Proceedings Volume 2010 (format .pdf) - SimpBTH

etween SD and LD response of the same genotype was tested using t-test forindependent samples. Percentage data were subjected to angular transformation andSE number data to square root transformation before analysis and inverselytransformed for presentation. The results were expressed as the frequency of rootsections regenerating SE and the mean number of SE per regenerating root sectionduring 12-week period. An index of somatic embryo-forming capacity (EFC) wasused to evaluate cumulative effect of both the mean SE number and frequency ofregeneration, and it was calculated as follows: EFC = (mean number of SE perregenerating section) x (% of regenerating sections) / 100.3. RESULTS AND DISCUSSIONSeedling's root sections cultivated on both photoperiods began to proliferateafter a week of culture, and first differences were observed at the end of the firstsubculture. SE appeared only from roots of genotype 110 exposed to LD. Theregeneration of this genotype was delayed in SD for 2-3 weeks. During the secondsubculture 23 new genotypes regenerated, and 12 of these regenerated only in LD.Finally, two genotypes regenerated in the third subculture in LD only, and fourgenotypes were irresponsive. By the end of the experiment, out of 26 responsivegenotypes, 9 regenerated only from explants exposed to LD. The frequences ofregenerating root explants and the SE mean number were higher in LD than in SD(Fig. 1a,b). ANOVA confirmed that both genotype and photoperiod significantlyaffected the regeneration process (P ≤ 0.00001), as well as their interaction. Hence,t-test for dependent samples was performed for each genotype to asess thedifferences between two photoperiods. This analysis confirmed the previousnotion. The frequencies of regeneration and the SE mean numbers of all genotypeswere higher in LD than in SD (Fig. 1a,b). The differences were even moreconspicuous when the EFC indexes were calculated (Fig. 1c). They weredramatically higher for LD, with no exceptions. The overall SE number, calculatedfor the whole period of 12 weeks, also varied significantly among genotypes andbetween photoperiods (not shown).The highest SE number was attained in genotypes 107, 110, 115, 119 and 125,which produced 243, 480, 220, 232, 352 SE respectively in LD, and 9, 22, 14, 34and 63 SE respectively in SD. The poorest response was in genotypes 102, 103,105, 128 and 130, which produced 15, 21, 19, 9 and 9 SE, respectively in LD, andamong them only genotype 102 regenerated 2 SE in SD.High variability among randomly chosen seedlings obtained in this study is inagreement with the results obtained in cultivar Nippon by Ishizaki et al. (2001).The later study was performed in LD only. However, Geekiyanage et al. (2006)obtained higher regeneration response of cultured cotyledons in SD then in LD, butonly at high light intensity of 90-100 µmol m -2 s -1 . We assume that high variability57