Propagação por rebentos e germinação de sementes in vitro da alcachofra

Abstract

The Artichoke seedling production, usually done through buds and, at a lower scale, through seeds, is one of the limitation for crop expansion, due to seed segregation genetics, nonsatisfactory seedling survival and susceptibility to Erwinia sp. bacteria and other diseases. Micropropagation, on the other hand, is an option, but difficulties such as low multiplication rates and high explants contamination are still faced. So, in vitro seed germination may be an alternative to obtain healthy explants, in other words, plants frees of contaminations, for use in future in vitro cultivations. On that note, one aproach of investigation was developed at FAMV/UPF, aiming the shoots artichoke propagation and other aiming in vitro seed the artichoke germination. In the shoots artichoke propagation, artichoke shoots Nobre were planted in four substracts, three of them composed by 40% soil + 10% medium sand + 10% vermiculite, changing volume only in 40% composite, 40% coconut fiber, or 40% carbonized rice chaff, and the another one was composed by 50% of the commercial substract Horta 2® + 50% coconut fiber. Before planting, the buds were treated with indolebutyric acid (IBA) in doses of 0, 500, 1000 and 1500 mg L-1 (rhizome imersion for five seconds). The planting was in plastic tubettes kept in the greenhouse with microaspersion irrigation. The rooting in the surviving buds was 100%. The best rooting was obtained in the soil + carbonized rice chaff + sand + vermiculite and Horta 2 + coconut fiber substracts, combined with the 1000 mg L-1 of IBA treatment. Five experiments were conducted to evaluate in vitro seed germination, testing active chloride concentrations on seed aseptic technique; tegument treatment (kept intact, with side cuts and elimination); lighting conditions (light and dark); and two cultivation media (MS medium, with salts concentration reduced in half, MS medium, full strenger). In both cases, 30 g L-1 sucrose and 7 g L-1 agar were added, with pH adjusted to 5.6 with NaOH. The results showed that it is viable to obtain healthy artichoke plantlets Nobre for use as a source of explants in in vitro cultivation, from in vitro seed germination, which is higher when tegument was removed (63,4% a 77,5%), cultivated on full strenger MS medium or with salts concentration reduced in half, kept in the dark in the growth chamber. The aseptic seeds with alcohol 70% by 30 minutes and a subsequente event immersion in solution to contain 2% of active chlore for 10 minutes is efficient for reduce contaminations in seeds without tegument