Vegetative compatibility of cotton-defoliating Verticillium dahliae in Israel and its pathogenicity to various crop plants

Abstract

Verticillium dahliae isolates recovered from a new focus of severe Verticillium wilt of cotton in the northeast of Israel were tested for vegetative compatibility using nitrate non-utilizing (nit) mutants and identified as VCG1, which is a new record in Israel. Other cotton isolates of V. dahliae from the northern and southern parts of the country were assigned to VCG2B and VCG4B, respectively. VCG1 isolates induced severe leaf symptoms, stunting and defoliation of cotton cv. Acala SJ-2, and thus were characterized as the cotton-defoliating (D) pathotype, whereas isolates of VCG2B and VCG4B were confirmed as the earlier described defoliatinglike (DL) and non-defoliating (ND) pathotypes, respectively. This is the first record of the Dpathotype in Israel. The host range of representative isolates of each VCG-associated pathotype was investigated using a number of cultivated plants. Overall, the D isolates were more virulent than DL isolates on all tested host plants, but the order of hosts (from highly susceptible to resistant) was the same: okra (Hibiscus esculentus local cultivar), cotton (Gossypium hirsutum cv. Acala SJ2), watermelon (Citrullus lanatus cv. Crimson Sweet), safflower (Carthamus tinctorius cv. PI 251264), sunflower (Helianthus annuum cv. 2053), eggplant (Solanum melongena cv. Black Beauty), and tomato (Lycopersicon esculentum cv. Rehovot 13). The pattern of virulence of ND isolates differed from that of D and DL isolates, so that the former were highly virulent on eggplant but mildly virulent on cotton. Tomato was resistant to all cotton V. dahliae isolates tested. RAPD and specific PCR assays confirmed that the D isolates from Israel were similar to those originating from other countries.

First report of the presence of Verticillium dahliae VCG1A in Australia

“…The cotton defoliating strain T9 (the original defoliating pathotype from cotton in California) belongs to subgroup VCG1A (Bell 1994). Only isolates of this subgroup caused severe defoliation of cotton in previous studies (Daayf et al 1995;Korolev et al 2008). Thus, isolates strongly compatible with T9 (or strongly compatible with other testers) may be assigned to VCG1A (Korolev et al 2008).…”

“…Israeli nit testers of VCG2A, VCG2B, and VCG4B w e r e pr e v i o u s l y s h o w n to c o r r e l a t e w i t h t h e international OARDC reference strains (Korolev et al 2000;Korolev et al 2008;Rowe 1995). The cotton defoliating strain T9 (the original defoliating pathotype from cotton in California) belongs to subgroup VCG1A (Bell 1994).…”

Scientific opinion on the pest categorisation of Verticillium dahliae Kleb

“…Symptoms of Verticillium wilt diseases can vary between hosts; thus, there are no unique symptoms that develop on all plants infected by V. dahliae (Fradin and Thomma, 2006). Moreover, symptoms can vary depending upon strains (pathotypes) of the pathogen (Korolev et al, 2008;Jiménez-Díaz et al, 2012).…”

“…Host adaptation in V. dahliae may also give rise to quantum increments in virulence, as exemplified by development of the cotton and olive defoliating (D) pathotype that differs much in virulence from a non-defoliating (ND) one (Schnathorst and Mathre, 1966;El-Zik, 1985;Bejarano-Alcázar et al, 1996;Korolev et al, 2008;Erdogan et al, 2013). All D isolates so far identified are within the VCG1A (Jiménez-Díaz et al, 2012).…”

“…Isolates of the D pathotype from different geographic origins have been reported to be moderately to highly virulent but non-defoliating on artichoke, celery, flax, safflower and sunflower, mildly virulent on aubergine and tomato, and non-pathogenic to cowpea and muskmelon (Schnathorst and Mathre, 1966;Jiménez-Díaz et al, 2006;Korolev et al, 2008). According to Korolev et al (2008), isolates of the D pathotype from Israel were highly virulent on watermelon. In contrast, Schnathorst and Mathre (1966) reported that D isolates from USA were not pathogenic on watermelon.…”