Applicazione di miscele fertilizzanti composte da funghi micorrizici arbuscolari e concimi organici, di substrati innovativi e di tecniche di rigenerazione in vitro per l’ottenimento di una produzione di piante di pelargonio di qualità
Author(s)
Tullio, Monica
Date Issued
March 19, 2010
Type
Doctoral Thesis
Abstract
Floricolture is a discipline of horticulture concerned with the cultivation of flowering and
ornamental plants for gardens and for floristry, comprising floral industry. In Italy, is a productive division of the economy and it is fundamental for the image and for the diffusion of the made in Italy (D’Andrea, 2005).
During the last decade, there is the need to introduce to the consumers a high quality plants with the respect to the environment. In Europe and North America, most pot-grown ornamental plants are produced and sold in peat-based substrates. In conventional production systems, these substrates are usually supplemented with soluble fertilizers to achieve optimal supply of nutrients such as nitrogen and phosphorous. The “sustainable floriculture” discourages the use of synthetic chemical fertilizers and the use of peat is viewed critically because peat is a limited natural resource (Joosten and
Clarke, 2002). This generates problems for horticultural producers because high quality ornamental plants require substrates with high nutrient availability during a short growth period for an optimal development. So, two are the critical factors in the commercial flowering ornamental plants: the choices of the growing substrate and the fertilization method (Perner et al., 2007).
The research, performed within this phD course, had the goal to improve the pelargonium yield,
given a high quality plants with ecological growing tecniques. Pelargonium is one of the world’s most important bedding and pot plants. Recent figures show that the annual sales in Europe and North America are worth in excess of US$ 700 million annually. They are marketed as source of economically important geranium essential oil, too (Mithila et al., 2001).
Trials were carried out to test fertilizer mixtures (mycorrhizae and guano) and compost-peat based substrates for the increasing quality of pelargonium plants in a sustainable management system; on the first year, two fertilizer mixtures and the single constituents of the mixtures were administrated to the growing substrate. Afterwards, during the second year, the optimal dose of the fungal inoculum was identified in order to reduce the growing costs. Finally, on the third year, compostpeat
substrates, with or without the fertilizer mixture, were tested. Many pelargonium species were used (P. hortorum cv “Real polaris” and cv “Real sirius”; Pelargonium crispum- cv “pac angeleyes burgundi”; Pelargonium grandiflorum- cv “Lotus”). Experiments were conducted in a 18.000 m2 robot greenhouse (Albani and Ruggeri nursery) situated in Civitavecchia (Rm), central Italy and the analyses were performed in the labs of the ARC, Agricultural Research Council- Research Centre for the Soil-Plant System.
In this research, micropropagation method was applied such as an alternative technique for the
agamic propagation of pelargonium species. Little information is available on organogenesis and
plant regeneration of pelargonium using mature explants. Most available studies on plant
regeneration from P. x hortorum were achieved using very young explants such as hypocotyls or
cotyledons (Hassanein e Dorion, 2005). On the second year of the phD course, an efficient plant
regeneration protocol using mature pelargonium explants was carried out. Afterwards, during the
third year, bioreactors for pelargonium explants propagation were tested in order to improve the
regenerative efficiency and to reduce the culture time. Root mycorrhization technique in
pelargonium micropropagated plants, at the beginning of the acclimation phase, was tested for an increasing of the survival ability. The used pelargonium species, in these trials, were Pelargonium lemon fancy, Pelargonium tomentosum; Pelargonium crispum cv Minor and cv Pac angeleyes
burgundi; Pelargonium grandiflorum cv Lotus. The micropropagation trials were conducted in the
labs of the “La Tuscia” University of Viterbo, department GEMINI, in the labs of ENEA- Research
Centre CASACCIA and the analyses were performed in the labs of the ARC, Agricultural Research
Council- Research Centre for the Soil-Plant System.
The administration of the fertilizer mixture with 7,5 l/ m3 of fungal inoculum to the growing
substrate allowed to obtain pelargonium plants with better quality parameters such as fresh and dry shoot weight, leaf area, leaves number/plant, shoot height and chlorophyll content than those
obtained with the standard growing technique or with the administration of the single constituent of the mixture to the growing substrate. The lowered amount of the inoculum in the mixture
determines a positive outcome on the costs of the pelargonium growing, too. The positive effect of
this mixture on the plant quality remained with the use of a 20% compost-peat growing substrate.
The obtained plants showed better qualitative features and they had an high branching value than
the other ones, too. This parameter, in this growth stage (two months from the cutting transplant), is the only one which can influence the selling price. The root colonization from the arbuscular fungi was increased by guano since this parameter, in the plants grown with the fertilizer mixtures, was 1,4% higher than those grown with the fungal inoculum only. The administration of half dose of the
inoculum allowed to reach the same rate of root colonization obtained with the administration of the entire dose. The presence of compost in the growing substrate didn’t influence the mycorrhizal
symbiosis. In fact, pelargonium root system, after two months from the inoculation, were well
colonized (50% of root colonization). The behaviour of the pelargonium to the treatments was
different in relation to the considered species. Pelargonium x hortorum cv “Real polaris” answered
positively with high quality plants. The Pelargonium crispum cv “Pac angeleyes burgundi”
behaviour to the fertilizer mixtures can be explained with the lower root colonization rate than the P. x hortorum one. Besides, this species is a late species with a weak growth. The little size of the root systems of Pelargonium grandiflorum “Lotus” could be the reason of the lack of the effect of the treatments on the quality of the obtained plants. The growing tecnique of the potted pelargonium
which uses fertilizer mixtures (arbuscular mycorrhizae and guano) and a 20 % compost-peat
growing substrate, on the basis of the results obtained during the three years of the testing, can be used for obtaining high quality floricultural products in a sustainable management system.
The in vitro multiplication protocol which uses pelargonium mature explants allowed to obtained
high quality plantlets. This is an effective protocol and it can be considered an alternative technique for the agamic propagation of pelargonium species with cutting rooting difficulty. The use of bioreactors in the pelargonium micropropagation determined greater yield of multiplied plants in a
short time. The plantlets were more homogeneous for the shoot height and they had better quality
parameters at the beginning of the acclimation phase than the other obtained with the in vitro
standard techniques. It can involve important economic outcome in perfumery and in
pharmaceutical industry which use essential oils of these plants.
The mycorrhizal symbiosis with the arbuscular fungi was an efficient biotechnological tool in order to improve the qualitative parameters of the pelargonium plants. It influenced positively the survival of the micropropagated plants, during the acclimatation phase, assuring an improving of the yield, too. This positive effect was observed after 30 days from the inoculation and it remained in the next period, too.
Additional information
Dottorato di ricerca in Ortoflorofrutticoltura
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