Cucurbit Genetics Cooperative Report 17:128 (article 38) 1994
P.T. Della Vecchio, A.J. Vitti and R. Wierzbicki; M.A. Pavan
Agroflora S/A, Caixa Postal 427, 12900-000, Braganca Paulista SP, Brazil; FCA/UNESP – Departmento de Defesa Fitossanitaria, Caixa Postal 237, Botucatu, SP, Brazil
In a previous report (1) we presented the pedigree of some C. moschata breeding lines which showed field resistance to PRSV-W. As these lines were selected under natural field infection conditions, using plants of C. pepo cv. Caserta as control and spread rows, the mechanism of this field resistance is unknown. It was of interest to know the response reaction of these lines under mechanical inoculations to CMV. PRSV-W and WMV-II, which are the main viruses reported to occur on Cucurbitacease in Brazil.
Materials and Methods. Virus identification was previously made based on differential host reactions and serology. The inoculum of each virus was made by grinding leaves of C. pepo cv. Caserta showing strong symptoms of the respective virus in 0.02 M phosphate buffer (pH 7.0) containing 0.01 M sodium sulfite (1:10, w/v) and rubbing extracts on fully expanded cotyledons of 4-6 day old plants, previously dusted with 600-mesh carborundum. Twenty plants of each breeding line were inoculated for each virus.
Results and Discussion. The response reaction of the inbred lines to each virus is presented in Table 1. All lines showed susceptible response reactions to mechanical inoculation of PRSV-W and WMV-II. Inbred lines AF1075L and AF1094L, however, showed resistance to mechanical inoculation of CMV. Plants of both lines presented some mosaic symptoms on the first true ;eaves that completely disappeared as the plants developed. Back inoculations using leaves with no CMV symptoms taken individually from all these plants, were made on C. pepo cv. Assert for further investigation. No CMV symptoms were observed on the C. pepo plants, suggesting that the CMV virus is not multiplying in plants of the C. moschata inbred lines AF1075L and AF1094L.
Table 1. Response reaction of C. moschata breeding lines to mechanical inoculations of CMV, PRSV-W and WMV-II.
Response Reaction1 |
||||||
CMV |
PRSV-W |
WMV-II |
||||
| Inbred Lines |
R
|
S
|
R
|
S
|
R
|
S
|
| Piramoita |
0
|
20
|
0
|
20
|
0
|
20
|
| AF1075l |
20
|
0
|
0
|
20
|
0
|
20
|
| AF1094L |
15
|
0
|
1
|
19
|
0
|
20
|
1 R = Resistant, S = Susceptible
Literature Cited
- Della Vecchia, P.T., S.P. Terenciano, and A. Terenciano, 1993. Breeding bush types of C. moschata with field resistance to PRSV-W. Cucurbit Genet. Coop. Rpt. 16:70-72.