Colour Index

Data in Table 3 show for this characteristic a mean value above sufficiency and equal to 6.2.

From May to September 2013, ecotypes 1, 3 and 15 showed higher values; on average this index was equal to 6.5. In contrast accessions that showed the lowest value, equal to 6, were accessions 12, 16 and 17. These results are similar to those obtained in other researches who studied 40 accessions of native C. dactylon collected in Sicily (Southern Italy) in order to identify biotypes with good qualities for broadscale turf in the Mediterranean region (Leto et al. 2008).

Table 5 Ground cover percentage of ecotypes during the trial period (2013)

Values not having any letter in common are significantly different at P :s 0.05 (Duncan's test)

Turf Quality

During the entire period of experimentation, ecotypes that showed the highest mean values were 3, 13 and 14, respectively, with 6.7 to 6.1 and 5.9; they also showed a good preservation of quality from May 2013 to September 2013. Accessions 12 and 16 were ranked at the lowest level, with values respectively equal to 3.3 and 4.4. These extremely low values were due partly to the genotypic characteristics of accession and to a considerable extent of phytoplasma BGWL attacks, which have widely affected the aesthetic quality of ecotypes. The lower values of these ecotypes have strongly influenced the mean of turf quality during the whole period and also for single months.

Table 6 Results of salinity measurements

Green Cover Percentage

The coverage percentage showed a mean value generally equal to 67 %, in accordance with the findings of Volterrani et al. (1997) and Croce et al. (2001) in other Italian sites. Among the ecotypes compared, the one which showed the highest mean value was ecotype 3 (87 %); satisfactory values were also reported for accessions 13 and 1, with mean values equal to 84 and 77 %.

The lowest value was reached by genotype 12 (22 %). This anomalous value is partly imputable to the massive attack of BGWL, which continued during the entire period of the research.

The results of the experimental salinity carried out in 2013, of the 24 native ecotypes of C. dactylon, are shown in Table 6.

The salinity conditions have always had a depressing effect on all measured parameters (leaf area, dry weight, dry weight of roots, root/shoot ratio, etc.) as widely shown in Table 7.

Leaf area on average reduced to 296 cm2 from 824 cm2, while dry weight on average reduced to 4.5 from 8.1 g plant-1. The significant effect of salinity conditions on all studied accessions and significant difference between accessions as regards the ability to support salts into the nutrient solutions were observed. The interaction effect on leaf area parameter was also significant. Root/shoot ratio on average increased as the effect of salinity conditions, as expected. It increased on average to 0.55 g g-1 from 0.33 g g-1. On this parameter only salinity resulted in a significant effect. The dry weight percentage reduction of all studied accessions was also calculated.

3.4.1 Uptake of Na+ and Cl-

There was no significant difference between accessions as regards Cluptake. As regards Na+ leaf tissue concentration on average, it has increased respect to control, 12.0 mg g-1 and 1.2 mg g-1, respectively. It was also observed that the ability to limit the accumulation of sodium ions into leaf tissue varies between the different compared accessions.

The dendrogram which is obtained from the cluster analysis is a graphical representation of the level of aggregation among the studied accessions (Fig. 4). It clearly shows that the group of accessions on the left is well separated from other groups in the right. The samples on the left showed a greater resistance to salinity. In particular accession 3 is the best ecotype about salinity stress. This ecotype could be considered in future research programmes.

Table 7 Depressing effect of salinity on all measured parameters

Samples 1–24n_s ¼ samples without salt; Samples 1–24 s ¼ samples with salt; Measured parameters: LA leaf area, FW fresh weight, DW dry weight, RDW

root dry weight, R/S root/shoot ratio, l_f leaf length, L_f leaf width, l_i distance between internodes, [Na+] leaf tissue concentration, [Cl-] leaf tissue

Fig. 4 Tree based on the relationship between morphometric data, aesthetic, chemical and salt stress among 24 autochthonous Bermuda grass ecotypes with Ward's method and Euclidean linkage. Note: Samples 1–24n_s ¼ samples without salt; Samples 1–24 s ¼ samples with salt. Measured parameters: LA leaf area, FW fresh weight, DW dry weight, RDW root dry weight, R/S root/shoot, l_f leaf length, L_f leaf width, l_i distance between internodes, [Na+], [Cl-]