Histological and physiological aspects of growth responses and differentiation of pecan Carya illinoensis (Wang) Koch, tissues in vitro

Abstract

A variety of handling techniques, media preparations and tissue sources were used in combination to establish pecan tissues in vitro. Plantlets were produced on a sequence of three media. The first medium enlarged the buds on up side down nodal explants; the second medium induced root formation on reinverted nodal explants; the third medium produced plantlets. Eight plantlets were generated from modal explants. None were successfully established in soil. Possible reasons for low numbers of plantlets produced and their inability to survive in soil are discussed. The responses of pecan tissue to various physical and chemical regimes during the process of developing a suitable growth medium are also discussed. Some pecan tissues were found to be internally contaminated. A resident fungus, Alternaria sp., was demonstrated to be present in stored and fresh dormant buds by evidence including scanning electron micrographs and agar plating. Internal fungal contamination was absent in rapidly growing spring shoots, young pecan seedlings, and established pecan cultures as evidenced by scanning electron micrographs, agar plating and/or Hemalum staining of thin sections. Possible roles for a resident fungus are discussed.