Molecular characteristics of 20 isolates  of Corynespora  cassiicola from  16 different  locations of two  rubber   growing states  of  southern India  viz., Kerala  and  Karnataka, were  investigated using  random amplified polymorphic DNA  (RAPD) markers.  RAPD analysis clearly  indicated the existence  of at least seven different  genotypes of C. cassiicola.  Considerable genetic  variations were  detected among the  Kerala  isolates  and  three  of them,  KL01/97,  KL04/98 and  KL06/97 showed completely different  RAPD  profiles  from  others  with  each  of the  primers  tested. Putative virulence specific RAPD profile of Corynespora was identified among the isolates where the disease became epidemic in  Karnataka.   Genetic relationships were established among the  Corynespora  isolates.

The  hysteresis ratio  values  of  the  belt,  tread  and   the  carcass  sections, cut  from  three P195/75R14 size tyres of different construction  were determined.   The fractional contribution of each component to the tyre structural hysteresis ratio at zero inflation pressure was estimated using the respective component volume fraction.   The sum of the fractional hysteresis contributions  of each tyre component agreed with its structural  hysteresis ratio determined independently.    The contribution of the belt package was approximately 10 per cent irrespective of tyre construction.   The contribution  of tread  ranged  between 25 and 50 per cent and  that  of carcass,  about  30 to 55 per  cent  depending on  the  tyre  construction.

A method for somatic embryogenesis and plant regeneration   from immature   inflorescence of Hevea brasiliensis , clone RRII 105 is described. The influence   of different growth regulators and sucrose at various stages  of this pathway has also been investigated. Among the different growth regulators tested  for callus  induction,   synergistic effect of the  two  auxins  2,4-D and NAA  was  observed. Optimum  growth     regulator   combination   for    callus  induction   was found      to be     2,4-D/NAA/ KIN   ( 4.5  /2.7  /2.3 µM  ). Embryo  induction was  favoured by  both  BA and  zeatin  in the   presence  of low  levels  of NAA or  2,4 -D.   Significant increase in embryo induction  frequency was  observed in  the presence  of GA₃.   A higher sucrose  level was found to be essential for  effective  embryo induction as  well  as  maturation.   ABA did not  show any  positive  effect  on  embryo  maturation, eventhough lower  levels  of ABA  in the maturation medium enhanced proliferation and  further embryogenesis. Plant   regeneration frequency was  found to be higher  on  media  fortified  with  BA and  GA3.     Lower  sucrose  level was found to be beneficial  for plant regeneration.

Eleven  pathogenesis related  proteins (PR-proteins) were  detected in rubber (Hevea brasiliensis) tree  infected  with   Phytophthora  meadii.  New  anionic  peroxidase (PR-9 proteins) appeared  in the tolerant interaction. Induction of PR-proteins is correlated with resistant interactions between H. brasiliensis and   P. meadii.   Two  proteins corresponding to  molecular weights 29kD and 33kD were prominent in expression in the tolerant plants 24 h after inoculation with the fungal pathogen.  In vacua infiltration studies revealed the presence of similar proteins in the intercellular fluids, obtained from leaves.  New anionic   peroxidase bands appeared in the resistant plants   during interaction with   the  pathogen.   Similar   changes in  the  protein induction were  observed on  treatment with  salicylic  acid.  The  results  indicate an  induction of  tolerance in  tolerant  Hevea plants when   challenged  with   P. meadii.

A study on  the dynamics of bark  growth and  latex  vessel  formation in  Hevea brasiliensis  was conducted  in  plantations established in  rubber   growing area  of  Cote  d'Ivoire.   The study showed that bark formation and  increase  of the total number of latex vessels  are well described by  a  sigmoid  logistic  model.     Analysis  of  model  increase   characteristics revealed  that  half of  the  theoretical number of latex  vessels  are  produced within six  years  after  planting.   The bark  formation process  showed a  hyperbolic relationship with  time,  which  was  very  strong during the first six years.   Thereafter, the speed  of bark  thickening and  latex  vessel  formation decreased irrespective of  the  clone.    This  phenomenon may  be  considered as  an  indicator of  tapping maturity for  rubber   trees.

The status of nutrients in the soils of slope lands under Hevea brasiliensis in Mizoram at different altitudes (100-750 m above mean sea level) was determined for better understanding of nutrient availability and crop productivity.  The soils were low to medium in available nitrogen.  About 74 per cent of the soils could be rated  as deficient in Bray's-P.   The total and  available N, P and  K contents,  in general,  was  in  the order  of K>N>P.   The soils contained adequate to toxic amounts  of DTPA extractable Fe, Mn, Cu and  tested low in available Zn especially for soils of higher  elevation.   Total and  available  N and  P and  DTPA extractable  Zn  had a  significant  negative  relationship  with  altitude  whereas  DTPA-Fe and  Cu  were  positively related.   There was positive influence of silt on total N and of both organic carbon and silt on KMnO₄-N.  The total and Bray's-P were significantly positively related with pH, silt and clay content. The NH₄OAc-K was positively related with CEC.  The silt and clay contents had negative influence on DTPA extractable Fe and Cu while DTPA-Zn was positively related with silt, clay and pH.