Prediction of Germination Percentage Through Electrical Conductivity in White and Coloured Coated French Bean (Phaseolus vulgaris L.)

This study was conducted in the Seed Science and Technology Laboratory of the Department of Horticulture, Faculty of Agriculture, Ankara University, Ankara during the period from October to December 2021. Nine different white coated (Phaseolus vulgaris L. cvs Ribera, Barcino, Efsun, Anemon, Voltran, Alala, Allegra, Bond, Gaudi) and nine coloured coated (cvs. Balca, Senem, Taylor, Balkiz, Garrafal Enana, Pedro, Serapis, Vermando, Roland) registered French bean cultivars were obtained from different seed companies. All samples were kept at 4°C before use. Initial seed moisture content was determined by using the high-temperature oven method (ISTA, 2022). Seeds were kept at 100% relative humidity over a night (16 h) before the germination test to avoid imbibitional injury. Seeds with cracks on the seed coat were eliminated from the lots. A germination test was conducted on three replicates of 50 seeds in between wet towel papers for 8 days at 25°C (ISTA, 2022) in the dark. Towel papers were placed in plastic bags and placed into the incubator. Total (2 mm radicle emergence) and normal (well-developed seedlings) germination percentages were evaluated after 8 days. Electrical conductivity of leachate measurements was done on two replicates of 10 weighed (0.001 g) seeds of each lot in 50 ml distilled water after 2, 4, 6 and 8 hours of soaking at 20°C in dark. Utilizing a conductivity meter, the electrical conductivity of the leachates from each replication was determined (Type CG 855). The results were expressed as µScm^-1g^-1 to evaluate the variability in seed weight among French bean cultivars. Significant differences between experimental groups were assessed with one-way ANOVA, using the package for Social Sciences (IBM SPSS 21 package program) statistical program. Determination of coefficient (R²) values were determined to assess the relation between EC and total and normal germination.

Seed moisture content was changed between 13.0 and 15.7% in white, 13.1 and 14.7% in coloured cultivars. Changes in total and normal germination percentages and EC readings after 2, 4, 6 and 8 h were given in Table 1. Germination percentages and EC readings among the lots were changed significantly (P<0.05). Total germination percentages were above 93% in both white and coloured cultivars. Normal germination percentages ranged between 43 and 99% in white, 55 and 81% in coloured cultivars (Table 1). EC readings (µScm^-1 g^-1) were found to in between 28.4 and 73.5 after 2 h, 39.1 and 86.5 after 4 h, 44.0 and 95.8 after 6 h, 62.3 and 112.4 after 8 h in white cultivars. In coloured cultivars, EC readings were lower than those of white cultivars and ranged between 9.7 and 42.8 after 2 h, 19.8 and 52.8 after 4 h, 26.6 and 61.3 after 6 h, 31.8 and 69.2 after 8 h. Solute leakage was gradually increased as soaking time is extended in all seed lots. Lot 9 in white and lot 1 in coloured ones had lost the lowest amount of leakage but lot 6 in white and lot 7 had lost the maximum amount of solute leakage in coloured cultivars (Table 1). This was the same in all different EC reading hours.
 

 
There were close relationships between EC readings of seed lots and the percentages of total and normal germination percentages of white and coloured seed lots after all four EC reading hours (Fig 1 and 2). Significances in between EC readings and total germination ranged between R²= 0.728- 0.814, P<0.005-0.001 in white, R²=0.717-0.830 P<0.05-0.01 in coloured cultivars (Fig 1). Significances in between normal germination and EC readings ranged between 0.762 and 0.897 (P<0.05-0.01) in white and 0.800 and 0.848 (P<0.01) in coloured cultivars.
 

 

 
The high and significant correlation between EC values and germination percentages of total and normal seedlings suggests that conductivity readings can be an alternative to the germination test which requires 8 days in bean. Information about germination levels of commercial bean cultivars can be obtained within as short as two hours. Our results are in agreement with the prediction of germination by bulk conductivity in artificially aged cabbage and cauliflower (Mirdad et al., 2006; Demir et al., 2008), leek (Demir et al., 2012) and cress (Ozden et al., 2017) seeds. They concluded that seed ageing results in the loss of cell membrane integrity inducing an increase in solute leakage and reduced germination percentages. Khajeh Hosseini et al., (2010) reported that EC averages of single oilseed rapeseed at 24 hours of soaking were 4.9 µS cm^-1 g^-1 in seeds which produced normal seedlings. In legumes and maize seeds, results confirmed that EC of single seed leachate can be taken as a physiological index of seed germination (Steere et al., 1981; Davidson et al., 1994). Obviously, different seed weights may result in different leakage measurements. Weighing seeds prior to EC assessment and referring this measure to seed weight expressed in grams is a generally accepted experimental procedure (Hepburn et al., 1984). White French bean cultivars resulted in higher electrolyte leakage than those of coloured ones which are in agreement with earlier findings in this crop (Powell et al., 1986; Demir, 1996).

In conclusion, the EC test has a quick, cheap and simple method of detecting the germination potential of bean seed cultivars with various germination. This method may help the seed industry to decide the renewal time of seed lots during storage. EC assessment may be also used as a routine test in checking the germination quality of unsold seeds produced in previous years before marketing.

The author expresses gratitude to Turkish and Global Seed Companies for providing seed samples of French bean varieties as well as to Prof. Dr. Ýbrahim Demir, Ankara University, Faculty of Agriculture, Department of Horticulture, for enabling the use of his laboratory in this work.

None.