Rubber Science

RELATIONSHIP OF THE ANGLE OF LEAN OF TRUNK AND GROWTH ECCENTRICITY WITH TENSION WOOD FORMATION IN FOUR CLONES OF HEVEA BRASILIENSISResearch Articles
Pages 82 - 86
Francis Mathew & C.P. Reghu
- Abstract
- Keywords
The relationship between tension wood formation and growth eccentricity of leaning trunks for four clones of Hevea brasiliens (Tjir 1, GT 1, RRIM 600 and RRII 105) were studied. The growth eccentricity did not show consistent variation with respect to tree height. The leaning angle and proportion of tension wood were correlated for the clone RRII 105. For all the four clones the correlation between tree height and angle of lean was highly significant. Tree height and proportion of tension wood showed highly significant correlation for RRIM 600. The relationship between angle of lean and growth eccentricity was significant for GT 1.

Growth eccentricity, Hevea brasiliensis, Leaning angle, Pith eccentricity, Tension wood

EVALUATION OF NINE HEVEA BRASILIENSIS CLONES FOR MISTLETOE INFESTATION AND THE EFFECT ON LATEX YIELDResearch Articles
Pages 87 - 89
O. Nicholas Ogbebor, I. Victor Omorusi & A. Grace Evueh
- Abstract
- Keywords
Incidence of mistletoe on nine rubber clones consisting of three exotic (PR 107, RRIM 707 and GT 1) and six clones developed by Rubber Research Institute of Nigeria (Nig 800, Nig 801, Nig 802, Nig 803, Nig 804 and Nig 805) were evaluated. The effect of mistletoe on rubber production was also studied. GT 1 was more susceptible followed by Nig 801 with disease indices of 19.22 and 12.23 per cent respectively. RRIM 707 recorded the lowest disease index (2.37%). There was no correlation between mistletoe infestation and yield in the clone GT 1.

Hevea brasiliensis, Mistletoe infestation, Nigeria

REACTION OF HEVEA BRASILIENSIS CLONES AGAINST POWDERY MILDEW DISEASE IN NORTH EASTERN REGION OF INDIAResearch Articles
Pages 90 - 93
G. C. MondaI, H. K. Deka & D. Chaudhuri
- Abstract
- Keywords
The incidence and severity of powdery mildew disease caused by Oidium heveae were assessed in forty clones of Hevea brasiliensis in different experiments in Assam, Meghalaya, Tripura and northern West Bengal. At the mature stage of growth, the severity of powdery mildew disease was evaluated for three consecutive years during the peak time of the disease (March-April) after wintering. Sixteen clones were found to be moderately tolerant with infection grades ranging from 1.5 to 2.5. Due to repeated massive premature defoliation caused by the disease during March to May, die-back was noticed subsequently in clones PB 5/51, PB 235, RRII 300, RRII 51, RRII 105, RRII 5, RRII 430 and RRIC 105. These clones are therefore rated as highly susceptible to powdery mildew disease.

Clones, Hevea brasiliensis, Oidium heveae, Powdery mildew disease, North East India, West Bengal

ROOTSTOCK-SCION RELATIONSHIPS IN BUD GRAFTED PLANTS WITH SPECIAL REFERENCE TO HEVEA BRASILIENSISResearch Articles
Pages 94 - 107
P. Sobhana, James Jacob & M.R. Sethuraj
- Abstract
- Keywords
Although known to man for several centuries, the art of grafting has been first used in modern agriculture to perpetuate desirable phenotypic traits in fruit crops in Europe during the fifteenth century. Since the beginning it has been known that while the scion characteristics could be maintained, the rootstocks also played a major role in the growth and development of the scion. One of the most pronounced effects of rootstock has been in reducing the scion tree size and altering its shape, and this has been commercially exploited in crops like apple by the use of dwarfing rootstocks.
Bud grafting is the most popular means of propagation in Hevea brasiliensis, the natural rubber tree. There are no rootstock options available in rubber cultivation unlike in several fruit crops. The rootstocks of H. brasiliensis are grown from highly cross-pollinated seeds that have different genetic lineages. Rootstock heterogeneity has been known to be a source of intra-clonal variability in growth and yield in H. brasiliensis. It is suspected that the differences in the genetic make up between the rootstock and scion leads to subtle interactions, or "genetic conflict" between them. Such conflicts may gradually reflect at all levels of tissue organization- from the molecular to the phenotype levels of the scion.
Though generally considered to be an adverse factor, the rootstock effects could also be positive in terms of growth and development of the scion or endurance to environmental stress. But no attention has been made so far to exploit such positive rootstock-scion interaction in H. brasiliensis. A clear understanding of the stock-scion relationships can help us to identify the right combination of stock and scion for the best agronomic performance of the tree. This study reviews stock-scion interactions and discusses the need to focus on exploiting ideal stock-scion combinations in rubber cultivation.

Hevea brasiliensis

Digital library

Volume 20, Number 1 & 2, (December 2007) Articles 13 - 16