Prot, Jean-Claude

Van Gundy, S.D.

Horizon / Pleins textes

numbers of P. pene/rotrs ranged froin 75 to 6140 with a mean number of 1276 
nematodes/250 cc of soil. Losses of No. I tomatoes. or those exceeding 6.3 cm 
dianieter and without visual defects, ranged from 1.7 T/ha  to 15.5 T / h a  with a mean 
loss of 2.9T/ha due to nematodes. Number 2 tomato yields were generally unchanged. 
Nematode erfect on yield increased throughout the season until a mean loss of 30% of 
the No. I tomatoes occurred by the 4th picking: I n  general, low fertility treatments 
resulted i n  higher nematode numbers. Nematode numbers were affected negatively by 
increased N fertilization and leaf P but related positively to higher pH, soil and leaf 
Mg. Highest yield (58.1 T/ha)  of No. I tomatoes was obtained with 44.8, 112. I ,  336.2 
(NPK)at  pH 6.0and theadditional lossdue to nematodes wascalculated as 7 .8Tlha.  
Processing tomatoes have about 17%of the value per acre of those sold as fresh market 
tomatoes and potential loss determines the amount that can be spent on controlling 
lesion nematodes. Yield relationship reduced to its simplest form was: yield loss = 
\ b nematode numbers, where bis theslope ofa  line. Considerably higher numbers of 
lesion nematodes may therefore be tolerated in fields containing processing tomatoes 
than in those picked for fresh market. The data indicate that yield, mineral nutrition, 
and nematodes have many interesting and complex interactions. 
POSSIBLE RADOPHOLUS SIMILIS BIOTYPES REPRODUCING AND MI- 
GRATING ON RESISTANTCITRUS ROOTSTOCKS[POSIBIL~DAD DE BIO- 
TIPOS DE RADOPHOLUS SIMILIS REPRODUCIENDOSE Y TRANSMU- 
DANDOSE EN RAICES DE CITRUS RESISTENTE]. J. H. O'Bannon and H. W. 
Ford, U. S .  Department of Agriculture, Science and Education Administration. 
Agricultural Research, Prosser, Washington 99350 and Agricultural Research and 
Education Center, IFAS. Lake Alfred. Florida 33850, U.S.A. - - -  Radopholussimilis 
populations were found infecting Milam limon (Cirrus sp.), a R. similis resistant 
rootstock in two groves in central Florida. One, the Conway population, was found to 
infect and reproduce on Milam limon, Ridge Pineapple and Algerian Navel orange (C. 
auranrium), and Carrizo Citrange (C. sinensis x P. rri/olia/a) seedlings considered to 
be resistant to  highly resistant to R. simiiis. in significantly greater numbers than the 
R. similis population that causes the disease "spreading decline" of citrus. The second, 
Ward's population, was found to readily infect Milam seedlings. Both populations 
migrated from infected to  uninfected Milam seedlings in greenhouse soil tanks. In two 
years. the Ward population migrated further than the Conway population and 
appears to be more infective to Milam. 
INFLUENCE OF SOIL TYPE AND TEMPERATURE ON T H E  MIGRATION 
O F  MELOIDOGYNEINCOGNITA JUVENILES TOWARDTOMATO ROOTS 
[INFLUENCIA DEL TIPO DE SUELO Y DE LA TEMPERATURA SOBRE LA 
MIGRACION DE FORMAS JUVENILES DE MELOIDOGYNE INCOGNITA 
HACIA RAICES DE TOMATE]. J. C. Prot and S .  D. Van Gundy. Department of 
Nematology, University of California, Riverside. California 92521, U.S.A. - - - The 
effects of soil type and temperature on the migration of M. incognirajuveniles towards 
tomato roots were tested in 20-cm PVC columns attached to Styrofoam cups contain- 
ing the plants and separated from the root system by a 85-um screen. Juveniles that 
had migrated 20 cm and penetrated the roots were counted after staining the roots in 
0.05% cotton blue. Approximately 300 juveniles not more than 24 h old were intro- 
duced into the soil a t  the bottom of the column. At a constant temperature of 26OC the 
percent penetration in 10 days i n  soils containing: a) 8.8% clay (C) + 5.2% silt (S); b) 
10.2% C +  1 1.9% S :  c) 9.2% C +  16% S ;  d) 13.2% C +  l9.5%S; and e) 18.5% C +  23.5% S 
was 32. 13. 10, O and O, respectively. Migration in soil of composition a) was also 
I 
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studicd as a lunction 01  t i m e  at 14. 16, 1 H. 20 and 22'C. 1 he perccritjuvcnilcs lound i n  
the roots after 5 ,  IO, IS and 20 days was, respectively: O. I .  I .  2 at 14°C; O. 3, 3, 2 a t  
16°C; O, 7. 6. 8 at I8OC; I .  33, 34, 33 at 20°C; and 5. 35, 43, 40 at 22°C. These data 
indicate that increasing the fine soil particles has a limiting influence on the migration 
of M. incognifojuveniles. and that very fewjuveniles are able to migrateand penetrate 
roots when the temperature is less than 1 8 O C .  Also, i t  would appear that some 
juveniles have the ability to  migrate 20 cm whereas others d o  not, because penetration 
was not significantly different between 10 and 20 days at  18, 20, or 22OC. 
FEEDING PLUG FORMATION AND ULTRASTRUCTURE CHANGES IN 
COTTON ROOTS FOLLOWING RENIFORM, NEMATODE PARASITISM 
[FORMACION DE UN TAPON ALIMENTICIO Y CAMBIOS DE ULTRAE- 
STRUCTURA EN RAICES DE ALGODON PARASITADAS POR EL NEMA- 
i 
T O D O  RENIFORME]. R.V. Rebois, USDA, Nematology Laboratory. Plant Pro- 
tectin Institute, BARC-West, Beltsville, Maryland 20705.--- Susceptible Gossypium 
hirsutum 'Auburn 56' and moderately resistant G. orboreum 'Nanking' (C.B. 1402) 
seedlings were planted in vermiculite which was inoculated 3 days later with reniform 
nematodes, Rofylenchulus renyormis. At 3, I 1, and 24 day intervals following hocul- 
tation, roots were washed free of vermiculite. Roots were cut into 1 mm pieces and 
processed for examination by transmission electron microscopy. Within the first three 
days, the infective female passed intracellularly through the cortex, usually perpen- 
dicular to the root axis, and came t o  rest with its lips in contact with an endodermal 
cell. The female inserted approximately half of the conical part of thestylet (3 um) into 
a n  endodermal or  less frequently a pericycle cell (PC) to initiate feeding. This cell then 
became a prosyncyte, inital syncytial, or feeding cell (ISC). If the head or  body of the 
nematode penetrated and ruptured the wall of a PC, feeding did not appear to  be 
initiated. The portion of the stylet inserted in the ISC became surrounded with a 
cell-wall-like deposit o r  feeding plug (FP). The FP was thinner on the ventral or 
aperture side of the stylet and thicker on the opposite side. A feeding tube (FI-) like 
structure was seen in the ISCand often extended into the adjacent PC. The R a p p e a r s  
to  be formed from materials secreted through the stylet aperture which is located 
about I um fom the stylet tip. Portions of the FT near the stylet aperture were 
surrounded by smooth endoplasmic reticulum and electron dense spherical inclusions. 
The FT appeared in juxtaposition to  the plasmalem? covering the FP, immediately 
surrouhding the stylet aperture. Sections of the FT were found in the ICs and the 
adjacent P C  at  3, 1 I ,  and 24 day following inoculation. On days 3 to I I the syncytia 
consisted mainly of Pc's. Eleven to 24 days after inoculation, the infection was 
obscrvbd deep in the stelar area between xylem elements in both hosts. 
PATHOGENICITY AND CONTROL OF T W O  SPECIES O F  MELOIDOG YNE 
ON LATE SEASON SUNFLOWER [PATOGENICIDAD Y CONTROL D E  DOS 
ESPECIES D E  MELOIDOGYNE EN GIRASOLES]. J. R. Rich, Department of 
Nematology, University of Florida, Agricultural Research Center, P.O. Box 657, Live 
Oak, Florida, 32060 - - - Two field studies were initiated on August I I ,  1978, to 
determine the influence of Meloidogyne incognito and M. javonica on sunflower 
(Helionthus unnuus L.). In test A, the soil was previously cropped to  corn and was a 
sand moderately infested with 204 M. incognita, 47 Prarylenchus sp., and 20 Tricho- 
dorus christiei per 250 cm3 soil. Five nematicide treatments, each replicated 6 times, 
included: a control, aldicarb (Temik ISG), and carbofuran (Furadan 10G) and two 
phenamiphos (Nemacur 15G) treatments. Three nematicide treatments were applied 
at 2.98 kg a.i./ha in a 20 cm band over the seed row at-planting. and a n  additional 
0. R.  s. K8.M. fonds Uemelibiie 


Influence of soil type and temperature on the migration of Meloidogyne incognita juveniles toward tomato roots = influencia del tipo de suelo y de la temperatura sobre la migracion de formas juveniles de Meloidogyne incognita hacia raices de tomate

Influence of soil type and temperature on the migration of Meloidogyne incognita juveniles toward tomato roots = influencia del tipo de suelo y de la temperatura sobre la migracion de formas juveniles de Meloidogyne incognita hacia raices de tomate

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