Gibberella fujikuroi

Scientific Name Gibberella fujikuroi (Sawada) S. Ito [teleom.], Fusarium moniliforme Sheldon [anam.]
Synonyms Gibberella moniliforme [syn.], Fusarium fujikuroi Nirenberg [syn.]
Common Names English: Bakanae disease of rice, foot and stem rot; German: Bakanae-Krankheit; French: Maladie de Bakanae, gigantisme; Spanish: Bakanae
Description The ascomycetous fungus Gibberella fujikuroi, conidial stage F. moniliforme, causes bakanae, foot rot, seedling rot, grain sterility and discoloration.

Gibberella fujikuroi is predominately seed-borne; infected kernels may develop a reddish discoloration due to the presence of the pathogen's conidia.

Biology

Damage

Seedlings with bakanae emerge rapidly, remain tender and are significantly taller than non-infected plants. Severely diseased seedlings die before transplanting, and those that survive may die after transplanting. Heavily infected seed lots may produce both, stunted and elongated seedlings. Older infected plants show tall tillers with pale-green flag leaves well above the canopy of the healthy crop. Infected plants produce only few tillers and leaves dry up before maturity. In some cases, diseased plants survive until maturity, but are sterile and produce no or empty panicles. White powdery growth of conidiophores may be visible on lower parts of diseased plants. The panicles of healthy plants may be contaminated by spores and turn pink due to growth and sporulation of the fungus on hulls or kernels.

Lifecycle

Airborne ascospores can contaminate the panicle from heading to maturity, especially in rainy periods. The production of conidia and perithecia on diseased culms coincides with flowering and maturation. The pathogen may be also soil-borne; it can survive in the soil as thick-walled hyphae or macroconidia. The fungus produces hyaline, elliptical ascospores (10 - 20 x 4 - 7 µm, 1 - 3 septa), hyaline, oval to clavate, single-celled microconidia (5 - 12 x 1.5 - 2.5 µm) in chains, and hyaline, slightly curved macroconidia (25 - 60 x 2.5 - 4 µm) with a foot-shaped basal cell and 3 - 7 septa.

Occurrence

Additional Crop Information

Most obvious symptoms are produced in rice; other host plants include barley, millet, sugarcane, but also reports from the mimosoid tropical tree Leucaena leucocephala are available.

Agricultural Importance

G. fujikuroi produces a variety of biologically active compounds, e.g. fusaric acid causing stunting, gibberellin causing elongation of many plant species besides rice, and fumonisin which causes equine leuko-encaphalomalacia and is reported to be cancerogenic.

Control

Useful non-chemical contribution to Integrated Weed Management

Lightweight, infected seeds should be avoided. Beside chemical seed treatment, reports on efficacy of chlorine added to the soaking water as well as hot water treatments are available.

Chemical Control

As G. fujikuroi is primarily transmitted by seed, generally, seed dressings containing MBC fungicides such as thiophanate-methyl or thiram may effectively control bakanae disease of rice and other crops, but development of resistance to benzimidazoles has been observed. Newer seed treatments containing DMI fungicides (e.g. azoles) or QoI fungicides (also known as strobilurins) are very effective and have not shown any resistance problems up to now.

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