Postharvest Biology and Technology of Fruits, Vegetables, and Flowers

Chapter 17
Rhizosphere Microorganisms and Their
Effect on Fruit Quality
Víctor Olalde-Portugal and Hortencia Gabriela Mena-Violante
17.1 Introduction
This chapter summarizes some key aspects related to horticultural product quality when
plants form symbiotic associations with beneficial rhizosphere microorganisms such as
arbuscular mycorrhizal fungi (AMF) or plant growth–promoting rhizobacteria (PGPR).
The development of those highly compatible associations brings a variety of benefits to
nutritional status, health, growth, and development in plants. Several changes in host plant
biochemistry and physiology occurring during these symbioses have been documented.
Thus, fruit, vegetables, and grains may be modified not only in terms of biomass produced
but also in some of their quality attributes.
The term “quality” implies the absence of defects or the degree of excellence of a
product (Abbott, 1999), and it includes both sensory attributes that are readily perceived
by the human senses and hidden attributes such as safety and nutrition (Shewfelt, 1999).
The last objective of the production of fresh fruits and vegetables is to satisfy consumers,
and consumer satisfaction is definitely related to quality; thus, good quality of horticultural
products remains a prerequisite during production.
In the past few years, the changes in consumer attitudes and expectations associated
with cultural practices and concerns about the side effects of agrochemicals have led to
new perspectives on agricultural management. Research in this area has been oriented to
developing technological alternatives that increase crop yield and improve product quality
and lesser dependence on agrochemical inputs.
It is well known that the use of excessive nitrogen fertilizers is linked to nitrate contamination
of ground water and emissions of ammonia and nitrogen oxides into the atmosphere
(Bouwman, 1990; Houghton et al., 1990; Duxbury, 1994), while phosphate runoff in surface
waters has led to eutrophication of ponds and rivers (Sharpley et al., 2003). Enhanced
soil fertility and higher biodiversity found in organic plots may render agrosystems less
dependent on external inputs (Mäder et al., 2002). On the other hand, while comparing organic
and conventional production technologies, organic products have shown a significant
increase in vitamin C, iron, magnesium, and phosphorus content and a decrease in nitrate
content (Worthington, 2001). Additionally, the market tendencies indicated that the production
of organic products represented US$23 billion in 2002 (Willer and Yussefi, 2004).
Therefore, the development of organic agriculture has become increasingly important and
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