Aung, T.

Prot, Jean-Claude

Horizon / Pleins textes

Effects of crop rotations on Pratylenchus zeae and on yield 
of rice cultivar UPL Ri-5 
Tin AUNG* and Jean-Claude PROT** 
Plant Pathology Department, I.R.R.I., P.O. Box 933, 1099 Manila, Philippines. 
SUMMARY 
The effect of  corn,  cowpea,  mungbean,  rice,  and  sorghum on the  population  density of Pratylenchus  zeae were  tested  in  upland 
rice  field  conditions in the  Philippines. The three  cereal  crops  were  very  good  host of the  nematode. The two legumes  crops  were 
resistant to the  parasite, but two successive  croppings  with  these  crops  were  necessary to reduce  the  nematode  population  density 
to  a  low  level. The yield  of  rice  grown  after two crops  of  corn,  cowpea,  mungbean,  or  rice  was  correlated to the  population  densities 
of P. zeae detected at the  end of the  preceding  crop. The yield  of  rice  grown  after  cowpea  and  mungbean  was  significantly  higher 
than that obtained  after  cereal  crops. The yield  of  rice  after  rice  was 37 Y O  lower than  the yield  of  rice  after  cowpea.  Control  of P. 
zeae by  crop  rotation  using  cowpea  or  mungbean  is  feasible.  However,  since the surviving  nematodes  multiply  very  rapidly on rice, 
rotating will protect  only  one  rice  crop  in  the  case  of  a  continuous  cropping. 
BSUMf3 
Effets de différentes  rotations sur Pratylenchus  zeae et les rendements d’une culture de riz cv. UPL Ri-5 
Les  effets  de  cultures  de  maïs,  niébé,  haricot  mungo,  riz  et  sorgho sur les  densités  de  population  de Pratylenchus  zeae ont  été 
testés au champ sur un site  de  culture  de  riz  pluvial  aux  Philippines.  Les  trois  céréales  ont  permis une importante  multiplication 
de P. zeae. Les  deux  légumineuses  sont  apparues  résistantes au nématode  mais  deux  cultures  successives  de  ces  légumineuses  ont 
été  nécessaires  pour  réduire  très  fortement  la  densité  de  la  population.  Les  rendements  d’une  culture  de  riz  conduite  après  deux 
cultures  de  maïs,  niébé,  haricot  mungo ou riz  sont  corrélés  avec  les  densités de population  de P. zeae détectées à la fin de  la culture 
précédente.  Les  rendements  en  riz  obtenus  après  niébé  et  haricot  mungo  sont  significativement  supérieurs à ceux  obtenus  après 
céréales. Le  rendement  en  riz  obtenu  après un précédent  riz  est  inférieur  de 37 O/O à celui  obtenu  après un précédent  niébé.  Si  le 
contrôle  de P. zeae par culture  de  niébé  et  de  haricot  mungo  est  possible,  il  ne  protège  qu’une  culture  de  riz  car  les  nématodes 
survivants  se  reproduisent très rapidement  sur  riz. 
Pratylenchus  zeae Graham,  1951 is a Pest of maize, 
tobacco, Cotton, sweet  corn,  sugarcane,  and rice (Fortu- 
ner, 1976). It is also a Pest of rice in the USA, Brazil, 
Rhodesia, Ivory Coast, Cuba, Nigeria, India, and Pa- 
nama (IbaAez, 1970; Reyes, 1970;  Fortuner, 1976; 
Babatola, 1984). It is commonly associated with  upland 
rice in  the Philippines.  Another  member of the genus, 
Pratylenchus indicus Das, 1960, causes  significant yield 
reductions  (Prasad & Rao,  1978b; Prasad & Rao, 1983), 
and  metabolic  changes in rice  (Prasad,  Ramana & Rao, 
1982). P. indicus can  be  controlled by crop ro- 
tations, with different crops such as barley, wheat and 
mung bean  (Prasad & Rao 1978~).  The primary objec- 
tives of this study was to determine, in field conditions, 
the effect of five crops, rice, corn, sorghum,  mungbean, 
and cowpea, commonly  associated to  upland rice  ecosys- 
tem  in  the Philippines, on a population of P.  zeae and  the 
effect of this nematode on  the yield of a rice crop. 
Materials and methods 
The experiment was conducted on an upland rice 
field of the International  Rice  Research  Institute 
(I.R.R.I.) experimental farm from April 25 1987 until 
December 5 1988. The field was naturally  infested  with 
P. zeae. Four other plant-parasitic nematodes, Tylen- 
chorhynchus annulatus Criconemella onoensis. Hemicy- 
cliophora penetram, Helicotylenchus sp., were occasion- 
ally detected  on the field, but they were not taken  into 
consideration in this  study. Four  different  crop  sequen- 
ces were grown in 2 x 5 m plots, with  five  replications 
in a randomized  complete-block  design. The different 
crop  sequences were : sorghum (Sorghum vulgare 
Pers.)-cowpea (Vigna unguiculata L., Wa1p.)-cowpea- 
rice (O y z a  sativa L.), rice-mungbean (Phaseolus  mungo 
L.)-mungbean-rice, corn (Zea mays L.)-corn-corn-rice, 
and rice-rice-rice-rice. The different  varieties  used  were : 
* Current address : Agriculture Corporation, Applied Research Division, Bogon, Rangoon, Bunna. 
** ORSTOM nematologist. 
Revue Nénzatol. 13 (4) : 445-447 (1990) 445 
T. Aung & J . 4 .  Prot 
Table 1 
Effect  of  different  crops on a  population  of Pratylenchus zeae. 
Consecutive crops 
Initial 
population 
N/dm3 of soil 
Nzlmber of nematodesll  dm3 of soil + 1 g of roots* 
44 a** sorghum 1 833 a cowpea  694 a cowpea 6 a  rice  477 a 
73 a rice 3 130,a mungbean 1 O00 ab mungbean  28 a rice 1 210 b 
70 a corn 6 266 b corn  2  060 b corn  6  283 b rice  2  772 c 
72 a rice 2  994 a rice  2  063 b rice  4  40  b rice  2  748 bc 
* Average  of  five  replications. 
** In a  column,  means followed  by a cornmon letter are  not  significantly  different  at  the 5 O h  level  by Duncan's new multiple range test. 
sorghum CS101, cowpea T V  x 2724-0lFy mungbean 
Pag-asa 5 ,  corn Supersweet, and rice UPL Ri-5. The 
plants  were  grown  with the following row spacing and 
spacing  within the row : sorghum 50 cm-25 cm, cowpea 
25 cm-15 cm, mungbean 25 cm-5 cm, corn 50 cm- 
25  cm, and rice with  a row spacing of 25 cm at a  seeding 
rate of 50 kg/ha. No fertilizer was applied. The field was 
irrigated  as necessary and kept  free of weeds by hand 
weeding. The successive crops were seeded and harves- 
ted at  the following  dates : 1st  crop 25 April87-29  Au- 
gust  87,2nd  crop 8  October 87-1 1 February  88,3rd crop 
22 march 88-25 July 88, and  4th  crop 4  august 88-5 De- 
cember  88. The  fiist  crop was planted  after  a  9  months 
fallow. The aerial  parts of the crops were always removed 
from  the plots to avoid a  green  manure  effect. 
Nematodes  densities in each  plot, were assessed at  the 
beginning of the experiment, and  at harvest. At each 
sampling  time, five 200 cm3 soil samples and five root 
systems were collected at  random  from  each  plot. The 
soil samples were analyzed for nematodes by sieving 
(using  a 45 pm pore sive) and  Baermann funnel (48  h 
extraction  time).  For  each  root  sample  a  subsample of 
3 g of roots was macerated for 10 s in an electric 
blender, and  then placed on a  Baermann funnel  for 48  h. 
The yield of the final  rice  crop was measured on 3 r n 2  in 
the  centre of each  plot. 
Results  and  discussion 
The cereal  crops  tested in this  experiment : corn, rice, 
and  sorghum were good hosts for P. zeae (Table 1). They 
allowed high  multiplication  rates of the parasite  when  its 
initial population densities were  low, and they maintain- 
ed the levels of infestation  when  the  initial  population 
densities were high. On the  other  hand,  the two legume 
crops (cowpea and  mungbean) caused  a  decrease of the 
number of nematodes  present in  the soil. In this exper- 
iment, two successive crops of  cowpea or  rnungbean were 
446 
necessary to reduce drastically the nematode ' popu- 
lation  density. During  the evaluation of the nematode 
population, in  the  plots  where  cowpea  and  mungbean 
were grown, P. zeae was found mostly in  the soil, and 
only  a few individuals were observed in  the roots. These 
observations  seem  indicate that cowpea and  mungbean 
were resistant to P. zeae but that the nematode was 
capable to survive, in  the soil, the  duration of a  crop. 
The yields of the rice  crop  following the two legume 
crops were significantly higher than those  obtained  after 
corn  and rice (Table 2). A difference of 37 O/O in yield  was 
observed  between  rice  after rice and rice after cowpea. 
As in this  experiment, the aerial parts of the plants were 
removed from  the plots, the differences in yield can  not 
be  explained by a  green manure effect of the legume 
crops. 
At sowing of the last  rice  crop, the  population densi- 
ties of P. zeae were significantly lower after  the  legume 
crops than  after  the cereals (Table 1). Moreover, when all 
the plots were considered  individually the yield of the 
last  rice  crop was correlated  with the  population density 
Table  2 
Effect  of  different  crop  rotations on the yield 
of a final  rice  crop 
Crop rotations Last rice  crop yield 
k g h a  * 
sorghum-cowpea-cowpea-rice 1 126 a** 
rice-mungbean-mungbean-rice 868 b 
corn-corn-corn-rice  741 c 
rice-rice-rice-rice  710 c 
* Average of five replications.. 
** The yields followed by a cornmon letter are not significantly 
different at the 5 Yo level  by Duncan's new multiple  range test. 
0 
Effects of crop rotations on Pratylenchus  zeae 
of P. zeae detected  just  before sowing notwithstanding 
the variability observed (Fig. 1). However, a  significant 
difference in yield was observed between rice grown 
after cowpea and rice grown  after mungbean  (Tab. 2) 
when at the same time, the populations of P. zeae 
detected after the two legume crops were not signifi- 
cantly different. This could indicate a direct effect of 
the preceding crop  on the rice crop, or that  due  to  the 
Yield  (kglha) 
1400 
y = 1043.1 - 86.228~ RAZ = 0.489 
1200 - 
1 2 3 4 
log of nQ of nernatodesldm3 of soi1 
5 
Fig. 1. Linear  regression  between the yield of an  upland  rice 
crop  and the number of Pratylenchus zeae present  a  sowing 
time. 
variability and  the  reduced  number of replications the 
nematodes population densities detected after cowpea 
and after mungbean were not statistically different, 
while they  may  have  had  different  effect on  the rice crop. 
This last  hypothesis is supported by the fact that inocu- 
lation  with 30 Pratylenckus indicus per  young  seedling of 
the  upland rice cultivar Bala, the yield was decreased by 
34 O/O (Prasad & Rao, 1978b). The significant  difference 
between the nematode population densities observed 
after rice following cowpea and after rice following 
mungbean could  indicate that  the population of P. zeae 
present after mungbean was able to reproduce more 
rapidly  on rice and effect the yield more efficiently than 
the  one  left  after cowpea. 
This experiment  indicates that : 
- P. zeae may  reduce the yield of an upland  rice 
crop  by 37 O/o in field  conditions; 
- corn,  sorghum, and rice are  good  host  plants for P. 
zeae; 
- the nematode  can  be  controlled by crop  rotation 
with cowpea or mungbean. However in a continuous 
cropping, two crops of legumes  are necessary to decrease 
the  infestation to a low  level. Moreover, this practice will 
most  certainly  protect only one  rice  crop  as the multipli- 
cation  rate of the nematode is very high on rice. 
FUFERENCES 
BABATOLA, J. O. (1984).  Rice  nematode  problems in  Nigeria : 
their  occurrence,  distribution  and  pathogenesis. Trop. Pest 
Manag., 30 : 256-265. 
FORTUNER, R. (1976). Pratylenchus zeae. C.I.H.  Descr.  Pl.-pa- 
rasit.  Nematodes,  Set  6,  No.77. 
IBA~EZ, A. R. (1970). DetemtinaciBn de plantas hospederas  del 
nemcitodo Pratylenchus  zeae Graham 1951, bajo condiciones 
de invernadero. Thesis,  Panama  Universidad,  33  p. 
PRASAD, J. S., RAMANA, K. V., & RAo, Y.  S .  (1982).  Metabolic 
changes  in  rice due to  migratory  endoparasitic  root  nema- 
todes. J.  Res. Assam agric. Univ., 3 : 72-75. 
PRASAD, J. S. & RAo, Y.  S. (1978a).  Influence of crop  rotations 
on the population densities of the root lesion nematode, 
Pratylenchus indicus in  rice  and  rice  soils. Annals Zool. Ecol. 
anim., 10 : 627-633. 
PRASAD, J. S. & RA0 Y.  S. (1978b).  Potentiality of Pratylenchus 
indicus Das  1960,  the  root-@ion  nematode  as  a  new  pest of 
upland  rice. Annals Zool. Ecol. anim., 10 : 635-640. 
PRASAD, J. S. & RAo, Y.  S. (1983).  Influence of age of rice  plant 
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Acta œcol., 4 : 309-312. 
REYES, R. D. (1970).  Determinacion  de  la  eficiencia  de  diferen- 
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Accepté pour publication le 9 janvier 1990. 
Revue Ne'matol. 13 (4) : 445-447 (1990) 447 


Effects of crop rotations on Pratylenchus zeae and on yield of rice cultivar UPL Ri-5

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