Paddy Dwarfing | 27 Aug 2022

Why in News?

Recently, a mysterious disease hit the paddy crop causing “dwarfing” of the plants in Punjab and Haryana.

  • Scientists have decoded the mystery blaming it on ‘Southern Rice Black-Streaked Dwarf Virus’ (SRBSDV), named after Southern China where it was first reported in 2001.

What is Paddy Dwarfing?

  • The characteristic symptoms of rice dwarf disease are stunting of the plant and appearance of white chlorotic specks on foliage.
  • The height of the stunted plants showed a reduction from 1/2 to 1/3rd of the normal plants.
  • These plants had shallow roots and could be easily uprooted.
  • Such plants were observed in almost all the cultivated varieties in the farmers’ fields.
  • Dwarfing of plants was reported at 10% to 25% in general and in some cases, it exceeded 40%.
  • The incidence of stunting was more pronounced in early sown paddy crops, irrespective of the variety.

What is SRBSDV?

  • Southern rice black-streaked dwarf virus (SRBSDV) is a non-enveloped icosahedral virus with a genome of 10 double-stranded Ribonucleic Acid RNA segments, and is a novel species in the genus Fijivirus (family Reoviridae).
    • An Icosahedral Virus is a virus consisting of identical subunits that make up equilateral triangles that are in turn arranged in a symmetrical fashion.
  • The SRBSDV is transmitted by white-backed plant hopper (WBPH) in a persistent circulative and propagative manner.
  • In addition to rice, SRBSDV also infects different weed species as nymphs of WBPH can transmit the virus more efficiently as compared to adults.
    • Long-distance transmission of this virus may occur through WBPH migrating with typhoons and strong convection winds.

What Could be Done for Prevention?

  • Since there is no corrective measure for the viral disease, farmers should regularly monitor the crop for the presence of WBPH and a few plants should be slightly tilted and tapped 2-3 times at the base at weekly intervals.
  • If WBPH nymphs/adults are seen floating on water, then insecticides can be sprayed towards the base of the plants.
  • The farmers are advised to follow the transplanting dates advised by Punjab Agricultural University PAU since stunting was observed to be more in the early transplanted crops. It will not only help in managing viral disease but also save water.

UPSC Civil Services Examination Previous Year Question (PYQ)

Q. Consider the following: (2018)

  1. Birds
  2. Dust blowing
  3. Rain
  4. Wind blowing

Which of the above spread plant diseases?

(a) 1 and 3 only
(b) 3 and 4 only 
(c) 1, 2 and 4 only 
(d) 1, 2, 3 and 4

Ans: (d)

Explanation:

  • Extensive and severe epidemics of plant diseases are mostly the results of wind blowing including dust blowing which cause transmission of the pathogens. Hence, 2 and 4 are correct.
  • Splashing rain drops mostly transmit the foliar diseases from leaf to leaf, from shoot to shoot and even from plant to plant in case of closely spaced crops. Hence, 3 is correct.
  • Birds play a minor role in disease transmission in plants. It is mainly by way of dispersal of seeds of higher flowering plant parasite, etc. Hence, 1 is correct.
  • Therefore, option (d) is the correct answer.

Source: IE