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African Crop Science Journal
African Crop Science Society
ISSN: 1021-9730 EISSN: 2072-6589
Vol. 7, Num. 4, 1999, pp. 503-510
African Crop Science Journal, Vol. 7. No. 4, 1999

African Crop Science Journal, Vol. 7. No. 4,  pp. 503-510, 1999                                                              

Plant parasitic nematodes associated with common bean in Kenya and the effect of  Meloidogyne infection on bean nodulation

J.W. Kimenju, N.K. Karanja and I. Macharia
Faculty of Agriculture, University of Nairobi, P.O. Box 29053, Nairobi, Kenya

Code Number: CS99041

ABSTRACT

A study to determine the distribution and population densities of plant parasitic nematodes associated with beans was undertaken in Kakamega, Kiambu, Machakos and Siaya districts of Kenya.  Soil and root samples were taken from 25 randomly selected farms in each district.  Nematodes in the genera Meloidogyne, Pratylenchus, Scutellonema and Helicotylenchus were frequently recovered in the rhizophere of bean plants with varying densities in the different locations of the study.  Meloidogyne spp. and Pratylenchus spp. were the most predominant endoparasites occurring in 86 and 61% of the root samples, respectively.  Scutellonema and Helicotylenchus species were present in 80 and 59% of the soil samples, respectively.  Other nematodes found in association with bean plants were in the genera Tylenchorhynchus, Tylenchus, Criconemella, Aphelenchus, Hemicyliophora, and Trichodorus. Greenhouse tests were conducted to determine the effect of M. incognita infection on nodulation of bean genotypes.  With the exception of bean genotype M28, Meloidogyne infection caused significant (P< 0.05) reductions in nodulation.  In a second pot experiment, bean cv. GLP-24 was inoculated with Rhizobium leguminosarum bv. phaseoli  alone and in various combinations  with M. incognita.  Both nodulation and the dinitrogen fixation processes were adversely affected especially in plants where nematode inoculation preceded rhizobial inoculation.

Key Words:  Bean genotypes, East African highlands, Helicotylenchus spp., Meloidogyne incognita, Pratylenchus spp., Scutellonema spp., Tylenchorhynchus spp.

RÉSUMÉ

Une étude pour déterminer la distribution et la densité  de la population de nématodes parasitaires de plantes associés aux haricots a été initié dans les districts de  Kakamega, Kiambu, Machakos et Siaya au Kenya.  Les  échantillons des racines et de sols ont été  pris dans 25 fermes sélectionnées aléatoirement dans chaque districts.  Les nématodes des genres Meloidogyne, Pratylenchus, Scutellonema et Helicotylenchus  ont été fréquemment trouvés dans la rhizosphère des plantes de haricot avec des densité  variées dans differentes parties du pay.  Meloidogyne spp. et  Pratylenchus spp. étaient des endoparasites les plus dominants apparaissant dans 86 et 67% d’échantillons de racines, respectivement.  Les espèces de  Scutellonema et Helicotylenchus étaient présents dans 80 et 59% d’échantillons de sol respectivement.  Autres nématode trouvés en assoication avec la plante de haricot étaient des genres de Tylenchorhynchus, Tylenchus, Criconemella, Aphelenchus, Hemicyliophora et Trichodorus.  Avec exception du génotype M28, l’infection du Meloidogyne a  causé de réduction significative (P<0.05) dans la nodulation.  Dans le deuxième essai en pots des combinaisons de haricot avec  M. incognita ont été considérées.  Ensemble les processus de dinitrification et de nodulation ont été défavorablement affectés spéciallement dans les plantes où les nématodes ont précédé l’inoculation du Rhizobium.  

Mots Clés:   Genotype de harricot, haute terre de l’Afrique de l’Est, Helicotylenchus spp., Meloidogyne incognita, Pratylenchus spp., Scutellonema spp., Tylenchorhynchus spp.

Introduction

Common beans (Phaseolus vulgaris L.)  are grown on an estimated  500,000 ha, in Kenya mainly in association with other crops, especially maize in Kenya (Wortmann and Allen, 1994; Gethi et al., 1997).  The average yields of 750 kg ha-1 are often low compared  to a  potential  1500 - 2000  kg  ha-1 (Rheenen et al., 1981).  The main constraints to bean production in descending order of importance are diseases, low soil fertility and insect pests (Otsyula and Ajang, 1995).

Root-knot (Meloidogyne spp.) nematodes are recognised as a major constraint to bean farming, causing up to 60% yield losses in heavily infested fields (Ngundo and Taylor, 1974).  Infection by root-knot nematodes is also known to suppress nodulation and hence nitrogen fixation in leguminous plants (Karanja, 1988; Siddiqui and  Mahmood, 1994).  Although Meloidogyne species are known to cause enormous losses on common bean, information on nematode populations in the bean growing areas of Kenya is lacking.  This study was undertaken to determine the population density and frequency of occurrence of plant parasitic nematodes associated with common bean in Kenya and to determine the effect of root-knot nematodes on bean nodulation.

Materials and Methods

Sample collection.  A survey of nematodes associated with dry bean was carried out in Kakamega, Kiambu, Machakos and Siaya districts between May and July 1998.  Twenty soil and bean root samples were collected from each of the 25 randomly selected farms in each district.  Plants were gently uprooted and a trowel was used to dig out soil from the bean rhizosphere to a depth of 25 cm.  All the roots obtained from each farm were placed in a polythene bag but only about 3 kg of the composite soil sample from each farm was transported to the laboratory.

Nematode damage assessment and extraction.  Ten plants from each sample were examined for damage by root-knot nematodes.  Damage due to root-knot nematodes was rated using a root-gall index scale of 0-10 (Bridge and  Page, 1980).  Nematodes were extracted from two 200 cm3 soil volumes using the sieving and filtration method described by Hooper (1990).  The root-knot nematodes were extracted from two batches of 5 g roots each using the maceration/filtration technique (Hooper, 1990).  Extracted nematodes were fixed in hot 4% formalin.  Identification of nematodes to genus level was done using an identification key and descriptions by Mai and Lyon (1975).  Nematode population levels were determined from a counting slide under a compound microscope and expressed either as number per 200 cm3 soil or 5 g roots. 

Effect of Meloidogyne infection on bean nodulation in different bean genotypes. Twenty bean genotypes were used in this test.  Bean lines E1, E3, E4, NOB, M14, M24, M26, M28, M29, M30, L31, L32, L40 and L45, improved for multiple disease resistance, were obtained by the University of Nairobi Bean Improvement Project (Kimani et al., 1993).  Bean lines KK8, KK14, KK15 and KK22 were selected because of their resistance to root rot pathogens (Otsyula and Ajanga, 1995) while two of the commonly grown cultivars, GLP-24 and GLP-1004, were included as checks.

Plastic pots with a 15 cm diameter were filled with 2:1 (v/v) heat-sterilised loam soil: sand mixture and placed in a greenhouse.  Bean seeds were surface sterilised using procedures  described by Somasegaran and Hoben (1994).  Four bean seeds were planted in each pot but thinning was done at emergence to leave two seedlings per pot.  All plants were inoculated at emergence with Bradyrhizobium leguminosarum biovar phaseoli strain 446 supplied by the Microbial Resource Centre (MIRCEN) of the University of Nairobi.  Two ml of a rhizobial culture containing ca. 1x109 cfu ml-1 was pipetted into indentations made in the root zone of each plant (Somasegaran and Hoben, 1994).

For each bean line, five pots were infested with 2000 juveniles (J2) of M. incognita at emergence.  The juveniles were obtained by immersing galled tomato roots in sterile distilled water for 7 days (Omwega et al., 1988).  The juveniles were suspended in 10 ml sterile distilled water.  Surface soil was removed to expose some roots to which the inoculum was added and the soil was replaced.  Treatments were arranged in a completely randomised design with 5 replications.  Plants were maintained in the greenhouse with regular watering.  The experiment was terminated six weeks after soil infestation with nematodes.  Plants were gently uprooted from the pots and shaken to remove adhering soil.  The total number of nodules on each plant was recorded before taking a random sample of 10 nodules for use in determining the percentage of those that were effective (pinkish in colour).

Effect of time of inoculation with Meloidogyne on bean nodulation.  Pots were filled with heat-sterilised loam soil: sand mixture as described above.  Three bean cv. GLP-24 seeds were planted in each pot but thinning was done at emergence to leave one seedling per pot.  Treatments consisted of plants inoculated with R. leguminosarum bv. phaseoli strain 446 alone at emergence, plants inoculated with strain 446 and M.incognita at emergence, plants inoculated with Rhizobium at emergence and M. incognita 10 days after emergence (DAE), and plants inoculated with M. incognita at emergence and strain 446 at 10 DAE.  Treatments were arranged in a completely randomized design with 10 replications.   Analysis of variance of the data was done using MSTAT-C (1990),  and means  compared using Least Significant Difference (LSD) tests.

Results

Nematodes associated with beans.  Nematodes belonging to ten genera, Meloidogyne Goeldi, Pratylenchus Filipjev, Scutellonema Andrassy, Helicotylenchus Steiner, Tylenchorhynchus Cobb, Tylenchus Bastian, Hemicycliophora de Man, Criconemella Taylor, Aphelenchus Bastian and Trichodorus Cobb, were found associated with beans in Kakamega, Kiambu, Machakos and Siaya districts (Table 1).  The predominant ectoparasites were in the genera Scutellonema and Helicotylenchus, with overall occurrences of 80 and 59%, respectively.  The endoparasitic nematodes, Meloidogyne and Pratylenchus species, were present in 86 and 61% of the root samples, respectively.

Table 1.  Occurrence of plant parasitic nematodes in soil and bean roots collected from Kakamega, Kiambu, Machakos and Siaya districts in Kenya

Nematode genus

% frequency of nematode occurrence per district

 

Kakamega

Kiambu

Machakos

Siaya

Overall

 

         

Soil

         
           

Meloidogyne

96

42

84

72

74

Pratylenchus

96

48

80

48

68

Scutellonema

100

80

64

76

80

Helicotylenchus

76

80

24

56

59

Tylenchorhynchus

12

36

52

32

33

Tylenchus

4

8

12

0

6

Criconemella

0

0

8

0

2

Aphelenchus

0

8

4

0

3

Hemicycliophora

0

44

0

0

11

Trichodorus

0

8

0

0

2

           

Roots

         
           

Meloidogyne

96

80

88

80

86

Pratylenchus

76

32

76

60

61


Numbers of the predominant nematodes belonging to the genera Meloidogyne, Pratylenchus, Scutellonema and Helicotylenchus varied significantly (P < 0.05) between districts (Table 2). Numbers of all plant parasitic nematodes in soil and root samples were highest in Kakamega district (Table 2).  Nematode densities were lowest in soil and root samples from Siaya and Kiambu districts, respectively.

Table 2. Mean population density of the predominant plant parasitic nematodes recovered from soil and bean roots collected from Kakamega, Kiambu, Machakos and Siaya districts in Kenya1

Nematode                                      

Mean population density in 200 cm3 soil or 5 g roots per district

         
 

Kakamega

Kiambu

Machakos

Siaya

Soil

       
         

Meloidogyne

127 a*

43 c

102 ab

54 bc

Pratylenchus

251 a

21 b

42 b

56 b

Scutellonema

244 a

102 b

33 b

62 b

Helicotylenchus

71 a

41ab

11 b

17 b

         

Other nematodes

99

36

33

7

         

Roots

       
         

Meloidogyne

564 a

250

393 b

320 bc

Pratylenchus

79 a

10 b

18 b

40 b

1Data are means of 25 samples
*Means followed by the same letter (s) along rows are not significantly (P< 0.05) different by Least significant difference test

Nematode damage.  The most obvious symptoms of  nematode damage were galls on roots caused by Meloidogyne species.  Levels of damage varied (P < 0.05) among the districts, with highest and lowest root galling being observed in Kakamega and Kiambu districts, respectively (Fig. 1).  Symptoms of damage by nematodes from the other groups were non-characteristic, appearing mainly as reduced growth and yellowing of foliage.

Effect of Meloidogyne infection on nodulation of different bean genotypes.  Numbers of nodules on bean plants infected with M. incognita were significantly (P < 0.05) lower than in control, with the exception of lines E1 and M28 (Table 3).  Reduction in nodulation ranged from 35.4% in line NOB to 100% in line E4.  Numbers of nodules in plants inoculated with M. incognita were significantly (P < 0.05) different among the bean genotypes.  For instance, no nodules were observed on the roots of bean line E4 inoculated with  nematodes  as compared to more than 111 nodules on roots of bean line NOB.  Meloidogyne infection caused significant (P < 0.05) reduction in proportions of effective nodules in the bean genotypes tested, with the exception of bean cv. GLP-24 (Table 3).

Table 3. Numbers of nodules and percentage of effective nodules in Meloidogyne-infected and non-infected bean plants

Bean genotype

Nodule numbers in:

Effective nodules (%) in

 

Inoculated1

Control2

Inoculated

Control

         

GLP-24

90.0

166.8

70.0

98.0*

GLP-1004

20.0

58.6

14.0

50.0

NOB

111.2

172.2

72.0

90.0

KK8

70.2

132.2

36.0

78.0

KK14

88.6

161.8

38.0

88.0

KK15

77.4

157.6

40.0

80.0

KK22

38.0

124.6

32.0

62.0

E1

42.6

92.8

20.0

74.0

E3

19.4

121.4

8.0

40.0

E4

0

54.0

0

76.0

M14

1.4

30.2

0

68.0

M24

45.4

99.8

22.0

62.0

M26

41.6

92.4

10.0

58.0

M28

25.4

39.2*

20.0

70.0

M29

27.6

59.4

46.0

74.0

M30

9.2

28.0

8.0

38.0

L31

32.2

116.6

36.0

70.0

L32

32.4

107.8

34.0

66.0

L40

4.6

40.0

12.0

44.0

L45

19.0

46.2

18.0

50.0

         

LSD (P < 0.05)

19.9

24.7

15.2

12.6

         

1Inoculated = Nematode-infected, 2Control = Nematode-free; Data are means of five replications

Effect of time of inoculation with Meloidogyne incognita on bean nodulation.  The number of nodules was significantly (P< 0.05) higher in bean cv. GLP-24 plants inoculated with rhizobia alone than in plants inoculated with combinations of rhizobia and M. incognita (Table 4).  Plants inoculated with nematodes at emergence and with rhizobia 10 days after emergence (DAE) had the lowest number of nodules on their roots.  The percentage of effective nodules was significantly (P < 0.05) higher in bean plants inoculated with rhizobia alone than those inoculated with rhizobia and M. incognita (Table 4).  Plants inoculated with nematodes at emergence had lower (P < 0.05) proportions of functional nodules than those inoculated with nematodes 10 DAE.

Table 4. Effect of Meloidogyne infection on bean nodulation and functioning of nodules in bean cv. GLP-24 plants1

Treatments

Nodule number/plant

Effective nodules (%)

     

Rhizobium alone at emergence

96.5 a2

83.0 a

Nematode + Rhizobium (both at emergence)

74.4 b

48.8 c

Nematode (at emergence) + Rhizobium (10 DAE)

54.2 c

47.4 c

Rhizobium (at emergence) + Nematodes (10 DAE)

78.2 b

66.0 b

DAE = Days after emergence
1Data are means of 10 replications.  2Means followed by the same letter along the columns are not significantly (P < 0.05) different by Least significant difference test

Discussion

The present study revealed that nematodes in the genera Meloidogyne, Pratylenchus, Scutellonema and Helicotylenchus are widely distributed in bean fields in Kenya.  Density and frequency of occurrence of nematodes in the four genera were highest in Kakamega district.  Warm and wet conditions prevailing in the district (Jaetzold and Schmidt, 1983), coupled with a high cropping intensity of P. vulgaris are ideal for most plant parasitic nematode population build-up.  Incidence and population densities of the predominant nematodes were, however, low in Kiambu district in spite of high cropping intensities in the district.  This could be attributed to the high amount of cow manure, obtained from zero-grazing units, incorporated into the soil in most farms (Woomer et al., 1998).

The high frequency of occurrence of Meloidogyne species in bean fields in Kakamega, Kiambu, Machakos and Siaya districts supports previous reports that root-knot nematodes are commonly associated with beans in Kenya (Hollis, 1962).  Damage caused by the nematodes varied significantly among the districts. Variation in damage can be attributed to many factors such as differences in bean cultivars and types, environmental factors and their interactive effect on nematode densities and parasitism (Egunjobi, 1974; Griffin et al., 1996).

Our study showed that Pratylenchus spp. are common inhabitants of the rhizosphere of bean plants.  Lesion nematodes, especially P. zeae, is a serious pest on maize in Kenya (Kimenju et al., 1998).  Maize and beans are usually grown together in the small-scale holdings in Kenya (Wortmann and Allen, 1994; Gethi et al., 1997).  Therefore, pathogenicity of Pratylenchus spp. associated with beans and their influence on bean growth needs to be determined.

The finding that Meloidogyne infection suppresses bean nodulation in bean plants is consistent with previous reports (Karanja, 1988; Siddiqui and Mahmood, 1994).  Biotic factors that affect nodule formation or dysfunction of existing nodules include nematode, viral and fungal infections (Tu et al., 1970; Bowen, 1978;  Orellana et al., 1978; Khan, 1993).  Several plant parasitic nematodes with different modes of parasitism have adverse effects on nodulation through competition for ecological niches and nutrients, and  suppression of lateral root formation, thus reducing sites for nodule formation and early degradation of nodules because of nematode infection (Taha, 1993).

Numbers of nodules on plants inoculated with M. incognita were significantly different among the bean genotypes tested in this study. This indicates that nematodes had variable effects on nodulation in different bean genotypes.  Conflicting observations have been made on the effect of nematode infection on bean nodulation (Hussey and Barker, 1976; Verdejo et al., 1988; Siddiqui and Mahmood, 1994).  Our results show that the bean genotype used may influence the impact of nematode infection on nodulation.

In the present study, bean nodulation was more adversely affected when inoculation with M. incognita preceded Rhizobium inoculation.  In a related study, Sharma and Khurana (1991) reported that growth and nodulation of bean plants were normal in treatments where Rhizobium inoculation preceded nematode inoculation.  However, inoculation with M. incognita prior to Rhizobium interfered with growth and nodulation in beans.

Variation in nodulation ability among the bean lines used in this study was clearly demonstrated.  These findings indicate that nitrogen fixation can be improved through selection of bean genotypes with high nodulation potential.  However, presence of nodules is only a prerequisite for symbiotic nitrogen fixation but not a reliable parameter for measuring nitrogen fixation in legume-rhizobia symbiosis.

Conclusions

Plant parasitic nematodes in the genera Meloidogyne, Pratylenchus, Scutellonema and Helicotylenchus are widespread in bean growing areas in Kenya.  The wide distribution and the enormous losses associated with root-knot (Meloidogyne spp.) nematodes justifies the development of control strategies that are acceptable to small scale bean growers.  The influence of especially Pratylenchus spp. (which are recognised as important pests on maize) on growth and yield of this crop needs to be determined. 

Interference of root-knot nematodes with bean nodulation and effectiveness of the nodules formed was clearly demonstrated.  This implies that nematode control should be incorporated in programmes aimed at improving soil fertility through symbiotic nitrogen fixation.

Acknowledgement

The authors are grateful for financial support from the Rockefeller Foundation under Forum for Agricultural Resource Husbandry. Mr. L.M. Kagema of the Department of Crop Protection, University of Nairobi is acknowledged for technical assistance.

References

Bowen, G.D. 1978.  Dysfunction and shortfalls in symbiotic responses.  In:  Plant Disease: An Advanced Treatise, Vol. III. Horsfall, J.G. and Cowling, E.B. (Eds.), pp. 231-236.  Academic Press, New York.

Bridge, J. and Page, S.L.J. 1980.  Estimation of root-knot nematode infestation levels on roots using a rating chart. Tropical Pest Management 26:296-298.

Egunjobi, O.A. 1974.  Nematodes and maize growth in Nigeria. I.  Population dynamics of Pratylenchus brachyurus in and about the roots of maize in Ibadan.  Nematologica 20:181-196.

Gethi, M., Muriithi, F.M., Macharia, N. and Njoroge, K. 1997.  Maize/bean intercropping system in medium potential areas of Kenya: Farmers’ practice and research challenges. African Crop Science Conference Proceedings 3:756-770.

Griffin, G.D., Asay, K.H. and Horton, W.H.  1996.  Factors affecting plant-parasitic nematodes on rangeland grasses.  Journal of Nematology 28:107-114.

Hollis, J.P. 1962.  A survey of plant parasitic nematodes and their control in Kenya.  Food and Agriculture Organization Plant Protection Bulletin 10:97-106.

Hooper, D.J. 1990.  Extraction and processing of plant and soil nematodes. In: Plant Parasitic Nematodes in Subtropical and Tropical Agriculture.  Luc, M., Sikora, R.A. and Bridge, J. (Eds.), pp. 45-68. CAB International, Wallingford.

Hussey, R.S.and Barker, K.R. 1976.  Influence of nematodes and light sources on growth and nodulation of soybean.  Journal of Nematology 8:48-52.

Jaetzold, R. and Schmidt, H. 1983.  Farm Management Handbook of Kenya, Vol. II. Ministry of Agriculture, Nairobi, Kenya.

Karanja, N.K. 1988.  Selecting Rhizobium phaseoli strains for use with beans (Phaseolus vulgaris L.) in Kenya.  Ph.D Thesis, University of Reading, UK. 221pp.

Khan, M.W. 1993.  Mechanisms of interactions between nematodes and other plant pathogens. In: Nematodes-Interactions. Khan, M.W. (Ed.), pp.175-202.  Chapman and Hall, London.

Kimani, P.M., Mwang’ombe, A.W. and  Kimenju, J.W. 1993. Performance of advanced generation bean lines selected for multiple disease resistance.  In:  Proceedings of the Third Regional Workshop on Bean Research in Eastern Africa, 1-4 March, 1993, Thika, Kenya.  Allen, D.J. and Buruchara, R.A. (Eds.),  pp. 29-38. CIAT, Dar- es-saalam.

Kimenju, J.W., Waudo, S.W., Mwang’ombe, A.W., Sikora, R.A. and Schuster, R.P. 1998.  Distribution of lesion nematodes associated with maize in Kenya and susceptibility of maize cultivars to Pratylenchus zeae. African Crop Science Journal 6:367-375.

Mai, W.F. and  Lyon, H.H. 1975.  Pictorial Key to Genera of Plant-Parasitic Nematodes.  Comstock Publishing Associates, London. 219pp.

MSTAT-C. 1990. Version 1.4 Software. Michigan State University, USA.

Ngundo, B.W. and Taylor, D.P. 1974.  Effect of Meloidogyne spp. on bean yields in Kenya. Plant Disease Reporter 58:1020-1023.

Omwega, C.O., Thomason, I.J. and Roberts, P.A. 1988.  A nondestructive technique for screening bean germ plasm for resistance to Meloidogyne incognita. Plant Disease 72: 970-972.

Orellana, R.G., Sloger, C. and Miller, V.L. 1978.  Rhizoctonia-Rhizobium interactions in relation to yield parameters of soybean.  Phytopathology 68:577-582.

Otsyula, R.M. and Ajanga, S.I. 1995.  Control strategy for bean root rot in western Kenya. In: Proceedings of the Second Meeting of the Bean Pathology Working Group. Allen, D.J. and Buruchara, R.A. (Eds.), pp. 71-76. CIAT African Workshop Series No. 37, Kampala.

Rheenen, H.A., van Hasselbach, O.E. and Muigai, S.G.S. 1981.  The effect of growing beans together with maize on the incidence of bean diseases and pests.  Netherlands Journal of Plant Pathology 87:193-199.

Sharma, P. and Khurana, A.S. 1991.  Studies on interactions of Meloidogyne incognita and Rhizobium strains on symbiotic nitrogen fixation in mungbean (Vigna radiata L.) Wilczek. Indian Journal of Ecology 18:118-121

Siddiqui, Z.A.  and  Mahmood, I. 1994.  Interraction of Meloidogyne javanica, Rotylenchulus reniformis, Fusarium oxysporum f. sp. ciceri and Bradyrhizobium japonicum on the wilt disease complex of chickpea.  Nematologia Mediterranea 22:135-140.

Somasegaran, P. and Hoben, H.J. 1994.  Handbook for Rhizobia: Methods in Legume-Rhizobium Technology.  Springer-Verlag, New York. 450 pp.

Taha, A.H.Y. 1993.  Nematode interactions with root-nodule bacteria.  In:  Nematode-Interactions. Khan, M.W. (Ed.), pp. 175-202. Chapman and Hall, London, UK.

Tu, J.C., Ford, R.E. and Quiniones, S.S. 1970.  Effect of soybean mosaic virus and/or bean pod mottle virus infection on soybean nodulation.  Phytopathology  60: 518-523.

Verdejo, M.S., Green, C.D. and Podder, A.K. 1988.  Influence of Meloidogyne incognita on nodulation and growth of pea and black bean. Nematologica 34:88-97.

Woomer, P.L., Bekunda, M.A., Karanja, N.K., Moorehouse, T. and Okalebo, J.R. 1998.  Agricultural resource management by smallhold farmers in East Africa.  Nature and Resources 34:22-33.

Wortmann, C.S. and Allen, D.J. 1994.  Africa bean production environments: their definition, characteristics and constraints.  Network on Bean Research in Africa.  Occasional Paper Series No. 11, CIAT, Dar-es-saalam.


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