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Redgram sterility mosaic disease (SMD) Photo: Shobhit Gosain · CC BY-SA 3.0 · source ↗

Redgram sterility mosaic disease (SMD)

Sterility mosaic disease (SMD), often called the "green plague" of pigeonpea, is the most damaging viral disease of redgram (pigeonpea, Cajanus cajan) in India. It is caused by Pigeonpea sterility mosaic emaravirus 1 and 2 (PPSMV-1 and PPSMV-2, family Fimoviridae) and transmitted by the eriophyid mite Aceria cajani. The disease is endemic across all major pigeonpea-growing tracts — Maharashtra, Karnataka, Andhra Pradesh, Telangana, Madhya Pradesh, Uttar Pradesh, Bihar and Jharkhand — and causes losses of 30 to 100 percent on susceptible cultivars.

Identification and symptoms

The cardinal symptom is partial or complete sterility — affected plants flower poorly or do not flower at all and bear no pods. Foliar symptoms are: mosaic mottling of young leaves, reduction in leaf size, bunchy and bushy growth, pale-green appearance and excessive branching. Three symptom types are recognised in the field — severe (chlorotic ring spots and complete sterility), mild (mosaic without sterility) and ring spot (yellow ring spots on leaves, partial sterility). Severely infected plants stand out as bushy, leafy patches in an otherwise pod-bearing crop.

Hosts and lifecycle

The pathogen is restricted to Cajanus cajan and a few wild Cajanus species; it does not infect other pulses. The eriophyid mite Aceria cajani survives between seasons on ratoon and perennial pigeonpea, on wild Cajanus and on volunteer plants. Mites carry the virus persistently and disperse by wind, intercrop movement and aerial drift. Infection peaks in the post-monsoon vegetative phase (45-90 DAS) when temperature is 25-30 deg C and relative humidity 65-85 percent. Plants infected within 45 DAS are completely sterile; later infection causes partial sterility on the upper canopy only.

Economic impact

Yield loss is approximately equal to the proportion of plants infected before flowering. ICAR-IIPR and ICRISAT surveys have documented endemic levels of 5-30 percent in Telangana and northern Karnataka and outbreak years of 50-90 percent in central Karnataka, Adilabad and Mahabubnagar. SMD is the leading reason for the gap between potential and realised pigeonpea yields in dryland tracts; AICRP-Pigeonpea reports that resistant variety adoption is the single largest source of pigeonpea productivity gain in the past three decades.

Management

  • Resistant varieties: ICPL 87119 (Asha) is the flagship SMD-resistant variety widely grown in Telangana and Karnataka. Maruti (ICP 8863), Bahar, BSMR 736, BSMR 853, BRG 1, BRG 2, BRG 3, TS-3R and LRG 52 are other SMD-resistant releases. Older varieties such as LRG-41 are susceptible.
  • Cultural: rogue and burn diseased plants within 30-45 DAS; remove perennial pigeonpea hedges and ratoon plants which act as reservoirs; avoid sowing alongside infected fields; deep summer ploughing.
  • Mite management: spray dicofol 18.5 EC at 2 ml/L or fenazaquin 10 EC at 1 ml/L or propargite 57 EC at 1 ml/L at 30 and 45 DAS in disease-prone areas; seed treatment with imidacloprid 70 WS at 5 g/kg gives early protection.
  • Integrated: combine resistant variety + rogueing + targeted miticide spray; isolation of seed plots from commercial fields.

See also: ICPL 87119 Asha Redgram, Maruti Redgram, LRG 41 Redgram.

Sources

  1. Sterility mosaic disease of pigeonpea. ICAR-Indian Institute of Pulses Research, Kanpur.
  2. Pigeonpea sterility mosaic virus. ICRISAT, Patancheru.
  3. Pigeonpea diseases and management. AICRP MULLaRP.