mariem lotfi

In Tunisia, Pyrus communis ‘Arbi’ is broadly imperiled by Erwinia amylovora. The breeding of resistant rootstocks is an effectual control strategy for disease management. Therefore, a sound protocol for micropropagation and for the extensive production of high-quality plantlets was developed.

Three groups of LED treatments were carried out: (1) 100% blue (B) LED, (2) 100% red (R) LED and (3) 50% B + 50% R (=BR) LED. Stock plants were micropropagtaed on modified Murashige and Skoog (MS) medium with half concentration of NH4NO3 and KNO3.

Throughout the propagation stage, red LED displayed important advantages: it produced optimal shoot height and leaf surface. The least leaf area was obtained with fluorescent light. The blue / red combination yielded considerable amelioration. Shoot weight/callus weight was maximal, along with shoot number and shoot length. The root formation of in vitro grown pear plantlets was greatly influenced by the various light types and by the incorporation of a new root-promoting substance, phenyl acetic acid (PAA). When combining red light and PAA, 89 % of rooting was observed in pear plantlets. The acclimatized pear vitroplants achieved rapid growth without morphological anomalies.

 In order to improve the survival rates of the acclimatized vitroplants, the acclimatization stage needs to be further studied.

 The study compared the impact of different combinations of monochromatic blue and red LED lights and phenyl acetic acid against that of fluorescent light during the micropropagation, rooting and acclimation of a resistant pear (Pyrus communis L., cv. Arbi).

In Tunisia, pear cultivars are widely threatened by the attack of fire blight disease. Cultivation of tolerant cultivars is an effective control strategy for disease control. For this purpose, a reliable protocol was established for micropropagation of local Pyrus communis and Pyrus syriaca L. and for large-scale production of high-quality plantlets. Research Using apical explants, different media and hormones were tested to establish a micropropagation procedure for local Tunisian Pyrus communis cultivars ‘Arbi’, ʻMaltiʼ, ʻMahdia 6ʼ and ʻMoknine 10ʼ and for Pyrus syriaca. Disinfection with 4% HgCl2 treatment for 20 minutes showed the highest percentage of plant survival. Successful initiation of the cultures was achieved on MS basal medium supplemented with 0.25 mg L-1 BA. During the proliferation stage, optimal shoot multiplication was obtained on MS medium with a half concentration of NH4NO3 and KNO3 supplemented with 0.1 mg L-1 IBA and 2 mg L-1 BA, but for maximum shoot length the BA concentration needed to be lowered to 1 mg L-1. A rooting rate of 100% and the highest root length and root number were attained on Cheng medium supplemented with 1.0 mg L-1 IBA. Pear vitroplants were successfully acclimatized on S2 substrate, composed by peat moss. Research limitations: Vitroplants acclimatization step needs to be well studied for the improvement of theacclimatized vitroplant survival rates by reducing the symptoms of crown rot. Originality/Value: This efficient optimized in vitro protocol will be successfully applied for large multiplication of high quality of Tunisian Pyrus vitroplants and cultivars.