D. W. Dickson

Ultrastructure, Morphology, and Sporogenesis of Pasteuria penetrans.

ABSTRACT Pasteuria penetrans is a bacterial parasite of root-knot nematodes that shows great potential as a biocontrol agent. Scanning and transmission electron microscopy were used to study the ultrastructure, morphology, and sporogenesis of four isolates of P. penetrans. The effects of different Meloidogyne spp. and tobacco cultivars on sporangium size and morphology of endospores attached to the cuticle of second-stage juveniles (J2) of root-knot nematodes also were investigated. The P. penetrans isolates and their origins were P-20 from M. arenaria race 1 in Levy County, FL; P-100 from Meloidogyne sp. in Pasco County, FL; B-4 from Pratylenchus scribneri in Seminole County, FL; and P-120 from Meloidogyne spp. in Alachua County, FL. Sporangia of the four isolates were identical morphologically and similar in their dimensions, ranging from 2.39 to 3.42 mum in diameter and from 1.38 to 2.38 mum in height. Different Meloidogyne spp. and tobacco cultivars had no effect on sporangium size. Endospores attached to J2 were visualized in three forms: endospores retaining the sporangium wall, endospores covered with a thin exosporium, and endospores without covering. Sporogenesis of P. penetrans was similar to that of other gram-positive bacteria and generally matched the seven-stage scheme reported for Bacillus thuringiensis.

Detection of Heterodera glycines on soybean in Brazil

The soybean cyst nematode (Heterodera glycines) was detected and identified on soybean (Glycine max) during a survey made in 65 soybean fields on 52 farms in six states in central Brazil during March-June 1992. The infested sites were located near the municipalities of Irai de Minas and Nova Ponte, Minas Gerais; Chapadao do Ceu and Apore, Goias; Chapadao do Sul, Mato Grosso do Sul; and Campo Verde, Mato Grosso. The large geographic region represented by these infested sites likely means that H. glycines is widely established in Brazil (.)

Uptake, accumulation, and metabolism of carbofuran and fenamiphos by the phytoparasitic nematodes Meloidogyne javanica and M. incognita

Abstract This study used 14 C-labeled carbofuran and fenamiphos to show that carbofuran was extremely unstable in Meloidogyne incognita and M. javanica . After 48 hr of exposure, approximately 2% of the total radioactivity was recovered as parent and 3–5% as 3-hydroxy-carbofuran and 3-keto-carbofuran. Over 90% of the applied 14 C was associated with the water-soluble metabolites. In contrast, fenamiphos was rather stable in both nematode species, with approximately 70 and 30% of the total radioactivity recovered as parent and fenamiphos sulfoxide, respectively. Metabolite uptake studies showed that fenamiphos reached equilibrium within the nematodes after approximately 24 hr, whereas carbofuran did not reach an equilibrium even after 96 hr of incubation. These data indicate that the difference in biological activity (fenamiphos is about 10 times more active than carbofuran) is due largely to the rapid metabolization of carbofuran and the biological stability of fenamiphos in nematodes

Phoma heteroderae sp. nov. isolated from eggs of Heterodera glycines

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