SELECTION AND CLASSIFICATION OF MANGO ROOTSTOCKS IN THE NURSERY STAGE

Mango is commonly propagated with unselected seedling rootstocks, which might be responsible for the variation in the performance of trees of the same clone in the orchard. No attempt has yet been made to classify mango rootstocks on the basis of their vigour as has been done in apple. The dwarf stocks may be of great value in modern mango orcharding. With a view to selecting dwarfing rootstocks in mango, a systematic search was made using various selection criteria used by earlier workers in apple (5, 6, 7).

The investigations were carried out with 31 different rootstocks comprising of own rooted varieties-Dashehari, Langra, Chausa, Totapari Red Small, Neelum, Bombay Green and the seedlings raised from open pollinated seeds of the above varieties. Besides mono-embryonic varieties, poly-embryonic and wild species of Mangifera indica L. were also included in the studies.

The following selection criteria were used:

1. growth of stem;
2. root characters;
3. anatomy of stem:
   1. bark percentage,
   2. area of metaxylem,
   3. no. of vessel;
4. anatomy of root:
   1. bark percentage,
   2. area of vessel,
   3. no. of vessels per unit area,
   4. no. of wood fibres per unit area;
5. petiole anatomy;
6. respiration of leaf discs;
7. stomatal count of dorsal side of leaf.

The bark percentage of root was used as a base index in determining the efficiency of the other selection criteria. The growth of stem was found to be negatively correlated with the bark percentage of root. The root morphology (figures 1, 2, 3) could not be correlated with vigour. The grouping of rootstocks on the basis of growth of stem, stomatal count, vessel size of root (figures 4, 5) and number of wood fibres per unit area tallied with the classification made on the basis of bark percentage of roots. The stem anatomy, petiole anatomy and respiration of leaf discs were not found to be helpful in mango, although Miller et al (7) obtained good correlation between respiration of leaf discs and percentage