Proposal for commercial classification of the gerbera capitulum based in the flower overlap index

The aim of this work was to propose a methodology for commercial classification of gerbera ́s capitulum based on the trans flowers overlap coefficient. Three to eight capitula of twenty-eight cultivars of gerbera cut flower and seven non-commercial accesses were used. The width measurement of the trans flowers group (internal ray flower) as well as the sum of the width of the trans and ray flowers (external ray flower) groups were taken from each capitulum. The average of each access and the overlap coefficient were calculated (CS = width of the trans flowers group / Σ of the width of the trans and ray flowers groups) and submitted to the multivariate analysis, to verify the grouping by the average Euclidian distance matrix. It is proposed that gerberas with CS= 0.01 to 0.15 be classified as simple, CS= 0.16 to 0.40 as semi-double and CS superior to 0.41 as double. The overlap coefficient (CS) can be used to systematize the classification of the gerbera capitula, reducing the divergences in the classification and the subjectivity in the decisions of producers, florists and breeders.


Proposta para classificação comercial dos capítulos de gérbera com base no coeficiente de sobreposição das flores
Objetivou-se neste trabalho propor uma metodologia para classificação comercial dos capítulos de gérbera com base no coeficiente de sobreposição das flores trans. Foram utilizados três a oito capítulos de vinte e oito cultivares de gérbera com aptidão para corte e sete acessos não comerciais. Em cada um dos capítulos realizou-se a medição da largura do conjunto das flores trans (flores do raio interno) e a soma da largura do conjunto das flores trans e do raio (flores do raio externo). Com isso, calcularam-se os coeficientes de sobreposição das flores trans (CS= largura do conjunto das flores trans / Σ da largura do conjunto das flores trans e do raio) e submeteram-se os dados à análise multivariada, com a finalidade de verificar o agrupamento mediante matriz de distância euclidiana média. Propõe-se que gérberas com CS= 0,01 a 0,15 sejam classificadas como simples, CS= 0,16 a 0,40, semidobradas e CS superior a 0,41, dobradas. O coeficiente de sobreposição pode ser utilizado para sistematizar a classificação dos capítulos de gérbera, reduzindo as divergências e a subjetividade nas decisões de produtores, floricultores e melhoristas. is formed by many flowers called floscules, which lye in a common receptacle, surrounded by involucral bracts (phyllaries) organized in one or more series (Barroso, 1991). The gerbera capitulum is a highly organized structure, formed by different kinds of flowers: ray flowers (flowers from the external ray), trans flowers (flowers from the internal ray) and the disc flowers. The ray flowers are female and the disc flowers are hermaphrodites, which can be grouped in fertile hermaphrodites and functionally male flowers. The trans flowers present pistils, whose anthers are absent or poorly developed and presents corolla with ligule and two lips; the superior lip presents intermediate length among the disc and the ray flowers lip lengths. Botanically, the gerbera capitulum is classified as actinomorphic, which means it presents radial symmetry (Cabrera & Klein, 1973;Barroso, 1991;Yu et al., 1999;Elomaa & Teeri, 2001 1990), a double capitulum is the one which presents more than one row of ray flowers. It demonstrates the divergence and the difficulty in the definition of a gerbera classification towards the capitulum type for commercial finality.

MATERIAL AND METHODS
Plants were grown in a semi-protected environment, which was constituted by an impermeable cover (low-density 0.15 mm thick turbid polyethylene film) surrounded by a 50% shadowed with retractile transparent plastic drapery, which allowed the transmittance of 30% of the solar global radiation. Plants were grown on polyethylene contents filled with 5 litters of the commercial substrate Rendimax Floreira (turf + bentonite) mixed at the same proportion to carbonized rice husk, which presented the following characteristics: density: 345 g L -1 ; porosity: 70%; pH = 6.4; electric conductivity: 0,66 mS. Plants were manually irrigated whenever it was necessary. Liquid fertilizers were applied once a week and two solutions (A or B) were applied on each week. Solution A was constituted by 0.8 g L -1 calcium nitrate, 0.4 g L -1 ammonium nitrate, 0.01 g L -1 "tenso ferro" and 0.001 g L -1 borax. Solution B was composed by 0.7 g L -1 potassium nitrate, 0.6 g L -1 magnesium sulphate, 0.15 g L -1 MAP and 0.01 g L -1 of "tenso cocktail" (Guiseline, 2002).
Three to eight capitula of each accession were evaluated at the moment they reached the commercial stadium, which was considered when two of the disc flower rows were opened. In each of the capitula the width of the trans flowers set was measured (LFT) and the sum of the LFT and the ray (LT) (Figure 1) was calculated. Then, the overlap coefficient (CS) was obtained by the ratio LFT/LT. The parameters were submitted to the multivariate analysis by the average Euclidian distance estimative (DEM) and, after, to the generation of a dendrogram by the complete ligation method. Statistical analyses were performed by Genes program (Cruz, 2001).

RESULTS AND DISCUSSION
The obtained overlap coefficients varied from 0.03 to 0.64, which indicated difference among the capitula in relation to the trans flowers overlap. When the classification criteria of the Brazilian Ministry of Agriculture, Livestock Proposal for commercial classification of the gerbera capitulum based in the flower overlap index  (2007)). Passo Fundo, UPF, 2008. andFood Supply (MAPA, 2007) and the classification criteria based on the overlap coefficient were compared, the results matched highly (80.5%) in the types of capitula. It indicated the similarity among results and the possibility of adoption of an objective criterion based on linear measures for the cultivars description.
Through the grouping analysis (Figure 2), the formation of three groups was verified. The group 1 was formed only by the accessions which presented capitula with CS ranging from 0.03 to 0.09; the second grouped capitula whose CS ranged from 0.16 to 0.34; and the third, from 0.41 to 0.60. The most divergent accessions were 'Tonga' (simple capitulum) and 'Junk Frau' (double capitulum) (DEM= 2.95) and the most similar ones were 'Orca' and 'Cosmo Dino' (DEM= 0.0). For the most divergent accessions, the CS ranged from 0.03 cm ('Orca') to 0.64 cm ('Junk Frau'). Hence, it is proposed here to classify as simple capitula the ones with CS between 0.01 and 0.14; as semidouble capitula when CS is between 0.15 and 0.35 and as double capitula the ones whose CS is equal or superior to 0.36 (Figure 2). The capitulum classification criterion based on the trans flowers overlap coefficient, which is proposed by this paper, might support the current gerberas capitula classification models, which are subjective and contradictive. Some authors consider as double capitula the ones which present a widened trans flowers row (Kloss et al., 2004), without differentiation among the semi-double and double capitula, since all of them present a widened trans flowers set. However, the widthbased criterion to classify a capitulum as double is not exact. For Rogers & Tija (1990), gerbera with a single row of radian flowers are considered as simple flowers and the ones with more than one line are considered double. Nevertheless, this criterion does not match the classification which is carried out by growers, who classify gerbera as simple, semi-double and double. Moreover, if that first method of classification were used, then possibly all the cultivars would be classified as double, since there are many cultivars classified as simple even though they Table 1. Gerbera accessions, overlap coefficient, classification of the gerbera capitula by subjective criterion (MAPA) and by the overlap coefficient (CS) (acessos de gérbera, coeficiente de sobreposição e classificação dos capítulos pelo critério subjetivo (MAPA) e pelo coeficiente de sobreposição (CS)). Passo Fundo, UPF, 2008.
Commercial classification of gerbera capitula: S = simple capitulum; SD = semi-double capitilum and D = double capitulum. Controversies in the gerbera capitula classification among the current and the proposed criteria are enhanced by gray (classificação comercial dos capítulos de gérbera: S = capítulo simples; SD = capítulo semidobrado e D = capítulo dobrado. Em destaque, sombreado, controvérsias na classificação dos capítulos de gérbera utilizando os critérios atuais e o proposto).  (MAPA, 2007). The greatest divergences occurred in semi-double capitulum flowers (Table 1), which can also be noticed in the dendrogram. In the dendrogram, difficulties in establishing groups can be noticed when CS are superior to 0.15. The Orange cultivar, classified by the MAPA (2007) methodology as simple, would be classified as semi-double by the overlap coefficient method (0.16). The A7 accession, classified by the MAPA (2007) methodology as semi-double, did not present a CS value high enough to match this classification (CS= 0.06) and was classified as simple. The Pink Elegance cultivar presents divergences in its commercial classification and is controversially recognized by growers as a double or as a semi-double flower. By the overlap coefficient method, its CS value (0.32) would classify it as a semi-double flower. The Eyecatha cultivar presented CS= 0.46 and would