Nikolaos Koutinas

Flower Induction and Flower Bud Development in Apple and Sweet Cherry

ABSTRACT As a result of studies conducted in the last 20–30 years, new information has been obtained about the flower bud formation in apple and cherry, including some data about the presence of genes determining the reproductive organs of the apple. Some issues about the flower induction, histological transformation of the apical meristem, morphological differentiation of the flower buds, factors and conditions influencing the flower bud formation and the quality of the reproductive organs are discussed in this survey. Some attention has been paid to the tree pruning, summer pruning in particular, the fertilization, irrigation and treatment with growth regulators, by means of which processes of flower bud formation can be regulated.

Morphological Differentiation of Flower Buds in Own-Rooted and Budded Apple Trees

ABSTRACT In the period from the year 2002 to the year 2005 the morphological differentiation of flower buds in adult own-rooted trees (produced by trench layering) and the ones budded on seedling rootstock in the apple cultivar Golden Resistant, was studied. The onset of morphological differentiation was observed in the third ten-day period of the month of June and the second ten-day period of July, with no significant differences between the own-rooted and budded plants. No differences were established both in the rate of initiation of the leaf-like appendages (bud scales, transitional leaves, true leaves and bracts) on the bud axes, and also with respect to the “critical number of appendages”. The “critical number of appendages” including bud scales, transitional leaves, true leaves and the first bract, was comparatively identical according to years (15–16 in number). The obtained information about the morphological differentiation of flower buds in the own-rooted apple trees can serve as a valuable reference point in clarifying the flower bud formation processes in the in vitro propagated apple plants which have been of particular interest lately.

THE TRANSITION TO FLOWERING IN APPLE

ABSTRACT In spite of numerous studies on the process of apple flower bud formation some events, particularly genetic control of transition to reproductive development, have not been investigated in details. In the last two decades several genes such as SQUA/AP1 and FLO/LFY, related to flower initiation and development in the model angiosperm species Antirrhinum majus and Arabidopsis thaliana have been indentified and characterized. Lately, homologues/orthologues of these genes, MdMADS1-MdMADS11, MdAPl, AFL, AFL1 and AFL2, have been isolated from apple. Their temporal and special expression suggests that they may play central roles in development of floral meristem, flower organs and/or fruits of apple. Special attention has been paid to the apple gene MdTFL1, highly homologous to Arabidopsis TEL1, which maintains the identity of inflorescence meristem. Using transgenic approach it is possible to suppress TFL1-like genes, that delay flowering and to reduce the juvenile phase in woody plants, including apple.

Molecular detection of bacteria in plant tissues, using universal 16S ribosomal DNA degenerated primers

Highly specific, sensitive and rapid tests are required for the detection and identification of covert bacterial contaminations in plant tissue cultures. Current methods available for this purpose are tedious, time consuming, highly error prone, expensive, require advanced technical expertise and are sometimes ineffective. We report here the development of a sensitive polymerase chain reaction (PCR) based method for the rapid detection and identification of bacteria occurring in plant tissue cultures. A total of 121 16S ribosomal DNA (rDNA) coding regions from 14 different groups of bacteria, algae and plants, available in the Gene Bank/European Molecular Biology Laboratory databases, were aligned and several conserved DNA sequences of bacterial origin were identified. From those, five degenerated primers were designed in order to amplify only the bacterial DNA present in mixed plant/bacteria genomic DNA extracts. A known amount of bacterial suspension of either covert Pseudomonas or covert Bacillus were added to in vitro plant leaves and total plant/bacterial DNA extracted using three different methods to determine the lowest number of bacteria required to be present in order to allow their detection. The highest sensitivity of the bacterial cell detection was 2.5 × 106 cells of both Bacillus and Pseudomonas inoculums, using template DNA prepared by the MiniPrep method. Generation of PCR amplification fragments was achieved only for the 16S rDNA bacterial gene by using four combinations of degenerated primers. Successive sequence analysis of these amplified fragments led to the rapid detection and molecular identification of bacteria covertly associated with plants.