Rhizosphere Microorganisms and Their Effect on Fruit Quality - Postharvest Biology and Technology of Fruits, Vegetables, and Flowers - page 367

Tomato shelf life

100

80

98 85

90

60 75

75

50

40

50

20

20

0

8 15 22 30 8 15 22 30

Days after harvest

Tec-Myc - Fos-K + Dinactiv -
Bio-Tilis

Conventional treatment

Fig. 17.1 Effect of plants inoculation with AMF and PGPR on tomato fruit shelf life. Tec-Myc, AMF-based
inoculant; Bio-Tilis, B. subtilis -based inoculant; Dinactive, fertilizer; conventional treatment.

17.4.3 Composition

As mentioned before, microorganisms associated with plant roots cause biochemical and
physiological changes in host plants. Such changes are mirrored in seed quality in terms of
relative abundance of storage products such as proteins and lipids. For example, soybeans
show an increased content of oil (5.3%) and protein (1.5%), while the content of soluble
sugars and starch decrease (21.8 and 11.6%, respectively), when plant roots are inoculated
with Rhizobium (Achakzai et al., 2003). Inoculant formulations improved the number of
nodules, grain yield, seed protein concentration, and grain nitrogen content over the non-
inoculated (including the N fertilizer) treatments. The most pronounced effect of AMF has
been enhanced P nutrition of host plants (Kothari et al., 1991; Al-Karaki and Al-Raddad,
1997). In seeds, the relative abundance of storage products such as proteins and lipids is
altered by plant inoculation with AMF (Bethlenfalvay et al., 1994; Al-Karaki and Clark,
1999). Bethlenfalvay et al. (1994) studying pea ( Pisumsativum L.) concluded that the pres-
ence and intensity of AMF colonization altered the response of seed lipid metabolism in
response to increasing P availability, which in turn affected the protein and lipid ratios.
Thus, the plant P status can affect seed protein/lipid (Pro/L) balances (Bethlenfalvay et al.,
1997). However, different relationships between seed lipid and protein contents in wheat
( Triticum durum L.) plants inoculated or noninoculated with AMF indicated that the AMF
effects on seed composition could be distinct from those mediated by P nutrition provided
through conventional means (Al-Karaki and Clark, 1999).
It is known that organically grown produce possessed higher levels of antioxidants
(Asami et al., 2003). In pepper fruit, vitamin C content is altered by root plant inoculation
with AMF. Bagyaraj and Sreeramulu (1982) found that the ascorbic acid content of the green
chilli was increased in inoculated plants (up to 11%) supplied with the half-recommended P.
However, Oke et al. (2005) observed that phosphorus fertilizer application did not appear to
stimulate the content of vitamin C in tomato fruits. Although it is possible that the beneficial