The study assessed resistance across 46 yam varieties and investigated how physiological and hormonal traits correlate with disease defense. Their findings, based on pathogen inoculation, microscopy, gene expression, and hormone profiling, shed light on how wax content, stomatal behavior, and ABA levels work together to resist fungal invasion.
The greater yam (Dioscorea alata L.) is a vital staple food across tropical regions, especially in Africa and Asia. However, its cultivation faces serious setbacks due to anthracnose, a fungal disease caused by species of the Colletotrichum genus. While chemical control remains the dominant strategy, it raises issues of toxicity, environmental pollution, and resistance. To build sustainable and safe crop protection, identifying naturally resistant varieties is key. Plants defend themselves using structural barriers such as wax and stomatal control, along with biochemical responses regulated by hormones like ABA. These mechanisms, when properly understood, can inform breeding programs aimed at enhancing disease resistance in yams and reducing reliance on agrochemicals.
A study (DOI: 10.48130/tp-0025-0013) published in Tropical Plants on 30 June 2025 by Qinghong Zhou & Sha Luo’s team, Jiangxi Agricultural University, not only identifies Colletotrichum alatae as a new yam pathogen but also opens the door to breeding high-quality, disease-resistant varieties for long-term.
To identify the causal agent of anthracnose in greater yam, researchers isolated the pathogen from infected leaves and cultured it on potato dextrose agar (PDA). Morphological analysis revealed traits typical of Colletotrichum species, including radial colony growth and darkening aerial hyphae. Molecular characterization followed: sequencing of the internal transcribed spacer (ITS) region showed >99% similarity to both C. gloeosporioides and C. alatae, while further analysis of the rDNA CAL region confirmed the pathogen as C. alatae. Next, 46 greater yam varieties were subjected to in vitro inoculation to assess disease resistance, which was classified into five levels. Results showed a wide range of resistance: 16.3% were immune, 23.3% resistant, while 45.3% were susceptible. To understand physiological traits linked to resistance, leaf stomatal density and wax content were measured. Immune varieties like D-28 showed lower stomatal density and higher wax content than susceptible varieties like D-404. Stomatal closure after infection was more pronounced in resistant varieties, impeding fungal entry. Scanning electron microscopy confirmed that C. alatae hyphae penetrated through open stomata, with faster fungal growth in susceptible varieties. Hormone profiling revealed that abscisic acid (ABA) levels surged early in resistant varieties and were linked to stomatal closure. External ABA application enhanced resistance in susceptible plants by reducing lesion spread. Finally, defense enzyme assays showed that resistant and immune varieties rapidly increased the activity and expression of key enzymes like peroxidase (POD) and phenylalanine ammonia-lyase (PAL), whereas the response in susceptible varieties was delayed. Collectively, these findings highlight a multi-layered defense involving physical barriers, hormonal signaling, and enzymatic responses that contribute to anthracnose resistance in greater yam.
This research provides a valuable roadmap for developing anthracnose-resistant yam cultivars through traditional breeding or biotechnological approaches. By selecting varieties with high wax content, low stomatal density, and robust ABA signaling, breeders can enhance natural disease resistance. The findings also suggest potential in using ABA-based sprays as a sustainable, chemical-free control strategy.
###
References
DOI
10.48130/tp-0025-0013
Original Source URL
https://doi.org/10.48130/tp-0025-0013
Funding Information
This research was funded by the National Natural Science Foundation of China (32460767), and the Jiangxi Provincial Key Research and Development Project of China (Grant Nos 20232BBF60007 and 20212BBF61004).
About Tropical Plants
Tropical Plants (e-ISSN 2833-9851) is the official journal of Hainan University and published by Maximum Academic Press. Tropical Plants undergoes rigorous peer review and is published in open-access format to enable swift dissemination of research findings, facilitate exchange of academic knowledge and encourage academic discourse on innovative technologies and issues emerging in tropical plant research.