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

Flávio Gilberto Herter,Anderson Carlos Marafon,Fernando José Hawerroth,Idemir Citadin,Luciano Do Amarante

doi:10.1590/s0103-90162011000400011

Flávio Gilberto Herter, Anderson Carlos Marafon + Show 3 more

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https://doi.org/10.1590/s0103-90162011000400011

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Abstract

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).

Highlights

The southern region of Brazil has developed the cultivation of temperate fruit trees, especially apple (Malus domestica Borkh.), grape (Vitis vinifera L.), peach (Prunus persica (L.) Batsch) and plum (Prunus salicina Lindl.) cultures, but the pear (Pyrus sp.) culture did not show the same development, due to irregularity of the production and low yield of the orchards
Interactions (p ≤ 0.05) between factors occurred to the total soluble sugars (TSS), reducing sugars (RS) and starch contents and to cell wall acid invertase (CWAI) and sucrose-phosphate synthase (SPS) activities (Table 1)
The total soluble sugars concentrations were higher in wood tissues of T2 treatment and in bud tissues of T2 and T3 treatments

Summary

Introduction

The southern region of Brazil has developed the cultivation of temperate fruit trees, especially apple (Malus domestica Borkh.), grape (Vitis vinifera L.), peach (Prunus persica (L.) Batsch) and plum (Prunus salicina Lindl.) cultures, but the pear (Pyrus sp.) culture did not show the same development, due to irregularity of the production and low yield of the orchards. Among the main limiting factors are: indefinition of the rootstocks, low rates of floral differentiation, high levels of flower bud abortion (variable with the cultivar, location and weather conditions) and lower percentage of fruit set (Nakasu et al, 1995). In temperate-zone deciduous fruit trees, the most important factor in release dormancy is the accumulation of a certain amount of chilling (Lang, 1996). Lack of chilling, associated with mild winter conditions, results in abnormal patterns of budbreak and development in temperate fruit trees (Mauget and Rageau, 1988) and is known as the main factor of pear flower bud abortion in Brazil (Petri et al, 2002; Petri and Herter, 2002) and New. Zealand (Klinac and Geddes, 1995; Do Oh and Klinac, 2003). The occurrence of intermittent hot days during dormancy period, with temperatures higher than 27oC, delayed the release dormancy more than mild temperature fluctuations (2 to 3oC)

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