Taraxacum kok-saghyz (rubber dandelion) is being developed as an alternative to Hevea brasiliensis (the Para rubber tree), the sole commercial source of natural rubber. Both Hevea bark and rubber dandelion roots contain pipe-like, multinucleate vessels known as laticifers, which produce latex rich in rubber particles. This study presents a histological analysis of laticifer ontogeny and development in rubber dandelion using multiple microscopy techniques. Rubber particles were detected in cells as early as eight days after seed germination, preceding laticifer differentiation. Laticifers were first observed 14 days after germination, originating from the pericycle and regions outside the primary phloem, and were present in all roots by day 16. Only articulated, anastomosing laticifers were formed in rubber dandelion roots. In mature roots, the highest numbers of laticifers occurred near the crown, gradually decreasing toward the root tip. In contrast, laticifer density was greatest in regions where the root diameter was smallest. Although no clear correlation was observed between laticifer number and rubber particle concentration, these findings provide valuable insights into laticifer development and may serve as a basis for early-stage prediction of rubber concentration and yield in rubber dandelion roots.

Changes in land use systems fundamentally alter global biogeochemical cycles and significantly affect the Earth's climate regulation. The impact of converting natural forests into rubber plantations on soil properties, nutrient dynamics and carbon sequestration in the Western Ghats region of Kerala, a biodiversity rich and ecologically sensitive area was assessed. The variations in soil properties across the different land use systems such as natural forest and rubber under first and second cycle of cultivation were compared. The results revealed that rubber cultivation accelerated soil acidification and led to a significant reduction in cation exchange capacity (CEC) as well as the availability of essential nutrients such as potassium (K), calcium (Ca) and magnesium (Mg) in soil. As the planting succession increased the same trend was observed. The indiscriminate land conversion activities resulted in more than 50 per cent reduction in total nitrogen (TN), total carbon (TC) and organic carbon (SOC) in the soil. The SOC stock in rubber plantations was two times lower than the forest, indicating a substantial decline in soil carbon storage. In all the land use systems, recalcitrant C (carbon) fractions predominated over the labile C, with the highest values recorded under the natural forest. Lower values of the carbon management index (CMI), coupled with a reduced carbon pool index (CPI) in the rubber plantations indicated a marked deterioration of soil quality in these systems. As the number of rubber planting cycles increased, gradual recovery of carbon and nitrogen levels was observed, indicating that rubber ecosystems can conserve nutrients and restore carbon over time. Therefore, despite the initial losses in soil quality and carbon stocks due to forest conversion, rubber plantations can function as a substitute for forests in terms of conserving and replenishing soil nutrients and carbon pools. These findings highlight the need for sustainable land management practices in rubber plantations to minimize soil degradation, enhance carbon sequestration and maintain ecological integrity.

Under the Participatory Clone Evaluation programme (PCE) Phase 2, fourteen pipeline clones and three check clones were simultaneously planted during 2010 in a Central Large Scale Trial (CLST) and an on-farm trial (OFT), for evaluation of their growth, yield and other secondary traits. Regarding girth in the opening year, pipeline clone P 044 (56 cm) performed on par with RRII 414 (57 cm) and RRII 430 (56 cm). P 080 and P 070 attained girth of more than 50 cm. Regarding mature girth in CLST, P 044 showed on par performance with P 080 and better than RRII 414 and RRII 430. P 044 had a girth increment on par with highest girthing clone RRII 414. In OFT, P044 recorded highest girth, which was comparable with RRII 430 and RRII 414. In CLST, P 070 had a tappability which was comparable with RRII 430. P 044 and P080 along with RRII 414 possessed more than 70 per cent tappability. In the OFT, P070 followed by P044 and P027 showed better tappability. In the CLST, P044 and P 099 recorded highest yield performing on par with RRII 430 and RRII 414. In the OFT, P 044 registered highest yield followed by RRII 430. P070 gave a yield which was comparable with RRII 105 and RRII 414. In the CLST, in the 3rd year of tapping, P019 had the highest leaf retention after abnormal leaf fall disease. In the 8th year of tapping in the CLST, P 080 and P 019 were found to be most tolerant. In the OFT, P019, P080, P070, P 054 and P 044 had more than 50 per cent LR. Regarding TPD in the CLST, P064 had the highest incidence of TPD while P 044 had the lowest TPD. In the OFT, P 092 had maximum TPD while P 044 had the lowest TPD. Regarding genetic parameters, yield over five years indicated moderate genetic control (broad-sense heritability; H-0.55). Based on growth, yield and prevalence of TPD in both CLST and OFT, pipeline clone P 044 emerged as a superior selection with up to 23 per cent yield improvement in yield over RRII 105. Another pipeline clone P 070 showed on par yield performance with RRII 414, RRII 430 and RRII 105 in the OFT and also possessed high level of tolerance to ALF disease. Based on the present study and based on results on previous appreciable performance of these clones in other small scale and large scale trials, the hybrid clone P 044 (86/29; RRII 105 x PR 107) and the open-pollinated half-sib progeny P070 (HS PB 252/132) were selected and recommended for upgradation in planting recommendation for growers.

 A clonal nursery population of 49 genotypes involving polyclonal selections, latest introductions and popular RRII clones were evaluated. Height and girth of the young clones, dry rubber yield and incidence of pink disease were recorded. Promising clones were identified based on girth attained by the fifth year after planting and the average yield for three years. The study showed that there exists significant variation among the 49 clones for the traits studied. Maximum plant height was recorded in IRR 5, a recently imported clone from Indonesia compared to RRII 430. Polyclonal selections such as M 1172, C 734, T 1478 and M 612 showed significantly higher values for plant height over RRII 430. After five years of planting, superior girth was recorded in A 1378, T 1458, C 1863, IRR 5 and M 1170 compared to RRII 430. Among the RRII 400 series clones, the highest girth was recorded in RRII 417. In the third tapping year, seven clones viz. A 1393, C 1836, T 1458, A 1378, C 1863, A 816 and M 1170 showed superior yield to RRII 430. The average yield over the three years showed that clones A 1393, T 1458, A 1378, C 1836, C 1863, A 816 and D 753 were superior to the check clone RRII 430. Among the RRII 400 series clones, the highest yield was recorded in RRII 417 followed by RRII 430, RRII 422 and RRII 414. Eight clones from the population viz. T 1281, M1170, A 1367, T 1286, D 1317, T 1478, M 590 and C 743 showed yield on par with RRII 430. Coefficient of Variation was lower for growth parameters compared to yield of clones showing more uniformity for growth among clones than for yield. Hierarchical clustering of the 49 clones for girth, dry rubber yield and incidence of pink disease in the population showed that 14 polyclonal selections, RRII 430 and IRR 5 were green to white in the colour scale for all the traits. The third-year yield was a strong contributor to the mean yield. Pink disease was seen as independent of growth and yield from the colour scale. The clones that showed superiority to RRII 430 for yield and also the clones that were on par with RRII 430 will be pipeline clones that may be tested further in large scale trials and on-farm trials for further validation.

 Translationally Controlled Tumour Protein (TCTP) is a highly conserved, multifunctional protein found in plants and animals. It plays a crucial role in regulating cell growth, stress responses, programmed cell death (apoptosis) and in supporting immune functions. Given its vital functions, TCTP has emerged as a key focus in plant biotechnology for enhancing stress tolerance and promoting vegetative growth. The present study aims to develop a plant transformation vector for overexpressing TCTP gene in Hevea brasiliensis, towards enhancing its vegetative growth and tolerance to abiotic/biotic stresses. The construct prepared was based on the binary vector pSiM24, harbouring an expression module for GUS gene and was utilized as the backbone for the new construct. The source vector plasmid, extracted from the E. coli cells, was subjected to double digestion and the GUS reporter gene was released from the vector. The identity of putative TCTP gene, amplified from the Hevea brasiliensis clone RRIM 600, was confirmed by sequencing. The coding region of this fully characterised TCTP was cloned into the double digested and linearized pSiM24 vector via infusion cloning technique. Successful incorporation of the TCTP gene in the source vector was confirmed by sequencing, followed by its transfer to Agrobacterium tumefaciens strain AGL-1 for Agrobacterium mediated genetic transformation of Hevea brasiliensis callus. Putative transformed cell lines were obtained from the infected callus. The transgenic plants once developed are expected to have augmented growth and stress tolerance, making them ideal for planting in stress prone, non-traditional areas.

Natural rubber, predominantly synthesized by Hevea brasiliensis, is a vital biopolymer with unique physicochemical properties essential to numerous industries. Despite its economic importance, the enzymatic mechanism, underlying its biosynthesis is not yet fully elucidated. While the upstream steps leading to isoprene monomer production mediated predominantly via the mevalonate (MVA) pathway are relatively well understood, the downstream polymerization processes responsible for assembling these monomers into high molecular weight polyisoprene with the characteristic chain length of natural rubber remain poorly characterized. Available information suggests that cis-prenyltransferases (CPTs) and other proteins like Rubber Elongation Factor (REF) and SRPP (Small Rubber Particle Protein) which, together with the HRT1-REF bridging protein (HRBP), form a functional rubber transferase complex on the surface of rubber particles which facilitates the chain elongation. While CPT is known to interact with REF and SRPP, HRBP is thought to stabilize the above complex on the surface of rubber particles facilitating the polymerization of isopentenyl pyrophosphate (IPP) into high molecular weight polyisoprenes. Current research has identified and cloned several isoforms of CPT and HRBP and their expression profiles suggest tissue- specific and developmentally regulated roles in latex-producing cells. Additionally, functional studies including heterologous expression in yeast and other model systems have demonstrated the catalytic potential of these enzymes. However, the exact molecular mechanisms and the specific role of different variants of these enzymes and their inter-regulatory mechanism leading to IPP chain initiation, elongation and termination still remains unresolved. This review discusses the various studies on CPT and HRBP, the two critical genes in the above process and prospective approaches including structural biology, in vitro reconstitution and synthetic biology that may bridge the current knowledge gaps and enable the engineering of rubber biosynthesis mechanism for crop improvement in Hevea as well as in the evolvement of in vitro biological systems for rubber synthesis