Influence of silver thiosulfate ethylene inhibitor on in vitro growth of Vasconcellea quercifolia shoots

Abstract

The Vasconcellea quercifolia is a native species, belonging to the Caricaceae family, which is resistant to Papaya ringspot virus that can be used in plant breeding programs for commercial papaya cultivars. The objective of this study was to investigate the influence of silver thiosulfate, an inhibitor of ethylene action, during the in vitro growth of Vasconcellea quercifolia shoots. Shoots around two inches long were inoculated on MS medium supplemented with 20 g L-1 sucrose, 10 ppm ascorbic acid, 0.1 μM BA and 1 μM IBA. The silver thiosulfate was filter-sterilized and different concentrations (0, 0.1, 1, 10 and 100 μM) were added to the autoclaved medium. Each treatment consisted of 10 replicates and the experiment was performed in duplicate. After 30 days of culture in a growth chamber, the following parameters were evaluated: (i) intensity of callus formation, (ii) number of green leaves, (iii) number of leaves showing chlorosis, (iv) explant length, (v) number and (vi) root length. The use of STS was statistically significant regarding callus formation at the shoots base, shoot length, number of green leaves, number of roots and root length. Higher callus formation was observed in the absence of silver thiosulfate. Longer explants (23 and 18 mm) were observed in the absence or presence of 0.1 μM silver thiosulfate, respectively. The highest silver thiosulfate concentration (100 µM) caused a reduction in the number of green leaves. The use of 0.1 and 1 µM STS showed better results for number of root (3.8 and 2.3) and root length (67 and 49 mm), respectively. The results show that ethylene interferes in the in vitro growth of Vasconcellea quercifolia shoots.