Fruit Research Station, Anantharajupet, Andhra Pradesh
1. Budded trees (on certain prolific stocks) in both sweet orange and acid lime have generally been found to be more vigorous growers, earlier and heavier croppers than seedling trees in the initial bearing life of the trees. In later years, however, the seedling trees in acid lime are found to perform as well as, if not better than, budded trees, while in sweet orange, yields in budded trees have been found to gradually deteriorate as they age due to their higher susceptibility to diseases than seedling trees.
2. In sweet orange, the budded trees usually come to bearing nearly 5–6 years earlier than seedlings. But, in acid lime, this earliness in favour of budded trees has been found to be barely one year or so over the seedling trees.
3. In either fruit, budded trees in general have been found to be more or less susceptible to some of the serious citrus diseases, leading to earlier decline or deterioration in yields, whereas seedling trees have generally been the most resistant of all.
4. Among budded trees, both sweet orange and acid lime trees on their own respective stocks has been comparatively less susceptible to diseases than those on other more prolific stocks.
5. The twin advantages of earlier bearing and heavier cropping of budded plantations in the initial bearing life have largely been oft-set by their earlier decline, whereas the seedling trees, though slow growing in the initial stages and late bearing, appear to possess potentially a longer bearing life as the trees age, due to their inherent disease-resistant nature.
6. In sweet orange, the seedling trees and the trees on their own sweet orange stock have generally produced fruits of better eating quality in most seasons, than those on other more prolific stocks. In acid lime, no such differences have been found, the seedling trees producing as good quality fruits as budded ones.
7. Variations in individual tree yields in both sweet orange and acid lime have been as widely divergent in clonal progenies as in the unworked seedling trees. The popular belief that clonal progenies ensure more uniform productivity in the orchard than seedling progenies has not been substantiated from the actual experimental evidence thus far available from progeny tests, at any rate, in these two citrus species.
8. In acid lime, in view of the equally good and even better performance of the seedling trees in their adult bearing life, the hardier nature of the seedling trees as compared with budded ones, the very small difference of about a year or so in precocity between budded and seedling trees in reaching bearing age and the usual difficulties encountered in the vegetative propagation of this fruit, it would appear that vigorous apogamic seedlings may as well be preferred for commercial planting to budded trees.
9. In sweet orange, where prolonged bearing life is desired, a similar selection -of vigorous seedlings or of budded trees on sweet orange stock for orchard planting is likely to be the most advantageous in localities where disease infestation is most severe.
10. Finally, it should be emphasized here that these conclusions or inferences can by no means be extended to all perennial fruits or other tree crops. At best they can only be perhaps applied to the two species of citrus discussed herein; where on account of the occurrence of high heterozygosity or bud mutation, a mere bud selection and perpetuation of the same through clonal means cannot be depended upon for securing uniform productivity in the orchard. Moreover, thep occurrence of a fairly high degree of polyembryony in these species seems to offer a safer, quicker and a more practical means of exploitation in securing the desired results than vegetative propagation of selected parental buds.
Selective vegetative propagation has no doubt its own virtues in the field of horticulture. But the problem that is at present confronting the citrus industry is largely in the field of disease infestation, where virus infection is also suspected. It is now well recognised that vegetative propagation can never be a panacea in the field of disease resistance. Fortunately, however, most virus diseases are not seed borne and as such, seed propagation seems to offer a unique advantage over, asexual propagation in securing the desired end in these two species of citrus.
