Tissue culture derived plantlets are usually very delicate, and have weak root system and exhibit high mortality rates upon their transfer from in vitro culture vessel to ex vitro conditions. These plantlets therefore need to undergo a gradual adaptation from in vitro to natural conditions through a process of hardening / acclimatization. Controlled hardening procedures are therefore necessary to ensure high survival rates of plants and to correct abnormalities. Under such conditions, plants rapidly get converted from a heterotrophic state to an autotrophic mode along with the development of a fully functional root system and better control on stomatal and cuticular transpiration. The present review describes the characteristic variations commonly observed in in vitro developed plantlets like limited photosynthesis, reduced epicuticular wax, dysfunctional stomata, etc. Moreover, some methods for the successful acclimatization of in vitro generated plantlets are also discussed.

Among the various constraints faced by rubber growers in India, climate change has growing importance affecting productivity and profitability. Rising temperature, changing rainfall patterns, increasing drought and frequent natural calamities were experienced in various rubber growing regions. An attempt was made to study the deviation of maximum and minimum temperature from the optimum requirement of rubber in South and North East India. Through an extensive analysis of weather data spanning three decades from various meteorological stations across different regions, the study unveiled a discernible trend of escalating maximum temperatures. Certain areas exhibited notable alterations in temperature patterns, alongside a decreasing number of months with optimum temperature. This impact accentuates the imperative for tailored adaptation measures, particularly in regions like Kottayam, which face significant challenges. Overall, the findings highlighted necessity for region-specific adaptation strategies to support rubber growers in coping with the adverse effects of climate change. Ensuring the continued productivity and economic viability of the rubber industry requires proactive measures to address increasing temperature deviations from optimal growth conditions. The study advocated for the adoption of resilient rubber clones like RRII 430 and innovative management practices to mitigate adverse effects of climate change on rubber cultivation, safeguarding sustainability of the industry. Understanding these temperature patterns can also aid in developing more resilient rubber clones and better forecasting models to predict yield based on climatic data.

The use of heavy machinery in farming activities offers numerous benefits. However, excessive and unnecessary reliance on these machines can adversely affect the soil’s physical, chemical and biological properties. To assess the effect of different land preparation methods practiced for establishing rubber plantations on soil erosion and physico-mechanical properties of highly weathered lateritic type of soils under rubber cultivation in Kerala, a field experiment was initiated during 2010. The experiment was laid out in a randomised block design with four treatments and five replications. The land preparation methods evaluated were (a) pitting, terracing and tilling rubber inter rows for pineapple intercropping by earth mover (Hitachi) (b) pitting and terracing by earth mover (Hitachi) with zero tilled rubber inter rows (c) pitting by tractor mounted hole digger and manual terracing with zero tilled rubber inter rows and (d) manual pitting and terracing (standard practice). Soil samples were collected from the inter row areas of rubber plantation at four depths viz. 0-15, 15-30, 30-45 and 45-60 cm and analyzed to determine physical properties such as bulk density and porosity, as well as the mechanical property aggregate stability, both before and after land preparation. Results of the study indicated that during the initial years of land preparation, significant decrease in bulk density, increase in porosity and hydraulic conductivity at all soil depths were observed in plots where pitting, terracing and tilling operations were carried out using earth movers. The aggregate stability of soil was not influenced by land preparation methods. Soil loss estimation revealed that the inter row tilled plots showed a higher rate of erosion up to sixth year of land preparation compared to zero tilled soil. In tilled soil, approximately 39 per cent more soil was lost during the first year after land preparation. A positive correlation between hydraulic conductivity and soil erosion was also observed up to the fifth year of land preparation. Comparative cost analysis indicated that pitting and terracing by earth mover saved about 50 per cent of cost of cultivation compared to standard method (manual). The paper also emphasized the need for reorientation of land management strategies, particularly when intercropping pineapple in rubber plantations.

The ever-increasing demand for natural rubber has necessitated expansion of rubber cultivation to marginal areas which experience extreme climatic conditions viz. drought stress during summer and cold stress during winter. The drought prone areas require clones with drought tolerance potential for girth, growth rate and yield to survive and perform well. In this study, attempts were made to evaluate a set of 49 Hevea clones grown in a drought-prone region of Maharashtra in terms of girth, dry rubber yield and major component traits of yield. Based on juvenile yield, six high yielding and five low yielding experimental clones along with four check clones were selected for further assessment with anatomical (bark thickness and number of latex vessel rows), physiological (CO2 assimilation rate) and biochemical (levels of ATP, sucrose and thiols in latex)parameters. Under drought stress conditions, the CO2 assimilation rate and the latex ATP levels exhibited a significant positive correlation with yield while the sucrose and thiol levels had significant negative correlation.The stepwise multiple regression analysis among the parameters studied indicated CO2 assimilation rate and latex [ATP] as the most significant predictors for yield, accounting for 72 per cent of the total parameters contributing for yield. Based on rank sum analysis, the high yielding experimental clones 114, 66 and 69 were found superior to the drought tolerant check clones RRII 208 and RRIM 600 under drought stress conditions. This study revealed promising clones with drought tolerance potential which have to be further subjected to large scale evaluation to identify the most climate resilient clone/s suitable for drought prone regions.

In regions where rubber cultivation is prevalent, rainfall is of great importance as it is one of the major climatic factors affecting latex production from rubber trees. While optimum rainfall can lead to increase in yield by increasing soil moisture, it can also decrease productivity by hindering tapping schedule. A trend analysis of historical rainfall data (1963-2022) of Kottayam district of Kerala was carried out using modified Mann Kendall test. The study period was divided into two, the first period from 1963 to 1992 and the second period from 1993 to 2022. Analysis of data indicated that summer rainfall showed increasing trend while rainy days during southwest monsoon period showed a decreasing trend. While the first period (1963-1992) showed rising trend in rainfall and rainy days in June, second period (1993 to 2022), witnessed a decline in rainfall and rainy days. Rain-free days increased during the southwest monsoon and decreased in October. Additionally, the analysis indicated a rise in heavy rainfall events in the first period, contrasted by an increase in very light rainfall during the second period. Drought analysis of Kottayam region showed that four moderate drought events occurred, one in the first period of study and three in the second period of study. From the 60 year analysis of rainfall it was understood that, in the traditional belt of rubber cultivation, rainfall and rainy days showed a decreasing trend in the annual and southwest monsoon period. Contradictory to the annual and southwest monsoon rainfall, average of summer and northeast monsoon rainfall and rainy days increased during 1993 to 2022 period. Change in rainfall pattern has to be taken into consideration by farmers and policy makers for maximising production from rubber trees.

The study was undertaken with the objective of evaluating performance of 12 new Hevea clones in the pipeline in the central large scale trial under Phase 1 of the Participatory Clone Evaluation programme in the traditional rubber growing area in India. Growth of two pipeline clones P 21 and P 61 was comparable with that of the most vigorous clone RRII 414 at the time of opening (51.4, 49.1 and 51.9 cm respectively). P 61 also showed very high girth increment rate on tapping (3.6 cm yr-1), and was superior to all three checks (2.3 - 2.5 cm yr-1) for this trait. In terms of average yield over four years, clone P 21 with 64.8 g t-1 t-1 was superior to all other clones including the three check clones (46.0 – 50.7 g t-1 t-1), while clones P 67 and P 74 (59.0 and 51.2 g t-1 t-1 respectively) were on par with the controls. P 21 recorded the least incidence of ALF and Colletotrichum diseases, while P 74 showed very low incidence of pink disease. P 74 was on par with RRII 430 and RRII 414 for bark structural features viz. thickness and number of latex vessel rows. Performance of promising clones will be continued to be evaluated and compared with that of the satellite on farm trials.