Powdery mildew of Allium species caused by Oidiopsis taurica in Brazil

Abstract

T he Alliaceae family comprises one of the leading groups of plants in terms of economic importance, including major vegetable crops such as garlic (Allium sativum L.), leek (A. porrum L. syn. A. ampeloprasum), onion (A. cepa L.), and bunching onion (A. fistulosum L.) (Brewster, 1994). In Brazil, these vegetables are primarily cultivated under open field conditions. However, seedlings for transplantation, plants employed in controlled crosses during breeding programs, and tissue culture-derived virus-free garlic plantlets are often cultivated under either greenhouse or plastic house conditions. REIS, A.; BOITEUX, L.S.; PAZ-LIMA, M.L.; SILVA, P.P.; LOPES C.A. Powdery mildew of Allium species caused by Oidiopsis taurica in Brazil. Horticultura Brasileira, Brasília, v.22, n.4, p.758-760, out-dez, 2004. (Maffia et al., 2002; Zambolim et al., 2000). However, an apparently undescribed powdery mildew disease was observed affecting a range of Allium species in distinct Brazilian growing regions. This disease was first noticed on garlic and leek accessions in Brasília (Federal District) and in field-grown onion cultivars in Belém do São Francisco (Pernambuco State) during successive growing seasons (from 2000 to 2003). In this work, the occurrence of a powdery mildew disease on Allium species in Brazil was described as being caused by the fungus Oidiopsis taurica Salmon (syn. O. sicula Scalia). Powdery mildew of MATERIAL AND METHODSOpen field-grown plants of leek showing atypical powdery mildew-like symptoms were collected in Brasília (Federal District). Similar symptoms ABSTRACTOidiopsis taurica Salmon (Syn. Oidiopsis sicula Scalia) was identified as the causal agent of a powdery mildew disease occurring on distinct Allium species in Brazil. This disease was initially observed in plastic house and field-grown garlic (Allium sativum) and leek (A. porrum) accessions in Brasília (Federal District) and in field-grown and greenhouse onion (A. cepa) cultivars in Belém do São Francisco (Pernambuco State) and Brasília, respectively. Typical symptoms consisted of chlorotic areas on the leaf surface corresponding to a fungal colony. These lesions turned to a brownish color with the progress of the disease. Fungi morphology was similar to that described for O. taurica. Endophytic mycelium emerging through estomata, light pale conidia were dimorphic (lanceolate primary conidia and somewhat cylindrical secondary conidia), fibrosin bodies were absent, conidia formed predominantly single (not in chains), and appressoria were non-lobed. Its sexual stage, Leveillula taurica (Lev.) Arnaud, was not observed. Inoculations were performed with the O. taurica isolates from distinct Allium hosts. These isolates were also pathogenic to sweet pepper and tomato, indicating an apparent absence of host specialization. One bunching onion (A. fistulosum) accessions was not infected by O. taurica suggesting that this species might carry useful resistance alleles to this pathogen. This is the first formal report of a powdery mildew disease on specie...

Statistical analysis of machine learning techniques for predicting powdery mildew disease in tomato plants

“…Lastly, the plant leaves may start withering. Usually, older leaves are more prone to this disease than the younger ones (Holliday, 1980;Correll et al, 1988;McGrath et al, 2001;Haroun, 2002;Reis et al, 2004). However, powdery mildew does not contaminate the fruit or stem of the tomato plant, but it can diminish the quality of tomato fruit, lessen the growth of the plant and can gradually decrease the tomato production (Braun, 1987;Jones and Thomson, 1987;Farag, 2003).…”

EVALUATION OF NUTRITIONAL COMPOSITION OF LEEK (Allium porrum, Aliaceae).

“…O alho-porro compõe a família Aliaceae, esta família tem grande importância econômica uma vez que nela estão incluídas espécies mundialmente e rotineiramente consumidas, como a cebola (Allium cepa), o alho (Allium sativum L.) e o próprio alhoporro (Allium porrum L.) (REIS et al, 2004).…”

Powdery mildew of ornamental species caused by Oidiopsis haplophylli in Brazil

“…In Brazil, powdery mildew outbreaks caused by O. haplophylli have been reported on processing tomatoes, freshmarket tomatoes and sweet peppers in several Brazilian States (3,8,11,12,13). The host range of O. haplophylli is expanding in the country with several new reports on distinct vegetable and ornamental hosts (10,11,13). Oidiopsis haplophylli has not been reported as seed-transmissible, therefore, it is more likely that this fungus was introduced in Brazil via infected ornamental pot plants (11).…”