Understanding the genes that govern tea plant (Camellia sinensis) architecture and response to drought stress is urgently needed to enhance breeding in tea with improved water use efficiency. Field drought is a slow mechanism and the plants go through an adaptive process in contrast to the drastic changes of rapid dehydration in case of controlled experiments. We identified a set of drought responsive genes under controlled condition using SSH, and validated the identified genes and their pattern of expression under field drought condition. The study was at three stages of water deficit stress viz., before wilting, wilting and recovery, which revealed a set of genes with higher expression at before wilting stage including dehydrin, abscissic acid ripening protein, glutathione peroxidase, cinnamoyl CoA reductase, calmodulin binding protein. The higher expression of these genes was related with increase tolerance character of DT/TS-463 before wilting, these five tolerant progenies could withstand drought stress and thus are candidates for breeding. We observed that physiological parameter like water use efficiency formed a close group with genes such as calmodulin related, DRM3, hexose transporter, hydrogen peroxide induced protein, ACC oxidase, lipase, ethylene responsive transcription factor and diaminopimelate decarboxylase, during wilting point. Our data provides valuable information for the gene components and the dynamics of gene expression in second and third leaf against drought stress in tea, which could be regarded as candidate targets potentially associated with drought tolerance. We propose that the identified five tolerant progenies on the basis of their drought tolerance can thus be utilised for future breeding programmes.
Background
Shifting cultivation (locally known as “jhum”) is a major driver of deforestation and loss of ecosystem services in rainforests. For developing any effective conservation of biodiversity and carbon service program, an in-depth understanding to the recovery of vegetation and carbon after abandonment of jhum is essential. We estimated species richness, abundance and composition of trees, shrubs and herbs, carbon distribution in aboveground and belowground components along a chronosequence of jhum fallow in northeast India, and elucidated the factors affecting the recovery processes of jhum fallows.
Methods
Species composition and other plant community attributes, carbon storage in different pools were studied in 5 jhum fallows (< 5, 5–10, 11–15, 16–20, 21–25 years old) and an old-growth forest. The data were subjected to linear mixed effect modeling using R-package “nlme” for identifying the important factors contributing to the recovery of vegetation and carbon.
Results
Species composition varied significantly (P < 0.05) between jhum fallows and old-growth forest. Tree density varied from 28 stems ha−1 in 5 years old jhum fallow to 163 stems ha−1 in old-growth forest. Both biomass carbon in all components and soil organic carbon were significantly (P = 0.01) lower in jhum fallows than in the old-growth forest except living non-woody biomass component. The recovery of aboveground biomass carbon was faster during early successive years than the mid-successive jhum fallows. Total ecosystem carbon and soil organic carbon stock in the oldest jhum fallow was 33% and 62% of those in the old-growth forest, respectively. The fallow age was found to be the most important explanatory factor in the recovery process of vegetation and carbon stock in re-growing fallows.
Conclusion
The shifting cultivation fallows gradually recovered both vegetation and carbon and are potential repository sites for biodiversity conservation, which may take much longer time to reach up to old-growth forest in northeast India.
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