In rubber, the current propagation method of grafting on to unselected seedlings, maintains intraclonal heterogeneity for vigour and productivity and hence a great improvement may be expected by using micropropagation in vitro. Micropropagation with nodal and shoot tip explants derived from seedlings are possible as with mature clonal explants. The major problem in using clonal material from mature trees of Hevea is the failure to produce an adequate tap root system necessary for tree stability, and the poor response to culture conditions. The latter problem has been over come to a significant level by in vitro micrografting. Recently, there has been an increasing interest in the induction of somatic embryogenesis in Hevea using different explants, media compositions and conditions, especially for use in genetic transformation studies. Successful somatic embryo formation and plant regeneration have been reported by a few researchers in different countries using limited genotypes of Hevea. Attempts to induce somatic embryos from high yielding Sri Lankan clones have not been successful until the late 1990s. The frequency of somatic embryo induction was found to be very low and non-synchronous, its germination remained very difficult and thus Hevea embryogenic system needed further investigation. There is no large scale commercial application of tissue culture techniques for mass propagation of clonal Hevea as yet, either by microcuttings or by somatic embryogenesis. However, there is sufficient progress at research level to suggest that tissue culture of Hevea can and should be further developed.
Hevea brasiliensis (Muell Arg.) undergoes annual leaf shedding commonly known as wintering. The wintering period in the traditional rubber growing areas in the Wet Zone of Sri Lanka is from December to February followed by flowering and flushing in March. Tapping rest during wintering is recommended in certain countries while in some other countries year round tapping is practiced. In Sri Lanka, until early1970s winter resting was practiced, but this is not being practiced at present. Incidence of tapping panel dryness appears to be high with currently recommended clones and hence the objective of the present study was to investigate on the effect of winter resting on the annual yield and tapping panel dryness in rubber clones. Experimental trials were conducted for two consecutive years (2018 and 2019) with three clones viz., RRIC 100, RRIC 121 and RRISL 203 at the Substation of RRISL at Kuruwita in Ratnapura district. Treatments tested were continued tapping with no winter rest (T1), resting during the wintering period (T2) and once in six days tapping during the wintering period (T3). Trees were tapped at S/2d3(once in three days) intensity. Data were collected on latex volume, bark consumption and TPD incidences. Results for two years showed higher g/t/t/ in all three clones when rested during the wintering period in both years as compared to those with no winter rest. Significantly higher annual total crop (kg) was recorded for T1 when compared to T2 in all three clones for both years. Though total number of partially and totally dry trees of winter rested trees of clones RRIC 100 and RRIC 121 were low, the differences were not significant. In terms of profits obtained as indicated by economic analysis, resting the trees during wintering resulted in the highest profits, followed by d6 tapping during the same period. Winter rest should be tested for a longer duration (4-5 years) for all the clones recommended at present that are vulnerable to tapping panel dryness.
Studies were carried out on the effect of seed coat removal and nitric oxide (NO) donor sodium nitroprusside (SNP) treatment on germination and growth of seedling and budded plants of rubber (Hevea brasiliensis). Interaction effects were observed between seed coat treatment and SNP treatments for germination time and percentage germination. Decoated seeds germinated earlier and improved synchronicity than intact seeds (with seed coat) and achieved 50% germination within nine days. SNP treatment at all four concentrations (20, 50, 100 and 200 µM) hastened the germination and increased the percentage germination especially when decoated seeds were used. Shoot and root attributes of seedlings (stock plants) derived from the seeds treated with SNP, especially at 50-100 µM, were significantly improved as compared to those from control and mock treated seeds. Growth of the budded plants were better when stock plants derived from SNP treated seeds were used. Therefore, NO treatment coupled with decoating could effectively be utilized to improve the germination and growth of seedling and budded plants of rubber. To our knowledge, this is the first report on redox priming of rubber seeds with SNP.
Data available from three experiments conducted during 1939 and 1953 on the dry rubber yield of mother tree genotypes and clones derived from them by bud grafting were analyzed. These experiments comprised of 64 mother genotypes belonging to 23 families. Three to five bud grafted trees have been derived from each of these mother trees within one year and the age difference between the mother trees and clones were about one year. In all three experiments the dry rubber yields in budgrafts from the high yielding mother trees have reduced. The reduction was highest and significant in budgrafts derived from the highest yielding mother trees. On the other hand the yields of the budgrafts from the low yielding mother trees have increased significantly. The percentage deviation of clone yield with respect to the yields of mother trees shows a regular variation in all the three experiments that could not be expected solely due to the stock/scion interaction. But it is most probably a combined effect resulting from the branch characteristics inherited to the budgraft and the stock/scion interactions. This is an indication that the high yields of mother trees are not transferred to the clones through budgrafting and is an important phenomenon that needs further studies.
Budgrafting is currently the most popular method of propogation of rubber. The objective of this study was to determine the effect of the budwood on bud grafting success, sprouting and the scion growth. In the first part, the positional effect of individual buds was observed using brown budwood of two clones. There was no regular pattern in grafting success but, after a few successful grafts, there were one or two unsuccessful ones. Also, there were a certain percentage of dormant buds. Sprouting time also did not show any correlation with the position of the bud. The duration was different for two clones, 20 days for PB 217 and 60 days for clone PB 255. The shoot originating height was tested in the second part of this study using green shoots. Some bush nurseries were pollarded at 50 cm and 180 cm of clones RRIC 100 and RRIC 121. The differences were varied between the shoots of two original heights. However, the source bush trees were about 2-3 years old and therefore, these results are according to the expectation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.