II. Horticultural performance of ‘Honeycrisp’ grown on a genetically diverse set of rootstocks under Western New York climatic conditions

A field experiment with 31 rootstocks representing a genetically diverse group of rootstocks featuring ‘Honeycrisp’ as the scion was planted in 2010 at Geneva, NY USA. Rootstocks included three from the Malling series (UK), nine from the Budagovsky series (Russia), 16 from the Cornell Geneva series (USA) and three from the Pillnitz series (Germany). Over the first 8 years (2010–2017) we measured final tree size (trunk cross-sectional area: TCA) and cumulative yield. In the last 4 years we measured fruit soluble solids, bitter pit incidence, biennial bearing, and leaf zonal chlorosis. Tree size varied dramatically with the largest trees on B.70-20-20 and smallest trees on B.71-7-22. Setting the most vigorous rootstock at 100% we categorized rootstocks into 5 size categories: sub-dwarfing class (10–25%), dwarfing class (25–35%), semi-dwarfing class (35–50%), semi-vigorous category (50–70%) and vigorous class (70–100%). Cumulative yield varied 8 fold between the highest yielding rootstock (CG.3001) and the lowest yielding rootstock (B.71-7-22). We calculated theoretical yield per ha by multiplying cumulative yield per tree by a theoretical optimal tree density (trees/ha) based on tree size (TCA). The dwarfing rootstocks G.814, G.41TC, G.11 and B.10 had the highest yields per hectare while the most vigorous rootstocks B.70.20.20 and B.71-7-22 were the least productive. Theoretical cumulative yields varied from a high of 400 t/ha to a low of 50 t/ha, an 8-fold difference. Rootstock also influenced the incidence of bitter pit with the lowest levels of bitter pit with the rootstocks B.10, CG.2034, B.71-7-22, G.41N, CG.4003, G.202N, G.214, and Supporter 3. Considering bitter pit, yield, and optimum tree density, the theoretical yield of bitter pit free fruit varied from a high of 340 t/ha to a low of 35 t/ha, almost a 10-fold difference. The dwarfing rootstocks B.10, G.11, G.41TC, G.214 and G.814 had the highest yields per hectare of bitter pit free fruit. Rootstocks B.9 and M.26 had significantly lower cumulative bitter pit free yield/ha. These data indicate that rootstock not only has a large influence on mature tree cumulative yield but also bitter pit incidence which combine to create a large economic impact of rootstock choice on the long-term economic result of an orchard. This leads to the need for “designer rootstocks” which combine the rootstock characteristics needed to maximize the economic potential of each scion cultivar.info:eu-repo/semantics/acceptedVersio

Modelling physiological and environmental factors regulating relative fruit set and final fruit numbers in apple trees

Chemical thinning of apple (Malus domestica Borkh.) has been practised for 50 years but it remains an unpredictable part of apple production with large variations from year to year and within years. Carbohydrate availability to support young fruitlet growth may play a significant role in apple tree response to chemical thinners, especially when the carbohydrate supply is the limiting factor for fruit growth. To address the carbohydrate component, we have tested the MaluSim model that integrates many environmental and tree physiological factors as a tool to predict chemical thinner response. The model suggests that carbon supply-to-demand variations may explain some of the great variations in thinning spray response. Relative fruit set and final fruit number per tree were affected by the carbohydrate balance within 2 days before the spray and up to 5 days after. There was a period, 15–29 days after bloom that thinners showed higher action. The greater the carbohydrate supply relative to demand, the greater the relative set and the final fruit number. This suggested that carbohydrate supply-demand balance may be a baseline for thinner responses, and that integrative modelling of these balances can be useful in understanding variation in thinning responses. Apple relative fruit set and final fruit number per tree could be modelled relatively well with consideration of initial flower density, the carbohydrate balance model, and cumulative growing degree-days since bloom.info:eu-repo/semantics/acceptedVersio

Natural fruitlet abscission as related to apple tree carbon balance estimated with the MaluSim model

Apple trees produce many more flower clusters than needed for a full crop, but natural early season flower and fruitlet abscission drastically reduce the final fruit number. Natural fruit abscission varies significantly year to year. There have been attempts to try to model apple fruit abscission in the past. However, due to the great complexity of a perennial crop system in a dynamic environment with significant plant manipulations, regulatory processes and controlling environmental variables have been difficult to elucidate. In 1995, a field trial was planted at the New York State Agricultural Experiment Station in Geneva, New York with 3 apple cultivars (‘Delicious’, ‘Gala’, and ‘McIntosh’). Beginning in 2000 and for 18 years thereafter, we recorded the natural whole-season fruit abscission of untreated trees that received no chemical or hand thinning. We also estimated early season patterns of carbohydrate supply-to-demand each year with a carbon balance model. These data were used to correlate tree carbon balance status and other environmental variables with natural fruit abscission responses. In general terms, natural set, defined as final fruit/flower cluster, of ‘Gala’ averaged ˜1 fruit for each flower cluster (fruit set = 0.9), whereas fewer fruits were set on ‘Delicious’ and ‘McIntosh’ (fruit set = 0.7 and 0.6, respectively). Fruit set of ‘Gala’ was less variable than of ‘Delicious’ or ‘McIntosh’, and there was a clear pattern for decreasing fruit set when the number of initial flower clusters per tree increased. Fruit weight was less dependent on fruit number for ‘Delicious’ and ‘McIntosh’ than for ‘Gala’. Multiple regression models indicated that number of flower clusters per tree and average carbohydrate balance between 0–60 degree days (DD) after bloom and 300–360 DD after bloom were the main significant variables that explained 60–80% of the variability in natural fruit set or final fruit number. For ‘Delicious’, temperatures of the previous fall also explained a significant amount of variation in final fruit set and final fruit number. For ‘Gala’, carbon balance from bloom to shortly after petal fall and when fruits were about 18 mm were the two main periods, which were more sensible to carbohydrate deficiency triggering fruit abscission. A later susceptible period was also observed for ‘McIntosh’, suggesting a larger thinning window for this cultivar.info:eu-repo/semantics/acceptedVersio

Long-term Performance of ‘Delicious’ Apple Trees Grafted on Geneva® Rootstocks and Trained to Four High-density Systems under New York State Climatic Conditions

We conducted a large (0.8 ha) field experiment of system × rootstock, using Super Chief Delicious apple as cultivar at Yonder farm in Hudson, NY, between 2007 and 2017. In this study, we compared six Geneva® rootstocks (‘G.11’, ‘G.16’, ‘G.210’, ‘G.30’, ‘G.41’, and ‘G.935’) with one Budagovsky (‘B.118’) and three Malling rootstocks (‘M.7EMLA’, ‘M.9T337’ and ‘M.26EMLA’). Trees on each rootstock were trained to four high-density systems: Super Spindle (SS) (5382 apple trees/ha), Tall Spindle (TS) (3262 apple trees/ha), Triple Axis Spindle (TAS) (2243 apple trees/ha), and Vertical Axis (VA) (1656 apple trees/ha). Rootstock and training system interacted to influence growth, production, and fruit quality. When comparing systems, SS trees were the least vigorous but much more productive on a per hectare basis. Among the rootstocks we evaluated, ‘B.118’ had the largest trunk cross-sectional area (TCSA), followed by ‘G.30’ and ‘M.7EMLA’, which were similar in size but they did not differ statistically from ‘G.935’. ‘M.9T337’ was the smallest and was significantly smaller than most of the other rootstocks but it did not differ statistically from ‘G.11’, ‘G.16’, ‘G.210’, ‘G.41’, and ‘M.26EMLA’. Although ‘B.118’ trees were the largest, they had low productivity, whereas the second largest rootstock ‘G.30’ was the most productive on a per hectare basis. ‘M.9’ was the smallest rootstock and failed to adequately fill the space in all systems except the SS, and had low cumulative yield. The highest values for cumulative yield efficiency (CYE) were with ‘G.210’ for all training systems except for VA, where ‘M.9T337’ had the highest value. The lowest values were for all training systems with ‘B.118’ and ‘M.7EMLA’. Regardless of the training system, ‘M.7EMLA’ trees had the highest number of root suckers. Some fruit quality traits were affected by training system, rootstock or system × rootstock combination.info:eu-repo/semantics/publishedVersio

Alternativas de raleio químico da macieira ‘Fuji suprema’

Resumo – O raleio de frutos da macieira, além de evitar a alternância da produção, é uma das práticas culturais mais importantes para melhoria do calibre e da qualidade dos frutos. O raleio químico é amplamente utilizado na cultura da macieira, pois reduz a necessidade de mão de obra e permite que a atividade seja executada em um período adequado. Combinações deraleantes de floração e pós-floração têm proporcionado resultados mais efetivos para cultivares com alta frutifcação efetiva. O objetivo do trabalho foi avaliar a resposta à aplicação de combinações de raleantes de floração e pós-floração na macieira ‘Fuji Suprema’. Os experimentos foram conduzidos de 2011 a 2013 avaliando a combinação de benziladenina (BA) com GA4+7+BA, ácido nafaleno acétco (ANA) e etefon, utilizados em diferentes concentrações e épocas de aplicação. Os raleantes de floração e pós-floração são eficientes para macieira ‘Fuji Suprema’. Os raleantes de floração GA4+7+BA e BA e as combinações de BA com ANA ou BA com etefon em pós-floração apresentam os resultados mais próximos do raleio manual, sendo recomendados para raleio de frutos na cultura da macieira.Abstract – The fruit thinning of an apple tree is one of the most important cultural practices for increasing fruit size and quality, in addition to avoiding the alternation of production. Chemical thinning is widely used in apple growing, because it reduces the need for labor and allows the activity to be performed in an appropriate period. Combinations of flowering and post-flowering chemical thinners have provided more effectve results for cultivars with high fruit set. The aim of this work was to evaluate the response of the application of combinations of flowering and post-flowering chemical thinners in ‘Fuji Suprema’ apple tree. The experiments were conducted from 2011 to 2013 evaluating the combination of benzyladenine (BA) with GA4+7+BA, ANA and ethephon, used in different concentrations and times of application. The flowering and post-flowering chemical thinners are efficient for ‘Fuji Suprema’ apple tree. The flowering chemical thinners GA4+7+BA or BA and the post-flowering chemical thinner BA combined with ANA or ethephon presented the closest results to hand thinning, being an efficient alternative.

Effect of tree type and rootstock on the long-term performance of ‘Gala’, ‘Fuji’ and ‘Honeycrisp’ apple trees trained to Tall Spindle under New York State climatic conditions

In 2006, two 0.3 ha orchard trials were established at two sites (Dressel farm in Southeastern New York State and VandeWalle farm in Western New York State) to compare two tree types (feathered trees and bench-grafted trees) on five rootstocks [three Geneva® rootstocks (G.11, G.16, G.41) with one Budagovsky rootstock (B.9) and one Malling rootstock (M.9T337)] as controls. ‘Gala’ and ‘Fuji’ were used as scion cultivars at Dressel farm and ‘Gala’ and ‘Honeycrisp’ as the scions cultivars at VandeWalle farm. At each location, trees were planted at 3,262 trees ha−1and trained to a Tall Spindle (TS) system. Location, tree type and rootstock interacted to affect tree growth, production and fruit quality of each scion cultivar. ‘Gala’ trees from VandeWalle (Western NY State) were more productive (33% more production) than those from Dressel Farm (Southern NY State), because they produced more fruits per cm−2 and fruit size was bigger. When comparing the two tree types (feathered and bench-grafted) at both locations and across all rootstocks (B.9, G.11, G.16, G.41, and M.9T337), feathered trees were similar in tree size after 11 seasons as bench-grafted ones, except for ‘Fuji’ at Dressel farm where bench-grafted trees were 27% smaller than feathered trees. The bench-grafted trees had lower cumulative yield per hectare, cumulative yield efficiency, and cumulative crop load than the fully feathered trees. Finally, when comparing all 10 tree type × rootstock combinations, for ‘Fuji’, feathered trees with G.11, for ‘Gala’, feathered trees with G.41, and for ‘Honeycrisp’, feathered trees with G.16 were the combinations with the highest cumulative yield, high yield efficiency and crop loads, low biennial bearing, and with slightly significant larger fruits.info:eu-repo/semantics/acceptedVersio

Vegetative characteristics of pear trees grafted on quince and Pyrus calleryana.

Quince has been used as an alternative of rootstock for pear trees because of its dwarfing effect which allows better tree vigor control, fruiting precocity and yield influence. However, highlighting the issue of rootstock versus cultivar, some combinations show severe problems regarding graft incompatibility. The main characteristics seen by incompatible combinations are cell necrosis and vascular discontinuity at the graft interface, leading to a rupture of the union or a slow tree decline. Therefore, the study aimed to evaluate the influence of different quince and Pyrus calleryana on vegetative growth of pear trees through combination performance, scion x rootstock. The work was carried out at the Centro Agropecuário da Palma in Capão do Leão, RS, from March 2007 to March 2009. The assessed cultivars were Carrick, Packham s Triumph and Williams, and the rootstocks were: P. calleryana and the quinces Adams, Alaranjado, Alongado, BA29, Berreckzi, Champion, D Angers, D Vranja, De Patras, Du Lot, Inta267, MC, Meliforme, Pineapple, Portugal and Smyrna. Tree height, increment of tree height; canopy volume; rootstock, union and scion diameters; diameters increment of rootstock, union and scion; fresh pruning weight and specific leaf area. The rootstock P. calleryana showed superior vigor for the three cultivars whether compared with all evaluated quince rootstocks. Incompatibility between plants is not individually defined only by the overgrowth at the graft union. Both observation and comparison of the all tree characteristics due scion/rootstock combination is of fundamental importance to diagnose incompatibility. Tree height, canopy volume and fresh pruning weight are the representative variables of pear tree vigor. The cultivar Carrick showed reduced vigor (64% in relation to P. calleryana) and compatibility with the quince rootstocks (in descending order of vigor): ‗Inta267 , ‗D Vranja , ‗BA29 , ‗Champion , ‗Portugal , ‗Pineapple , ‗Adams , ‗MC , ‗Berreckzi and ‗Meliforme . ‗Alaranjado and ‗Du Lot were incompatible with this cultivar. The cultivar Packham s showed reduced vigor (46.5% in relation to P. calleryana) and compatibility with the quince rootstocks (in descending order of vigor): ‗Smyrna , ‗D Angers and ‗Alongado . ‗Adams was incompatible with this cultivar. The cultivar Williams showed reduced vigor (60.4% in relation to P. calleryana) and compatibility only with the quince rootstocks (in descending order of vigor): 'Champion , ‗Meliforme and 'Du Lot . ‗BA29 , 'Smyrna , ‗Berreckzi , 'D Vranja , ‗De Patras and ‗MC were incompatible with this cultivar.O marmeleiro é usado como uma alternativa de porta-enxerto para pereiras por possuir efeito ananizante, permitindo melhor controle do vigor da planta, e por induzir precocidade na frutificação e produtividade. No entanto, considerando o assunto porta-enxerto versus cultivar, algumas combinações apresentam sérios problemas de incompatibilidade de enxertia. As principais características mostradas pelas combinações incompatíveis são necrose celular e descontinuidade vascular na interface do enxerto, a qual leva a uma ruptura da união ou um lento declínio da planta. Neste contexto o projeto teve por objetivo avaliar a influência de diferentes porta-enxertos de marmeleiros e Pyrus calleryana sobre o crescimento vegetativo de plantas de pereira através do comportamento da respectiva combinação copa x porta-enxerto. O trabalho foi desenvolvido no Centro Agropecuário da Palma, Capão do Leão, RS, no período de março de 2007 a março de 2009. As cultivares testadas foram Carrick, Packham s Triumph e Williams, e os porta-enxertos: P. calleryana e os marmeleiros Adams, Alaranjado, Alongado, BA29, Berreckzi, Champion, D Angers, D Vranja, De Patras, Du Lot, Inta267, MC, Meliforme, Pineapple, Portugal e Smyrna. As variáveis avaliadas foram altura de planta; incremento de altura de planta; volume de copa; diâmetro de tronco do porta-enxerto, da cv. copa e do ponto de enxertia; incremento do diâmetro do tronco; massa verde de poda e área foliar específica. O porta-enxerto de pereira P. calleryana mostrou-se superior em vigor se comparado com todos os marmeleiros estudados para todas as cultivares. A incompatibilidade entre plantas não é definida, isoladamente, apenas pelo engrossamento na união de enxertia. A observação e comparação conjunta das características da planta, devido a combinação copa/porta-enxerto é de fundamental importância para diagnosticar incompatibilidade. Altura de planta, volume de copa e massa verde de poda foram as variáveis representativas de vigor de pereiras. A cultivar Carrick apresentou vigor reduzido (64% em relação a P. calleryana) e compatibilidade com os porta-enxertos de marmeleiros (em ordem decrescente de vigor): ‗Inta267 , ‗D Vranja , ‗BA29 , ‗Champion , ‗Portugal , ‗Pineapple , ‗Adams , ‗MC , ‗Berreckzi e ‗Meliforme . Os porta-enxertos ‗Alaranjado e ‗Du Lot foram incompatíveis com esta cultivar. A cultivar Packham s apresentou vigor reduzido (46,5% em relação a P. calleryana) e compatibilidade com os porta-enxertos de marmeleiros (em ordem decrescente de vigor): ‗Smyrna , ‗D Angers e ‗Alongado . O porta-enxerto ‗Adams foi incompatível com esta cultivar. A cultivar Williams apresentou vigor reduzido (60,4% em relação a P. calleryana) e compatibilidade apenas com os porta-enxertos de marmeleiros (em ordem decrescente de vigor): 'Champion , ‗Meliforme e 'Du Lot . Os porta-enxertos ‗BA29 , 'Smyrna , ‗Berreckzi , 'D Vranja , ‗De Patras e ‗MC foram incompatíveis com esta cultivar

Desenvolvimento das estruturas reprodutivas da macieira (Malus domestica Borkh.) sob diferentes condições climáticas

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro de Ciências Agrárias, Programa de Pós-Graduação em Recursos Genéticos Vegetais, Florianópolis, 2014.A cultura da macieira apresenta grande importância econômica no cenário mundial visto o grande volume de frutos produzidos e comercializados. No Brasil, a cultura da macieira é explorada principalmente na região Sul do país, devido suas condições climáticas subtropicais temperadas serem as mais parecidas às condições exigidas pela planta na obtenção de produções razoáveis de maçãs. No entanto, dentre os elementos climáticos, a temperatura pode ser considerada um dos fenômenos que mais tem influência sobre a cultura, desde a formação floral até a produção final; sendo um dos fatores responsáveis pelas irregularidades de produções. Diante disto, e com o intuito de gerar conhecimentos e informações sobre a cultura da macieira, este trabalho procurou entender os possíveis efeitos ambientais e climáticos, e seus limites qualitativos e quantitativos, sobre a aclimatação das plantas e de suas estruturas reprodutivas. Durante os anos de 2010 à 2014, foram realizadas as avaliações que envolvem o processo do desenvolvimento floral e reprodutivo de duas cultivares de grande importância econômica mundial, =Gala e =Fuji . Tais avaliações incluíram a caracterização da iniciação e diferenciação morfológica de gemas, da morfologia e biologia floral, e do comportamento fenológico e produtivo das plantas; sendo que as mesmas foram direcionadas sobre as duas principais estruturas de frutificação das plantas, brindilas (gemas axilares e terminal) e esporões. Grande parte do trabalho foi realizado na região de Caçador, localizada no Estado de Santa Catarina a uma latitude de 26°50 S, longitude de 50°58 W e altitude de 950m. No entanto, uma outra região, do Estado de Ohio nos Estados Unidos, a qual, devido as condições climáticas locais, é caracterizada como ideal para o cultivo da macieira, foi utilizada para servir como base de referência para alguns dos estudos aqui realizado. Dez estádios morfológicos foram definidos, do meristema vegetativo à formação dos órgãos florais de inflorescências de gemas da espécie Malus domestica Borkh. A iniciação floral foi influenciada pela cultivar e estrutura. O desenvolvimento floral de gemas da cv. Fuji foi mais rápido que da cv. Gala, e entre as estruturas, os esporões de ambas cultivares formaram-se mais precocemente que as gemas axilares e a terminal das brindilas. A transição floral parece ser regulado por sinais intrínsecos da planta. No entanto, a transição entre os demais estádios de diferenciação parece sofrer considerável influência dos sinais ambientais, principalmente das temperaturas. Flores de macieiras das cvs. Gala e Fuji provenientes de regiões de clima temperado foram mais desenvolvidas morfologicamente que flores de macieira cultivadas sob condições subtropicais. Sob as condições ambientais da região brasileira em estudo, estigmas apresentaram-se mais receptivos na abertura das flores, ou talvez, anteriormente a esta. Diferentemente da região norte americana, onde os estigmas alcançaram a máxima receptividade entre as 24-48 horas após a abertura das flores. Na região de Caçador, flores de gemas terminais de brindilas apresentaram, em geral, melhor qualidade morfológica dos órgãos reprodutivos femininos e masculino. As diferenças encontradas no início de brotação e florescimento entre as estruturas de frutificação dependeram grandemente das condições climáticas do ano em questão. Sob condições de altas temperaturas após o tratamento de quebra de dormência, há maior sincronia fenológica entre as estruturas, e vice e versa. Gemas de esporões necessitam de menor acúmulo térmico para brotarem, principalmente esporões de Gala . Além da baixa frutificação efetiva, gemas axilares de ambas cultivares apresentaram frutos com baixa qualidade morfológica (massa fresca e diâmetro de fruto). Frutos provenientes de terminais de brindilas tendem ser mais arredondados e com maior massa fresca do que frutos das axilares e dos esporões, em ambas as cultivares. Sob as condições climáticas de Caçador, SC, a cultivar Fuji foi mais estável produtivamente que a cv. Gala. O favorecimento de brindilas na cv. Gala, seja através de podas, arqueamento ou outras técnicas específicas, deve ser preconizado quando se deseja garantir boa frutificação efetiva, altas produtividades, e frutos de melhor calibre. Na cv. Fuji, apesar de terminais apresentarem os melhores frutos, a frutificação dos esporões tendeu ser mais estável durante os anos, Para esta cultivar, ambas estruturas poderiam ser preconizadas.<br>Abstract : Apples are one of the most valuable fruit crops in the world because of the significant amount produced and commercialized. In Brazil, apples are mainly grown in the south since these areas possess the most suitable climatic conditions for reasonable productions. Among climate elements temperature may be considered the most significant phenomenon affecting the process of fruit production, from flower bud formation through harvest. Also, it is one of the factors responsible for irregular cropping. Thereafter, this work tried to understand the possible environmental and climatic effects, qualitative and quantitative limitations, on the acclimation of both trees and fruiting habits. From 2010 to 2014, the process of flower and fruit development of the two main apple cultivars, Gala and Fuji, were evaluated. Measurements were done separately on the three types of buds, spurs, and both terminal and axillary buds of one year shoots. Morphological characterization of bud initiation and differentiation, flower biology and morphology, flowering phenology and fruit production were studied. The trials were mainly carried under the Brazilian conditions, in Caçador, SC, Brazil (latitude 26°50?S, longitude 50°58?W, altitude of 950m). However, a second region located in Ohio State, in the United States, was included as a reference for some of the studies such as bud differentiation and flower biology, since it shows great climate conditions for growing apples. Ten morphological bud stages of Malus domestica Borkh were defined, from the vegetative meristem to floral organs differentiation. Flower initiation was affected by cultivar and bud type. Floral development of =Fuji? buds was faster than =Gala? buds. Among the buds types, flower initiation and differentiation occurred first in spurs, then in axillary and terminal buds, successively. Floral transition seems to be triggered by intrinsic signals; whereas the transition between the stages seems to be considerably affected by environmental conditions, mainly temperatures. The morphological development of apple flowers =Gala? and =Fuji? were greater under temperate climate than subtropical conditions. Under the environmental conditions of the region in south of Brazil stigmas reached the optimumreceptivity at anthesis or earlier; whereas in the region in North America pollen reached a maximum germination 24-48 hours after flower opening. In Caçador, terminal flowers on one year old long shoot showed higher morphological qualities of the female and male floral organs than spurs and axillary. Flowering and bud break onset of the different bud types greatly depended on the year assessed; warmer springs induced to a synchronized onset between the different buds. Spur buds requires less heat-unit accumulation at budbreak, specially =Gala? spur buds. In general, axillary buds of both cultivars showed low fruitset and produced smaller fruits (weight and diameter). Terminal buds on long shoots of both cultivars induced rounder and heavier fruits than axillary and spur buds. Under the climate conditions of Caçador =Fuji? was productively more stable than =Gala?. In order to ensure good fruitset, high yields and larger fruits, one year shoots should be preferred in the tree management practices of =Gala? such as pruning, bending or other techniques. Although in =Fuji?, terminal buds of long shoots produced high quality fruits, the fruitset of spurs tended to be stable among years; therefore, both bud types should be preconized