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Verticillium wilt of olive is best managed by resistant cultivars, but those currently available show incomplete resistance to the defoliating (D) Verticillium dahliae pathotype. Moreover, these cultivars do not satisfy consumers' demand for high yields and oil quality. Highly resistant rootstocks would be of paramount importance for production of agronomically adapted and commercially desirable olive cultivars in D V. dahliae‐infested soils. In this work, resistance to D V. dahliae in wild olive clones Ac‐13, Ac‐18, OutVert and StopVert was assessed by quantifying the fungal DNA along the stem using a highly sensitive real‐time quantitative polymerase chain reaction (qPCR) protocol and a stem colonization index (SCI) based on isolation of V. dahliae following artificial inoculations under conditions highly conducive for verticillium wilt. Ac‐13, Ac‐18, OutVert and StopVert showed a symptomless reaction to D V. dahliae. The mean amount of D V. dahliaeDNA quantified in stems of the four clones ranged from 3.64 to 28.89 pg/100 ng olive DNA, which was 249 to 1537 times lower than that in susceptible Picual olive. The reduction in the quantitative stem colonization of wild olive clones by D V. dahliae was also indicated by a sharp decrease in the SCI. Overall, there was a pattern of decreasing SCI in acropetal progression along the plant axis, as well as correlation between positive reisolation and quantification of pathogen DNA. The results of this research show that wild olive clones Ac‐13, Ac‐18, OutVert and StopVert have a valuable potential as rootstocks for the management of verticillium wilt in olive.

Aims The potential of grafting susceptible cultivars onto resistant rootstocks was evaluated for the control of Verticillium wilt in olive.

Fifty-seven wild olive accessions collected from the Mediterranean basin were screened under greenhouse conditions for their resistance to verticillium wilt. Plants were root-dip inoculated. One defoliating and one non-defoliating isolate of Verticillium dahliae, both obtained from diseased plants in southern Italy, were used. Plants of the highly susceptible cv. Cima di Mola, frequently used as a rootstock in Apulia, were also included in this test. Disease reactions were evaluated on the basis of external symptoms, vascular browning and by calculating areas under disease progress curves (audpc). On the basis of Audpc values and external symptom severity, accessions were grouped into four phenotypic groups: highly resistant, moderately resistant, susceptible and highly susceptible. Three accessions showed high resistance to both V. dahliae pathotypes. Forty resistant plants were selected from accessions that had shown the highest levels of resistance. Clones were obtained from each of these plants by in vitro micropropagation for further testing. Ten clones showed the resistance characteristics of their original mother plants, while others suffered greater levels of disease severity than their mother plants. Several new olive rootstocks were identified that were highly resistant to verticillium wilt and could be included in breeding programmes for resistance of olive to V. dahliae

Among 146 accessions of Lycopersicon pimpinellifolium, 132 of L. esculentum var. cerasiforme and 53 of L. peruvianum screened for resistance to powdery mildew, caused by Oidium lycopersici, a wide variation in reactions was found. Two plants of L. esculentum var. cerasiforme accession LA-1230 were resistant. One resistant symptomless plant of accession LA-1230, designated LC-95, produced homozygous resistant progenies. LC-95 was crossed with cv. Marmande (susceptible parent) and F 1 , F 2 and backcrosses to the resistant and the susceptible parents were derived. These genotypes were grown in glasshouses at 23ЊC and 95-100% RH and inoculated with O. lycopersici. The F 1 plants were susceptible. F 2 and backcross segregations fitted the hypothesis of a single recessive gene which is here designated ol-2.

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Verticillium wilt is becoming an increasing concern in artichoke production because the rapid spread of the disease to new growing areas has led to declining production. Scientists from Italy, Spain, and the United States combine to bring us up to date on diagnosis of the disease, its epidemiology and life cycle, as well as management strategies, current and forthcoming.