Proceedings of the XLV Italian Society of Agricultural Genetics - SIGA Annual Congress

Salsomaggiore Terme, Italy - 26/29 September, 2001

ISBN 88-900622-1-5

Poster Abstract

PEACH ROOTSTOCKS, INDUCING DIFFERENT CANOPY DEVELOPMENT TO GRAFTED CULTIVAR, REFLECT GENOMIC AND MORPHOLOGICAL DIVERSITY AND DIFFERENT PLASMA MEMBRANE OXYGEN INFLUXES IN ROOT

MULEO R.*^,****, MANCUSO S.**, IACONA C.***, INTRIERI MC.*^,****, MAGGI E.**, LORETI F.***, BUIATTI M.****

* Dipartimento Produzione Vegetale, Tuscia University

muleo@unitus.it

** Dipartimento di Coltivazione e Difesa delle Specie Legnose, Pisa University

*** Dipartimento Ortoflorofrutticoltura, Florence University

**** Dipartimento Biologia Animale Genetica, Florence University

chloroplast DNA, ISSR markers, Non-invasive vibrating oxygen-selective probe, Rootstock, Prunus persica L.

Fruit trees are usually grafted on rootstocks that are genetically different from the cultivars. The rootstock has a relevant agronomic significance, because it greatly affects vigour and productivity, a fact that gives relevance to the control mechanisms concerned with the initiation and development of new roots. Recently, molecular and genetic studies have increased the knowledge about root formation. Genes involved in asymmetric division of cells, cell fate decision, lateral root development and auxin signal have been isolated, with the help of the large number of A. thaliana mutants. Despite this, very little is understood about how adventitious root formation is regulated in woody plants, as in this case the approach using morphogenetic mutants is very difficult. With the aim to enrich the knowledge about adventitious rooting formation and the regulation of vigour in fruit trees, we began to study three peach rootstocks, PSA5, PSA6 and PSB2, that have been selected at the Department of Fruit Science and Crop Protection of Pisa University, from a population of seedlings, and are able to induce different both vigour in grafted peach cultivars and adventitious root formation. Molecular, physiological and morphological approaches have been used with the aim to characterise the rootstocks.

PSB2 showed the highest percentage of rooted cuttings, while the lowest value was detected for PSA5. The number of roots per cutting was highest in both PSB2 and PSA6 genotypes. Histological analyses of apex of adventitious and primary roots showed differences among the three rootstocks. From the analysis of trnT/trnD, non-coding region of chloroplast DNA, a difference at the nucleotide level was detected, while no difference was detected in the DNA mitochondrial NAD-reductase sequence. A total of 14 ISSR primers were screened and amplification profiles obtained through simple repeat containing primers were able to reveal polymorphism among the genotypes and cultivar Armking (Ar) used as a control. Out of a total number of 76 analysed fragments 15 were polymorphic. The amplified band data were reported in a matrix and processed by the RAPD Distance Program, version 1.04, to obtain a similarity matrix. 2 fragments one of about 800 bp the other of about 700 bp, present in PSA6 and Armiking and absent in PSA5 and PSB2, were cloned and sequenced. From the analyses of data bank the largest fragment shown a high similarity with a desaturase gene. A molecular analyses on the self-pollinated progeny of all genotypes are in progress. The three rootstocks showed the same spatial organisation in net O₂ influxes which were characterised by two distinct peaks, the first in the division zone and the second in the elongation zone at positions 0.5-0.7 mm and 2-2.5 mm from the root apex, respectively. The magnitude of the oxygen influxes was different in the three genotypes. Peak values for PSB2 and PSA6 averaged 55.6 pmol cm^-2 s^-1 in the elongation zone and 30.2 pmol cm^-2 s^-1 in the division zone, while in the mature zone oxygen influx averaged 14.3 pmol cm^-2 s^-1. Instead, PSA5 showed significantly lower values of O₂ influx with 31.3 pmol cm^-2 s^-1 in the elongation zone, and 18.1 pmol cm^-2 s^-1 in the division zone. O₂ fluxes studies showed a rhythmic regime characterised by regular oscillations with specific periods of about 8.1 min for PSA6 and PSB2 and 9.2 min for the PSA5 genotype. PSB2 and PSA6 are more similar to each other than to PSA5, independently of the type of parameters at all levels and dramatically difference is evident in PSA5. A bio-period on oxygen influxes which is independent from environmental factors and linked to genomic diversity is for the first time demonstrated in roots.