Effects of Verticillium dahliae on tomato root morphology considering plant growth response and defence

Abstract

The soilborne pathogen Verticillium dahliae invades its host via the root, and spreads systemically throughout the plant. Although a functional root system of appropriate size is essential for water and nutrient uptake, to date, effects of pathogens on root morphology have not been frequently investigated. Therefore, this study aims to improve knowledge of how V. dahliae infection impairs root morphological characteristics of tomato, considering plant growth and physiological responses, particularly those involved in defence in roots and leaves over a growing period of up to 28 days postinoculation. Verticillium dahliae infection suppressed the growth of both shoot and root. Diseased plants developed a smaller leaf area, and exhibited a reduction in the rate of photosynthesis and stomatal conductance. An early response to pathogen invasion in the host root was the up-regulation of several defence-related genes, such as proteinase inhibitor II (Pin2), b-1,3-glucanase A (GluA) and two pathogenesis-related genes (PR-1a, PR-1b). However, this response did not prevent colonization of the roots by the pathogen. Although a high variability in pathogen density was found within the root system, a significant increase of both the specific root length and surface area was observed in response to pathogen invasion; these traits correlated with water use efficiency. Morphological changes of the root may represent an adaptive response evolved to sustain the supply of both water and nutrients in the presence of the pathogen.

Use of RGB Vegetation Indexes in Assessing Early Effects of Verticillium Wilt of Olive in Asymptomatic Plants in High and Low Fertility Scenarios

“…V. dahliae infection has been characterized as consistent with water deficit stress as a consequence of xylem blockages caused by the fungus as well as host defense mechanisms [9,42,43]. Results obtained for stomatal conductance and chlorophyll fluorescence in this study (Table 2) did not show differences due to inoculation, and since both these parameters may be used as indicators of water status these results suggest effects that mimic water stress were not present, notwithstanding other physiological changes detected.…”

Cultivar-Dependent Responses of Eggplant (Solanum melongena L.) to Simultaneous Verticillium dahliae Infection and Drought

“…Plant growth reduction can be the outcome of a pathogen infection ( Johnstone et al, 2005 ). Results by Buhtz et al (2017) demonstrated that V. dahliae infection greatly compromised plant growth of tomato plants. Nevertheless, this reduction can limit the water requirements of the plant thus improving plant survival during the simultaneous imposition of drought as shown in other studies ( Xu et al, 2008 ).…”

“…Interestingly our results indicate further that significant interactions of cultivar, drought and V. dahliae stresses were also obtained. One of the most common suite of traits that plants utilize to circumvent the stressful environments is the reduced stem/root ratio, thus optimizing the use of their available resources ( Chapin et al, 1993 ; Gargallo-Garriga et al, 2014 ; Koevoets et al, 2016 ; Buhtz et al, 2017 ; Pandey et al, 2017 ). Even though, this was not shown in the double interaction, there was a significant difference in the cultivars effect (as single factor) and in the triple interaction.…”

Species-Specific Impact of Fusarium Infection on the Root and Shoot Characteristics of Asparagus

“…Root growth is an important indicator for the development and progress of diseases induced by soil-borne pathogens [ 32 , 33 ]. The attack or frequency of host infection by pathogens is influenced by root growth traits such as root length, diameter, surface area, and volume.…”