Detección temprana de mutantes de banano tolerantes o resistentes a Sigatoka negra (Mycosphaerella fijiensis, Morelet) en condiciones de vivero

There are several diseases that attack bananas, but the main one is the black Sigatoka (Mycosphaerella fijiensis, Morelet), which attacks the leaves, reducing their photosynthetic capacity, thus lowering the output on farms. Fungicides to control the disease cause pest resistance, great damage to the environment and also to the people who live and work on banana plantations. To control this disease some alternatives have been sought, although genetic improvement is the best way. Conventionally in this crop, to get a new genotype is extremely difficult because of sterility and parthenocarpy conditions, for this reason, improvement through mutagenesis using physical and chemical mutagens and the tissue culture technique as a complement to get resistant or tolerant mutants to diseases have been used. As in several studies to cause mutations, Gamma rays and ethylmethanesulfonate have been used, in this case doses 0, 20, 40, 50, 60, 70, 80, 100, 120, 140, 150, 160, 180, 200, 250, 300, 350 and 500 Gy of radiation were applied. For EMS doses 0, 0.5, 1 and 2% were applied for two times: 3 and 6 hours. The plant material used for this study were apical meristems and microcorms of Williams cultivar (AAA) subgroup Cavendish, which were managed under in vitro conditions and nursery respectively. These explants were evaluated 30 days after application of mutagens to determine the percent mortality produced by these agents. To determine the median lethal dose probit method was used. Thus the LD50 was determined as 56.64 Gy in the Quito´s irradiator and 58.32 Gy in the irradiator of Aloag. The LD50 in microcorms could not be determined because of the total mortality of these plant material. In the assay with EMS, LD50 for apical meristems was 0.83 % that represented 120 mg of EMS in the mutagenic solution or 120 uL of 4.83 mM the EMS / L while in microcorms was 0.38 % representing 57 mg of EMS in the mutagenic or 57 uL solution of EMS in (0.56 mM / L) solution. To complete 10,000 plants, the survivors explants were micropropagated in the Biotechnology Laboratory of the Experimental Station Dr. Errique Ampuero Pareja of INIAP; nevertheless only 1936 were put in nursery where the chlorophyll content of the leaves were measured before being inoculated with mycelial solutions (Mycosphaerella fijiensis, Morelet) of 2.06 x 106 mycelial fragments / mL as concentration. This fungus was developed in the Laboratory of Pathology of the station. In nursery, the banana plants were evaluated according to the Stover’s method modified by Ghaul where the development and evolution of spots of Sigatoka according to the scale of Fouré, was evaluated to determine the severity index in each plant and determine the Weighted Average Infection (PPI), which is an indicator of resistance or tolerance, plants with the lowest PPI were identified. Phenotypic variations were determined, where the dose of 2 % to 2.89 % -3h had the highest number of phenotypic variation followed by doses of 40 Gy and 100 variations with 1.60 % each; furthermore the type of variation presented was analized, thus "striped leaves" with 7.8 % and" long slim leaves" with 2.48 %; Finally, 78 days after, the chlorophyll content was measured again for comparison with the initial measurement, where low chlorophyll in the final measurement was revealed, which was presumable due to the destruction of leaf area caused by black Sigatoka.

• Κύριος συγγραφέας: Valarezo Pacheco, Alex Vladimir (author)
• Μορφή: bachelorThesis
• Γλώσσα: spa
• Έκδοση: 2015
• Θέματα: Detección temprana; Mutantes de banano; Sigatoka negra; Vivero
• Διαθέσιμο Online: http://dspace.utb.edu.ec/handle/49000/1073