Punjab, Jullundur
Bombay State, Poona
1. The influence of certain rootstocks propagated both from seeds and cuttings on the tree vigour and cropping of Marsh Seedless grapefruit has been studied over a period of three years.
2. The initial advantage in tree size and cropping noticed in case of vegetatively propagated rootstocks in the first seven years of the life of the trees persisted- during the period of three years of the study.
Although the trees on vegetatively propagated rootstock continue to be of bigger size as compared to those on seedling rootstocks, the study of growth rates shows that on the whole relative rate of growth is lower in case of vegetatively propagated rootstocks, thus showing that bigger size of trees on vegetatively propagated rootstocks is nob going to last.
3. The vegetatively propagated root-stocks induced consistently higher yield as well as better increase in growth as compared to those induced by apogamic seedling stocks during all the three years under study
4. The trees on Kharna Khatta have given the outstanding performance so far as yield is concerned as they have been consistently yielding higher annual crops as well as commulative cropping. The trees on Sweet Lime and Citron have yielded the least crop while those on Rough Lemon and Shaddock have yielded crop inferior in size to those on Kharna Khatta alone.
5. The size of trees on Rough Lemon has been the biggest while that" on Sweet Lime and Citron has been the smallest. The size of trees on Kharna Khatta and Shaddock, though quite big as compared to those on Sweet Lime and Citron has been smaller than those on Rough Lemon.
6. The increase in growth and cropping of trees on Sweet Lime and Citron during the period under study has been very slight, thus showing the unsuitability of these two rootstocks.
7. The study of growth rates show that Kharna Khatta tends to impart greater vigour to the plants in the nursery stage, but the relative rate of growth is lower than in case of Rough Lemon, thus showing the superiority of Rough Lemon for inducing vigour from the very start of the experiment. The relative rate of growth is very low in case of both Sweet Lime and Citron. The study shows the decided inferiority of Citron rootstock.
8. The high negative correlation between growth increment and cropping observed in the previous years was found to be absent during the period covered by the present study. This suggests that the experiments on manuring and other cultural practices should only be carried out after 4–5 crops have been obtained so that the results are not vitiated by the inherent antagonism between growth and cropping during the first 4–5 crops.
