Phomopsis stem blight

Diaporthe tulliensis is a pathogenic fungus responsible for the disease commonly known as Phomopsis stem blight. This fungal pathogen primarily impacts the lupin (Lupinus) genus, causing significant physiological disruption and structural damage to the host plant. It is globally recognized as a major limiting factor in lupin production, particularly in regions with conducive climatic conditions.

The host range of this pathogen is primarily restricted to lupin species, including narrow-leafed, white, and yellow lupins. The fungus acts as a hemibiotroph, initially surviving on dead tissue or crop residues and subsequently invading living host tissues. Its ability to persist within infected seeds is a critical factor in the long-distance dissemination of the disease across different agricultural areas.

Clinical symptoms of the disease include the appearance of brownish necrotic lesions on stems, petioles, and pods. A characteristic feature is the development of pycnidia, appearing as small, dark dots embedded within the necrotic lesions. As the infection progresses, affected stems become brittle and may break, causing plant death and significantly reducing the final grain yield.

The development and spread of Diaporthe tulliensis are heavily influenced by environmental factors, most notably temperature and moisture. Frequent rainfall and moderate temperatures provide the necessary conditions for spore production and secondary infection cycles. High humidity during the flowering and pod-filling stages is particularly detrimental, as it facilitates the rapid colonization of reproductive structures by the pathogen.

The economic impact of this disease is severe, stemming from direct yield losses and reduced forage quality. Contaminated lupin residues or grain can contain mycotoxins, making them unsuitable for animal feed. To mitigate the risks, growers should adopt integrated management strategies:

• Sourcing certified, disease-free, and treated seed stocks.
• Implementing strict crop rotation intervals of at least 3–4 years between lupin crops.
• Managing crop residues through deep burial to minimize inoculum levels.
• Applying fungicides during critical growth stages when environmental conditions favor disease pressure.
• Selecting and planting resistant cultivars tailored for local climate conditions.