‘Priming’ protects Piper nigrum L. from Phytophthora capsici through reinforcement of phenylpropanoid pathway and possible enhancement of Piperine biosynthesis

Abstract

Piper nigrum L. (black pepper), a woody perennial spice crop indigenous to India is positioned at the phylogenetically unique basal lineage of angiosperms. Cultivation of this major spice crop is constrained by rampant fungal and viral infections leading to a lack of disease-free planting material. The major disease that poses severe threat to P. nigrum plantations and nurseries is ‘quick wilt’ caused by the oomycete Phytophthora capsici, which affects the leaf, stem, spike, collar and root. In this paper, we report the consequence of priming in modulating Piper nigrum defense against Phytophthora capsici. Glycol Chitosan (GC) was used to infiltrate detached leaves of mature P. nigrum plants. It was observed that pre-treatment of GC for 24 hours resulted in significant reduction of disease symptoms in infected leaves, as evidenced by the marked decrease in the size of lesions, and also delayed the appearance of symptoms up to 72 hpi. Experiments repeated in P. nigrum seedlings under controlled growth conditions indicate that delayed disease symptoms of GC pre-treated leaves do not spread to healthy uninfiltrated leaves suggesting a priming-associated systemic defense response. An ROS-mediated manifestation of Hypersensitive Response (HR) induced by Chitosan was also evident in pre-treated leaves. A corresponding visual indication of increased lignification was observed, which correlated with an enhanced lignin content of GC-treated leaves. Enhanced callose deposition was also apparent in GC infiltrated leaves, establishing a stimulatory effect of GC in triggering HR through ROS production, enhanced lignification and callose deposition. Key genes of the core phenylpropanoid and isoprenoid pathways along with major defense signalling pathway genes of P. nigrum, including pathogenesis-related genes and hormone signalling genes showed significant transcript enrichment consequential to GC treatment. A significant quantitative enhancement in Piperine content was evident in GC-infiltrated leaves. The systemic nature of priming on disease protection was established through experiments conducted in rooted cuttings monitored for 30 days after disease infection. This is the first report that provides strong molecular evidence endorsing the twofold advantage of defense priming in P. nigrum by improving crop protection with a concomitant enhancement in Piperine biosynthesis.

Validation of reference gene stability for normalization of RT-qPCR in Phytophthora capsici Leonian during its interaction with Piper nigrum L.

“…This protein has been observed to induce necrotic responses in the host plant Nicotiana benthamiana 25 . Previous research from our lab has shown that P. capsici initiates hyphal growth in P. nigrum within 6 hpi and proliferates extensively on the leaf, resulting in the formation of progressing necrotic lesions within 24 hpi 40 . Our analysis of NPP1 gene expression in this study aligns with these findings, revealing a peak expression between 12 and 24 hpi, followed by a decrease by 48 hpi.…”

“…However, there is a noticeable scarcity of studies focusing on this aspect, particularly in the field of crop plants 37 and phytopathogens 38 . Piper nigrum , commonly known as black pepper is an important non-model spice crop that is susceptible to a highly destructive disease called quick-wilt or foot rot caused by the pathogen, Phytophthora capsici 39 , 40 . The suitability of different RGs in conducting expression studies in the host plant ( P. nigrum ) in response to P. capsici infection has been reported earlier 37 .…”

Identification of Piper species that are resistant to Phytophthora capsici, Meloidogyne incognita, and waterlogging in Vietnam

“…Crop loss due to pathogens represents a major challenge for the black pepper industry. Two common pathogens severely affecting black pepper cultivation are Phytophthora capsici and Meloidogyne incognita (Indu et al, 2022; Mahadevan et al, 2016; Tran et al, 2019; Truong et al, 2010; Verma et al, 2023). In addition, it is well known that black pepper plants require well‐drained soil (Nair, 2011; Sadanandan, 2000), which means that black pepper cultivation is hampered in parts of Asia where frequent rainfall and flooding are common.…”