Transcription profiling of the chilling requirement for bud break in apples: a putative role for FLC-like genes.

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.

Functional diversification of the dehydrin gene family in apple and its contribution to cold acclimation during dormancy.

Dehydrins (DHN) are proteins involved in plant adaptive responses to abiotic stresses, mainly dehydration. Several studies in perennial crops have linked bud dormancy progression, a process characterized by the inability to initiate growth from meristems under favorable conditions, with DHN gene expression. However, an in-depth characterization of DHNs during bud dormancy progression is still missing. An extensive in silico characterization of the apple DHN gene family was performed. Additionally, we used five different experiments that generated samples with different dormancy status, including genotypes with contrasting dormancy traits, to analyze how DHN genes are being regulated during bud dormancy progression in apple by real-time quantitative polymerase chain reaction (RT-qPCR). Duplication events took place in the diversification of apple DHN family. Additionally, MdDHN genes presented tissue- and bud dormant-specific expression patterns. Our results indicate that MdDHN genes are highly divergent in function, with overlapping levels, and that their expressions are fine-tuned by the environment during the dormancy process in apple.

Induction and overcoming of dormancy of grapevine buds in response to thermal variations in the winter period / Indução e superação da dormência de gemas de videiras em resposta a variações térmicas no período hibernal

ABSTRACT: This study quantified the chilling requirements for the induction and overcoming of endodormancy (chilling-controlled physiological dormancy) of grapevines buds. Cuttings of the cultivars Chardonnay, Merlot and Cabernet Sauvignon were collected in vineyards in Veranópolis-RS in the winter period of 2019 and 2020. The cuttings were kept at a constant temperature of 7.2 °C or daily cycles of 7.2/18 °C for 6/18 h, 12/12 h or 18/6 h, up to 600 chilling hours (CH). Every 50 CH, part of the cuttings from each treatment was transferred to a temperature of 25 °C for daily assessment of the budburst in the green tip stage. The cultivars had different chilling requirements for inducing and overcoming endodormancy, reaching a total of 150 CH for 'Chardonnay', 300 CH for 'Merlot' and 400 CH for 'Cabernet Sauvignon'. Of these, 50 CH were required to induce endodormancy in cultivars Chardonnay and Merlot and 100 CH for cultivar Cabernet Sauvignon. Dormancy evolution did not differ between cultivars in response to thermal regimes, with a temperature of 18 °C inert to the accumulation of CH. Precocity and uniformity of budburst were higher after chilling requirements were met during endodormancy for each genotype.

RESUMO: Este estudo visou quantificar as necessidades de frio para a indução e superação da endodormência (dormência fisiológica controlada por frio) de gemas de videiras. Estacas de das cultivares Chardonnay, Merlot e Cabernet Sauvignon foram coletadas em vinhedos em Veranópolis-RS, no período hibernal de 2019 e 2020. As estacas foram submetidas a temperatura de 7,2 ºC constante ou a ciclos diários de 7,2/18 °C por 6/18 h, 12/12 h ou 18/6 h, até 600 horas de frio (HF). A cada 50 HF, parte das estacas de cada tratamento foi transferida para a temperatura de 25°C, para avaliação diária da brotação das gemas, em estádio de ponta verde. As cultivares tiveram necessidades distintas de frio para indução e superação da endodormência, atingindo um total de 150 HF para 'Chardonnay', 300 HF para 'Merlot' e 400 HF para 'Cabernet Sauvignon'. Destes totais, 50 HF foram necessárias para indução da endodormência nas cultivares Chardonnay e Merlot e 100 HF na cultivar Cabernet Sauvignon. A evolução da dormência não diferiu entre cultivares em resposta aos regimes térmicos, sendo a temperatura de 18 °C inerte ao acúmulo de HF. A precocidade e uniformidade de brotação das gemas foram maiores após suprido o frio na dormência para cada genótipo.

Chemical thinning of flowers and fruits of the peach cultivar Coral with hydrogen cyanamide / Raleio químico de flores e frutos de pessegueiro cultivar Coral com cianamida hidrogenada

ABSTRACT: Chemical treatment is a mean to accomplish fruit thinning; although its efficiency depends on the compound used, application time, and dosage. Effect of the chemical hydrogen cyanamide (CH2N2) on the thinning of flowers and fruits of the peach cultivar Coral was assessed in this study. Treatments consisted of five doses of CH2N2 (0, 0.2, 0.4, 0.6, and 0.8%) spray application to the point of run-off, at two stages (50% and 100% flowering). The experiment was conducted in a completely randomized design with six replicates and one plant per plot. The following parameters were assessed: percentage of flowers thinned at 25 days after spraying, percentage of fruits thinned, fruiting index, production per plant, fruit mass, diameter and length, flesh firmness, soluble solids (SS) and titratable acidity (TA). Concentrations of 0.6 and 0.8% CH2N2application at 50% flowering resulted in thinning 84.4 and 84.7% of the flowers and 0.4% CH2N2 at 100% flowering thinned 87.3%, values close to index assessed in manual thinning (88.0%) experiments. The highest production per plant was recorded for treatments with CH2N2 application at 50% flowering, resulting from a high percentage of flowers opening after spraying the chemical thinner. As such, flowers opening late were not affected by the chemical, thereby ensuring a higher fruiting index. Peach yield with 50% CH2N2 was not significantly different from yield observed for manual treatment, and 0.6% spray was reported to be the optimal dosage. Treatment with 0.6% CH2N2 application at 50% flowering was not significantly qualitatively different from manual thinning. CH2N2 application is efficient for the thinning of 'Coral' peach flowers and fruits.

RESUMO: O tratamento químico consiste numa ferramenta para raleio de frutos, porém sua eficiência depende do produto, época de aplicação e concentração a ser empregado. Avaliou-se a cianamida hidrogenada (CH2N2) no raleio químico de flores e frutos de pessegueiro cv. Coral. Os tratamentos consistiram na aplicação de cinco doses de CH2N2 (0; 0,2; 0,4; 0,6 e 0,8%), por pulverização até o ponto de escorrimento, em duas épocas (50% e 100% da floração). O experimento foi realizado em delineamento inteiramente casualizado, com seis repetições e uma planta por parcela. Avaliaram-se: % de flores raleadas aos 25 dias após a pulverização, % de frutos raleados, índice de frutificação, produção por planta, massa, diâmetro e comprimento de fruto, firmeza de polpa, SST e AT. As concentrações 0,6 e 0,8% de CH2N2 a 50% de floração ralearam 84,4 e 84,7% das flores e a 0,4% de CH2N2 a 100% de floração raleou 87,3%, valores aproximados ao índice obtido no raleio manual (88,0%). A maior produção por planta ocorreu nos tratamentos com CH2N2 a 50% de floração, decorrente do elevado percentual de flores abertas após a pulverização do raleante químico, as quais não foram atingidas pelo produto, garantindo maior índice de frutificação. A produção com CH2N2 a 50% não diferiu estatisticamente do tratamento manual, sendo 0,6% a dosagem que conferiu valores absolutos superiores. O tratamento 0,6% de CH2N2 a 50% de floração não diferiu estatisticamente em termos qualitativos do tratamento raleio manual. A aplicação de CH2N2 apresenta-se eficiente no raleio de flores e frutos de pessegueiro 'Coral'.

Desfolha em videiras americanas e viníferas na fase de pré-maturação dos frutos / Defoliation of american and vinifera grapevines in the pre ripening of fruits

Foram avaliadas possíveis interferências que a localização da folha removida mediante desfolha em videira apresenta sobre o rendimento e qualidade dos frutos. As cultivares 'Niagara Branca' e 'Concord', ambas Vitis labrusca, e 'Cabernet Sauvignon' e 'Merlot', ambas Vitis vinifera, foram utilizadas em sistema de condução em espaldeira, na safra 2006/2007. O experimento foi conduzido em delineamento de blocos casualizados, com quatro repetições e quatro plantas por parcela, sendo testados 4 tratamentos: T1 (testemunha - sem desfolha), T2 (retirada das folhas localizadas opostas aos cachos), T3 (retirada das folhas do sarmento localizadas abaixo dos cachos) e T4 (retirada das folhas do sarmento localizadas abaixo e opostas aos cachos). As cultivares da espécie Vitis labrusca receberam um tratamento adicional T5, constando na retirada das folhas acima dos cachos. A aplicação dos tratamentos foi realizada na fase de mudança de cor das bagas para as cultivares 'Concord', 'Merlot' e 'Cabernet Sauvignon' e início do amolecimento das bagas para a cultivar 'Niagara Branca'. Avaliaram-se, após a colheita, a produção por planta, a massa dos cachos, os teores de sólidos solúveis (SS), a acidez titulável, (AT) e o pH dos frutos. Observou-se que a desfolha até a altura do cacho não influenciou na quantidade e na qualidade dos frutos. Porém, quando a desfolha foi realizada acima dos cachos, ocorreu um atraso na maturação das uvas americanas. Essa condição implica não ser necessária a desfolha seletiva até a altura dos cachos nas videiras estudadas, quando realizada na fase início de amadurecimento dos frutos.

This study aimed to evaluate the interference that the location of the leaf removed by defolation in grapevine has on fruits quality and yield. Such experiment was performed using Niagara Branca and Concord, both Vitis labrusca, and Cabernet Sauvignon e Merlot, both Vitis vinifera, trained in a unilateral cordon system during the 2006/2007 harvesting. The experiment was disposed in a randomized block design, with four replications and four plants per plot. The following treatments were tested: T1 (no defoliation), T2 (removal of leaves located in the opposite side of the grapes), T3 (removal of leaves located under the grapes) and T4 (removal of leaves located under and in the opposite side of the grapes). The Vitis labrusca received an additional treatment (T5) consisting of leaves removed above the grapes. These treatments were applied during the change of berries color for Concord, Cabernet Sauvignon and Merlot grapes and in the beginning of berries softening for Niagara Branca grape. After the harvesting, the grapevine production, cluster weight, total soluble solids, total titratable acidity and pH were evaluated. It was observed that the defoliation until the grapes height did not influence the quantity and quality of grapes. However, when the defoliation was carried out above the clusters, there was a delay in the maturation of american grapes. This condition shows that is not necessary a selective desfolation until the clusters height on grapevines, when it is realized during the initial fruit ripening phase.