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)

Water content in pear tree tissues during the dormancy period under mild winter conditions

O objetivo deste trabalho foi avaliar a umidade ponderal (UP) em diferentes tecidos das cultivares de pereira Kieffer (Pyrus communis) e Housui (Pyrus pyrifolia), durante a dormência, em condições de inverno ameno. Foram avaliadas plantas do pomar experimental da Embrapa Clima Temperado, Pelotas, RS. Utilizou-se o delineamento experimental inteiramente casualizado, em esquema fatorial 3x4x5, que consistiu em três tecidos (gema, casca e lenho), quatro porções de ramos (terminal, mediana, axial e esporões) e cinco datas de coleta, em 2005 (1/7, 3/8, 6/9, 23/9 e 13/10), com parcelas subdivididas e três repetições. Houve aumento na UP do lenho na cultivar Kieffer até a metade da dormência, com subsequente redução a partir desta fase, o que pode ser atribuído ao aumento na UP observado nas gemas após satisfação da exigência em frio e superação de dormência. Na cultivar Housui, a insatisfação da exigência em frio, associada à ocorrência de altas temperaturas durante o inverno, refletiu-se na redução da UP e na desidratação das gemas durante a dormência. A dinâmica da água em tecidos de pereira é diretamente influenciada pelo acúmulo de frio hibernal e depende da exigência em frio de cada cultivar.The objective of this work was to evaluate the water content (WC) in different tissues of the Kieffer (Pyrus communis) and Housui (Pyrus pyrifolia) pear cultivars during dormancy, under mild winter conditions. Plants from to the experimental orchard of Embrapa Clima Temperado, Pelotas, RS, Brazil, were evaluated. A completely randomized block design, in a 3x4x5 factorial arrangement, consisting of three tissues (bud, bark and wood), four portions of branches (terminal, median, axial and spurs) and five sampling dates in 2005 (7/1, 8/3, 9/6, 9/23 and 10/13), distributed in split‑plots, with three replicates, was used. There was a WC increase in the wood of the Kieffer cultivar until the middle of the dormancy period and a subsequent decrease after this phase, which could be attributed to the increase in WC observed in buds after the satisfaction of chilling requirement and dormancy. In the cultivar Housui, unsatisfactory chilling requirement, associated with the occurrence of high temperatures during the winter, reflected in the reduction of WC and in bud dehydration during dormancy. Water dynamics in pear tree tissues is directly influenced by cold accumulation during dormancy period and depends on the cold requirement of each cultivar

Water content in pear tree tissues during the dormancy period under mild winter conditions

O objetivo deste trabalho foi avaliar a umidade ponderal (UP) em diferentes tecidos das cultivares de pereira Kieffer (Pyrus communis) e Housui (Pyrus pyrifolia), durante a dormência, em condições de inverno ameno. Foram avaliadas plantas do pomar experimental da Embrapa Clima Temperado, Pelotas, RS. Utilizou-se o delineamento experimental inteiramente casualizado, em esquema fatorial 3x4x5, que consistiu em três tecidos (gema, casca e lenho), quatro porções de ramos (terminal, mediana, axial e esporões) e cinco datas de coleta, em 2005 (1/7, 3/8, 6/9, 23/9 e 13/10), com parcelas subdivididas e três repetições. Houve aumento na UP do lenho na cultivar Kieffer até a metade da dormência, com subsequente redução a partir desta fase, o que pode ser atribuído ao aumento na UP observado nas gemas após satisfação da exigência em frio e superação de dormência. Na cultivar Housui, a insatisfação da exigência em frio, associada à ocorrência de altas temperaturas durante o inverno, refletiu-se na redução da UP e na desidratação das gemas durante a dormência. A dinâmica da água em tecidos de pereira é diretamente influenciada pelo acúmulo de frio hibernal e depende da exigência em frio de cada cultivar.The objective of this work was to evaluate the water content (WC) in different tissues of the Kieffer (Pyrus communis) and Housui (Pyrus pyrifolia) pear cultivars during dormancy, under mild winter conditions. Plants from to the experimental orchard of Embrapa Clima Temperado, Pelotas, RS, Brazil, were evaluated. A completely randomized block design, in a 3x4x5 factorial arrangement, consisting of three tissues (bud, bark and wood), four portions of branches (terminal, median, axial and spurs) and five sampling dates in 2005 (7/1, 8/3, 9/6, 9/23 and 10/13), distributed in split‑plots, with three replicates, was used. There was a WC increase in the wood of the Kieffer cultivar until the middle of the dormancy period and a subsequent decrease after this phase, which could be attributed to the increase in WC observed in buds after the satisfaction of chilling requirement and dormancy. In the cultivar Housui, unsatisfactory chilling requirement, associated with the occurrence of high temperatures during the winter, reflected in the reduction of WC and in bud dehydration during dormancy. Water dynamics in pear tree tissues is directly influenced by cold accumulation during dormancy period and depends on the cold requirement of each cultivar

Época e intensidade de ocorrência da necrose floral em gemas de pereira japonesa cultivar Housui durante o inverno

The commercial exploration of the pear culture in Brazil has little expression, being the internal consumption supplied by imports. The lack of edafoclimatic adaptation of the commercial cultivars of interest andthe flower bud abortion are the main problems for the development of this crop. The aim of this study was to evaluate the occurrence time and the intensity of the flower bud necrosis in pear trees cv. Housui (Pyrus pyrifolia) during the winter period. The experiment was conducted in 2007, using plants belonging to the orchard of Embrapa Clima Temperado, in Pelotas, RS, Brazil. The buds were collected at five different moments (May 24th, June 20th, July 19th, August 21st, and September 18th), fixed in a solution of formalin, acetic acid and alcohol and dissected under a stereoscopic microscope. The parameters evaluated were the percentages of healthy buds and buds withmoderate and severe necrosis. At the beginning of the winter the symptoms were not present in practically any buds. The buds were seriously affected in the final period of dormancy, when the symptoms began rising from a negligible level to a sharp peak toward the end of the winter.A exploração comercial da cultura da pereira tem pequena expressão no Brasil, sendo o consumo interno provido por meio de importações. A falta de adaptação edafoclimática das cultivares de interesse comercial e oabortamento floral são os principais problemas para o desenvolvimento dessa cultura. O objetivo deste trabalho foi avaliar a época e a intensidade de ocorrência da necrose floral em gemas de pereira japonesa cultivar Housui (Pyrus pyrifolia) durante o inverno. O experimento foi realizado em 2007, utilizando-se plantas pertencentes à coleção instalada na Embrapa Clima Temperado em Pelotas, RS. Foram coletadas gemas em cinco épocas (24/5, 20/6, 19/7, 21/8 e 18/9), as quais foram fixadas em solução de formol, ácido acético e álcool (FAA) e dissecadas sob um microscópio estereoscópico. Foram avaliadas as percentagens de gemas sadias e com necrose leve e severa. A maioria das gemas não apresentou sintomas de necrose até a metade do inverno. A severidade da necrose se intensificou a partir da metade do inverno, atingindo praticamente todas as gemas no final do período de inverno

Persistence of the red ring nematode in the roots and in the rhizosphere of recently eradicated coconut palms

Red ring disease is one of the primary diseases that attacks the coconut palm (Cocos nucifera L.) in Brazil. This lethal disease is caused by a nematode (Bursaphelenchus cocophilus) and can spread via contaminated tools or by the South American palm weevil (Rhynchophorus palmarum). The goal of this research was to determine the persistence of nematodes within the roots and the rhizosphere of recently eradicated coconut palms, cultivated in the coastal region of the state of Alagoas. Soil and root samples from coconut palms with advanced symptoms of red ring disease were collected up to 6 months after the eradication of the plants. Sample processing was conducted at the Ecology and Insect Behavior Laboratory of the Federal University of Alagoas. Sample collection was ended when B. cocophilus were no longer found in the laboratory tests. B. cocophilus were able to survive in the coconut palm roots for at least 118 and 133 days after felling (DAF), in Coruripe and São Miguel dos Milagres, respectively. B. cocophilus could migrated from the roots to the soil, where they were found until 76 and 88 DAF, in Coruripe and São Miguel dos Milagres, respectively