Date of Award:

5-1983

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Plants, Soils, and Climate

Department name when degree awarded

Plant Science

Committee Chair(s)

J. L. Anderson

Committee

J. L. Anderson

Committee

G. D. Griffin

Committee

J. H. O'Bannon

Committee

J. A. Veech

Committee

W. F. Campbell

Committee

D. W. Davis

Committee

B. A. Haws

Abstract

Duration of embryogenic development of a Nebraska population of Nacobbus aberrans at 15 and 25 C were 51 and 9-10 days respectively. The first juvenile (J1) molted in the egg and the nematode emerged as J2. Kochia and sugarbeet root leachates did not significantly affect the percent of cumulative egg hatch. Temperature significantly affected juvenile emergence (P= 0.05), as less than 1, 5, and 20% of the eggs hatched at 5, 10 and 15 C, respectively. More than 70% of the eggs hatched at 20 and 25 C. At 25 C, postembryogenic development from egg to egg was completed in 48 days. All juveniles, young females, and all males were migratory endoparasites. Young females were able to leave swollen roots where they had developed and later re-enter the same roots or nearby roots to become sedentary and form true galls. Thirty days after J2 inoculation specimens were detected in root tissues at 10, 15, 20 and 25, and 30 C, but not at 5 C. At 23 C, 50 percent of the root stele was destroyed by juveniles within 25 days after inoculation. Syncytia formation was only associated with adult females.

Three N. aberrans physiological races were distinguished: 1) the "Sugarbeet" biotype that attacks sugarbeet but not potato; 2) the "Potato" biotype that attacks potato and sugarbeet, and 3) the "Pepper" biotype that attacks pepper but not potato.

Heterodera schachtii, Meloidogyne hapla, and Nacobbus aberrans either alone, or in various combinations with each other, when inoculated at a concentration of 12 J2/cm3 of soil, caused significant (P = 0.01) suppression of growth of 'Tasco AH14' sugarbeet seedlings. Meloidogyne hapla and H. schachtii decreased growth of sugarbeet more than N. aberrans over a 60 day period. The ratio between final (Pf) and initial (Pi) population densities of N. aberrans was lower (P. = 0.01) than that of H. schachtii and M. hapla over 30 and 60 days. Nacobbus aberrans is considered to be less aggressive on sugarbeet than H. schachtii or M. hapla. Sections of sugarbeet roots infected simultaneously with H. schachtii and N. aberrans showed the H. schachtii and N. aberrans syncytia located in peripheral and central root position, respectively.

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