Cucurbit Genetics Cooperative Report 4:38-40 (article 21) 1981

Sources of Resistance to Viruses in Lagenaria siceraria

R. Provvidenti

New York State Agricultural Experiment Station, Cornell University, Geneva, NY 14456

In 1977, we reported (2) that an accession of Lagenaria siceraria, PI 391602 from China, was resistant to squash mosaic virus (SqMV), watermelon mosaic virus 1 (WMV-1), watermelon mosaic virus 2 (WMV-2). and that an occasional plant was resistant to cucumber mosaic virus (CMV). In 1978, Greber (1) also reported resistance to WMV-1 and MWV-2 in an accession of the same species from Queensland, Australia. Since it is known that some of these viruses are frequently destructive where L. siceraria is cultivated, additional germplasm of this species was evaluated with CMV, SqMV, WMV-1, WMV-2, tobacco ringspot virus (TRSV), and tomato ringspot virus (TmSV). These last two viruses are transmitted by nematodes and are found with a certain frequency in New York State (3).

Plants of 18 lines representing 12 countries were screened for resistance under greenhouse and field conditions. All plants received from one to three inoculations and those which, upon assay, were found free of systemic infection, were transferred to the field for further evaluation. Plants were rated resistant if, at maturity, they were still free of systemic infection.

From the results given in Table 1, it is evident that resistance was found in one or more lines to five of the six viruses used. Resistance to CMV was confined to PI 269506, PI 271353, and a few plants of PI 391602. In these lines, virus infection was confined to the inoculated leaves. However, further testing using a large number of CMV isolates revealed the existence of two strains able to infect systemically these resistant lines. All lines were resistant to SqMV and the plants responded with a few, small and often inconspicuous necrotic local lesions. This hypersensitive reaction greatly localized viral infection. Resistance to TmRSV was found in PI 188809 and PI 271353, in which plants reacted only with localized infection. Resistance to WMV-1 was more common and was detected in plants of PI 188809, PI 271353, PI 280631, PI 288499, PI 391602 and the Hawaiian cultivar Hyotan. Resistance to WMV-2 was found in plants of PI 271353, PI 391602, 'Hyotan', ad G-24386. All plants resistant to WMV-1 and/or WMV-2 were free of local and systemic symptoms, but virus infection occurred in inoculated leaves of some plants.

Three lines, PI 271353, PI 391602, and 'Hyotan', were resistant to both WMV-1 and susceptible to WMV-2, or vice versa, suggesting that resistance to these viruses in conferred by different genetic factors. As a source of multi-resistance, PI 271353, from India, appears to be the most valuable for a breeding program. However, no information appears to be available on the mode of resistance to these or any other virus affecting L. siceraria.

Viral resistance in L. siceraria can be also useful in separating viruses which may occur simultaneously in naturally infecting cucurbit plants. We have used this host to free CMV, WMV-1, or WMV-2 when found in association with SqMV, or to separate WMV-1 from WMV-2 or vice versa. Although most of the lines, when inoculated with SqMV, reacted with a few and sparse necrotic local lesions, an occasional plant responded with numerous lesions which remained small and rather distinct for a long time. Thus, using selected plants, it may be possible to use L. siceraria as a local lesion host for qualitative and quantitative assay of SqMV. In this respect, Lagenaria is potentially more valuable than Cucumis metuliferus (4).

Table 1. Reaction to cucumber mosaic virus (CMV), squash mosaic virus (SqMV), tobacco ringspot virus (TRSV) tomato ringspot virus (TmRSV), watermelon mosaic virus 1 (WMV-1), and watermelon mosaic virus 2 (WMV-2) of accessions of Lagenaria siceraria.

Accession	Origin	CMV	SqMV	TRSV	TmRSV	WMV-1	WMV-2
PI 181913	Syria	S	R	S	S	S	S
PI 188809	Philippines	S	R	S	R	R	S
PI 197437	Ethiopia	S	R	S	S	S	S
PI 269506	Pakistan	R*	R	S	S	S	S
PI 270456	Mexico	S	R	S	S	S	S
PI 271353	India	R*	R	S	R	R	R
PI 273663	Ethiopia	S	R	S	S	S	S
PI 287533	Italy	S	R	S	S	S	S
PI 287534	Italy	S	R	S	S	S	S
PI 280631	S. Africa	S	R	S	S	R	S
PI 280636	S. Africa	S	R	S	S	S	S
PI 288499	India	S	R	S	S	R	S
PI 349591	New Guinea	S	R	S	S	S	S
PI 391602	China	S/R*	R	S	S	R	R
PI 414369	India	S	R	S	S	S	S
Paphos	Cyprus	S	R	S	S	S	S
Hyotan	Hawaii	S	R	S	S	R	R
G-24386	California	S	R	S	S	S	R

R = Resistant (no systemic infection).
S = susceptible (systemic symptoms).
* = some strains may cause systemic infection

Literature Cited

1. Greber, R. S. 1978. Watermelon mosaic virus 1 and 2 in Queensland cucurbit crops. Aust. J. Agr. Res. 29:1235-1245.
2. Provvidenti, R. 1977. Evaluation of vegetable introductions from the People's Republic of China for resistance to viral diseases. Plant Dis. Reptr. 61:851-855.
3. Provvidenti, R., R. W. Robinson, and H. M. Munger. 1978. Resistance in feral species to six viruses infecting Cucurbita. Plant Dis. Reptr. 62:326-329.
4. Provvidenti, R. and R. W. Robinson. 1974. Resistance to squash mosaic virus and watermelon mosaic virus 1 in Cucumis metuliferus. Plant Dis. Reptr. 58:735-738.