FIELD PHYTOPROTECTION OF Coffea arabica MOTHER PLANTS, DISINFECTION AND CALLOGENESIS INDUCTION

In Chiapas, Mexico, there are high-yielding coffee plants adapted to the local climatic conditions. The presence of microorganisms in the explants makes developing protocols for cloning these genotypes in vitro difficult. The objective of this work was to evaluate how field and in vitro microorganism management affected asepsis and the induction of callogenesis in leaf explants of agronomically important coffee plants. Drought-tolerant genotypes were obtained from aseptic explants and cell cultures using a participatory study, agronomic, and in vitro techniques. Five accessions (ITTGj 1-5) were selected from a 21-year-old Borbon cultivar. The present study was conducted over two flowering cycles, evaluating the effect of field management on explant asepsis on the first and the callogenic response caused by the culture medium, the transport solution, and the genotype, on the second. Sixty days before explant collection, biweekly applications of calcium polysulfide (10 % v v-1), copper oxychloride (2 g L-1), and Zingiber officinale extract (20 g L-1) reduced fungal contamination by 100 % and bacterial contamination by 90 %. Field explant transportation in 200 mg L-1 citric acid and ascorbic acid solution reduced oxidation in explants and in vitro cultures. Proembryogenic friable corns were formed with the combination of 4.4 µM BAP (6-benzylaminopurine) and 7.25 µM 2,4-D (2,4-dichlorophenoxyacetic acid) at 45 days of culture, with genotype four showing the best response. Field management was effective for the aseptic establishment of Coffea arabica cultures in vitro, and the combination of BAP and 2,4-D used was an appropriate growth regulator for the induction of callogenesis.