PRE-TREATMENT WITH CYTOKININS IN Bouteloua curtipendula (MICHX.) TORR. TO INCREASE PLANTLET REGENERATION

Abstract

Sideoats grama [Bouteloua curtipendula (Michx.) Torr.] is one of the most widely cultivated forage species in semi-arid areas of the USA and Northern Mexico; it is an apomictic recalcitrant species with great forage attributes. The objective of this study was to evaluate pre-regeneration treatments using cytokinins to increase the frequency of regeneration. Induced morphogenic calli from mature caryopses of sideoats grama cv. El Reno cultured on basal Murashige and Skoog (MS) medium and supplemented with three levels of 2,4-dichlorophenoxyacetic acid (2,4-D) (2, 3 and 4 mg L^-1) in presence of 0.15 mg L^-1 of 6-benzylaminopurine (BAP) were subjected to two cytokinins-based treatments prior to the regeneration process [BAP (MSB) and BAP-KIN-TDZ (MSBKT)] for 10 days, and subsequently transferred to regeneration medium MSBK (2 mg L^-1 BAP and 1 mg L^-1 kinetin) and sub-cultured every 20 days until completing the regeneration process. Data were analyzed by logistic regression,
negative binomial and mixed model. Statistical differences (P ≤ 0.05) in callus induction frequency were recorded at different levels of 2,4-D, the highest being 2 mg L^-1 showing the highest. Pretreatment based on MSB improved plantlet regeneration response as the level of 2,4-D increased in calli induction treatments, while lower levels increased the frequency of calli development. The highest regeneration response was observed in calli induced at 3 and 4 mg L^-1 of 2,4-D (P ≤ 0.05). Pretreatments with cytokinins proved to be a key factor for regeneration of sideoats grama cv El Reno plantlets.