INVESTIGATION ON THE GENETIC BASIS OF ENVIRONMENTAL STRESS IN FRUIT TREE CROPS

Plant stress can be divided into two major categories: abiotic stress and biotic stress. Abiotic stress happens when plants are exposed to the environment either physically or chemically. There is an emergency in developing crop varieties that are tolerant to abiotic stresses to ensure food security and safety in the coming years. Multiple abiotic stress like drought, heat, frost at flowering and nutrient deficiency can cause an erratic fruiting behavior or following extreme events, the death of the plants. Plants require an optimal level of nutrients and essential minerals for their growth and development that are mainly acquired from soil by their roots. Nutrient deficiency is an environmental stress that can seriously affect fruit production and quality. In the past decades, agriculturalists relied only on the traditional methods to identify the stresses. In this postgenomic era, called the “omic” era, transcriptional and translational research on model plants has provided many valuable information on many horticultural species. In the present dissertation, the objective of the first study was to identify, and map key genes involved in drought response on leaves across different crops. The study is the first to provide RNA-Seq data analysis related to transcriptomic responses towards drought across different fruit tree crops. The second study was conducted to identify essential genes involved in general plant abiotic stress conditions and those involved in specific and unique in different abiotic stresses. A pipeline composed of pathway and gene set enrichment analysis, protein-protein interaction networks, and gene visualization tools were employed. The next study aims to identify genes that serve as potential targets to develop cultivars with enhanced drought and salinity resistance and/or tolerance across different fruit tree crops in a biotechnological sustainable way. An “omic” experimental plan was developed to investigate and understand a physiological stress presumably due to nutritional deficiencies causing premature flower bud abscission in pistachio that leads to alternate bearing behavior. The aim of this analysis was to provide insights into the transcript changes between inflorescence buds and fruits in bearing and non-bearing shoots to identify the molecular mechanism causing premature inflorescence bud abscission, which is linked to alternate bearing in the Italian pistachio cultivar Bianca. Key molecular physiological conclusions were generated based on the identification of conserved gene sets, pathways, and gene networks involved in abiotic stress resistance/tolerance. The experiment provides a valid approach to ask additional questions with respect to how plants respond to stress. Identifying key information in transcriptomic data is very important, especially when the “omic” study deals with plant responses to stresses in field conditions where a high number of variables and disturbing factors may affect the analysis. The proper understanding of plant stress response mechanisms under specific stresses can draw a better view for improving worldwide food production.