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Fusarium wilt of cotton and desi resistance Photo: Shree_clips B · Pexels License · source ↗

Fusarium wilt of cotton and desi resistance

Fusarium wilt of cotton — caused by Fusarium oxysporum f. sp. vasinfectum — is a soil-borne vascular disease that has historically devastated upland Gossypium hirsutum cotton in central and south India. The defining feature of the Indian fusarium-wilt story is the strong inherent resistance carried by diploid desi cotton (G. arboreum) — a major reason ICAR-CICR is reviving desi varieties under HDPS programmes.

Pathogen identification

The pathogen is a soil-borne fungus that survives as chlamydospores in plant residue and soil for years. Indian populations correspond to F. oxysporum f. sp. vasinfectum races prevalent in tropical Asia (race "Indian"). The fungus infects through root tissue, colonises the xylem and produces toxins (fusaric acid) that disrupt water transport.

Symptoms

  • Early symptoms: leaf yellowing of lower leaves first, then progressing upward.
  • Wilting of plants during midday despite moist soil; recovery at night becomes incomplete.
  • Vascular browning visible on stem cross-section — diagnostic.
  • Stunted plant with fewer bolls; severely infected plants die before fruit-set.

Diseased patches in the field expand year-on-year if the same cotton crop is grown continuously on the same Vertisol.

Hosts and lifecycle

Cotton (Gossypium spp.) is the principal host. The fungus is highly host-specific and does not seriously affect rotation crops such as sorghum, maize or pulses. Disease pressure correlates with: (a) continuous cotton monoculture, (b) heavy clay Vertisols with poor drainage, (c) soil temperatures of 25-30 °C and (d) high nematode populations (especially Meloidogyne incognita) which create root entry wounds.

Geographic distribution

Wilt is a chronic problem in pockets of central zone — parts of Vidarbha, Marathwada, Khandesh, north Karnataka and Telangana (Cotton Zone System Cicr). North zone (Punjab-Haryana) is largely free; south zone has spotty incidence.

Resistance and management

The single most powerful management tool is host-plant resistance. Almost all G. arboreum desi cottons (Cotton American Vs Desi Vs Egyptian) are inherently resistant to F. oxysporum f. sp. vasinfectum — a result of co-evolution with the pathogen in the South Asian centre of origin. CICR desi varieties PA-08, PA-528, PA-740 and CICR-2 carry strong wilt resistance and are recommended for wilt-sick blocks.

Among G. hirsutum, resistance has been bred through introgression from desi sources. PAU variety F-846 and CICR varieties LRA-5166 and Suraj show useful field tolerance. Bt hybrids vary widely; some commercial hybrids are highly susceptible.

Cultural management includes (a) crop rotation with non-host crops (sorghum, maize, pulses) for 3-4 years; (b) adequate drainage to avoid waterlogging; (c) balanced potash fertilisation; (d) soil solarisation in nursery blocks; (e) nematode management via Pseudomonas fluorescens or carbofuran 3 G application. Soil application of Trichoderma viride @ 5 kg/ha mixed with FYM provides partial biocontrol.

See also Cotton American Vs Desi Vs Egyptian, Cotton Zone System Cicr, Cotton Bacterial Blight, Cotton Cotton Leaf Curl Virus Clcuv.

Sources

  1. Fusarium wilt of cotton. ICAR-CICR Pathology Research.
  2. Wilt resistance in G. arboreum. Indian Phytopathology.
  3. Cotton wilt management. KVK package of practice.