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Cucurbit Genetics Cooperative Report 15:31-32 (article 11) 1992

Non-linkage of Bitterness and Resistance to Red Spider Mite in Cucumber

N.P.S. Dhillon

Punjab Agricultural University, Vegetable Research Station, Jalandhar - 144 001, India

The role of bitterness (caused by cucurbitacins) in cucumber resistance to twospotted spider mite (Tetranychus urticae) is not conclusive. North American researchers reported that bitterness caused resistance to spider mite (2, 3). However, in Europe, De Ponti and Garrettsen (6) hypothesized only a genetic relation in terms of linkage of genes for resistance and bitterness. Interestingly, the resistant non-bitter lines of cucumber selected in The Netherlands were susceptible to twospotted spider mite in the United States, and the resistance of bitter lines was inconsistent (7). Those data support the earlier results of causal relation between resistance and bitterness.

Red spider mite (Tetranychus cinnabarinus) is a major pest of cucumber in India and other tropical countries like Pakistan, Bangladesh, Sri Lanka and Burma. It is closely related to T. urticae (1). It is an economically important pest of cucumber in Europe and North America.

The objective of this research was to investigate further the relationship between bitterness and resistance to red spider mite, and to evaluate the germplasm of cucumber reported to be resistant to twospotted spider mite for resistance to red spider mite.

Methods. During March, 10 plants of each of 16 lines were sown in the field in a completely randomized design. The 16 lines consisted of 4 pairs of near isogenic bitter and non-bitter lines ('Hokus', 'Nimbus', 'Marketmore 70', 'Marketmore 72', Marketmore 76', 'Marketmore 80', 'Poinsett 83-10 Bi' and 'Poinsett 83-10 bi'), and 8 bitter lines (PI 163222, PI 178885, PI 218036, PI 220860, 'Ohio MR 200, 'Robin 30', 'Taipei No. 1' and 'Aodai'). Bed width was 0.75 m and plants were spaced 25 cm apart. Observations on damage index were recorded during the peak natural infestation period of the middle of May. Damage was assessed on a scale of 1 to 5 (1 = slight damage; 5 = heavy damage) described by De Ponti (4). At each observation, five leaves per plant were evaluated and their mean value represented he damage index of the plant. The experiment was run twice in two years.

Results. In both years, the cucumber lines tested were susceptible to T. cinnabarinus (damage index .3). Bitter cucumber lines 'Hokus', 'Marketmore 70', 'Marketmore 76', and 'Poinsett 83-10 Bi' did not differ in damage level from their near-isogenic non-bitter counterpart (Table 1). An unreplicated trial involving single plants of each of those lines behaved similarly at two different sites in a farmer's field (data not presented). That suggests no causal relation between bitterness and resistance to T. cinnabarinus.

Using the same set of bitter and non-bitter isogenic lines of cucumber ('Hookups', 'Nimbus', 'Marketmore 70' and 'Marketmore 72'), De Ponti (5) also observed that resistance of cucumber to T. urticae was not related to bitterness. Eight other bitter lines of cucumber were also found susceptible to T. cinnabarinus (Table 2). In the Netherlands, those lines proved resistant to T. urticae (4).

Table 1. Mean damage index of 4 pairs of near isogenic (Bi vs, bi) cucumber lines tested for resistance to T. cinnabarinus under field conditions.

 
Damage rating (0 - 5)
Cultigen
Bitterness
Origin
Year 1
Year 2
Hokus
+
Netherlands
3.6
3.7
Nimbus
-
Netherlands
3.2
3.4
Marketmore 70
+
USA
3.5
3.6
Marketmore 72
-
USA
3.5
3.6
Marketmore 76
+
USA
3.5
3.1
Marketmore 80
-
USA
3.3
2.8
Poinsett 83-10 Bi
+
USA
3.7
2.9
Poinsett 83-10 bi
-
USA
3.8
3.0

Table 2. Mean damage index of 8 bitter cucumber lines evaluated for resistance to T. cinnabarinus under field conditions.

 
Damage rating (0 - 5)
Cultigen
Origin
Year 1
Year 2

PI163222

India
3.9
3.0
PI178885
Turkey
3.8
3.0
PI218036
Iran
3.7
3.1
PI220860
Korea
4.0
3.3
OHIO MR 20
USA
4.0
3.3
Robin 50
USA
3.9
3.4
Taipai No. 1
Taiwan
3.8
3.5
Aodai
Japan
3.8
3.5

Acknowledgement. I wish to thank Drs. S.P.C. Groot and H,M, Munger for supplying the seeds.

Literature Cited

  1. Boudreaux, H.B. 1956. Revision of the twospotted spider mite (Acarina : Tetranchidae) complex, Tetranychus telarius (Linnaeus). Ent. Soc. Amer. 49: 43-48.Dacosta, C.P. and C.M. Jones. 1971. Cucumber beetle resistance and mite susceptibility controlled by the bitter gene in Cucumis sativus L. Science 172: 1145-1146.
  2. Gould, F. 1978. Resistance of cucumber to Tetranychus urticae: Genetic and environmental determinants. J. Econ. Ent. 71: 680-683.
  3. Ponti, O.M.B. de. 1978. Resistance in Cucumis sativus L. to Tetranychus urticae Koch. 3. Search for sources of resistance. Euyphytica 27: 167-176.
  4. Ponti, O.M.B. de. 1980. Resistance in Cucumis sativus L. to Tetranuchus urticae Koch. 6. Comparison of near isogenic bitter and non-bitter varieties for resistance. Euphytica 29: 261-265.
  5. Ponti, O.M.B. de, G.G. Kennedy and F. Gould. 1983. Different resistance of non-bitter cucumbers to Tetranychus urticae in the Netherlands and the USA. Cucurbit Genet. Coop. Rpt. 6: 27-28.
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