Submitted to: Bean Improvement Cooperative Annual Report
Publication Type: Other
Publication Acceptance Date: 2/9/1995
Publication Date: N/A
Interpretive Summary: Plant biologists often clone (make many identical copies) of plants in the laboratory. Clones of common bean (Phaseouls vulgaris L.) are often produced by carefully cutting the tips of shoots which contain the growing bud and placing the shoot-tips on a special growth medium inside a glass dish or flask. The dish or flasks are sealed with plastic film to keep yeasts and molds from entering the flasks and growing on the medium, and to keep the medium from drying out. However, bean shoot-tips often do not grow in flasks, thus, limiting the efficiency of the cloning procedure. An experiment was conducted in which the glass dishes were sealed in two different ways. One-half of the dishes were tightly sealed with plastic film as usual while the other half were sealed with a special porous tape. Plant growth was inhibited in the tightly sealed dishes but not so in the dishes sealed with porous tape. Ethylene and CO2, naturally occuring gases, ,were found in the dishes sealed with porous tape. The results of the experiment suggest that ethylene is a powerful inhibitor of growth of bean plants in glass dishes. The use of porous sealing material allowed the ethylene to escape from the inside dish environment to the outside air. Successful bean clones can be achieved when the glass dishes are sealed with a porous material that prevents the medium from drying out; yet allows free gas exchange between the air inside and outside of the dishes.
Technical Abstract: Long term sustainability of in vitro cultures of common bean (Phaseolus vulgaris L.) has not been achieved. Ethylene may cause growth inhibition of bean plantlets in vitro. An experiment was conducted to study the effect of ethylene on plant growth and development of common bean cultured in vitro. Ethylene inhibitors and vessel sealing materials that permitted free exchange of gas between the in vitro and ex vitro environments were used t selectively remove ethylene from culture vessels. Shoot tips from 5-7 day-old seedlings from 'Seafarer' navy bean, 'Jamapa' black bean, 'UI-114' pinto bean, and 'Colorado de Tapiosca' small-red bean were plated on MS media in petri dishes or Erlenmeyer flasks. Petri dishes were sealed with surgical tape or two layers of parafilm; Erlenmeyer flasks were sealed with porous foam or parafilm and cork stoppers. The surgical tape and porous foam stoppers permitted free gas exchange while parafilm and cork stoppers tightly sealed the culture vessels and permitted no gas exchange. The ethylene inhibitors, silver nitrate 10.0 mg/l or aminoethoxyvinyl-glycine 0.2 mg/l, were added to the culture medium. Plant growth was inhibited in the tightly sealed culture vessels. Shoot-tip growth was noteworthy when plantlets were grown in culture vessels in which free exchange of gases occurred. Ethylene and CO2 accumulated in the tightly sealed culture vessels. However, in culture vessels sealed with surgical tape or porous foam stoppers ethylene was not detected. The use of cultural vessel sealing materials that prevent desiccation of cultures yet allow free gas exchange between the in vitro and ex vitro environment may be the breakthrough needed to achieve long-term sustainability of bean tissue cultures.