An Effective Inoculation Method for Phytophthora capsici on Black Pepper Plants

Summary

Pinpricking the basal head of the black pepper plant is a brief and time-saving method to damage it. Here, we provided detailed steps with a video for infecting black pepper plants.

Abstract

Piper nigrum L. (black pepper) is a typical woody vine that is an economically important spice crop across the world. Black pepper production is significantly impacted by root rot disease caused by Phytophthora capsici, which has seriously influenced the industry development as a "choke point" problem. However, the molecular genetic mechanism of resistance in black pepper is unclear, leading to slow progress in the development of new black pepper varieties. An effective inoculation and precise sampling system for Phytophthora capsici on black pepper plants is essential for studying this plant-pathogen interaction. The main aim of this study is to demonstrate a detailed methodology where the basal head of black pepper is inoculated with Phytophthora capsici, while also providing a reference for the inoculation of woody vine plants. The basal head of the black pepper plant was pinpricked to damage it, and mycelial pellets covered the three holes to retain the moisture so the pathogen could infect the plant well. This method provides a better way of solving the instability that is caused by traditional inoculation methods including soil drench or root dipping. It also provides a promising means for studying the mode of action between plants and other soil-borne plant pathogens in agricultural precision breeding.

Introduction

Black pepper (Piper nigrum L.) is a woody climber and one of the most important spice crops. It is known as the "King of Spices"¹ and is cultivated in over 40 countries and regions throughout Asia, Africa, and Latin America. Phytophthora root rot is the most devastating disease of black pepper, and is caused by the oomycete Phytophthora capsici. This pathogen also infects cucurbits, eggplants, chili peppers, and tomatoes^2,3. With black pepper, an entire crop can sometimes be decimated by this disease. The expansion of pepper planting areas is restricted as a result of ....

Protocol

1. Preparation of black pepper cutting plants for infection

1. Take a five-node cutting, approximately 40 cm long with a diameter of 0.5 cm, from a healthy and vigorously growing orthotropic branch of black pepper using a disinfected pruning knife or secateurs. Prune the lower three nodes of the plagiotropic branches, with the upper two nodes left with approximately 10 leaves intact.
2. Prepare rooting substrate containing soil and animal manure (cow dung or sheep dung) at a ratio of 1:1. Autoclave the rooting substrate at 121 °C for 20 min.
3. Insert the cuttings into the rooting substrate at an angle of approximately 50&#....

Results

Figure 1 shows the symptoms of black pepper leaves following P. capsici inoculation. Figure 2 shows the symptoms of black pepper stems following P. capsici inoculation. The pathogen infected the black pepper at the basal stem; symptoms including leaf yellowing, wilting appearing, xylem browning, and vessel blacking gradually appearing. Figure 3 shows most of the genes expressed differently after inoculation with

Discussion

In this study, the basal head was pinpricked to damage and provide an effective inoculation system in the black pepper plant. Mycelial pellets then covered the three holes to retain moisture and enable the pathogen to infect the plant well. Following inoculation, the leaves turned yellow and dropped off and the inoculated plants died. No lesions developed in the control plants. Most genes expressed differently following inoculation with Phytophthora capsici in comparison to the control group. Fungal diseases are.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Agar powder	Solarbio	A8190
Clean bench	Haier
Dextrose	Xilong Scientific	15700501
High temperature sterilizing oven	Zaelway
Petri dish plates	Biosharp	BS-90-D