Apple production depends on the fulfilment of a chilling requirement for bud dormancy release. Insufficient winter chilling results in irregular and suboptimal bud break in the spring, with negative impacts on apple yield. Trees from apple cultivars with contrasting chilling requirements for bud break were used to investigate the expression of the entire set of apple genes in response to chilling accumulation in the field and controlled conditions. Total RNA was analysed on the AryANE v.1.0 oligonucleotide microarray chip representing 57,000 apple genes. The data were tested for functional enrichment, and differential expression was confirmed by real-time PCR. The largest number of differentially expressed genes was found in samples treated with cold temperatures. Cold exposure mostly repressed expression of transcripts related to photosynthesis, and long-term cold exposure repressed flavonoid biosynthesis genes. Among the differentially expressed selected candidates, we identified genes whose annotations were related to the circadian clock, hormonal signalling, regulation of growth, and flower development. Two genes, annotated as FLOWERING LOCUS C-like and MADS AFFECTING FLOWERING, showed strong differential expression in several comparisons. One of these two genes was upregulated in most comparisons involving dormancy release, and this gene's chromosomal position co-localized with the confidence interval of a major quantitative trait locus for the timing of bud break. These results indicate that photosynthesis and auxin transport are major regulatory nodes of apple dormancy and unveil strong candidates for the control of bud dormancy.

The molecular control of bud dormancy establishment and release is still not well understood, although some genes have already been demonstrated to play important roles in this process. The dormancy-associated MADS-box (DAM) genes were first identified in the peach EVERGROWING locus and are considered the main regulators of bud dormancy control. In this work, the apple (Malus × domestica Borkh.), a perennial plant adapted to temperate climates that displays cycles of growth and bud dormancy, was screened for the presence of DAM genes. The candidate genes retrieved were characterized in comparison to DAM genes from other species. Four of them (MdDAM1-4) are structurally very similar to the reported DAM genes. When apple genomic segments containing these candidates were compared to the peach EVERGROWING locus, a highly conserved noncoding region was detected inside their largest intron. Similar sequences were also identified inside introns of apricot and pear DAM genes. Organ expression patterns revealed that MdDAM1-4 are mainly expressed in dormant buds and seeds, with low transcript accumulation in vegetative structures. In addition, the MdDAM genes showed seasonally oscillating patterns of steady-state messenger RNA (mRNA) levels and were downregulated by artificial chilling. Motif analyses in the promoter and in the intronic conserved region of the MdDAM genes disclosed some clues to the regulation of the expression patterns observed. Possible roles for the conserved intronic sequence in dormancy regulation are discussed.

Fluctuations in winter chilling availability impact bud dormancy and budburst. The objective of this work was to determine chilling requirements to induce and overcome endodormancy (dormancy controlled by chilling) of buds in different grape cultivars. ‘Chardonnay’, ‘Merlot’ and ‘Cabernet Sauvignon’ shoots were collected in Veranópolis-RS vineyards in 2010, and submitted to a constant 3 °C temperature or daily cycles of 3/15 °C for 12/12h or 18/6h, until reaching 1120 chilling hours (CH, sum of hours with temperature ≤ 7.2 °C). Periodically, part of the samples in each treatment was transferred to 25 °C for budburst evaluation (green tip). Chilling requirements to induce and overcome endodormancy vary among cultivars, reaching a total of 136 CH for ‘Chardonnay’, 298 CH for ‘Merlot’ and 392 CH for ‘Cabernet Sauvignon’. Of these, approximately 39, 53 and 91 CH are required for induction of endodormancy in the three cultivars, respectively. The thermal regimes tested (constant or alternating) do not influence the response pattern of each cultivar to cold, with 15 °C being inert in the CH accumulation process. In addition, time required to start budburst reduces with the increase in CH, at a rate of one day per 62 CH, without significant impacts on budburst uniformity.

-The objective of this work was to evaluate the effect of heat waves on the evolution of bud dormancy, in apple trees with contrasting chilling requirements. Twigs of 'Castel Gala' and 'Royal Gala' were collected in orchards in Papanduva, state of Santa Catarina, Brazil, and were exposed to constant (3°C) or alternating (3 and 15°C for 12/12 hours) temperature, combined with zero, one or two days a week at 25°C. Two additional treatments were evaluated: constant temperature (3°C), with a heat wave of seven days at 25°C, in the beginning or in the middle of the experimental period. Periodically, part of the twigs was transferred to 25°C for daily budburst evaluation of apical and lateral buds. Endodormancy (dormancy induced by cold) was overcome with less than 330 chilling hours (CH) of constant cold in 'Castel Gala' and less than 618 CH in 'Royal Gala'. A daily 15°C-temperature cycle did not affect the endodormancy process. Heat waves during endodormancy resulted in an increased CH to achieve bud requirements. The negative effect of high temperature depended on the lasting of this condition. Chilling was partly cancelled during dormancy when the heat wave lasted 36 continuous hours or more. Therefore, budburst prediction models need adjustments, mainly for regions with mild and irregular winters, such as those of Southern Brazil.

RESUMOO manejo adequado da poda permite alterar a fenologia da videira, modificando os períodos de colheita, inclusive com potencial de obtenção de mais de uma safra por ciclo vegetativo. Diante desse potencial avaliou-se uma época de poda seca no inverno (08/08/05) e duas épocas de poda verde (04/11/05 e 02/12/05) nas cultivares Niagara Branca e Concord, ambas Vitis labrusca, visando obter duas safras no mesmo ciclo vegetativo. O experimento foi realizado na safra 2005/2006 em videiras cultivadas em sistema de espaldeira, localizadas em Eldorado do Sul -RS. Variáveis associadas à fenologia, produção por planta, peso dos cachos, sólidos solúveis totais (SST), acidez total titulável (ATT) e relação SST/ATT foram analisadas para as safras obtidas. O ciclo fenológico das plantas podadas no inverno foi de 156 dias para a 'Niagara Branca' e 161 dias para a 'Concord', com colheita realizada em meados de janeiro. Por sua vez, o ciclo fenológico das brotações oriundas das podas verdes realizadas em 04/11/2005 e 02/12/2005 foi, respectivamente, de 127 e 113 dias, para a 'Niagara Branca', e 134 e 120 dias para a 'Concord', com colheitas realizadas em meados do mês de abril. A época de poda verde realizada em 04/11/05 permitiu maior produção por planta e cachos de maior peso, independentemente da cultivar, comparativamente à 02/12/05. A qualidade dos frutos foi semelhante entre as safras, mostrando apenas diferenças significativas entre cultivares, expressa numa menor ATT e maior relação SST/ATT para a 'Niagara Branca'.Palavras-chave: Vitis labrusca; fenologia; manejo da poda; segunda colheita. ABSTRACTThe adequate pruning management of grapevine permits to change its fenology, modifying the crop periods and creating conditions for two annual harvests. A winter pruning period (08/08/05) and two periods of summer pruning (04/11/ 05 and 02/12/05) were evaluated in order to obtain two annual harvests, using Niagara Branca and Concord grape varieties (both Vitis labrusca). This experiment was performed during the 2005/2006 season in grapevines conducted by cordon training in Eldorado do Sul county, Rio Grande do Sul, Brazil. Variables associated to fenology, plant production, weight of grapes, total soluble solids, total titratable acidity and ratio total soluble solids by total titratable acidity related to harvests were analyzed. The fenology of plants pruned in winter was 156 days for 'Niagara Branca' and 161 days for 'Concord', and the harvest was performed around January, 15th. Regarding the summer pruning performed on 04/11/05 and 02/12/05, fenology cycle of shoots was 127 and 113 days for the 'Niagara Branca' and 134 and 120 days for the 'Concord', respectively. Harvest was realized in middle April, 15th. The summer pruning realized in 04/11/05 provided higher production per plant and grapes of higher weight, independent of cultivar, when compared to the 02/12/05 pruning. Fruit quality was similar among the harvests, with significant differences between cultivars expressed by smaller total titratable acidity and higher ...

ResumoUm método biológico foi desenvolvido para caracterizar o estado de dormência de gemas de macieira, em condições controladas. Estacas (brindilas ou ramos de ano, com 20-25 cm) de 'Castel Gala' e 'Royal Gala' foram amostradas durante o período hibernal, avaliando-se diferentes regimes de frio e de calor para induzir a brotação. Testaram-se contrastes no processamento do material vegetal (estacas de nós isolados x intactas), na exposição ao frio para superação da dormência em câmaras incubadoras (plantadas em potes com espuma fenólica x embaladas em filme plástico, na posição vertical ou horizontal) e ao calor para indução da brotação em câmara de crescimento (base imersa em água x plantadas em espuma fenólica). Estacas intactas e em posição vertical durante o frio representaram melhor as condições de interação natural entre as gemas do que nós isolados, sendo a brotação das gemas laterais fortemente influenciada pela dominância apical. O acondicionamento das estacas em filme plástico, durante o frio, permitiu maximizar o espaço interno das incubadoras e o número de gemas em avaliação, em relação ao plantio de estacas em potes. No calor, estacas intactas em espuma fenólica apresentaram melhor conservação e sobrevivência das gemas ao longo do período de avaliação, se comparadas às que ficaram com bases imersas em água. As condições mais adequadas para avaliar a evolução do estado de dormência em gemas de macieira foram as que utilizaram estacas intactas embaladas na posição vertical durante os tratamentos de frio, com acompanhamento da brotação no calor após fixar as estacas em espuma fenólica. A padronização da metodologia contribui para obter melhores resultados no desenvolvimento de modelos fisiológicos da dormência. Palavras-chave: Malus domestica, fisiologia vegetal, dominância apical AbstractA biological method was developed to evaluate the dormancy state of apple buds under controlled conditions. Cuttings (20-25 cm long) of 'Castel Gala' and 'Royal Gala' were sampled during the winter period, evaluating different cold and heat regimes to induce budbreak. Contrasts were tested in plant material processing (single node x intact cuttings), cold storage method to break dormancy in incubator chambers (planted in pots with floral foam x wrapped in plastic film, vertically or horizontally) and budbreak method in plant growth chambers (base immersed in water x planted in floral foam). Intact cuttings stored vertically in the cold represented better the natural interactions between buds than 1 Engº s Agrº s , Drs. Pesquisadores da Fundação Estadual de Pesquisa Agropecuária, FEPAGRO. RSC 470, Veranópolis, RS.

ResumoO uso de fungos micorrízicos na produção de mudas de videira é importante alternativa para acelerar o desenvolvimento inicial das plantas. Este trabalho teve por objetivo avaliar o comportamento de dois FMA sobre o crescimento vegetativo de três porta-enxertos (PE) de videira. Foram utilizados os FMA Glomus etunicatum e Scutellospora heterogama e os PE SO4, Paulsen 1103 e 043-43. Os PE, oriundos de micropropagação, foram transferidos e aclimatizados em copos plásticos de 300 mL e após 58 dias transplantados para sacos plásticos de 2 L de capacidade, contendo como substrato uma mistura de casca de arroz carbonizada e Plantmax® na proporção de 1:1 v/v. Utilizaram-se, como inóculo, 20 g de solo rizosférico mais fragmentos de raízes contendo as estruturas dos FMA, adicionados ao substrato na fase de aclimatização. Aos 135 dias após inoculação, foram avaliadas as massas de matéria fresca e seca das raízes e parte aérea, comprimento de raízes e parte aérea, diâmetro de colo e teores de nutrientes da parte aérea. Os FMA Glomus etunicatum e Scutellospora heterogama proporcionaram melhor nutrição e maior crescimento vegetativo dos porta-enxertos de videira, se comparadas as plantas testemunhas. Os benefícios oriundos da simbiose dependeram da combinação específica entre o isolado fúngico e a variedade de porta-enxerto utilizada, sendo o 043-43 beneficiado preponderantemente pelo FMA Glomus etunicatun e o SO4 e Paulsen 1103 por Glomus etunicatum e Scutellospora heterogama.Palavras-chave: endomicorrizas, propagação, mudas, Vitis sp. Use of arbuscular mycorrhizal (AMF) fungi in micropropagated grape rootstocks AbstractThe use of mycorrhizal fungi is an activity of great importance to accelerate the initial development of grape seedlings. This work aimed to evaluate the effects of two AMF on the vegetative growth of three grape rootstocks. Such experiment used the arbuscular mycorrhizal fungi Glomus etunicatum and Scutellospora heterogama, and the rootstocks SO4, Paulsen 1103 e 043-43. The micropropagated rootstocks were transferred and acclimated in 300 mL plastic cups, and after 58 days were transplanted to 2 L plastic bags containing a mixture of carbonized rice husks and Plantmax® on the proportion 1:1, as substrate. The inoculum consisted of 20 g of rhizospheric soil and roots fragments containing the structures of AMF added to the substrate during the acclimatization stage. Fresh and dry matter of roots and shoots, length of roots and shoots, stem diameter and nutritional status of shoots were evaluated after 135 days of inoculation. The AMF Glomus etunicatum and Scutellospora heterogama provided better nutrition and greater vegetative growth of rootstock varieties when compared to the non-inoculated plants. The benefits of symbiosis were depended on the specific combination of the fungal isolate and rootstock variety employed, with 043-43 benefited mainly by AMF Glomus etunicatun and SO4 and Paulsen 1103 by Glomus etunicatum and Scutellospora heterogama.

RESUMO -Este trabalho objetivou avaliar a fenologia, a demanda térmica e a produtividade das cvs. Niagara Branca, Niagara Rosada e Concord submetidas a uma poda seca no inverno e a uma poda verde no final da primavera, visando à obtenção de duas safras de uva por ciclo vegetativo. O experimento foi conduzido em vinhedo pertencente à Estação Experimental Agronômica de Eldorado do Sul-RS, na safra de 2007/2008. As plantas foram submetidas a duas épocas de poda de inverno (22-07-07 e 20-08-07), em cordão esporonado, e duas épocas de poda verde (15-11-07 e 17-12-07), mediante desponte do sarmento a partir da quarta gema acima do último cacho. Os subperíodos fenológicos considerados da videira foram: vegetativo, compreendendo da poda à brotação e da brotação à floração; e reprodutivo, abrangendo da floração à colheita. Os respectivos intervalos tiveram um acompanhamento com base no acúmulo de graus-dia. A produção por planta, sólidos solúveis totais e acidez total titulável foram avaliados em ambas as safras.As cultivares necessitaram aproximadamente de 1.500 graus-dia para completar seu ciclo, tanto na primeira como na segunda safra. A poda de inverno antecipada aumentou a duração do ciclo fenológico das plantas comparativamente à poda de agosto, devido ao aumento do subperíodo poda/floração nas videiras podadas precocemente. A antecipação da poda de inverno antecipou a colheita da primeira safra, possibilitando obter uvas precoces com maior valorização de mercado. A duração do ciclo fenológico da segunda safra foi menor se comparada à primeira safra, devido às temperaturas mais elevadas decorridas no desenvolvimento das plantas submetidas à poda verde. A produtividade da segunda safra foi maior quando a poda seca foi realizada em agosto, associada à poda verde em novembro. Nas plantas submetidas à poda verde, obteve-se uma segunda colheita em meados de março/abril, oferecendo vantagens econômicas ao viticultor e ampliando a disponibilidade da fruta ao consumidor. Termos de indexação: manejo da poda, soma-térmica, épocas de colheita, Vitis labrusca. THERMAL REQUIREMENT, PHENOLOGY AND PRODUCTIVITY OF NIAGARA BRANCA, NIAGARA ROSADA AND CONCORD CULTIVARS SUBMITTED TO TWO HARVESTS BY VEGETATIVE CICLEAbstract-This study aimed at tracking phenology, thermal demand and productivity of Niagara Branca, Niagara Rosada and Concord grapevines subjected to a dry pruning in winter and a green pruning in the end of spring, focused on obtaining two grapes harvests by vegetative cycle. The experiment was performed at Eldorado do Sul's Agronomic Experimental Station, Rio Grande do Sul State, Brazil, during the 2007/2008 harvesting. The plants were subjected to two dates of pruning in winter (07/22/07 and 08/20/07), performed by means of a short pruning, and two green pruning dates (11/15/07 and 12/17/07), performed by pruning the shoot starting from the fourth bud above the last grape cluster. The grapevine phenological sub periods considered were the vegetative, ranging from the pruning to sprouting and from the sprouting to floweri...