1-MCP effect on flesh firmness was similar to the effect on ethylene production and skin color, and slightly slower on starch degradation. The effects of AVG on ethylene production, skin color and acidity were more substantial than on loss of flesh firmness. The results show that the treatment of ‘Royal Gala’ apple trees with the sprayable formulation of 1-MCP represents an additional method for management of fruit maturation and harvest.

Uso da desfolha para indução da brotação de atemoleiras 'Gefner'

aBstract- The use of cultural practices that allows production scheduling of atemoyas trees is for exploration of this crop. The shoot defoliation induces budbreak of atemoyas in certain weather conditions, with other cultural techniques, may control the production times. Thus, the aim of this study was to evaluate different defoliation treatments on budbreak induction of atemoyas trees growing at tropical conditions. The experiment was conducted in a commercial orchard located in Limoeiro do Norte/CE, Brazil, using five years old atemoya trees ‘Gefner’, grafted on sugar apple rootstock. Thereabout ten days after harvest was held pruning production and then applied the treatments: 1) control (without defoliation); 2) hand defoliation, 3) urea 150 g L -1 ; 4) urea 150 g L + mineral oil 24 mL L -1 ; 5) urea 150 g L + copper sulfate 10 g L -1 ; 6) copper sulfate 10 g L -1 + mineral oil 24 mL L -1 ; 7) urea 150 g L + mineral oil 24 mL L -1 + copper sulfate 10 g L -1 ; and 8) ethephon 2.4 mL L. All chemical treatments tested induced defoliation and budbreak of ‘Gefner’ atemoya trees, especially foliar applications of ethephon 2.4 mL L

EFFECT OF THIDIAZURON CONCENTRATION AND APPLICATION PERIOD ON ‘ROYAL GALA’ APPLE FRUITING AND PRODUCTION

ABSTRACT ? ?Gala? apple trees have low fruit set in restrictive pollination situations, being an obstacle to the achievement of high production rates in orchards in southern Brazil, which can be minimized by the use of growth regulators. The aim of this study was to evaluate the effect of thidiazuron concentrations in ?Royal Gala? apple fruiting and production, grown in mild winter conditions. The experiment was conducted during the 2011/2012, 2012/2013 and 2013/2014 crop years in Fraiburgo, SC, on ?Royal Gala? apple trees in Marubakaido rootstock M9 with filter. In all evaluation cycles, the experimental design was a randomized block with factorial arrangement (6x2) with six TDZ concentrations and two application forms, with six replicates, and the experimental unit consisting of one plant. The TDZ concentrations of each treatment were applied split into two seasons. The first application was performed on pink bud stage (E2) and the second application was in full bloom stage (F2). The variables evaluated were: fruit set (%), return bloom (%), number and weight of fruits per plant, mean fruit weight (g) and average number of seeds per fruit. Data were submitted to analysis of variance, in which for significant variables by the F test, analysis of contrast and polynomial regression were performed in order to evaluate the response of variables with increasing TDZ concentration. TDZ is effective even at low concentrations, increasing the production and fruit set of ?Gala? apples in the climatic conditions of southern Brazil. Index terms: Malus domestica Borkh., growth regulators, cytokinin, fruit set.

USE OF METAMITRON AS AN APPLE THINNER

ABSTRACT - The aim of this study was to evaluate the efficacy of metamitron or metamitron plus benzyladenine as a post-bloom thinner on ?Baronesa? and ?Fuji? apples. Three experiments (rate, timing and BA combination) were conducted during two crop seasons, 2013/14 and 2014/15 at the experimental station located in Cacador, SC. Fruit set, fruit drop, yield per tree, fruit size and flowering return were assessed. The efficacy of metamitron was affected by time of application, and when applied at petal fall, promoted the proper adjustment of the production load of plants. Yield per plant reduces, whereas the allocation of fruits in categories of greater size increases proportionally to the increase in the metamitron concentration applied. However, there is excessive fruit drop with the use of high concentrations. The addition of BA to metamitron also promoted fruit drop; however, no difference was observed between single application of metamitron and BA addition. Metamitron shows great potential to be used as thinner for apples, since it reduces the number of fruits per tree. Index terms: Malus domestica, post-bloom thinning, fruit drop, return bloom, fruit quality.

METAMITRON REPLACING CARBARYL IN POST BLOOM THINNING OF APPLE TREES

ABSTRACT Carbaryl or the mixture of carbaryl with NAA (naphthalene acetic acid) or BA (benzyladenine) are the post-bloom chemical thinners most widely used in apple thinning in Brazil. The marketing restriction of carbaryl demands new options of apple post-bloom thinners, requiring the evaluation of others compounds for this purpose. Metamitron is one of the substances that may be used in chemical thinning of apples. Metamitron was evaluated at two concentrations, alone or in mixture with BA, in ?MaxiGala?, ?Fuji Suprema? and ?Fred Hough? apple cultivars. Applications of metamitron at 384 mg L-1 and at 768 mg L-1 in a mixture with BA, ranging from 40 mg L-1 to 80 mg L-1, sprayed on fruits with diameter ranging from 5 to 25 mm were compared ith the standard treatment and hand thinning. The experimental design was a randomized complete block with 4-6 repetitions of a single plant. The variables analyzed were: fruit set (%); percentage of floral clusters with 1, 2, 3, 4 or more fruits; fruit yield (kg); verage fruit fresh mass (g) and percentage of dropped fruit after thinning. Metamitron alone or in combination with BA reduced production per plant and significantly increased the fresh weight of fruits in all cultivars tested. Metamitron at 800 mg L-1 resulted in excessive fruit thinning, especially in ?MaxiGala? cultivar. Metamitron or metamitron + BA have potential to compose the program of chemical thinning of apple trees to replace carbaryl. Index terms: Plant growth regulators, concentration, fruit set, fruit production. Resumo O carbaryl ou a mistura de carbaryl com ANA (acido naftaleno acetico) ou BA (Benziladenina) sao os produtos mais utilizados no raleio quimico da macieira no Brasil. Com o cancelamento do registro do carbaryl como raleante de pos-floracao, sao necessarias novas alternativas, sendo importante testar diferentes raleantes com esta finalidade. Dentre as substâncias passiveis de utilizacao no raleio da macieira insere-se o metamitron. O objetivo deste estudo foi avaliar a resposta da aplicacao de metamitron no raleio das macieiras ‘Fuji Suprema’, ‘MaxiGala’ e ‘Fred Hough’. O uso de metamitron foi testado em duas concentracoes, so ou em mistura de tanque com BA, e comparado com BA e BA + etefom, em tres cultivares de macieira: ‘Maxigala’, ‘Fuji Suprema’ e ‘Fred Hough’. Aplicacoes de 384 mg L-1 e 768 mg L-1 de metamitron em mistura com BA de 40 mg L-1 e 80 mg L-1 aplicado em frutos de 5 a 25 mm de diâmetro foram comparadas com ‘tratamento-padrao’ e raleio manual. Foi usado o delineamento experimental em blocos ao acaso com cinco a seis repeticoes. As variaveis analisadas foram: frutificacao efetiva (%), percentagem de cachos florais com 1; 2; 3; 4 ou mais frutos por inflorescencia, producao por planta (kg), numero de frutos por planta, massa media dos frutos (g) e percentagem de queda de frutos apos o raleio. O metamitron so, ou em combinacao com BA, reduziu a producao por planta e aumentou a massa media dos frutos em todas as cultivares estudadas. Metamitron a 768 mg L-1 resultou em excessivo raleio, especialmente na ‘MaxiGala’. Metamitron ou metamitron + BA tem potencial para compor o programa de raleio quimico da macieira em substituicao ao carbaryl. Termos para indexacao: Regulador de crescimento, concentracao, frutificacao efetiva, producao.