Optimizing micropropagation of drought resistant Pyrus boissieriana Buhse

Abstract

The present study concentrated on introducing a micropropagation protocol for a drought resistant genotype from , which is the second most naturally widespread pear species in Iran with proper physiological and medicinal properties. Proliferating microshoot cultures were obtained by placing nodal segments on MS medium supplemented with BAP and IBA or NAA. The highest number of shoots (27 shoots per explant) were obtained with 1.5 mg l BAP and 0.05 mg l IBA, but this combination did not produce shoots of desirable length (>1.7 cm). Combination of 1.75 mg l BAP and 0.07 mg l IBA was the best for the shoot multiplication in with a sufficient number of shoot production (22.33 shoots per explant) and relatively more appropriate shoot length. The larger and greenish leaves were obtained when PG was added to the best multiplication treatment. Microshoot elongation was carried out in 1/2 and 1/4 MS medium containing 50-100 mg l PG with different concentrations of IBA or NAA at intervals of 30-60 days. Significant increase in shoot length was detected after 45-60 days of culture in the presence of PG. The highest shoot length (8 cm) was recorded on 1/2 MS medium supplemented with 0.5 mg l IBA and 100 mg l PG. GA negatively affected number and length of shoots and generally caused generation of red leaves. The highest percentage of root induction (100%) and root length (9 cm) were obtained on 1/6 strength MS medium supplemented with 0.005 mg l IBA. All plantlets were hardened when transferred to ex vitro conditions through a period of 25-30 days. The results suggest axillary shoot proliferation of could successfully be employed for propagation of candidate drought resistant seedling.

In vitro arrow cane (Gynerium sagitatum Aubl.) multiplication in double phase medium

“…Because of this external energetic support, when transferred to ex vitro conditions, plants must have plenty of carbohydrate reserves in organs, such as leaves and stems, that serve as "life boat" effect before newly photosynthetic active leaves are formed. Therefore, micropropagated plants with larger organs will store more nutritional reserves and will have more opportunities to successfully withstand adaptation when transferring to natural environment (Kane, 1996;Resende et al, 2016;Zakavi et al, 2016).…”

Micropropagation of arrow cane, Gynerium sagittatum (Aubl.) P. Beauv. cv. Criolla, Criolla 1, and Martinera, in a double-phase medium

“…Under in vitro conditions, plant medium and the environment prevent plant tissue from dehydration and favor nutrient uptake without root formation. However, for ex vitro conditions, in vitro rooting provides the mechanisms for normal growth and development of the plant in open field conditions (Choudhary et al, 2017;Zakavi et al, 2016). In vitro adventitious root formation is usually promoted by auxin supply in the culture medium (Ozdemir et al, 2014;Resende et al, 2016).…”

“…Shoots cultured in NAA supplied medium formed three times more roots than those cultured in the absence of NAA; the response even increased when compared to previous arrow cane in vitro rooting studies Suárez et al, 2009). Good quality in vitro rooting is not only the formation and proliferation of adventitious root but also root characteristics such as length and width (Benavides et al, 2016;Rodríguez et al, 2015;Zakavi et al, 2016). During the transfer to ex vitro conditions, shoots with shorter roots are easy to handle and do not require trimming, which produces stress and open wounds (Kane, 1996).…”

“…This fully humid environment prevents activation of mechanisms such as stomata closure and cuticle accumulation, intended to avoid dehydration. Since in vitro leaf structure is prone to rapid dehydration when transferred to ex vitro, plants must be placed in an environment with high water saturation (irrigation fog systems) and low light intensity (shade house) to avoid plant loss (Bukhari et al, 2016;Zakavi et al, 2016). In the present research, regardless of cultivar and stage of micropropagation (shoot multiplication or in vitro rooting), cultures transferred to ex vitro conditions fully adapted and survived (100 % survival), as reported in previous studies Suárez et al, 2009).…”