Nacobbus Aberrans

Development of the False Root-knot Nematode, Nacobbus aberrans, on Sugarbeet 1 R . N . INSERRA,-" N . VOVI.AS," G . D. GRIFFIN," a n d J. L. ANDERSON 4
Abstract: T h e duration of the embryogenic development of Nacobbus aberrans ( = N. batati[ormis) took 9-10 days at 25 C and 51 days at 15 C. T h e J~ molted in the egg; hence
the Je emerged from the egg. T h e effect of distilled water attdroot leachates of kochia and sugarbeet was investigated at 5, 10, 15, 20, and 25 C. Root leachates did not significantly affect the percent of cumulative hatch of eggs, but temperature did significantly affect emergence of juveniles (p = 0.05). Less than 1, 5, and 20% of eggs hatched at 5, 10, and 15 C, respectively. T h e percent of cumulative hatch at 20 C was four times greater than at 15 C, whilethe highest percentage of juveniles emerged at 25 C. T h e duration of postembryogenic development froth J2 inoculation until the appearance of mature females with egg mas~s took 38 days, and the life cycle from egg to egg was completed in 48 (lays at 25 C. All immature stages, young females and males were migratory endoparasites. Young females were able to leave the root swellings, where theydeveloped from juvenile stages, and re-enter the root, where they formed a true gall and became sedentary. Thirty days after inocnlation with J., nematodes, specimens were detected in root tissues at 10, 15, 20, 25, and 30 C, h u t not at 5 C. Five days after inoculation at 23 C ( ± 2 C), juveniles had penetrated the roots and caused slight swellings of the tip and axis of sugarbeet feeder roots.Large cavities extended from the cortical parenchyma to the periphery of the stelar area, and 50 % of the central cylinder was destroyed 25 days after inoculation at 23 C. No syncytia formation were detected in the sugarbeet root swellings infected with juveniles. Syncytia were associated only with adnlt females; hypcrplasia, abnormal proliferation of lateral roots, and asymmetry of root strnetnrewere additional anatomical changes induced by adult females. Only very smooth aunules but no cuticular ornamentatkms were noted by ,SEM on the perineal area of adult females. Key words: life cycle, embryogenesis, postembryogenesis, egg hatch, root leachates, histopathology, morphology. Journal ~f Nematology 15(2):288-296. 1983. f a l s e r o o t - k n o t n e m a t o d e Nacobbus a n d A l i e n ,a n e a r t i c species d i s t r i b u t e d i n N o r t h a n d S o u t h A m e r ica, is r e p o r t e d t o d a m a g e s u g a r b e e t (Beta vulgaris L.) a n d s o l a n a c e o u s c r o p s s u c h as p o t a t o (Solanum tuberosum L.) a n d t o m a t o (Lycopersicon esculentum M i l l . ) (3,8,12,13). I n f o r m a t i o n o n t h e b i o l o g y o f N. aberrans a n d a n a t o m i c a la l t e r a t i o n s c a u s e d b y its penetration of sugarbeet and tomato roots h a s b e e n r e p o r t e d (5,6,7,8,9,10). S c h t t s t e r e t The al. (10) reported that juveniles of N. and egg.

aberrans T h o r n e

aberrans ( = N. batatiformis T h o r n e

Received for Publication 4 June 1982. 1Journal Paper No. 2765. Portion of a Ph.D. dissertation submitted by the seniorauthor to Utah State University, Logan. 2Nematologists. USDA. ARS, Crops Research Laboratory, Utah State University, Logan, UT 84322. aNematologist. Istituto Nematologia agraria, C.N.R., 70126 Bari, Italy. 4Professor of Plant Science Dep~rlment, Utah State University, l,ogan, fIT 84322.

Schuster) (I1) did not molt in the C l a r k (1), h o w e v e r , s t a t e d t h a t N. aberrans ( = N.serendipiticus F r a n k l i n ) (11) e m e r g e d as J2 ( s e c o n d - s t a g e j u v e n i l e ) . O t h e r a s p e c t s o f t h e life cycle a n d h o s t r e l a t i o n s o f t h e nematode species are unclear. The purpose o f t h i s p a p e r w a s t o s t u d y (i) tile e m b r y o g e n i c d e v e l o p m e n t o f N. abe rrans ( = batatiformis) a t d i f f e r e n t t e m p e r a t u r e...