First Report of Vascular Wilt Caused by Fusarium redolens on Lentil in Italy.

Abstract

Lentil (Lens culinaris Medik.) is a traditional crop in Sicily, Italy. Near Villalba (Caltanissetta), a local lentil landrace, "Lenticchia di Villalba", is commonly grown. From 2002 to 2004, wilt was observed in five lentil fields (≈1 ha each) at rates from 5 to 20%. Affected plants were yellow and stunted with discoloration in the vascular tissue of stems and crowns. Pieces of brown vascular tissue from stems were disinfested in 2% sodium hypochlorite for 2 min, rinsed with sterile distilled water, placed on potato dextrose agar, and incubated at 23°C. Isolates with morphological characteristics of Fusarium oxysporum Schlecht.:Fr. (2) were consistently recovered from affected plants. For molecular identification of five isolates, the rDNA internal transcribed spacer (ITS) region and a portion of the elongation factor EF-1α were sequenced using ITS5/4 and EF1/2 primers, respectively (1). Two sequences of the ITS region were obtained: a 468-bp sequence from isolates ER1259, ER1260, and ER1275 (submitted as GenBank Accession No. EU159118) and a 483-bp sequence from isolates ER1274 and ER1276 (submitted as GenBank Accession No. EU281661). The two sequences shared 93% similarity. A sequence homology search using the NCBI BLAST program revealed that the first sequence had 100% homology with the ITS sequences of more than 50 F. oxysporum isolates of various formae speciales in GenBank and the second shared 100% homology with the ITS sequences of five isolates of F. redolens Wollenw. (e.g., GenBank Accession No. X94169 of the strain CBS 360.87). Amplification of the EF-1α produced a sequence from isolates ER1274 and ER1276 (submitted as GenBank Accession No. EU281660) with 99 to 100% homology to sequences of F. redolens and a sequence from strains ER1259, ER1275, and ER1260 (submitted as GenBank Accession No. EU281659) with 100% homology to that of more than 50 F. oxysporum strains in GenBank. Although F. redolens and F. oxysporum are morphologically similar, recent molecular studies have shown that they are distinct and phylogenetically distant species (3). On the basis of genetic sequences, isolates ER1274 and ER1276 were identified as F. redolens. These isolates were evaluated for pathogenicity on lentil. For each isolate, 10 2-week-old seedlings of "Lenticchia di Villalba" were inoculated by submerging roots in a suspension of 2.5 × 106 conidia/ml for 10 min. Plants were put into separate tubes containing 70 ml of a nutritional liquid medium (7 ml of HydroPlus Olikani per liter; Yara, Nanterre, France) and incubated in a growth chamber at 20°C with 12 h of light per day. Seedlings dipped in sterile water served as the control treatment. The pathogenicity test was repeated twice. Inoculated seedlings started to wilt 1 week after inoculation and developed root rot and vascular discoloration. After 2 weeks, 70% of the inoculated plants were affected by both isolates and 40 and 10% died when inoculated with ER1274 and ER1276 isolates, respectively. F. redolens was consistently reisolated from the stems of wilted plants. Noninoculated plants remained healthy. Currently, only F. oxysporum f. sp. lentis Vasud. and Sriniv. has been reported as the cause of Fusarium wilt of lentil. To our knowledge, this is the first report of F. redolens as a pathogen on lentil.