Cultivo in vitro de anteras de meloeiro

Abstract

The melon (Cucumis melo L.), belongs to Cucurbitaceae family, it is a vegetable of global importance. Haploidization is a technique that allows fast genes fixation by the use of dihaploids, facilitating to select genotypes with characteristics of interest. Dihaploidization is used to accelerate the breeding program of some cultivated species, being a promising alternative to reduce time to obtain homozygous strains. However, in melon, the efficiency of this method is low, mainly in haploid plants regeneration stage. The in vitro culture of anthers is a way to obtain haploids in Cucurbitaceae. Therefore, the objective of this work was to obtain melon haploid plants by in vitro culture of anthers. The botanical varieties used were: inodorus; cantalupensis and reticulatus. Anther explants, obtained from male floral buds in pre-anthesis stage,were used from plants kept in greenhouse. The anthers were split in half and inoculated into test tubes containing 10 mL of culture medium. In the calogenesis step, the anthers were placed in MS basic culture medium, supplemented with 2.0 mg / L 2,4-D. The experimental design was completely randomized in a 3x2x2 factorial scheme, with the following factors: three botanical varieties, two pre-treatments, cold (4 ± 1oC in the dark for 7 days) and the other in the heat (32 ± 1 oC, in the dark for 7 days), and two permanence time in the culture medium (at 14 and 28 days), totaling 12 treatments, with 60 replicates. The cultures remained for 28 days in the growth room at 25 ± 1 ° C under photoperiod of 16h light, and luminous intensity of 30μmolm-2s-1. No callus formation was observed in the induction phase. After 28 days, all explants were transferred to callus maturation medium (MS + 2.0 mg / L of 2.4 D + 0.5 mg / L of BAP). The calluses were formed from the first week in the maturation culture medium, remaining in this medium for 4 weeks. At 63 days after the in vitro inoculation of the anthers, the explants were evaluated for formation, size, oxidation and fresh mass of the calli. Data were submitted to Scott Knott's univariate analysis, and means were compared to each other at a 5% level of significance. There was a significant difference for callus formation, with cantalupensis being the most efficient variety among the three studied. The oxidation rate was minimal, not interfering with the conduction of the experiment. Cantalupensis variety, submitted to renewal of culture medium at 14 days, and the thermal shock at 32ºC in the dark for seven days, showed better callus formation and fresh mass. The pre-treatments allied to culture medium renewal or not and the growth regulators added to the culture media, were not effective for shoot formation, from the calli of the three botanical varieties studied.