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Substrates on the cuttings rooting of black pepper genotypes

The soil in the production of clonal seedlings of black pepper (Piper nigrum L.) contributes to fusarium and nematodes infestation in commercial crops, and thus the usage of alternative substrates might be a preventive control measure against these pathogens. The aim of this study was to investigate the rhizogenic behavior of the cultivars Bragantina, Iaçará and Guajarina of black pepper in different substrates. The experimental design was in randomized blocks in a 3x4 factorial design (cultivars: Bragantina, Iaçará and Guajarina x substrates: soil + organic compound (18%), vermiculite, carbonized rice hulls and commercial substrate), with four replications of 16 cuttings each. The evaluated characteristics were: survival (%); rooting (basal or nodal) (%); nodal rooting (%); basal rooting (%); number of nodal roots; number of basal roots; total number of roots; length of the largest nodal root (cm); basal root length (cm); nodal root volume (cm3); basal root volume (cm3); Total root volume (cm3); nodal root dry mass (mg); basal root dry mass (mg) and the total root dry mass (mg). There are differences within black pepper cultivars as to the characteristics related to the root system. The vermiculite substrate was the most suitable, and carbonized rice hull is not recommended for the adventitious rooting of cuttings of cultivars Bragantina, Iaçará and Guajarina.


Introduction
Different biological activities are attributed to the black pepper (Piper nigrum L.), belonging to the Piperaceae family. In Brazil, this species presents several utilities, being a widely consumed spice; however, the tropical climate of the country favors the development of fungi of the type Aspergillus spp. which produce mycotoxins detected on the grain, such as the aflatoxin B 1 , causing a great problem for being a powerful hepatocarcinogen described in mammals, and is classified in the Group 1 (carcinogenic to humans) by the International Agency of Research on Cancer (Prado et al., 2008). Other utilities are attributed to the black pepper, such as being a larvicide to the Aedes aegypti, of great importance for public health (Simas et al., 2007) and presents yet antibacterial property from its essence oil over food contaminants, in substitution to chemical additives (Trajano et al., 2009).  (Serrano et al., 2012;Secundino et al., 2014), where the quality of the root system, such as number, volume and root dry mass is fundamental in the survival and acceptability of the seedling in the field.
The employment of alternative substrates in the production of clonal seedlings of black pepper might be a preventive measure in the control of fusariosis and nematosis. These substrates might also help to increase the quality of the seedling, by proportionating, for example, higher number and, consequently, higher volume of roots. The production of quality seedlings is also related with the choice of adequate substrates, such as the propagule source, propagation method, growth regulators, containers, irrigation systems and nursery ambience.
It was aimed with this work to analyze the rooting of black pepper cultivars cuttings in different substrates.

Material and Methods
The work was conducted in the Centro After the preparing of the cuttings, they had their stem immersed until the insertion of the leaf, with exception of the leaf, in talcum with the concentration of 4000 mg kg -1 of indol-3-butyric acid (IBA) (Secundino et al., 2014).

Results and Discussion
In the present work there was significant interaction between the factors cultivars and substrates for the variables nodal rooting, rooting, number of nodal roots and root volume (  In the mixture soil + organic compound, comparing with the remaining studied substrates, it was verified that in spite of the best results of P, K, Mg, Ca, Ca + Mg, Zn, Mn, B and CTC, the highest density and lowest total porosity were observed with the highest distribution rate of particles in the smaller particle size <0,25 mm (37.01%) and in the particle size from 0.25 to 0.5 mm (22.49%) ( Table   1).
Nevertheless, in the present study, the basal rooting was higher (62.25%) with the cv.
Iaçará, followed by the cv. Guajarina (52.83%), independently of the substrate utilized (Table 3). As to the quality of the root system in the vermiculite substrate, the characteristics number and volume of nodal root were higher in the cv. Iaçará.This cultivar, in the vermiculite substrate, produced an average of 12.59 roots, that is, approximately six roots more than the cv. Guajarina and eight roots more than the cv.

Bragantina (Table 2). Cuttings of Piper mikanianum
Kunth Stend var. mikanianum presented higher number of roots in the vermiculite substrate, due to the good water retention and optimum space of air in the retention capacity, factors which turn possible the maintaining of an adequate supply of water for the rooting of the cuttings (Pescador et al., 2007).
The cv. Iaçará, independently of the substrate, also presented higher total root number, nodal and total root dry matter mass (Table 3) Iaçará and Cingapura.
Independently of the cultivar, the vermiculite was superior to the remaining substrates in increasing the characteristics basal rooting, basal and total root number and length of the bigger total and basal root (Table 4).
Regarding the length of the largest nodal root, total and basal root volume, total, nodal and basal dry mass, the vermiculite did not statistically differ from the commercial substrate (Table 4). Oliveira et al. (2009)  In the present work, the vermiculite and the commercial substrate were the ones which presented the highest total porosity (Table 1), what considerably contributed to the emission and growth of the root system. Dutra et al. (2012), also verified high porosity and low apparent density for the commercial substrate.
The vermiculite substrate presents low density (Table 1), which summed to its high porosity contributed to rate it as one of the best substrates, among those studied, concerning The commercial substrate also presents as an important characteristic a good composition of M.O., which might likely be a source humic substances directly related with root formation.
Sharangi & Kumar (2011)  The carbonized rice hull also resulted in cuttings with inferior results of basal root dry mass, not differing of the vermiculite substrate (Table 4).
The carbonized rice hull is a substrate which presented, as to its chemical characteristics the lowest CTC (2.4 cmol) ( Table 1) and was also the substrate which presented the lowest total porosity (41.81%) (Table 1).

Conclusions
The vermiculite is the most indicated substrate, and the mixture soil + organic compound is not recommended for the rooting of