Vol. 81 No: 6

Title:
Evaluation of the activity of aqueous extracts of some organic waste materials on in vitro-cultured shoots of 'M9' apple rootstock

Authors:
G. MARINO, G. MARCOLINI and M. TOSELLI

pp: 1015-1020

Abstract:
The present work investigated the effects of different aqueous extracts of organic waste compounds on growth, proliferation and photosynthetic activity in ´M9` (Malus × domestica Borkh.) shoot cultures, with the aim of determining the feasibility of using in vitro cultures as a tool for the rapid evaluation of organic amendments in agriculture. Aqueous extracts of the following organic waste compounds: cow manure (CM), sugarbeet industrial waste (SB), mixed grape, poultry and municipal solid waste (GPM), and citrus pruning and industrial waste (CPI) were prepared at a rate of 1:10 (w/v) compound:distilled water. The basal media used in the proliferation phase were: (i) PM1, modified Murashige and Skoog (MS) enriched with 4.4 μM 6-benzyladenine (BA); (ii) PM2, as PM1 but with a reduced cytokinin concentration (1 μM BA) to evaluate possible hormone effects; and (iii) PM3, 4.4 μM BA with reduced salt strength (0.33 × MS) to induce nutrient deficiency. Hormone-free medium with half-strength MS salts was used for rooting. All media were enriched with each extract at 0, 0.2, 2, 20 or 200 ml l^-1. Photosynthetic activity was measured on PM3 medium enriched with SB or CM. Standard culture conditions were 22° ± 2°C, with a 16 h photoperiod at 30 μmoles photosynthetically active radiation (PAR) m^-2 s^-1, but at 80 μmoles PAR m^-2 s^-1 to determine photosynthetic activity. Shoot weight increase in PM1 was not affected by the GPM and CPI extracts, while the growth trends of CM- and SB-treated shoots were described by a second-degree function with maxima at 2 ml l^-1 and 0.2 ml l^-1, respectively. Shoot proliferation for SB was represented by a quadratic curve (maximum at 2 ml l^-1), was linearly reduced as GPM increased, but was not affected by CM or CPI. Treatments did not significantly affect rooting percentage and root length; however root number was increased by SB at 2 ml l^-1. CO₂ fixation increased linearly with both SB and CM, despite reduced growth at the highest levels of extract.

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