Dataset Information

Benzylaminopurine application on two different apple cultivars (Malus domestica) displays new and unexpected fruitlet abscission features.

ABSTRACT: BACKGROUND AND AIMS: It has been previously shown that abscission of apple fruitlets is preceded by an increase in ethylene evolution and in the amount of transcripts for 1-aminocyclopropane-1-carboxylate oxidase (ACO), an enzyme catalysing the final step in ethylene biosynthesis. These events are concomitant with shedding induction and chemical thinning. There are several thinners but their mode of action and efficacy is poorly understood. One of them is benzylaminopurine (BA), a cytokinin believed to act by enhancing vegetative activity and stressing the competition between shoots and fruitlets, thus leading to fruitlet shedding. Nevertheless, the specific mechanism of action of BA and the variable effect depending on apple cultivar (easy or difficult to thin) are poorly understood. METHODS: Abscission, the amount of MdACO1 transcripts and other parameters were followed in immature apple fruits during the period of physiological drop. The cultivars studied were 'Golden Delicious' and the 'spur' type 'Red Delicious'. BA was used as a thinning agent and was sprayed 14 d after petal fall (DAPF). Fruitlets were divided into central (C) and lateral (L) fruitlet populations. KEY RESULTS: Fruitlet size was significantly different between C and L fruitlets but it did not differ much between the populations within the same cultivar. C fruitlets were characterized by basal ethylene evolution while L fruitlets displayed an increase in hormone biosynthesis during abscission induction. Cluster composition evaluated by the L/C ratio differed in the two varieties, being almost unchanged throughout abscission induction in 'Golden Delicious' and progressively decreasing in 'Red Delicious'. Shoot growth activity evaluated at the end of the season indicated a possible connection with both the ongoing abscission and BA application. MDACO1 transcripts were mainly detected in L fruitlets and the accumulation was related to total abscission in 'Golden Delicious', while in 'Red Delicious' expression was observed in both C and L fruitlets. CONCLUSIONS: BA probably exerts its thinning effect through vegetative growth. In the 'spur' type 'Red Delicious' the chemical is ineffective, probably due to a limited action on shoot growth due to genetic characteristics. The amount of MdACO1 transcripts in seeds is a good indicator of abscission.

SUBMITTER: Dal Cin V

PROVIDER: S-EPMC3243580 | biostudies-literature | 2007 Jun

REPOSITORIES: biostudies-literature

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Benzylaminopurine application on two different apple cultivars (Malus domestica) displays new and unexpected fruitlet abscission features.

Dal Cin Valeriano V Boschetti Andrea A Dorigoni Alberto A Ramina Angelo A

Annals of botany 20070430 6

<h4>Background and aims</h4>It has been previously shown that abscission of apple fruitlets is preceded by an increase in ethylene evolution and in the amount of transcripts for 1-aminocyclopropane-1-carboxylate oxidase (ACO), an enzyme catalysing the final step in ethylene biosynthesis. These events are concomitant with shedding induction and chemical thinning. There are several thinners but their mode of action and efficacy is poorly understood. One of them is benzylaminopurine (BA), a cytokin ...[more]

PMID: 17470901

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Project description:BackgroundThe necrogenic enterobacterium, Erwinia amylovora is the causal agent of the fire blight (FB) disease in many Rosaceae species, including apple and pear. During the infection process, the bacteria induce an oxidative stress response with kinetics similar to those induced in an incompatible bacteria-plant interaction. No resistance mechanism to E. amylovora in host plants has yet been characterized, recent work has identified some molecular events which occur in resistant and/or susceptible host interaction with E. amylovora: In order to understand the mechanisms that characterize responses to FB, differentially expressed genes were identified by cDNA-AFLP analysis in resistant and susceptible apple genotypes after inoculation with E. amylovora.ResultscDNA were isolated from M.26 (susceptible) and G.41 (resistant) apple tissues collected 2 h and 48 h after challenge with a virulent E. amylovora strain or mock (buffer) inoculated. To identify differentially expressed transcripts, electrophoretic banding patterns were obtained from cDNAs. In the AFLP experiments, M.26 and G.41 showed different patterns of expression, including genes specifically induced, not induced, or repressed by E. amylovora. In total, 190 ESTs differentially expressed between M.26 and G.41 were identified using 42 pairs of AFLP primers. cDNA-AFLP analysis of global EST expression in a resistant and a susceptible apple genotype identified different major classes of genes. EST sequencing data showed that genes linked to resistance, encoding proteins involved in recognition, signaling, defense and apoptosis, were modulated by E. amylovora in its host plant. The expression time course of some of these ESTs selected via a bioinformatic analysis has been characterized.ConclusionThese data are being used to develop hypotheses of resistance or susceptibility mechanisms in Malus to E. amylovora and provide an initial categorization of genes possibly involved in recognition events, early signaling responses the subsequent development of resistance or susceptibility. These data also provided potential candidates for improving apple resistance to fire blight either by marker-assisted selection or genetic engineering.

Dataset Information

Benzylaminopurine application on two different apple cultivars (Malus domestica) displays new and unexpected fruitlet abscission features.

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Benzylaminopurine application on two different apple cultivars (Malus domestica) displays new and unexpected fruitlet abscission features.

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