Govt. Citrus Fruit Research Station, Burnihat, Assam
Twelve distinct varieties of Citrus of Assam, rerpesenting nine different species, have been employed as a stock for six different scion types. The observation is based on a small population of eight to twenty four plants for each stock-scion combination. The results of different stionic interactions have been reported after eight years of orchard life from the date of planting in 1942. These are summarised below.
(1) The stock Bira-jora (C. medico) does not appear to show any affinity for the Khasi mandarin orange (C. reticulata) and Valencia Late orange (C. sinensis) as scions. The graft symbionts are wholly incompatible.
(2) The Pati-Lebu (C. limon, a citron-lemon type) as a stock for the Khasi mandarin (C. reticulata) and Valencia Late (C. sinensis) is also a complete failure. The plants show symptoms of mottle-leaf, dwarfing, with a tendency to incline on one side.
(3) The stock Pani-jamir (C limon) imparts vigorous growth to the Khasi mandarin orange (C. reticulata), Valencia, Malta Blood-red, and Washington Navel (C. sinensis) in the early years. But with advance in age the symptoms of incompatibility progressively appear. It is unsuitable as a stock for all the four scions.
(4) The Soh-synteng (C. limon) is quite incompatible as a stock for the Khasi mandarin orange (C. reticulata). Valencia, and Washington Navel (C, sinensis).
(5) The Soh-myndong (C. jambhiri) sppear, so far, to be perfectly compatible with the Khasi mandarin orange (C. reticulata), Valencia Late, and Mosambi (C. sinesis) as scions. With the Washington Navel orange and the Duncan grapefruit (C. paradisi) it appears to produce somewhat medium sized trees, although the growth is fairly vigorous and healthy. With the exception of these two scions the remaining three varieties are prolific on this stock. Granulation of pulp-vesicles is particularly marked in the Washington Navel.
(6) The stock Kata jamir (C. jambhiri) generally is compatible with all the scions, viz., the Khasi mandarin orange, Valencia Late, Mosambi and Washington Navel. All the graft combinations are associated with vigorous growth, although there is a slight tendency for dwarfing in the case of the Washington Navel. With the exception of the Washington Navel which is a shy bearer, yielding granulated fruits, all others seem to be prolific in yield, producing normal fruits.
(7) With the Khasi mandarin orange (C. reticulata) as scion, the Soh-sarkar (C. karna) produces a normal tree but later the tree declines progressively. It appears to be unserviceable as a stock for the Khasi mandarin orange.
(8) With the Khasi mandrin orange and Valencia Late, the stock Karun jamir (C. aurantium) does not show any great affinity and develops symptoms of mottle-leaf after a period of four to seven years. It's compatibility with the above two scions appears to be dubious.
(9) The Rabab-tenga (C. maxima) seems to be a suitable rootstock for propagating the grape fruit (Duncan). With other scions, viz. the Khasi mandarin orange, Valencia Late, and Washington Navel, it is found to be incompatible.
(10) The Sat-kara (C. macroptera) is found to be wholly incompatible with the Khasi mandarin orange (C. reticulata) as scion. Overgrowing of stock is prominently marked at the point of union and symptoms of mottle-leaf appear after about five years of orchard life.
(11) It seems doubtful whether the Khasi mandarin orange (C. reticulata) will prove to be a compatible stock for the Mosambi (C. sinensis) as the grafts are inclined to be somewhat dwarf and to lack vigour.
(12) Compatibility of the Ada-jamir (C. assamensis) with the Khasi mandarin orange (C reticulata) is dubious. The stock outgrows the scion considerably at the point of union and symptoms to mottle-leaf appear after a lapse of about -seven years.
