Graduate Teaching in Postharvest Science

Graduate students in postharvest specialties can select from a number of relevant courses in the horticulture, food science and human nutrition, agricultural engineering, and plant pathology departments. Complete course listings for these departments can be found in the graduate catalog.


HORTICULTURE 6331-POSTHARVEST PHYSIOLOGY

Instructor: D.J. Huber

General Course Description: Physiology, biochemistry, and molecular biology of fruit, vegetative, and floral organs after harvest. Current theories and research will be surveyed with emphasis on the understanding and control of cellular processes important for the storage and quality maintenance of harvested plant organs.

Course Objectives

To familiarize students with the relationships between plant organ type, function, and the relevance of these attributes to anticipated postharvest behavior and predictive handling protocols for specific commodities

To familiarize students with organ type and function, and of the cellular implications of these attributes as they influence performance in the postharvest environment

To familiarize students with the current literature in postharvest science, exposing them to the critical thinking skills required to adequately judge and evaluate the relevance of scientific findings.

Course Overview: Physiology, biochemistry, and molecular biology of fruit, vegetative, and floral senescence following harvest. Mechanisms contributing to senescence and deterioration phenomena, including apoptosis and other forms of programmed cell death (PCD). Membrane and cell wall metabolism, low-temperature injury, radical oxygen species, apoptotic-driven death phenomena, ethylene biosynthesis, reception, and signal transduction, low-oxygen storage, and postharvest pathology.

Topics (order and priority subject to change):

Overview of postharvest biology -- (PowerPoint presentation)

Definitions and terminology -- Senescence, apoptosis, programmed cell death

Quality and maturity/harvesting indices

  • subjective vs objective
  • destructive vs nondestructive

    Growth kinetics, sink activity, and consequences of harvest

  • single-sigmoidal growth
  • double-sigmoidal growth

    Senescence of plants and plant organs - general features

  • protein and carbohydrate changes
  • ultrastructural changes

    Membrane structural/functional changes in senescing organs

  • Concepts fluidity, microviscosity, lateral phase separation, membrane fusion
  • Membrane conformation: lamellar, hexagonalI, hexagonalII

    Radical oxygen species: generation and control in senescence and aging

    Ethylene biosynthesis

    Regulation of ethylene biosynthesis

  • ACC synthase, ACC oxidase

    Genetic modification of ethylene biosynthesis

    Ethylene binding, mode of action, signal transduction

  • ethylene analogs -- inhibitory vs active

    Patterns of ripening/senescence

  • climacteric organs
  • nonclimacteric organs
  • System I/System II ethylene

    Respiration climacteric

  • relevance to ripening: detached versus attached organs

    Respiraton and metabolic homeostasis

    Fruit softening

    Cell wall changes in ripening fruit and other senescing organs

    Senescence of cut flowers

    Vascular plugging: bacterial and physiological

    Chilling injury

  • symptoms
  • mechanism
  • control in the postharvest environment

    Fresh-cut processing of fruits and vegetables--problems and solutions

    Physiology and biochemistry of commodities in CA storage

    Postharvest pathology

  • latency, quiescence, appresoria-cuticle interactions
  • infection progession and host responses
  • symptom expression

    Factors influencing pathogen development

  • pathogen enzymes
  • host defense-mechanisms (phytoalexins/elicitors)
  • --constitutive
  • --inducible

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