ABSTRACT
The continual detection of a slow (I1) esterase band in greenhouse cultures of Meloidogyne konaensis isolated from the field led to a hypothesis that the nematode may be polymorphic for esterase. A survey of coffee fields demonstrated at least four esterase phenotypes were present in Meloidogyne recovered. An F1 phenotype predominated (60% of the females), but an I1 phenotype was also common (30% of samples). A series of greenhouse and laboratory experiments were undertaken to understand this polymorphism. Esterase phenotype was not affected by development at 22 masculine, 25 masculine, or 33 masculineC on tomato. Two different esterase phenotypes (I1 and F1-I1) were detected after M. konaensis was grown on tomato for several generations, even in single-egg-mass lines derived from an F1 female. Three isolates of M. konaensis differing in esterase phenotype (F1, I1, and F1-I1) did not differ morphologically but did differ in their parasitic ability. Only the F1 isolate parasitized Coffea arabica. The F1-I1 isolate had greater reproduction on Lycopersicon esculentum and Cucumis sativus than either the I1 or F1 isolate. The mechanism of the development of the polymorphism has yet to be determined. However, the F1 esterase may be useful as a marker for future research on parasitism of coffee by M. konaensis.
ABSTRACT
Pasteuria penetrans is a promising biological control agent of plant-parasitic nematodes. This study was conducted to determine effects of temperature on the bacterium's development in Meloidogyne arenaria. Developmental stages of P. penetrans were viewed with a compound microscope and verified with scanning electron microscopy within each nematode at 100 accumulated degree-day intervals by tracking accumulated degree-days at three temperatures (21, 28, and 35 degrees C). Five predominant developmental stages of P. penetrans were identified with light microscopy: endospore germination, vegetative growth, differentiation, sporulation, and maturation. Mature endospores were detected at 28, 35, and >90 calendar days at 35, 28, and 21 degrees C, respectively. The number of accumulated degree-days required for P. penetrans to reach a specific developmental stage was different for each temperature. Differences were observed in the development of P. penetrans at 21, 28, and 35 degrees C based on regression values fitted for data from 100 to 600 accumulated degree-days. A linear response was observed between 100 to 600 accumulated degree-days; however, after 600 accumulated degree-days the rate of development of P. penetrans leveled off at 21 and 28 degrees C, whereas at 35 degrees C the rate decreased. Results suggest that accumulated degree-days may be useful only in predicting early-developmental stages of P. penetrans.
