RESEARCH WORK

Effect of bioactive products combined with the microbial biopreparate Azotofos on the growth of Paspalum salam

Gertrudis Pentón ¹, Inés Reynaldo² , R. Medina¹ y G. Onono³

¹Estación Experimental de Pastos y Forrajes «Indio Hatuey» Central España Republicana, CP 44280, Matanzas, Cuba

E-mail: gertrudis.penton@indio.atenas.inf.cu

²Instituto Nacional de Ciencias Agrícolas, La Habana, Cuba

³Facultad de Agronomía, Universidad de Matanzas «Camilo Cienfuegos», Matanzas, Cuba

ABSTRACT

In order to evaluate the effect of bioactive products and their combination with Azotofos on the growth of Paspalum salam (Paspalum vaginatum Sw. cv. Salam), two trials were conducted. A randomized block design was used with three repetitions and the bioactive products Pectimorf® (based on pectins) and BIOBRAS-16® (based on brassinosteroids), and their combination with the microbial biopreparate Azotofos, which consists in a mixture on humic support of Pseudomonas sp. and Azotobacter chroococcum. In the first experiment six treatments were established from the bioactive products, the microbial biopreparate and their combination. The second trial consisted in testing different imbibition times of the propagules in Pectimorf®. A significant superiority was found 30 days after planting in the percentage of rooted cuttings in the treatments with BIOBRAS-16® and Pectimorf®, higher than 89%; while the control did not exceed 69%. The combination of Pectimorf® with Azotofos increased the percentage of rooted cuttings. Regarding the total cumulative biomass, the best result was obtained in the treatment with Pectimorf (0,84 g/individual). As to the imbibition time, the treatments hydrated control and non-hydrated one did not exceed 69% of rooted cuttings; significantly different from the imbibition time 60 min, which reached 100%. Pectimorf ® was concluded to be the best alternative to stimulate the growth of P. vaginatum cv. Salam. The results also indicated that the cuttings must remain imbibed in Pectimorf® for 60 minutes.

Key words: Biomass, Paspalum salam, rooting

INTRODUCTION

The Paspalum Linn. genus belongs to the family Gramineae, subfamily Panicoideae, and originated in tropical America. At present it is widely distributed throughout the American continent and in Australia. It adapts well to hot climates and includes species that are well developed on soils with low fertility and poor drainage (Martínez et al., 1986).

Paspalum vaginatum cv. Salam appears to be a promising drought- and salinity-resistant species (Hernández et al., 1998), which with an adequate irrigation regime can reduce up to 25% of the water consumption as compared to Bermuda grass and it also allows saving between 25 and 50% of the fertilizers (Duncan, 2006).

The reproduction is apomictic (Martínez et al., 1986); for which planting can be done by means of vegetative seed (through rhizomes and stolons) preferably in the spring months. However, its slow establishment and little precocious development force to look for options that guarantee higher competition in early stages, regarding the accompanying flora. Bioactive products and their combination with microbial biopreparates constitute an alternative, which is also environment-friendly.

It is known that when plants are inoculated with beneficial bacteria and fungi, which transform nitrogen and other macronutrients and micronutrients, a remarkable increase is produced in the nutrient absorption and translocation processes (Pulido et al., 2003). This causes higher growth, improvement of plant hydric indicators and induction of the root system development (Morte et al., 2001; Dell'Amico et al., 2002). Regarding bioactive products, Góngora et al. (2004) highlighted the inducing effects of the mechanisms of tolerance to salinity and drought stress, from the pretreatment to tomato and rice seeds with plant growth promoting substances, based on substances analogous to brassinosteroids or oligogalacturonids, and their interaction with micorrhyzal fungi. Other authors have referred to Fitomas-E®, BIOBRAS-16® and EnerPlant®, as successful biostimulators. Yet, at present Quitosana and Pectimorf® are also used.

The use of microbial biopreparates is particularly successful in the Paspalum genus. Its capacity to associate to nitrogen fixing-transforming and phosphorus solubilizing soil microorganisms is known. Benzion and Quesenberry (cited by Martínez et al., 1986) inoculated several genotypes of P. notatum with Azospirillum brasilensi JM 125 A2 and found them to increase their dry weight from 18 to 22,9% and just one diploid was the only genotype which decreased its dry weight. Pereira (cited by Martínez et al., 1986) referred to the effectiveness of the association of P. notatum with Azotobacter paspali.

The objective of this work was to evaluate the effect of two bioactive products and their combination with a biopreparate based on Pseudomonas sp. and Azotobacter chroococcum on the initial growth of Paspalum salam (P. vaginatum Sw. cv. Salam).

MATERIALS AND METHODS

The trials were conducted at the Experimental Station «Indio Hatuey» located between 22º 48' 7" latitude north and 81º 2' longitude west, at 19,01 masl, in Matanzas province, Cuba. The experimental period was 30 days, and it was framed within February and March, 2009.
Total rainfall was relatively low (table 1), which is in correspondence with the mean of the period belonging to the first months of the year; this season being acknowledged as the most dried in Cuba.

The evaluated species was P. vaginatum cv. Salam. The vegetative material was obtained from a basic seed bank. The cuttings were selected from the mid zone of the plants, with a length of 15 cm and four buds or more.

Planting was made in polystyrene trays, divided into 144-cm3 cubbyholes; they remained exposed to open air throughout the experimental period. The substratum used consisted in a mixture of sandy soil, extracted from the Varadero golf course (Cuba), and organic matter from earthworm humus, in 2:1 ratio. Irrigation was applied every two days.

All the products were applied at the moment of planting. They consisted in:
• Pectimorf®, based on pectins, obtained at the Laboratory of Plant Physiology and Biochemistry of the National Institute of Agricultural Sciences (Havana, Cuba). It was applied at a rate of 10 mg/L, by the method of propagule immersion.
• BIOBRAS-16®, based on brassinosteroids, produced by the School of Chemistry of the University of Havana (Cuba). It was applied by the method of propagule immersion.
• Azotofos, a microbial preparate consisting in a mixture on humic support of Pseudomonas sp. and A. chroococcum. It was applied at a rate of 10 mg/L, by the immersion method.

Experiment 1. Effect of bioactive products and their combination with Azotofos.
The treatments were the following:
• Control hydrated for 30 minutes in clear water.
• Azotofos
• Azotofos + Pectimorf®
• Azotofos +BIOBRAS-16®
• Pectimorf®
• BIOBRAS-16®

The following measurements were made:
1. Percentage of rooted cuttings (%).
2. Total biomass weight (g/individual).

Experiment 2. Effect of imbibition time in Pectimorf®.
The treatments were the following:
• Control without hydration before planting.
• Control hydrated for 120 minutes in clear water.
• Imbibition for 30 minutes in Pectimorf.
• Imbibition for 60 minutes in Pectimorf.
• Imbibition for 90 minutes in Pectimorf.
• Imbibition for 120 minutes in Pectimorf.

The following measurements were made:
3. Percentage of rooted cuttings (%).
4. Maximum root length (cm).
5. Root biomass weight (g).

Mathematical analysis and design
In both experiments a randomized block design with three repetitions was used. The statistical pack used was Infostat, free version, through the ANOVA model and Duncan's comparison test. In the first experiment a multifactorial analysis was used; where the variation factors were the bioactive products and microbial preparates. In the second experiment, the variation factor was the imbibition time, for which a simple analysis was made.

RESULTS AND DISCUSSION

Table 2 shows the effect of Azotofos, Pectimorf® and BIOBRAS-16®, and their combinations. The combination of Pectimorf® with the microbial preparate meant a sensible analysis of the percentage of rooted cuttings, as compared to the control and each product separately. This corroborates the remarkable effect of the combination of Azotofos, which higher impact was shown in growth stimulation. Pectimorf® acted mainly on root development. BIOBRAS-16® and its combination with Azotofos produced a high percentage of rooted cuttings; which is accounted for by the significant influence of brassinosteroids on cell growth and the growth promoting bacteria present in the biopreparate, which in addition to facilitating the access of roots to mineral elements, exudates low molecular weight substances utilizable by the plant. All this leads to an increase of propagule vigor (Noriega, 2009).

Regarding total biomass the best result was obtained in the treatments with Pectimorf; which is justified by pectins being a majority component of the cell wall of plant organisms, where they act as some kind of cell cement which joins, through hemicelluloses, cellulose microfibrils, and contribute to their strength (Naranjo, 2005). These oligosaccharins are signaling molecules derived from the polysaccharides which compose the cell wall of plants and have in their constitution auxinic and cytoquininic elements similar to those of artificial growth regulators. They have been used in many crops with excellent results, similar to the ones obtained with BIOBRAS-16® (Jomarrón et al., 2000).

The combination of Azotofos with bioactive products and BIOBRAS-16® did not exceed the totals reached by the control.
Figures 1 and 2 show the effect of different imbibition times of the propagules in Pectimorf®, as compared to the untreated control. It can be observed that the treatments hydrated control and non-hydrated control had the lowest rooting values (59,5 and 69,8% of rooted cuttings) and differed significantly from the imbibition time of 60 minutes in Pectimorf®, which reached 100%. The highest values of maximum root length were reached in times 30, 60 and 120 minutes, in contrast with untreated controls.

Taking into consideration the suggestions made by Inés Reynaldo (personal communication) about the imbibition times from 15 to 30 minutes for vegetable seedlings, and between three and four hours for cucumber and okra seeds, the best result in this work with the imbibition time of 60 minutes indicates that the optimum volume of active substance that was spread inside the cells and its effect on the induction of the processes linked to rooting depend on the plant species and the propagation material.

Regarding the cumulative production of root green biomass (fig. 3), the 60-minute treatment had a significantly higher effect and there was a decrease from 90 minutes. The 90-minute treatment coincided with the worst response, which must be object of future research in order to further study the functioning of the bioactive product. The positive effect of Pectimorf® on the concentration and the adequate imbibition time, according to the specific crop, is determined by the action the product exerts on the physiological processes of cell enlargement and differentiation. According to González et al. (2002), the effect of this product on organogenesis is the most sensitive of all the studied ones, which confirms that it can regulate such a fundamental process for plant development, as organ formation.

According to Terrero (2010), in order to obtain a satisfactory response to Pectimorf between 5 and 20 mg of Pectimorf® are mixed in a liter of water, similar range as the one used for traditional hormones when expressed in units of molar concentrations. In this study the concentration was 10 mg, for which it is considered important to conduct tests with different concentrations to enhance the effect of the product, which offers, among its additional advantages, its solubility in aqueous medium (used to prepare culture media) and its stability under the conditions used to sterilize media (Terrero, 2010).

Acording this author, Pectimorf® (byproduct of the citrus fruit industry) has low cost and is available in the Cuban market, for which it constitutes an alternative in the substitution of traditional growth regulators. Núñez et al. (1996) proved that the oligosaccharin induces rooting and plant growth, and it also improves the soy-Bradyrhizobium symbiosis.

CONCLUSION

Pectimorf® is concluded to be the best alternative to stimulate the initial growth of P. vaginatum cv. Salam. The results also indicated that the cuttings should be kept imbibed in Pectimorf® during 60 minutes before planting.