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Cotton leaf curl virus (CLCuV) in north Indian cotton Photo: Shree_clips B · Pexels License · source ↗

Cotton leaf curl virus (CLCuV) in north Indian cotton

Cotton Leaf Curl Virus (CLCuV) is a whitefly-transmitted geminivirus that causes the most economically damaging viral disease of cotton in the north Indian zone — Punjab, Haryana, north Rajasthan and parts of west Uttar Pradesh. Epidemics in the late 1990s wiped out a quarter of the Punjab cotton crop and forced large-scale variety replacement.

Pathogen and vector

CLCuV is a complex of begomoviruses — Cotton Leaf Curl Multan Virus (CLCuMuV), Cotton Leaf Curl Kokhran Virus (CLCuKoV), Cotton Leaf Curl Burewala Virus (CLCuBuV) — together with associated betasatellite DNA. All are transmitted in a persistent, circulative manner by the whitefly Bemisia tabaci (see Whitefly In Cotton Chilli). Mechanical and seed transmission do not occur. Whitefly vector pressure determines outbreak severity.

Symptoms

Affected plants show curling and crinkling of leaves with downward or upward rolling. Veins thicken and darken; enations (leaf-like outgrowths) appear on the underside of leaf veins — a diagnostic feature. Plants become severely stunted; bolls are few, small and poorly developed. Early-infected plants (before flowering) may produce no harvestable cotton; late infections cause boll damage but partial yield is salvageable.

Geographic distribution

CLCuV is confined almost entirely to the north cotton zone (Cotton Zone System Cicr). The central and south zones do not record significant CLCuV outbreaks despite supporting heavy whitefly populations — the regional vector biotype and host begomovirus reservoir differ. PAU and CICR-Sirsa have documented periodic resurgences in Punjab-Haryana in 1996-98, 2007-08, 2015 and 2021-22.

Management

Resistance breeding is the principal control. PAU released CLCuV-tolerant G. hirsutum varieties (LH-1556, LH-2076) and the public-sector hybrid F-2228 BG-II carries some tolerance. Desi cotton (G. arboreum) is largely resistant (Cotton American Vs Desi Vs Egyptian) — recent CICR varieties PA-08 and PA-528 are being promoted as a CLCuV escape strategy in epidemic-prone tracts.

Cultural controls include (a) avoiding overlap with cotton on adjacent fields, (b) destroying alternative hosts — okra, tobacco, Sida and Hibiscus spp. — which harbour vector and virus, (c) rogueing early-infected plants, (d) timely sowing to avoid peak whitefly pressure.

Insecticidal vector control is curative at best. Diafenthiuron 50% WP @ 240 g/acre, pyriproxyfen 10% EC @ 250 ml/acre and spiromesifen 22.9% SC @ 200 ml/acre are recommended for whitefly. Repeated indiscriminate pyrethroid use has driven whitefly resurgence and is to be avoided.

Economic impact

The 1996-98 Punjab epidemic caused estimated losses of Rs 500-1000 crore and was the principal driver of the Bt cotton adoption surge in north India after 2002.

See also Whitefly In Cotton Chilli, Cotton Zone System Cicr, Cotton American Vs Desi Vs Egyptian, Cotton Fusarium Wilt Resistance.

Sources

  1. Cotton Leaf Curl Disease. ICAR-CICR Pathology Research.
  2. CLCuV management. Punjab Agricultural University, Ludhiana.
  3. Cotton leaf curl virus in north zone. Indian Phytopathology.