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  • Author or Editor: C. N. Roistacher x
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Abstract

The comparative analysis of leaf-oil components separated by vapor phase chromatography was tested on stubborn infected and non-infected sweet orange leaves as a possible new technique for detection of stubborn disease of citrus. Three leaf-oil components: citronellol, nerol, and geraniol were found reduced in the stubborn infected leaves, but the reduction was shown to be related to the smaller leaf size and not due to the stubborn pathogen. However, one component, linalool, showed an increase in stubborn or stunt infected leaves relative to respective controls. This increase was not related to leaf size, but probably due to the presence of the pathogen.

Open Access

Abstract

A 30 to 50% frequency of successful grafts was obtained by using 2-week-old dark grown seedlings as rootstocks and 0.14 to 0.18 mm long shoot tips as scions. The shoot tip was inserted into an inverted-T made at the top of the decapitated rootstock epicotyl. Most scion cultivars gave satisfactory grafts on ‘Troyer’ citrange, whereas lemon, lime and citron yielded successful grafts only on ‘Rough’ lemon. The grafted plants were allowed to develop in vitro under 16 hr daily exposure to 1000 lux Grow Lux illumination and were provided with a nutrient solution containing a high concentration (7.5%) of sucrose. The best source of shoot tips was the flush from defoliated branches of field trees or glasshouse plants. It was also possible to use shoot tips from flushes arising in excised lateral buds cultured in vitro. Grafted plants were transplantable to soil 5 to 8 weeks after grafting with over 95% survival. Preliminary data indicated recovery of cultivars freed from tristeza and psorosis viruses, stubborn spiroplasma and exocortis viroid. Pathogen-free plants showed no reversion to the juvenile phase.

Open Access

Abstract

Growth chamber studies with several common citrus species (Citrus sinensis (L.) Osb., C. aurantium L., C. reticulata Blanco, C. limon (L.) Burm) and a hybrid (C. sinensis × Poncirus trifoliata (L.) Rat) indicate abnormal growth developed during 2.5 months of sublethal high temperature stress. Hot treatment (38° day/28°C night) reduced shoot elongation and leaves were smaller, broader, and more upright than those on the warm (28°/22°) controls. Some leaves in the hot treatment were cordate in shape with abnormal venation. Growth of dormant axillary buds on decapitated shoots was inhibited with continuously maintained stress at 40° over an 8 day period. Buds were killed when stress was applied after they had commenced to swell. Young, partially grown leaves became distorted and faintly yellow-brown in color when given 40° for 8 days.

Open Access

Abstract

Individual shoot-tip-grafted budlines of ‘Willowleaf mandarin (Citrus reticulata Blanco) and ‘Temple’ tangor [C. reticulata × C. sinensis (L.) Osbeck] were grown to fruiting for evaluation. Fruits of both cultivars were highly uniform among shoot-tip cultures, indicating that this technique for producing disease-free citrus germplasm is reliable and does not increase the production of variant budlines.

Open Access

Abstract

Shoot apices, excised from Citrus cultivars of known virus content, were successfully grafted in vitro onto disease-free rootstock seedlings and some virus-free plants were obtained. The prolonged juvenile phase which characterizes disease-free nucellar lines was bypassed by this procedure.

Open Access