First report of P. nicotianae on jojoba in Argentina

G. Lucero¹, A.M. Vettraino², P. Pizzuolo¹ and A. Vannini²*

¹ Universidad Nacional de Cuyo, Argentina
² Dipartimento di Protezione delle Piante, Università degli Studi della Tuscia, Viterbo, Italy

*vettrain@unitus.it

Accepted for publication 11/04/05

Jojoba, Simmondsia chinensis, is a small tree that produces seeds containing a liquid wax, widely used in the cosmetic and pharmaceutical industries, and in human and animal food supplements. It is native to areas of northern Mexico and southern California. In Argentina, jojoba is cultivated in the northwest of the country, on more than 4000 Ha and it represents an important alternative economic enterprise in low-rainfall areas.

A survey carried out in northwest Argentina in 2004 revealed the presence of crown decline, collar and root rot of jojoba trees in several plantations. Symptoms consisted of changes in leaf colour, wilting and plant death (Fig. 1), with dead leaves remaining attached to the tree. Flame-shaped, dark necroses were present at the collar (Fig. 2). Symptoms were widespread along the planting rows.

Figure 1: Dead jojoba tree in a plantation in North West Argentina associated with the presence of P. nicotianae.

A Phytophthora spp. was isolated from infected tissues and soil removed from the root zone of symptomatic plants. Isolations were made by baiting with rhododendron leaves and plating on PARBhy medium. Isolates developed white fluffy colonies on PDA. Sporangia were non-caducous and ellipsoidal-to-ovoid in shape, with prominent papilla. Chlamydospores were terminal or intercalary. Oospores were not observed. 

Figure 2: Collar lesions on jojoba from which P. nicotianae has been isolated	Figure 3: Wilting of jojoba seedlings (left) artificially inoculated with P. nicotianae. Controls remained healthy (right)

Isolates were identified using morphological features and RFLP analysis of ITS region of rDNA using PhytID (http://www.phytid.org/). Isolates were identified as P. nicotianae (= P. parasitica) (Erwin & Ribeiro, 1996). Pathogenicity tests were conducted by soil infestation on 18 month-old jojoba seedlings using 2 isolates of P. nicotianae isolated from jojoba. Sporulation was induced by 24 h flooding of the soil. Inoculated plants wilted after five months (Fig. 3). Controls remained healthy. P. nicotianae was reisolated from the soil and roots of inoculated plants.

P. nicotianae causes root, stem and crown rots, as well as fruit and foliar blights, on many horticultural and woody plants including jojoba (Alcorn et al., 1989; Erwin and Ribeiro, 1996). To our knowledge this is the first record of P. nicotianae on jojoba in Argentina.

References

Alcorn SM, Orum TV, Matheron ME, 1989. Phytophthora leaf blight of jojoba (Simmondsia chinensis) in Arizona. Plant Disease 73, 444.

Erwin DC, Ribeiro OK, 1996. Phytophthora Diseases Worldwide. St. Paul, MN, USA: APS Press.

The British Society for Plant Pathology