In vitro response of gamma irradiated Vanilla planifolia jacks. Shoots in the face of water stress

Currently, premature fruit fall is one of the major problems in vanilla (Vanilla planifolia Jacks.) cultivation. This phenomenon has been related to its high susceptibility to drought, a consequence of the low genetic variability of this crop. For this reason, it is important to undertake genetic improvement programs to obtain genotypes with greater tolerance to drought. With this aim, the present work irradiated cluster shoots with different doses (0, 0.5, 1, 3, 5, 7, 9, 11, 13, 15, 17, and 19 Gy) of gamma rays. Subsequently, choose shoots of doses 0, 3, 7 and 13 Gy to subject them to in vitro selection to drought cultivate them in Murashige & Skoog (MS) medium, adding 0, 10, and 15% polyethylene glycol (PEG). The results showed a greater proliferation of irradiated shoots with doses of 0.5 and 1 Gy (8.88 ± 3.04 and 6.43 ± 0.98, respectively). Shoots irradiated with 0.5 Gy had faster growth (19.26 ± 6.87 mm), while those irradiated with 3 Gy showed a higher number of leaves (2.38 ± 0.71). The cluster shoots irradiated with 9, 15, 17, and 19 Gy lost their ability to multiply, unlike the shoots subjected to 13 Gy, which retained their capacity for vegetative reproduction. The best response to in vitro selection to drought was obtained with the dose of 13 Gy. These results highlight the usefulness of combining gamma radiation work with in vitro selection by PEG to obtain lines with tolerance to water deficits for use in improvement programs for this valuable crop.