Self-mating effect on growth traits and silymarin production for some selected lines among milk thistle (Silybum marianum L.) varieties

Abstract

Ten selected lines for each purple and white head flower varieties of milk thistle, Silybum marianum were assessed for five growth traits and silymarin production among three generations: open parents, selfing progenies and selfing offspring. Highly significant variations existed between lines, varieties and generations as well as their interactions in all tested traits. The line characters for each variety were subjected to analysis of variance only for open parents opposite to selfing offspring, and seemed highly significant variablities. The selfing offspring generation produced higher mean value in all purple variety traits except no. of flower heads. Contrarily, the parent generation produced higher values in all white variety traits except fruit yield (FY). Lines 34 and 9 for purple and white varieties respectively were the best lines in both open and selfing generations. Coefficient of variation, genotypic and phenotypic coefficients of variation as well as broad sense heritabilities and genetic advance for most of studied growth traits were improved in the selfing offspring generation to indicate that milk thistle traits were governed with additive gene effects. Fruit yield trait had the highest parent offspring regression and narrow sense heritability in both varieties. On the other hand lines 34, 22 and 28 in the purple as well as 9, 2 and 13 in the white variety were the highest, medium and lowest fruit yield, respectively and subjected for fruit content of silymarin using HPLC. Concentration and total yield of six detected silymarin compounds showed wide variations between lines, varieties and generations and ranged from 11.92 to 62.85mg/g and between 329.8 to 2121.3mg/plant, respectively. Selfing improved the silymarin contents in the purple lines, but reduced the content of white lines. Interesting to notice is that silymarin production has the same pattern of fruit yield trait, so selection should be based on this trait to produce new improved high yielding silymarin genotypes.