Genetic parameter variations among milk thistle, Silybum marianum varieties and varietal sensitivity to infestation with seed-head Weevil, Larinus latus Herbst
2006
Ottai, M.E.S. (National Research Centre, Giza (Egypt). Dept. of Genetics and Cytology) | Abdel-Moniem, A.S.H. (National Research Centre, Giza (Egypt). Dept. of Pest and Plant Protection)
Milk thistle, Silybum marianum (L.) Gaertn (Asteraceae) is a very important plant used for treatment of various liver diseases based on its content of silymarin. White and purple head flower varieties were used to study the genetic variations as a first breeding attempt for this plant under Egyptian conditions. Highly significant difference for seed index (SI) and significant differences for plant height (Ph), linear growth (Lg), number of total branches per plant (TB) and seed yields per plant (SY) were found between varieties in the first season. All the studied characters showed highly significant variations among the second season except number of primary branches per plant (PB) and flower diameter (Fd). Mean values, mean of top 10%, broad sense heritability, genotypic and phenotypic coefficients of variability, selection intensity, genetic advance as well as correlation and determination coefficients were computed and discussed for all ch aracters of Milk thistle varieties in both seasons. On the other hand, high population of the seed head flower weevil, Larinus latus Herbst (Coleoptera: Curculionidae) was observed and identified for the first record on Milk thistle varieties in Egypt. The plant is considered as mono host plant for this weevil. The weevil life cycle was studied and some biological and behaviours aspects were discussed on both Milk thistle varieties. Periods of pupal and adult stages had significant differences when weevil rearing carried out on white than on purple variety. Moreover, white variety as a host plant produced faster larval and pupal stages, while purple variety produced faster egg and adult stages.
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