Stem canker caused by Phomopsis spp. Induces changes in polyamine levels and chlorophyll fluorescence parameters in pecan leaves

Abstract

Pecan plants are attacked by the fungus Phomopsis spp. that causes stem canker, a serious and emerging disease in commercial orchards. Stem canker, which has been reported in several countries, negatively affects tree canopy health, eventually leading to production losses. The purpose of this study was to inquire into the physiology of pecan plants under stem canker attack by Phomopsis spp. To this end, pecan plants were inoculated with an isolate of Phomopsis spp. and several parameters, such as polyamines, proline, sugars, starch, chlorophyll fluorescence and canopy temperature were analysed. Under artificial inoculation, a high disease incidence was observed with symptoms similar to those in plants showing stem canker under field conditions. Furthermore, the infected stem showed dead tissue with brown necrotic discolouration in the xylem tissue. The free polyamines putrescine, spermidine, and spermine were detected and their levels decreased as leaves aged in the infected plants with respect to the controls. Chlorophyll fluorescence parameters, such as Sm, ψ EO, and QbRC decreased under plant infection and therefore the K-band increased. Canopy temperature and proline content increased in the infected plants with respect to the controls while sugar content decreased. These data suggest that stem canker caused by Phomopsis spp. induces physiological changes that are similar to those observed in plants under drought stress. To our knowledge, this is the first study that documents the physiological and biochemical effects derived from pecan-Phomopsis interaction.

The Identification and Role of the Key Mycotoxin of Pestalotiopsis kenyana Causing Leaf Spot Disease of Zanthoxylum schinifolium

“…For example, cold stress has been shown to cause a significant reduction in the soluble sugar content of Eupatorium adenophorum [59]. Similarly, when soybean roots were treated with the F. oxysporum mycotoxin, when or pecans were infected with Phomopsis spp., there was a decrease in soluble sugar content [60]. In our experiment, we observed a gradual decrease in the soluble sugar content of Z. schinifolium leaves over time following treatment.…”

Unveiling the Virulence Mechanism ofLeptosphaeria maculansin theBrassica napusInteraction: The Key Role of Sirodesmin PL in Cell Death Induction

“…Previously, we determined a similar pattern in changes in photosynthetic capacity in tobacco plants infected with the necrotrophic fungus B. cinerea (Rossi et al ., 2017). Pecan plants infected with the hemibiotrophic fungal species in the genus Phomopsis also show a decrease in chlorophyll fluorescence (Mantz et al ., 2021). It seems that the decline in photosynthetic activity is the result of a multifaceted process involving a decrease in transcript levels of genes encoding proteins involved in photosynthesis and also a decrease in the number of chloroplasts per cell, both in spongy parenchyma and palisade parenchyma (Figure 8).…”

Improvement of cold tolerance in maize (Zea mays L.) using Agrobacterium-mediated transformation of ZmSAMDC gene

“…High-performance liquid chromatography (HPLC) was used to determine the PA content of the plant leaves. 17 The Pro content of the maize leaves was analyzed using the acid ninhydrin method. 18 The thiobarbituric acid method was used to analyze the MDA content of the maize leaves.…”