In vitro Proliferation, Rooting and Acclimatization of Natanzi Pear Seedlings (Pyrus communis cv. Natanzi) with Mycorrhiza Fungi Infection

Natanzi, a native pear cultivar of Iran, is one of the Iranian high quality and commercial pear. True plant type can be produced with in vitro micropropagation. Micropropagation used for species that have long generation time, low levels of seed production, or seeds that do not readily germinate. Auxins in various concentrations are used for rooting depending on the different conditions of the tissue and culture medium. After propagation one of the problems with the production of plants through micropropagation is acclimatization. Low survival and poor growth of rooted seedlings in in vitro conditions after transferring to the environment, limits the use of tissue culture. The fungi symbiosis with root can enhance the success of this method. Natanzi pear propagation in Murashige and Skoog (MS) and propagated seedling acclimatization with mycorrhiza treatment were not reported. The aim of this study is evaluation the effects of various concentrations of BAP, IBA and GA3 on shooting, and NAA and IBA on rooting of Natanzi pear. In the second part of this experiment, the effects of mycorrhizal fungi on root development and absorption of phosphorus were evaluated. In this study one-year branch buds of P.communis cv. Natanz from a wild mature tree native in village Tame, Natanz city, Isfahan Province, were used as plant material. Natanzi pear cutting were propagated supplemented with MS media under factorial experimental designs with three replications. Shoot proliferation in MS and MS with half concentration by BAP, IBA and GA3 were studied. Four different levels of IBA and NAA under light and dark condition for rooting were studied. After rooting plants were transplanted into 10 cm×12 cm plastic pots. Transplant was made in conditions of high ambient humidity to reduce damage to the plantlets. At transplant, pots were filled with different sterilized substrates, composed of mixtures of a coco peat:perlit and peat moss:perlit at a 1:1 (v/v) ratio. Substrates were wetted before filling the pots. At transplant, plants were inoculated with the AM fungus Glomus mosseae and G. intraradices, in the form of a mixture of spores, soil, and infected clover roots. Ten grams of inoculum were placed in each planting hole about 1 cm below the roots, for a total treatment. 10 g of the autoclaved mixed soil used for inoculated control treatment. Acclimatization, seedling survival, colonization, phosphorus concentrations and some morphological characteristics of root such as root characteristic were evaluated under G. mosseae and G. intraradices infection. Also two different bed, coco peat:perlite and peat moss:perlite at a 1:1 (v/v) ratio were examined. At the end of the experiment, Roots plants were stained to assess mycorrhiza colonization using Phillips and Hayman method (????). Colonization percentages of colonization were measured using Giovannetti and Mosse method. The total P concentration of plants was assessed using standard analytical techniques. BAP (3 mg L-1) with IBA (0.5 mg L-1) is suitable of Natanzi pear proliferation under micropropagation condition. The highest rooting of Natanzi pear under in vitro condition were reported in MS and ½MS and 0.5 mg L-1 NAA under light and dark conditions, respectively. The results of experiments on Natanzi pear showed a positive effect of mycorhiza on the growth of infected seedlings compared to control treatments. Finally 100% of seedling were survived after acclimatization with mycorrhiza. Mycorrhiza increased the seedling length and root growth characteristics. No significant differences were observed in colonization of different mycorrhiza infection. Peat moss with no treatment (control) showed the most phosphorus concentrations and peat moss with G. mosseae mycorrhiza showed the most average root diameter. BAP and IBA (3 × 0.5 mg L-1) showed significant effect on proliferation and NAA (0.5 mg L-1) on rooting in MS respectively. Peat moss with G. mosseae is suitable to increase the acclimatization of Natanzi pear seedlings. Mycorrhiza increased the length of seedling and root growth characteristics during eight weeks of acclimatization. Natanzi pear seedlings showed the highest growth under G. intraradices treatment in peat moss. G. mosseae showed a significant effect on the average root diameter in peat moss. Results of leaf phosphorus concentration and root colonization percentage showed that there was no significant correlation between phosphorus concentration and colonization percentage.