Influence of various carbohydrates in shoot development in nodal culture of Guinean Anacardium occidentale genotypes

The influence of various carbohydrates in shoot development was studied in single nodal culture of Guinean cashew genotypes. Both apical and axillary nodal sections from one-and-half-year-old stock plants of elite selected cashews from Guinea-Bissau were used as explants. Six types of carbohydrates (sucrose, maltose, glucose, fructose, galactose and sorbitol) were tested separately at concentration of 83 mM. Sucrose, maltose and fructose showed the best performance and were additionally tested at concentrations of 0, 83 and 167 mM in order to evaluate the optimal concentration that promotes growth. These results indicated that the inclusion of a carbohydrate source is essential for shoot development. In the tested conditions the concentration of 83 mM was sufficient for shoot development since no significant differences were found when explants were cultured on a higher concentration. Moreover, the results showed that in spite of the concentration it is the type of carbohydrate that influences the shoot response. Maltose increased the number of developed shoots whereas fructose enhanced shoot length. These results suggested that a combination of these two carbohydrates could increase the yield of well-developed shoots in a single step. The effect of maltose and fructose was analysed separately and combined. The combination of fructose with maltose (each at 83 mM) promoted both the highest percentage of developed shoots and the highest shoot length when compared with the results obtained using these two sugars separately. With this study, we found a one-step carbohydrate combination that allowed overcoming the low yield of well-developed shoots observed in the current propagation system in Guinean cashew genotypes.