Preface

Studies involving *Arabidopsis thaliana* and other crop plants have continued to advance our knowledge of the mechanisms used by plants to survive in dynamic biotic and abiotic environments. Plants have adapted to diverse ecologies for ages; however, recent human migrations, agricultural activities, and climate change-induced phenomenon have forced plants to increasingly adapt to new environments. Furthermore, agricultural production is becoming progressively more vulnerable to climate variability and change characterized by altered frequency, timing, and magnitude of precipitation, temperature, and wind.

This book focuses on current morphological, anatomical, physiological, molecular, and genomic advances in plant defenses. It discusses advances in plant stress signaling mechanisms and molecular defense responses involving recently discovered biomolecules. It also discusses advances in gene expression changes, which can be inherited as described in epigenetic mechanisms and linked to observed phenotypic plant plasticity. The book also looks at emerging areas like plant growth-promoting microorganisms (PGPMs), which consist in a vast group of microorganisms found in the rhizosphere, on the root surface or associated to it. It examines the mechanisms of action of PGPMs, including their ability to produce different plant growth regulators or phytohormones.

The studies in this book indicate that researchers have found intriguing interactions among plants and their physical, microbial, and biotic environments. These interactions have been highlighted and linked to novel mechanisms, increasing our understanding of how sessile plants adapt and thrive in challenging environments. These studies consider the resilience and sustainability of plant genomes and epigenomes and the role they will play in the next generation of food systems.

Some of the other topics addressed in this book include the effects of hailstorms, control of secondary damages due to insect pests and diseases, the removal of fallen fruit to reduce the spread of disease and pests during their decay, analysis of wounds on branches and fruit thinning, and the effects of bud-breaking chemicals, bioregulators, and fertilizers on vegetative growth. In general, the major and chronic threats to ecosystem stability and sustainable agriculture are phytopathogenic microorganisms. The unlimited and regular use of chemical pesticides and fungicides can destroy soil ecology, degrade soil fertility, and disrupt the environment, causing harmful effects on human health and contaminating groundwater. However, our studies found that PGPMs are environmentally friendly and offer a promising way of obtaining sustainable soil fertility and plant growth, although indirectly. Nevertheless, antibiotic production is considered one of the most powerful and studied biocontrol mechanisms of PGPMs against phytopathogens.

> **Josphert Ngui Kimatu, BSc., Mphil., PGDE, Ph.D.** Professor, South Eastern Kenya University, School of Sciences and Computing, Department of Life Sciences, Kitui County, Kenya

## **Chapter 1**
