Download IRRN 1984 9 (6) - James Litsinger

A new rice virus disease in India
V. Mariappan, H. Hibino, and N. Shanmugam, Tamil Nadu Agricultural
University, Coimbatore, India
In late samba 1983, many rice varieties with yellow-orange leaves were observed in farmer fields and at
the University of Coimbatore. Only a few plants showed symptoms that resembled those of rice tungro
virus (RTV). Plants had mild stunting and increased tillering. Brown planthopper (BPH) Nilaparvata
lugens Stål was in the fields. Infected plants were collected and transmission tests were conducted by
using the green leafhopper (GLH) Nephotettix virescens Dist. and BPH.
Virus-free GLH adults given 4-day acquisition access feeding on source plants were transferred to 10day-old TN1 seedlings at 2 insects/seedling for 4-day inoculation access. The inoculated plants did not
develop disease symptoms (Table 1). Second-instar nymphs from a virus-free BPH colony were released
on source plants for 7-days acquisition access feeding, and then collected and released on 10-days-old
TN1 seedlings at 2 insects/plant for 10-days inoculation access feeding. The inoculated plants developed
yellow- orange leaves 25 days later. The plants were slightly stunted and had more tillers than the control
`plants. BPH-inoculated Oryza nivara developed similar symptoms but those exposed to GLH did not.
Dried leaves of infected TN1 plants were sent to IRRI for serological tests.
In a latex test using antiserum to rice grassy stunt virus (GSV), sap of the dried leaves reacted positively
up to 1:8 dilution; sap of GSV-infected fresh leaves collected at IRRI reacted positively at 1:512 dilution;
and sap of virus-free fresh leaves did not react, even at 1:1 dilution (Table 2).
We therefore identified the new disease as a strain of GSV. It is similar to GSV strain 2 in the Philippines.
So far there are no reports from India of BPH transmitted leaf yellowing.
Table 1. Transmission of the new virus to TNl and O. nivara by
N. virescens and N. lugens . Coimbatore, India, and IRRI.
Insect
N. virescens
N. lugens
TN1
Inoculated Infected
25
0
61
19
O. nivara
Inoculated
Infected
6
0
18
9
Table 2. Serological reaction of the sap of leaves infected with new virus or GSV to GSV antiserum
by latex test, IRRI.
Sample
Undiluted
Dried TN1 leaf infected with
+
new virus
Fresh TN1 leaf infected with GSV
+
Fresh TN1 leaf free from virus
–
+ = positive, – = negative.
2
+
+
–
Reaction to given sap dilution
4
8
16 32
64 128
+
+
–
–
–
–
+
–
+
–
+
–
+
–
+
–
+
–
256
–
512
–
+
–
+
–
Mariappan V, H Hibino, N Shanmugam. 1984. A new rice virus disease in India. International Rice
Research Newsletter 9 (6): 9-10.