A novel approach for the definition of the inorganic medium components formicropropagation of yellow passionfruit (Passiflora edulis Sims. F-flavicarpa Deg.)

Mineral defficiency symptoms were observed in leaves of yellow passionfruit plantlets gown in MS medium (Murashige and Skoog, 1962) with 1.0 mg 1(-1) (3.0 muM) gibberellic acid. Initially, leaves showed interveinal chlorosis, followed by bleaching of the leaves and retarded growth. Leaf mineral anal ysis was done and compared to mineral requirements suggested for passionfru it in the literature. Several modifications were made to the inorganic comp osition of MS medium, according to mineral deficiencies, mainly of Fe and C a, and possible toxicity of Cl. The concentration of the elements in the ne w medium (MSM) was based on the mineral composition of leaves of healthy pl ants. The chemical equilibrium was checked using the software Geochem (Spos ito and Mattigod, 1980) and final adjustments were made to ensure good avai lability of nutrients. To test the efficiency of the modified medium nodal segments were cultured in both MS and MSM supplemented with 3.0 mg 1(-1) (1 3.3 muM) 6-benzyladenine. After three subcultures mineral analysis of the l eaves was done. Severe mineral deficiency was observed on the leaves of pla ntlets cultured in MS, while plantlets cultivated in MSM had green leaves. A comparison of the mineral analysis of plantlets in both media showed a fa irly large increase in Ca, Cu, Fe, Mg and S and decrease in levels of B and Cl in plantlets cultivated in MSM. A slight increase or decrease in other elements was also observed. Subculture of the chlorotic plantlets into MSM showed that the visual symptoms of mineral deficiency disappeared in 2-4 wk .