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Online Rubber Clinic


There is provision for online live chatting with scientists/experts from 2 pm to 3 pm every working day. The user can also log on to the clinic at any time of the day for diagnosis on his own or for fixing an appointment with the expert. The Rubber Clinic will periodically organise group chatting on contemporary issues such as disease outbreaks etc. which will be advertised in the Clinic web pages well in advance. Rubber Producers Societies also could make use of the facilities of the clinic. The researchers can also benefit from the archived DDIS database of the clinic as resources for research programmes.

Indian introduced a new facility Online Rubber Clinic to intract the rubber cultivators with the scientists of RRII. I would like to appreciate Rubber Board for this valuable action. By receiving this information I joined this group and put my first about the remedy of  Brown bast which was my findings from experiments and experiences with the help of Dr. Thomas Varghees. However the action taken by the scientists and replied to the subject without the facility of interaction or to add any quiery.

The following is the scientific explanation from the Scientists of RRII.

Causative Agent:
It is generally presumed that tapping panel dryness (TPD) is, by and large, a physiological disorder resulting from tapping induced abiotic stress to Hevea trees. In the light of recent reports, involvement of pathogens in some types of TPD seems to be a possibility, although results are far from being conclusive. Detection of pathogens using R-PAGE( Return Poly Acrylamide Gel Electrophorosis) has shown the association of LMW RNA similar to viroid in TPD affected trees and its role in causing TPD is being studied. It is likely that various causes including both physiological and pathological may be responsible for TPD. But very little is known about the mechanism that triggers partial to complete inhibition of synthesis of rubber and latex in the affected tissues.
The general contention is that when the capacity of a tree to regenerate the latex harvested through tapping becomes inadequate, the tree succumbs to TPD. This is largely based on the common observation that overexploitation of the trees either due to frequent tapping and/or chemical stimulation leads to increased incidence of TPD. Investigations do not indicate that a deficient supply of carbon source for rubber biosynthesis was a limiting factor in TPD affected trees, because key intermediates of the rubber formation were found in large concentrations in the affected trees. Therefore excess drain of photosynthates through latex may not be the primary cause for TPD. The metabolic conversion of the precursors to the formation of rubber molecules is inhibited due to unknown reasons in TPD affected trees. Carbohydrates are known to accumulate in the latex even before the trees show symptoms of TPD indicating that inadequate availability of carbon was not the primary cause for TPD.
Several evidence suggested a relation between TPD and oxidative stress. Oxidative stress has been known to alter the normal metabolic pathways in a healthy tree by triggering a series of degenerative processes and may lower the respiratory activity and the energy status in the tissues. Conversion of intermediary metabolites to rubber is an energy consuming process and therefore this must be very sensitive to oxidative stress. Under oxidative stress, plants generally increases the production of free radical scavenging enzymes such as peroxidase, catalase, superoxide dismutase etc. and secondary metabolites like phenols melondialdehyde etc. In TPD trees these biomolecules were found in higher concentrations compared to normal trees. High peroxidases activity in TPD trees are capable of involvement directly or indirectly with several biological reactions including the regulation of plant growth regulators such as cytokinin, IAA, ethylene etc. Cytokinins are an essential group of plant growth regulators which mainly maintain the juvenility and retard senescence. Therefore maintenance of high content of cytokinins are very essential for an active metabolic functions of the rubber tree tissue including active rubber biosynthesis. Investigations showed that the reduced content of a certain group of cytokinin in the bark tissue was related to TPD which fully inhibited the rubber biosynthesis. Similarly, the cytokinin content had an inverse relationship with peroxidase enzyme activity and phenol content. The rubber molecule formation requires three distinct biochemical process such as initiation, elongation and termination. The hydrophobic rubber molecule is packed inside a rubber particle and the polymerization reaction is taking place at the particle surface with the help of an enzyme rubber transferase, which is bound to the rubber particle. The particle size analysis in the latex showed differences related to TPD incidence in the rubber particles produced. The rubber particles, on an average become comparatively smaller towards the later stages of TPD. Analysis in the rubber transferase activity showed an inverse relation with the rubber particle size. Therefore in the TPD samples, the variation in the particle size can be directly related to the chain elongation processes which appears to be interrupted due to the relatively low availability of its immediate substrate in TPD trees. The latex sample of ethylene stimulated trees also showed similar changes in the particle size distribution which closely resemble the particle size of TPD trees.
It is important to investigate the exact molecular level mechanism by which the rubber biosynthesis is inhibited during TPD and the biochemical modulations occurring, if any, at the initiation, elongation and termination processes of rubber biosynthesis during the onset of TPD. Study of the energy metabolism in relation to the impaired rubber biosynthesis in the laticiferous tissues of TPD trees may help to identify whether there exist any limiting steps involved in the energy utilization processes and the modulations occurring due to the action of growth regulators. This understanding is crucial to any attempts to overcome the disorder using any molecular biology techniques. Studies were also initiated to understand the effect of rootstock on TPD and examined if bud grafting from a TPD-affected tree increases the chances of TPD. It was noted that the genetic distance between rootstock and scion tissues was greater in TPD affected than the healthy trees. Investigations were shown that once a tree had shown TPD symptom in one tapping panel, it might easily develop this disorder in another panel. The reoccurrence of TPD in another panel of the tree indicates that TPD incidence is not a local phenomenon in the tree bark. This suggests either the involvement of a pathogen or the intrinsic susceptibility of the tree to the physiological disorder with out any involvement of a pathogen. The randomness in the occurrence of TPD and the obvious failure to transmit the syndrome through grafting TPD affected bark on healthy trees and vice versa suggest the involvement of intrinsic factors rather than any pathogen. However, likely intrinsic differences in the ethylene production capacity or tissue sensitivity to ethylene between different trees within a clone could explain the random nature of TPD occurrence.
Through RAPD analysis, it was shown that the genetic distance between the rootstock tissues ranged from 7-39 % because of their heterogeneousness. Our results indicate that the genetic distance between rootstock and scion tissues was greater in TPD affected than in healthy trees. Investigations are on to find if a greater genetic distance between the root stock and scion is causing any kind of genetic conflict between them resulting in any subtle, but specific expressions in the scion. The latex diagnosis (LD) can be used as a tool to predict overexploitation of the tree through over stimulation which may lead to TPD.  Biochemical studies indicated that the concentrations of sucrose and Pi in the latex become higher in trees 15 to 45 days before the onset of TPD.  Similarly, several investigations have pointed out that many types of proteins including heat stable proteins and LEA proteins are linked to TPD and all these are being used as putative protein markers for TPD/biotic stress in Hevea.

Occurrence:
Generally high yielding clones of natural rubber are often considered susceptible to the physiological disorder commonly termed Tapping Panel Dryness (TPD) earlier referred to as Brown Bast. It usually occurs when the harvesting of latex from the trees exceeds the physiological capacity of its regeneration. It is estimated that TPD leads to approximately 15-20% decrease in yield

Symptoms:
The common symptoms of TPD include an excessive late dripping of latex simultaneous with a drop in the dry rubber content of the latex in the initial phase and high DRC in the later stage.  Total inhibition of rubber biosynthesis occurs and no latex is produced towards the final phase. The most inportant symptom of TPD affected trees is partial or total drying of tapping panel which gives the name to the disorder.Besides cessation of latex flow, terminal symptoms like bulging, necrosis and cracking of the bark have been observed. Some clone specific TPD symptoms characterised by sloughing in PB 28/59 and scaling observed in clone RRIM 605 are also noticed. The symptoms are observed also on the root stock and root. In most of the partially affected trees, dry portion is confined only to the roots below the dry portion in the scion.

Clonal Susceptibility:  Control Measures: Management Practice to TPD
Giving tapping rest and changing the tapping panel are the generally followed plantation practices to mange TPD in rubber.   Tapping rest does result in some improvement in the TPD situation at least for a while and a small proportion of the TPD trees may make full recovery particularly when the trees are reopened on a new panel. It is observed that most high yielding clones are highly susceptible to the disease and hence it would be advantageous to follow 1/2 S d/3 tapping system to reduce the intensity of exploitation stress thereby reducing the TPD incidence in the population. As a curative measure, resting the trees without tapping for a considerable period is advised. Therefore, tapping can be resumed changing the tapping panel and following a low intensity tapping system.

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