Amélioration de l’aptitude à la callogenèse chez la pomme de terre Solanum tuberosm L somatique de la pomme de terre par la sélection de meilleurs équilibres hormonaux.

Abstract

The main objective of this investigation is to study the response of different potato explants Spunta and Kondor to callogenesis and somatic embryogenesis in the presence of combinations with NAA / BAP and 2,4-D / BAP. We opted from the start for the buds and internodes as explants. The color and texture of the calli vary according to the nature of the growth regulators and the presence or absence of light. With the NAA / BAP combination the Spunta variety develops the best callogenesis in all environments compared to the Kondor variety depending on the concentration of hormones, there is a range of variations of days required for callus initiation, the percentage of explants that have developed calluses, texture, color and degree of its formation. For the combination 2,4-D / BAP the results indicate that after three weeks of culture, the calli are moist, soft and friable in green and whitish-green and white with the NAA / BAP combination, and green, light green and brown color for both explant with all media with of 2,4-D / BAP combination. Callus growth varies according to culture conditions like light and temperature, callus incubated in the dark give brown colors and a friable to compact structure, while the calluses incubated in light show varying colors (green, light green, white and brown) that are due to the action of light on the photosynthetic pigments. The rate of callogenesis and fresh weight of calli are positively correlated with the concentration of auxin. The histological study of callus obtained from internodal explants after 3 and 60 days shows that cell division is produced in the epidermis only after three days of culture and then spread to the first layer of the cortex. During somatic embryogenesis the calluses of different explants develop with all media (1-2) buds and dense roots. Exceeding three months of incubation the calli are larger and begin to brown and lose the green color after degradation of chlorophyll. A surprising observation in our study which is the formation of microtubers from the callus of tubercle germs on M1 and M2 medium after 37 to 60 days of incubation. This research has made it possible to highlight the conditions necessary for callogenesis and somatic embryogenesis. In the end it is recommended to try to induce somatic embryogenesis by applying stress (osmotic, with ions, ABA ...), with the addition of organic and mineral nitrogen source for a period exceeding three months.