INFLUENCE OF CA2-BENZYLADENINE ON CHESTNUT (CASTANEA-SATIVA MILL) IN-VITRO SHOOT-TIP NECROSIS( AND 6)

Shoot apex necrosis affects in vitro chestnut cultures particularly du ring the rooting stage. Lack of cytokinins or Ca2+ deficiency in the c ulture medium have been reported to be responsible for occurrence of t ip necrosis, In the present research the effects of three Ca2+ levels (3, 9 and 18 mmol l(-1)) were tested on C. sativa 'Garrone rosso' and 'Clone 46' shoots treated for rooting. Tissue Ca2+ content of the apic al, middle and basal portion of both brown and healthy shoots was dete rmined, In a second trial the tip necrosis related effect of the local (tip) application of CaCl2 (3 mmol l(-1)), BA (5 mu mol l(-1)) and Ca Cl2 + BA (3 mmol l(-1) and 5 mu mol l(-1)) was tested on Clone 46 shoo ts, during rooting. With regard to Ca2+ concentration in the rooting m edium, no significant difference could be detected from the three test ed Ca2+ levels on tip necrosis but the highest one caused a drop in ro oting ability. Regardless of Ca2+ concentration, Garrone rosso showed a lower percentage of the disorder and a higher affinity for calcium i n terms both of uptake and ion translocation. The data of the second t rial showed that the local application of 5 mu mol l(-1) BA completely eliminated tip necrosis while the application of CaCl2 + BA delayed t he appearance of the disorder. Apex calcium content of shoots treated locally;revealed that the most the healthy tissue contained higher cal cium levels than the necrotic one, BA treated shoots contained the low est ion levels, independently from their status.