First Report of Tomato yellow leaf curl virus in Louisiana.

Tomato yellow leaf curl virus (TYLCV) is a begomovirus (Geminiviridae) that causes a serious disease of tomato throughout the world. In 1997, the strain from Israel of TYLCV (TYLCV-IS) was found infecting tomatoes in Florida for the first time in the United States (1). During late spring of 2000, approximately 90% of the tomato plants (Lycopersicon esculentum) in a farm near New Orleans exhibited severe stunting, leaf cupping, and chlorosis. Symptoms were similar to those caused by TYLCV. Whiteflies (Bemisia tabaci biotype B) were present in the field but in relatively low numbers. The effect on yield reduction varied from negligible (late infections) to 100% (early infections). Six selected plants showing symptoms were assayed by polymerase chain reaction (PCR) using begomovirus-specific primers. Capsicum frutescens infected with an isolate of Texas pepper virus from Costa Rica was used as positive control. DNA was extracted using Plant DNAzol Reagent (GIBCO BRL). PCR was conducted using degenerate primers AV494/AC1048 that amplify the core coat protein region of most begomoviruses (2). PCR yielded a DNA fragment of approximately 550 bp, suggesting that a begomovirus was associated with the disease. The amplified DNA of one field isolate was cloned and the nucleotide (nt) sequence determined. Sequence comparisons with other begomoviruses in the GenBank Database indicated that the Louisiana isolate shared 100% nt identity with TYLCV-IS (GenBank Accession X76319). Successful transmission (100%) to Bonny Best tomato were obtained with four groups of 10 whiteflies each (B. tabaci biotype B) that fed on TYLCV-IS infected tomato plants. Acquisition and transmission feedings were for 2 days. In all cases, the virus was diagnosed by the ability to reproduce typical TYLCV-like symptoms in tomato and PCR. The virus was also successfully graft-transmitted to tomato cv. Bonny Best, Nicotiana benthamiana, and tomatillo (Physalis ixocarpa) using scions from tomato plants infected with a whitefly transmitted virus isolate. This is the first report of TYLCV-IS in Louisiana. References: (1) J. E. Polston et al. Plant Dis. 83:984-988, 1999. (2) S. D. Wyatt and J. K. Brown. Phytopathology 86:1288-1293, 1996.

Red sea drillings.

Recent drilling in the Red Sea has shown that much of the basin is underlain by evaporites of a similar age to that of evaporites found in the Mediterranean Sea. These evaporites and their structural positions indicate that other brine areas are present-and, indeed, several others have been discovered.