Interception of pathogens during quarantine processing: an effort towards safe import of oilseed and vegetable Brassicas germplasm in India

Abstract

During 1976-2015, a total of ~75000 seed samples of oilseed and vegetable Brassicas germplasm received
from different countries were processed for quarantine clearance. Seed health testing resulted in interception
of 17 pathogenic fungi and one bacterium in 2628 samples from 23 countries. Decade wise (1976-1985;
1986-1995; 1996-2005; 2006-2015) analysis revealed the highest level infections in 948 (36.3%) during 1986-
1995 followed by 912 interceptions (34.9%) during 1996-2005 and lowest level of infections was intercepted
in 176 samples (6.7%) during 2005-2016. Risk analysis of the interceptions showed that among the pathogens,
Alternaria brassicicola was recorded in most of the infected samples (65.5%) followed by Xanthomonas
campestris pv. campestris (17.8%). Among countries, maximum interceptions were made from USA (26.3%)
followed by Canada (24.0%) which indicated that there is the highest risk of introduction of pathogens along
with Brassicas seeds from USA and Canada. Among pathogens intercepted, Leptosphaeria maculans
causing black leg from Australia and Canada and X. c. pv. campestris causing black rot of crucifers from
Canada are potential quarantine pathogens to India, hence the samples infected with L. maculans and
Fusarium solani were rejected and incinerated and samples infected with X. c. pv. campestris were salvaged
by giving hot water treatment at 500C for 20 min. before their release. Whereas, samples infected with other
pathogens viz., A. brassicae, A. brassicicola, A. raphani, A. solani, Bipolaris sorghicola, B. sorokiniana,
Botrytis cinerea, Cephalosporium maydis, F. oxysporum, F. verticillioides, Phoma sorghina, Rhizoctonia
bataticola, Sclerotium rolfsi, Verticillium albo-atrum were salvaged using fungicidal seed treatment before
their release. This could finally prevent entry or minimized spread of exotic pathogens into the country and
also promoted germplasm exchange for crop improvement. The interceptions of pathogens of quarantine
significance to India from different countries emphasizes the need of critical examination of imported oilseed
and vegetable Brassicas during the quarantine processing to safeguard our experimental as well as agricultural
fields from inadvertent introduction of associated pathogens or more virulent races/ strains of the existing
ones in the country