Tracking biochemical changes during adventitious root formation in olive (Olea europaea L.)

The activity of oxidative enzymes and the levels of free auxins were determined during adventitious root formation in olive explants. Rooting trials were performed both with in vitro-cultured micro shoots of the cultivar ‘Galega Vulgar’, treated with indole-3-butyric acid (IBA) and with salicylhydroxamic acid(SHAM) + IBA, as well as with semi-hardwood cuttings of the cultivars ‘Galega Vulgar’ (difficult-to-root)and ‘Cobrançosa’ (easy-to-root), treated with IBA. The auxin (IBA) was used in all experiments as a rooting promoter, while SHAM was used in micropropagation trials as rooting inhibitor, providing a negative control. Free indole-3-acetic acid (IAA) and IBA concentrations were determined in microshoots, as well as in semi-hardwood cuttings, throughout the rooting period at pre-established time-points. At the sametime-points, the enzymatic activity of polyphenol oxidases (PPO), peroxidases (POX), and IAA oxidase(IAAox) was evaluated in the microshoots. Microshoots treated with SHAM + IBA revealed higher POX and IAAox activity, as well as lower PPO activity, than those treated only with IBA. IAA levels were higher in IBA-treated microshoots during induction phase, but lower during early initiation phase. Incontrast, free IBA levels were higher in microshoots treated with SHAM + IBA during induction, but lower during initiation. A similar pattern of free auxin levels was observed in semi-hardwood cuttings of the two contrasting cultivars under evaluation. The similarities found on the auxin patterns of microshoots treated with SHAM and those of semi-hardwood cuttings of the difficult-to-root olive cultivar allow considering SHAM a reliable control for when simulation of a difficult-to-root behavior is necessary. The inhibitory effect of SHAM in root formation could be related with 1) the inhibition of alternative oxidase(AOX), leading to a down regulation of phenylpropanoid biosynthetic pathways, which would decrease the concentration of phenolic substrates for PPO; 2) an increase in IAAox activity resulting in lower free IAA levels or; 3) a defective conversion of IBA into IAA.

Quantification of free auxins in semi-hardwood plant cuttings and microshoots by dispersive liquid–liquid microextraction/microwave derivatization and GC/MS analysis

Several studies have suggested that differences in the natural rooting ability of plant cuttings could be attributed to differences in endogenous auxin levels. Hence, during rooting experiments, it is important to be able to routinely monitor the evolution of endogenous levels of plant hormones. This work reports the development of a new method for the quantification of free auxins in auxin-treated Olea europaea (L.) explants, using dispersive liquid–liquid microextraction (DLLME) and microwave assisted derivatization (MAD) followed by gas chromatography/mass spectrometry (GC/MS) analysis. Linear ranges of 0.5–500 ng mL 1 and 1–500 mg mL 1 were used for the quantification of indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA), respectively. Determined by serial dilutions, the limits of detection (LOD) and quantification (LOQ) were 0.05 ng mL 1 and 0.25 ng mL 1, respectively for both compounds. When using the calibration curve for determination, the LOQ corresponded to 0.5 ng mL 1 (IAA) and 0.5 mg mL 1 (IBA). The proposed method proved to be substantially faster than other alternatives, and allowed free auxin quantification in real samples of semi-hardwood cuttings and microshoots of two olive cultivars. The concentrations found in the analyzed samples are in the range of 0.131–0.342 mg g 1 (IAA) and 20–264 mg g 1 (IBA).

Diversity of new root nodule bacteria from Erythrina velutina Willd., a native legume from the Caatinga dry forest (Northeastern Brazil).

This study aims to evaluate the phenotypical characteristics of bacterial isolates from mulungu (Erythrina velutina Willd.) nodules and determinate their Box-PCR fingerprinting. All bacteria were evaluated by the following phenotypic characteristics: growth rate, pH change, colony color and mucus production. The bacterial isolates able to re-nodulate the original host were also evaluated regarding its tolerance to increased salinity and different incubation temperatures, ability to growth using different carbon sources, intrinsic antibiotic resistance and ?in vitro? auxin biosynthesis. The molecular fingerprints were set up using the Box-PCR technique and the isolates were clustered by their profiles. Among the 22 bacterial isolates obtained, eight were able to re-nodulate the original host. Among the nodule inducing isolates, some were tolerant to 1% of NaCl and 39° C and all of them metabolized the maltose, fructose, glucose, sucrose and arabinose, were resistant to rifampicin and produced auxin. The bacteria showed low genetic similarity among them and reference strains, which indicates the great genetic variability of the isolates. The results of this work are the first reports about the bacterial isolates able to nodulate this species. A more deep study of these bacteria may reveal the existence of isolates tolerant to environmental stresses and suitable as a future mulungu inoculant.

Identification of endophytic bactéria from micropropagated yacon (Smallanthus sonchifolius) crowing under autotrophic and Heterotrophic systems.

Yacon, Smallanthus sonchifolius, an Andean species. is a rich source of dictetíc oligofructans with low glucose content. proteins and phenolic compounds. These constituents have shown efficacy in the prevention of diet-related ehronic diseases, including gastroin-testinal disorders and diabetes |1,2|. Yacon is part of a research program at the National Center for Natural Products Research (NCNPR) and University of Mississippi Field Station to develop new alternative root crops for Mississippi while attempting to im-prove the diet of low incorne families. Yacon can be easily propa-gated by cultings. Virus and nematode infections have been re-ported on plants propagated by cuttings in Brazil. a country that hás adopted Yacon as specialty crop [3|. We have developed two culture systems. autotrophic and heterotrophic, to produce healthy plants. Herem we describe the presence of endophytic bactéria m micropropagated Yacon. In auxin free media, new roots were induced. Overa 15day period. the average root mduction per expiam was 5.45 to 8.75 under autotrophic and heterotrophic cul-tures, respectively. Root lenglh vaned between 3 and 60mrn. The presence of root hairs and lateral roots was noticed only in auto-trophic condilions. These beneficiai bactéria were identified and chemically ctiaracterized. Acknowledgement: This research work was partially supported by the USDA/ARS Cooperative Research Agreement No. 58-6408-2-009. Referentes; |1) Terada S. et ai. (2006] Yakugaku Zasshi 126(8): 665-669. (2| Valentová K. Ulri-chová j. (2003) Biomedical Papers 147: 119-130. [3| Mogor C. et ai, (2003) Acta Horticulturea 597: 311 -313.

3,5,6-trichloro-2-pyridinyloxyacetic acid as effective thinning agent for fruit of 'Montenegrina' mandarin.

2016