Resistance to Brevicoryne brassicae in horticultural brassicas

85

Euphytica 88: 85-96,1996 . © 1996 Kluwer Academic Publishers. Printed in the Netherlands .

Resistance to Brevicoryne brassicae in horticultural brassicas P.R. Ellis,' R . Singh, 2 D.A.C. Pink,' J .R. Lynn' & PL. Saw' ' Horticulture Research International, Wellesbourne, Warwick CV35 9EF, UK; 2 Haryana Agricultural University, Hisar 125004, India Received 8 February 1995 ; accepted 16 August 1995

Key words : Brevicoryne brassicae, cabbage aphid, Brassica oleracea, brassicas, host plant resistance

Summary A wide range of cultivated brassica accessions including broccoli, Brussels sprouts, Chinese cabbage, cauliflower, collard, kale and swede material was tested against the cabbage aphid, Brevicoryne brassicae, at HRI, Wellesbourne in the field and laboratory in both 1992 and 1993 . In the field, B, brassicae attack was assessed as the proportion of infested plants and the numbers of aphid colonies present . In the laboratory, aphid performance was measured in terms of the pre-reproductive and reproductive period, population increase, and insect mortality . Interpretation of the data was facilitated by plotting sorted accession means against normal order statistics . This statistical approach indicated the spread of variation amongst the accessions and permitted identification of extremes . Partial levels of antixenosis resistance were discovered in red brassicas . Glossy accessions of cabbage and cauliflower possessed antixenosis and antibiosis resistance that lasted throughout the season of crop growth in the field . Other accessions were shown to withstand aphid attack and therefore possessed tolerance . The laboratory studies provided information on mechanisms of antibiosis resistance . The potential value of the different sources of resistance is discussed . Introduction The cabbage aphid, Brevicoryne brassicae (L .), is one of the most serious pests of cruciferous crops throughout the world, particularly on horticultural and oil seed brassicas including broccoli, Brussels sprouts, cabbage, cauliflower, collard, kale, kohl-rabi, mustard, rape, swede and turnips . Large populations of aphids distort, stunt, and may even kill young plants by direct feeding action and indirectly the presence of aphids, cast skins and honeydew renders many crops unmarketable. In addition, the aphid can transmit several damaging viruses including cabbage ring necrosis, cauliflower mosaic, radish mosaic and turnip mosaic (Blackman & Eastop, 1984) . In recent years B. brassicae has been a problem to growers in the United Kingdom because of large populations developing under favourable conditions of mild winters followed by relatively warm summers and the intensive cultivation of brassicas with no breaks in cropping .

Repeated applications of insecticides are required to control B . brassicae infestations . Growing concern over the dependence of farmers on insecticidal control of this insect has emphasised the need for alternative control measures including the development of resistant cultivars that could be integrated with other control measures . These would offer a cheap, simple and environmentally-acceptable component in a crop protection programme (Ellis, 1990) . There have been numerous reports of resistance in brassicas to B . brassicae. In a recent review, Singh & Ellis (1993) cited 39 studies that were done between 1944 and 1993 ; more than 950 genotypes were tested of which 93 were reported to possess partial levels of resistance . The most promising cultivars and breeding lines cited in the literature were evaluated at Wellesbourne for resistance to B. brassicae in a breeding programme .

86 Materials and methods Plant material A wide range of brassica material was obtained from seed companies, research organisations and private breeders throughout the world, including several different accessions held in the Vegetable Gene Bank at HRI, Wellesbourne. Seventy-seven accessions representing eight brassica crops were tested in 1992 and 1993 (Appendix 1) . Seeds of accessions under test were germinated on filter paper in Petri-dishes in an incubator at 16° C . Seedlings were pricked out into Levington compost in containers which varied in size according to the requirements of the experiments . The susceptible control cultivars `Derby Day' cabbage and 'Oliver' Brussels sprouts were included in all experiments . Brevicoryne brassicae cultures Cultures of B. brassicae maintained in the insect rearing unit were replenished from wild populations each year. The aphids used for experiments were reared on a susceptible host plant, either Sinapis alba L. (Syn . Brassica alba (L.) Rabench .) cv. `Tender Green' mustard or cabbage cv . `Derby Day' . Host plants were raised in 38 x 38 x 38 cm perspex cages fitted with nylon mesh fronts and backs, in a controlled environment room maintained at 20° C, 70% r.h., with a 16 h day:8 h night regime . The aphids were subcultured every two weeks and transferred to fresh plants . Brevicoryne brassicae required for laboratory experiments were multiplied from this stock culture in the perspex cages described above. Field experiments Field experiments were done at HRI, Wellesbourne in a sandy loam soil . Prior to planting out the experiment, the ground received a base fertiliser of 231 :231 kg/ha of phosphorus and potassium, and 80 kg/ha of nitrogen after planting . No insecticides or fungicides were applied . The experiments received a pre-emergence treatment of herbicide using a mixture of 9 1/ha propachlor (Albrass; ICI) and 6 kg/ha chlorthal-dimethyl (Dacthal ; SDS Biotech), while any weeds emerging later in the season were removed by hand. Brassica cultivars and breeding lines were raised in trays in a glasshouse and then moved to frames or a cool glasshouse to harden plants off. Accessions were

tested in a pair of randomised block experiments that were planted in the field to coincide with the two migrations of the aphid that usually occur at Wellesbourne in July and September (Dunn & Kempton, 1971) . In most years, B. brassicae builds up to high populations which guarantee an intensive selection pressure on any brassica material planted out. In 1992 data were collected from two experiments located next to each other. One experiment was designated primarily for cabbage whitefly, Aleyrodes proletella, studies, the other for aphid studies . The planting dates were 12 May, 30 June 1992 and 5 May, 29 June 1993 . Each experiment used four replicate plots of each accession . To minimise inter-group competition, the different crops were grouped together. In 1992 and 1993, 40 plants arranged in eight rows of five plants constituted a plot, spaced 50 cm apart both within and between the rows . B. brassicae alatae were recorded to determine the number of insects alighting on a plant . The number of colonies (groups of aphids produced by an alate) per plant were counted on one occasion in the second plantings in 1992 and 1993 to record the build up of an infestation . Laboratory experiments Experiments examined factors that reduced aphid development or survival i .e . antibiosis. Test plants were raised in a glasshouse maintained at 18 ° C ± 2 ° C day and 10° C ± 2° C night with a 16 h day :8 h night regime supplemented by halogen lamps from November to March inclusive . Antibiosis resistance was investigated on cultivars or breeding lines that had been identified in the field as being less damaged or less infested with aphids . Ten plants of each accession were used in experiments and randomised in 36 x 26 x 10 cm plastic trays on benches in the insect rearing unit . Two clip cages (Van Emden, 1972) were fitted to the first and second expanded leaves on each test plant to give 20 cages per accession . Three B. brassicae adult apterae from the stock culture were relased into each clipcage on the underside of leaves and left for 16-18 h (overnight). On the following morning the adult and all but one nymph were removed from the leaf . Aphids were observed every other day for six days and then every day for a further five days to record data of production of first offspring - this gave a measure of the pre-productive period . The subsequent offspring produced were recorded and removed daily from the cage .



87

90

Giant Kale • Oliver

80

70

60 .

Italian Red Kale Yates Giant Red • NYR 7802

50 -3

-2

-1

0 1 Normal Order Score

2

3

Fig . 1 . Variability in the resistance to cabbage aphid of different brassica accessions .

Records of the reproductive period and mortality of the original nymph were collected . Statistical analysis

Data were subject to ANOVA using transformation as necessary - angular transformation for percentages, logarithms for the numbers of colonies and number of progeny. To assist in the interpretation of the results, the sorted accession means on the transformed scale were plotted against normal order statistics for all variates analysed (Nelder, 1971 ; Perry, 1986 ; Plackett, 1971) . On the same axes a line of slope equal to the standard error of the mean of the accessions was plotted (Nelder, 1971) . If there were differences between the accessions, the slope of the points will be steeper than that of the line . However, if there are homogeneous subsets of accessions then this will lead to subsets of the points having an atypically low slope, parallel to the plotted line . This procedure was done for each laboratory and field experiment .

To determine whether different characters measured in either laboratory or field were related to each other, correlation coefficients were calculated between the mean scores of accessions for one character with their mean scores for another . The experiments were combined for these analyses . The data on aphid survival were analysed as if there were twenty replicates because of the difficulties involved in analysing binomial data with multiple strata. The other laboratory data were analysed by taking the structure of two clip cages on each of ten plants into account .

Results Field experiments

In 1992 and 1993 large aphid migrations resulted in high infestation levels on the susceptible control plants . For example, the proportion of cv . `Derby Day' plants infested was 96, 92, 95 and 98% (backtransformed values) for the different platings in the two years . Graphs



88

90 80 70 60 50

• Harmony NYR-7802 Glossy Andes • • Broc-5 • Glazed Vales

40

• Green Glaze Intermediate

30

• Green Glaze Glossy

-3

-2 Fig. 2.

-1

0 1 Normal Order Score

2

3

Variability in the resistance to cabbage aphid of different brassica accessions .

of variety means plotted against normal order scores for the two plantings of 1992 are presented in Fig . 1 and Fig . 2 as two examples of the different patterns that can occur and how they were interpreted . In Fig. 1 most of the points lie on a continuous curve with a slope steeper than the standard error line . This indicates that in general there was marked variation for susceptibility to infestation by B. brassicae amongst the accessions. However, there is less variation among the more susceptible lines than the more resistant lines because at the top of the curve the slope approaches that of the standard error line. There are several 'outliers' on the graph . The Brussels sprouts cv. 'Oliver' and `Giant Kale' were more infested than any other accession and the red accessions `Ruby Ball', 'Rubine', 'Italian Red Kale' and 'Yates Giant Red', together with the glossy accession 'NYR 7802' were less infested than the majority of the accessions . In Fig . 2, most of the points lie on a line parallel to the standard error line indicating that there was no significant variation for infestation by B. brassicae among these accessions . However, eight cultivars did not fall on this line and were less infested than the

other accessions . These were the red Brussels sprouts 'Rubine', Chinese cabbage `Harmony' and the glossy accessions 'NYR-7802', `Glossy Andes', 'Broc-5', `Glazed Vates', `Green Glaze Intermediate' and `Green Glaze Glossy' . Results from these accessions for field and laboratory experiments are included in Table 1 and 2 . The level of B. brassicae infestation in the field was related to the waxiness of the leaves : thus the glossy genotype `Green Glaze' was the least infested whilst the waxy-leaved line was the most severely infested (Table 1) . The records of numbers of aphid colonies per plant showed that Brussels sprouts supported more aphids than any other crop . The glossy-foliaged accessions 'Broc-5', `Glazed Vates' and `Green Glaze Glossy' remained resistant throughout the season. The red cultivar 'Rubine' was the least infested of the Brussels sprouts but not as resistant as any of the glossy brassica cultivars . `Resistant Danish' was one of the least infested cabbage accessions late in the season .

89 Table 1 . A comparison of the resistance of brassica accessions to Brevicoryne brassicae in the field at Wellesbourne in 1992 and 1993

Crop

Broccoli Brussels sprouts

Cabbage

Cultivar/ accession

1992 % infested

No . of

(angle transformed) First Second planting planting

colonies (log)

'Broc 5'

46 .4

planting

(log)

planting

78 .8

-1 .0 2 .1 2 .3

49 .3

80 .8 86 .7

83 .5 81 .6

38.5 59 .1

-0 .3 1 .8 1 .9

2 .3 2 .5

'Rubine' 'NY 10127'

53 .5 67 .8

61 .7

0 .7

57 .8

39.9

1 .1

1 .7

'Derby Day'

79 .8

76 .8

65 .1

55 .0

1 .2

1 .2

'Minicole' 'Myatts Offenham

75 .8 80 .0 9 .38

'Ruby Ball' 'Yates Giant Red'

53 .7 55 .4

'Andes' 'Glossy Andes'

65 .6 64 .5

76 .5 46 .2

'NYR 7802' 'White Rock'

53 .9 72 .2

47 .7

Chinese cabbage

'Harmony'

Collard

'Green Glaze' 'Green Glaze

'Glazed Vates' 'Giant' 'Italian Red'

90.0 56 .4

S .E .M .

3 .91 (129)

Degrees of freedom

0 .5

65 .8

0 .4

0 .6 -0 .9 -0 .5

56 .4

75 .6

1 .0

0 .1

40 .0 73 .2

60.9

-0.3

-0 .4

-0 .7 -0.8

81 .0

2 .9

40 .2 28 .8

-0.9

63 .2

0 .8

44 .4 85 .5

-0.9 1 .3

53 .1

0 .9

50 .2 81 .5

Intermediate' 'Green Glaze Glossy' Kale

No . of colonies

(angle transformed) First Second

'Darkmar21' 'Oliver'

Compacta' 'Resistant Danish'

Cauliflower

1993 % infested

5 .97

0 .33

3 .90

5 .40

0 .25

0 .23

(108)

(83)

(51)

(51)

(51)

(51)

in parentheses

Laboratory experiments Pre-reproductive period The pre-reproductive period of aphids on `Derby Day' was consistent in the laboratory experiments and ranged from 8 .1-8 .9 days, the overall range for the 30 brassica accessions was 7 .2-11 .3 days (Table 2) . 'Resistant Danish' cabbage had a significantly longer pre-reproductive period than other accessions . There were no apparent differences between crop types for this parameter.

Reproductive period There were no consistent differences between brassica crops in the length of the reproductive period but differences within crops . Thus the reproduction period of B. brassicae on the Brussels sprout 'Darkmar 21' was significantly less (P = 0 .05) than that on 'Oliver' . Similar differences were observed with cabbage . For example, the reproductive period on 'NY 10127' was significantly shorter than on 'Yates Giant Red' . Aphids on 'Glossy Andes' cauliflower had a significantly shorter reproductive period than on the normal waxy-foliaged 'Andes' .

'Broc 5' 'Darkmar 21' 'Oliver' 'Rubine' 'NY 10127' 'Derby Day' 'Minicole' 'Myatts Offenham Compacta' 'Resistant Danish' 'Ruby Ball' 'Yates Giant Red' 'Andes' 'Glossy Andes' `White Rock' 'Green Glaze' 'Green Glaze Intermediate' 'Green Glaze Glossy' 'Glazed Vates' 'Giant' 'Italian Red'

Broccoli Brussels sprouts

S .E.M . (P = 0.05) Degrees of freedom in parentheses

Kale

Collard

Cauliflower

Cabbage

Cultivar/ Accession

Crop

0 .23 (101)

9.8

8 .5

8 .9 8 .2 9 .2

8 .2 8 .3

0.17 (81)

9 .9 8 .8

9 .7 8 .5 9.3

9.6 9 .0

9 .3

0 .33 (79)

7 .8 9 .2 8 .0 7 .2

11 .3

8 .1

8 .4

9 .6

Pre-reproductive period (days) Experiment 1 2 3

0.59 (101)

5 .7

5 .8

6 .4 10 .0 11 .4

4 .6 10 .1

0.64 (81)

7 .6 9.9

11 .0 7 .9 6.5

7 .8 11 .5

6.2

0 .81 (77)

6 .1 7 .8 5 .3 5 .9

4 .6

6 .9

4.8

8 .1

Reproductive period (days) Experiment 1 2 3

Table 2. A comparison of the resistance of brassica accessions to Brevicoryne brassicae in the laboratory

0.108 (101)

14 .1 (2 .7)

17 .7 (2 .9)

19 .0 (3 .0) 26 .3(3 .3) 26 .3 (3 .3)

8 .9 (2.2) 36 .1 (3 .6)

0 .084 (81)

19 .8 (3 .0) 28 .0 (3 .3)

26 .0 (3 .3) 16 .2 (2 .8) 14 .6 (2 .7)

17 .3 (2.9) 29 .7 (3 .4)

14.8 (2.7)

0.19 (77)

16 .1 14 .0 12 .0 20 .3

(2 .8) (2 .7) (2 .5) (3 .0)

6 .7(l .9)

21 .7 (3 .1)

12.0 (2 .5)

24.2 (3 .2)

No. of progeny (angle transformed values) Experiment 1 2 3

7 .7 (19)

35

20

31 11 5

28 18

5 .2 (13)

45 22

20 20 30

30 15

41

Experiment 1 2

Moratlity (%)

6 .7 (9)

6 15 0 15

21

5

5

20

3

91 Progeny The average number of nymphs produced by B . brassicae apterae ranged from 19 to 30 on the standard `Derby Day' . As would be expected, the numbers of progeny were related closely to the reproductive period ; fewest progeny were produced on plants where this period was short . The correlation coefficient was 0 .86 . There were significant differences between the 8 different brassica crops tested . Fewer nymphs were produced on cauliflower and collard compared with Brussels sprouts and cabbage . There were also significant differences between accessions within the two main groups of brassicas tested : Brussels sprouts and cabbage . Large number of progeny were born on certain red genotypes of cabbage ('Ruby Ball' and 'Yates Giant Red') and kale ('Italian Red Kale') . Mortality Mortality of B. brassicae on plants within an accession was very variable, and there were also large differences between accessions . Consequently, only one cultivar, `Giant Kale', had statistically significantly higher mortality than the standard `Derby Day' . Apart from the high correlation between number of progeny and reproductive period there were only two other significant correlations : mortality and % of plants infested in the field late in the season had a correlation of 0 .56 ; and mortality and pre-reproductive period had a correlation coefficient of 0 .35 .

Discussion The experiments described in this paper have shown that numerous sources of partial resistance to B . brassicae exist in horticultural brassicas . Field experiments demonstrated that certain accessions possessed antixenosis resistance which resulted in fewer aphids alighting on plants . The final assessment in the field indicated overall levels of resistance present in brassica material . The laboratory studies indicated that reduced development and survival along with tolerance were exhibited by the plants . It is notoriously difficult to interpret the results of variety trials, because the hypothesis testing approach may be inappropriate. Insect resistance is diffucult to assess because it is both multivariate and highly variable. The approach to analysis and interpretation taken in this paper is intended to facilitate the separation of resistant accessions and gain an understanding of

how resistance varies amongst the accessions under test . Although the two experiments planted in May and June of 1992 gave consistent results, there were significant interactions between genotype and environment when the two planting dates within a year were compared. Environmental factors can affect the performance of host plant and aphid and can therefore result in complex effects upon the insect/plant interaction . This highlights the importance of repeating resistance evaluation trials so that the accessions can be evaluated in several different environments . The different sources of resistance identified in this study can be grouped into a number of categories for the purposes of discussion . Significant differences in resistance were recorded between the brassica crops in aphid infestation in the field and in the laboratory . During the early stages of plant growth, fewer nymphs were produced on cauliflower and collard compared with Brussels sprouts and cabbage . In the field there were no differences between the crops in initial colonisation by aphids but, as the season developed, Brussels sprouts supported more colonies of aphids . Pimentel (1961) recorded significantly higher populations of B. brassicae on Brussels sprouts than on broccoli or collard . Several factors probably contribute to these differences between crops including plant architecture, size, and duration of growth . Thus, Brussels sprouts have a long season of growth in the field during the period of maximum aphid activity, they produce numerous large leaves arranged in several tiers that offer many niches for aphid colony development . The sprouts buttons themselves may also be heavily infested . In contrast, cabbage, cauliflower and collard produce a large rosette of leaves which, in the case of heading cabbage, may be tightly packed . These crops offer less foliage for the insect to reproduce on and many of the cultivars are shorter-lived (i .e . harvested at an earlier growth stage) than Brussels sprouts . Brassica crops also differ in their degree of waxiness and this may partly explain why some workers have found turnip to be moderately resistant to B . brassicae (Lamb, 1960) : this crop has foliage bearing little wax compared with most Brussels sprouts cultivars . Red foliage is believed to be an important factor conferring antixenosis resistance on brassicas to several pests but the reports in the literature on B . brassicae are contradictory . Radcliffe & Chapman (1965) compared eight cabbage cultivars and found that two red cultivars `Red Acre' and `Red Hollander' were the least infested early in the season, but late in the season they were the most heavily attacked . Similarly, Dunn

92 & Kempton (1971) found that the red Brussels sprouts 'Rubine' was apparently resistant early in the season but very heavily infested in the autumn . Two cabbage cultivars `Red Drumhead' and 'Yates Giant Red' were amongst the least attacked of 50 accessions in the spring at HRI-Wellesbourne, but became less resistant as the season progressed (Ellis & Hardman, 1988) . Verma et al . (1981) found that the green-foliaged cabbages `All Seasons', EC 99825 and `Round Sure Head' were the most resistant to aphid attack . None of the six red cabbage cultivars were promising in their field experiments . In the present study, seven red-foliaged brassica cultivars were tested against B. brassicae. The Brussels sprouts 'Roodnerf' and cabbages `Super Red' and `Red Drumhead' were not found to possess resistance . The red-foliaged Brussels sprouts 'Rubine' was initially less infested than other cultivars and, despite supporting increased numbers of aphids later in the summer, was shown to have significantly fewer colonies in the autumn than green-foliaged cultivars . However, even this reduced attack was not sufficient to prevent considerable damage and therefore red foliage is not a consistently reliable form of resistance to B. brassicae . Red foliage provides initial resistance to colonisation (antixenosis) but when aphids do colonise plants they develop rapidly, i .e . there is no antibiosis resistance. Glossy-foliaged brassica accessions have been shown to possess resistance to several pests (Dickson & Eckenrode, 1975, 1980 ; Ellis, 1992 ; Ellis & Hardman, 1988 ; Stoner, 1990, 1992) . This glossiness is associated with reduced amounts of surface wax and lower densities of wax crystallites on leaves compared with normal bloom accessions that are susceptible to pests . Five of the six glossy brassicas tested in 1992 and 1993 were significantly less colonised and damaged in the field than waxy accessions of the same crop, indicating a form of antibiosis resistance . They were found to support significantly fewer aphids and were significantly less damaged than waxy genotypes . Eigenbrode & Shelton (1992) showed that it is possible to modify leaf surface wax levels with applications of the herbicide S-ethyl dipropylthiocarbamate (EPTC) and that plants treated with this chemical were more resistant to the diamond-back moth than untreated plants . They suggested that treatment of plants with EPTC or similar compounds may have potential as an economic control measure for certain plants . It is not known whether EPTC would have similar effects on B. brassicae . Certain cultivars were shown to tolerate high populations of B. brassicae. This may be of value in fodder brassicas but is of little use for markets where

the mere presence of aphids or their cast skins renders a crop unsaleable . The glossy-leaved cultivars showed the highest levels of resistance to B. brassicae and may have value for the organic and amateur markets. A search is being made for higher levels of resistance within the Brassica oleracea genepool (Ellis et al ., 1995) and to exploit wild relatives of B . oleracea as sources of resistance (Singh et al ., 1994) . These, together with sources already identified may lead to an improvement of host resistance to B. brassicae . Although it is unlikely that such resistance will provide the sole means of control, it will be an important component of an integrated programme to control aphids, thereby resulting in a reduction of pesticide usage .

Acknowledgements We thank E. Kazantzidou, K. Phelps and A .D . Ramsey for assistance with the experiments . We are most grateful to MAFF and the CEC (Bursary Reference No . 5/cl 1 *-913100) for funding this research .

References Blackman, R.L. & V.F Eastop, 1984 . Aphids on the World Crops, An Identification Guide. John Wiley & Sons, New York . 466 pp . Dickson, M .H. & C.J. Eckenrode, 1975 . Variation in Brassica oleracea resistance to cabbage looper and imported cabbage worm in the glasshouse and field . J. Econ . Ent . 68 : 757-760. Dickson, M.H . & C.J. Eckenrode, 1980. Breeding for resistance in cabbage and cauliflower to cabbage looper, imported cabbage worm and diamond back moth . J . Amer. Soc . Hort . Sci . 10 : 782785 . Dunn, J .A . & D.P .H. Kempton, 1971 . Differences in susceptibility to attack by Brevicoryne brassicae (L .) on Brussels sprouts . Ann . Appl. Biol . 68 : 121-134. Eigenbrode, S.D . & A .M. Shelton, 1992 . Survival and behaviour of Plutella xylostella larvae on cabbages with leaf waxes altered by treatment with S-ethyl dipropylthiocarbamate . Ent. Exp . Appl . 62 :139-145 . Ellis, PR., 1990 . The role of host plant resistance to pests in organic and low input agriculture . Brit. Crop Prot . Counc. Monogr. 45 : 93-102 . Ellis, PR., 1992. Sources of resistance in brassicas to cabbage root fly, International Organisation for Biological Control/West Palaearctic Regional Section Bull. 1992 15 (4) : 94-101 . Ellis, P.R . & J .A . Hardman, 1988 . Investigations of the resistance of cabbage cultivars and breeders lines to insect pests at Wellesbourne. In : R . Cavalloro & C. Pelerents (Eds) . Progress on Pest Management in Field Vegetables, CEC/IOBC Experts Group Meeting 1985, pp. 99-105. Ellis, PR., PL. Saw & D .A.C. Pink, 1995. A glasshouse technique for evaluating Brassica oleracea genetic resources for resistance to Brevicoryne brassicae, the cabbage aphid . Acta Hort . (in press).

93 Lamb, K.P., 1960. Field trials of eight varieties of brassica field crops in the Auckland district . 1 . Susceptibility to aphids and virus diseases . New Zealand J . Agric . Res . 3 : 320-331 . Nelder, J .A ., 1971 . Contribution to discussion of paper by O'Neill and Wetherill. J . Royal Stat. Soc. B 36 : 244-246. Perry, J.N ., 1986 . Multiple-comparison procedures : a dissenting view. J. Econ . Ent . 79 : 1149-1155 . Pimentel, D., 1961 . An evaluation of insect resistance in broccoli, Brussels sprouts, cabbage, collards and kale. J . Econ . Ent . 54 : 156-158 . Plackett, R.L., 1971 . Contribution to discussion of paper by O'Neill and Wetherill . J . Royal Stat. Soc . B 36 : 242-244 . Radcliffe, E.B . & R .K. Chapman, 1965 . Seasonal shifts in the relative resistance to insect attack of eight commercial cabbage varieties . Ann . Ent. Soc . Amer. 58 : 892-897 . Singh, R . & P.R. Ellis, 1993 . Sources, mechanisms and bases of resistance in cruciferae to the cabbage aphid, Brevicoryne brassicae . International Organisation for Biological Control/West Palaearctic Regional Section Bull . 16 (5) : 21-35 .

Singh, R ., P.R. Ellis, D .A .C . Pink & K . Phelps, 1994 . An investigation of the resistance to cabbage aphid in brassica species . Ann. Appl . Biol. 125 : 457-465 . Stoner, K.A., 1990 . Glossy leaf wax and plant resistance to insects in Brassica oleracea under natural infestation . Env. Ent . 19 : 730739 . Stoner, K .A., 1992 . Density of imported cabbageworms (Lepidoptera : Pieridae), cabbage aphids (Homoptera : Aphididae), and flea beetles (Coleoptera : Chrysomelidae) on glossy and trichome bearing lines of Brassica oleracea . J. Econ . Ent . 85 : 1023-1030 . Van Emden, H .F, 1972 . Aphid Technology . Academic Press, London . 344 pp . Verma, T.S ., P.M . Bhagchandani,N . Singh & O .P. Lal, 1981 . Screening of cabbage germplasm collections for resistance to Brevicoryne brassicae and Pieris brassicae . Indian J . Agric . Sci . 51 : 302-305 .



94 Appendix List of Brassica accessions evaluated for their resistance to Brevicoryne brassicae in the laboratory and field at Wellesbourne in 1992 and 1993 Crop

Accession

Laboratory 1992

Field 1992

1993

Planting 1 2 Brassica oleracea L . var. italica Plenck. Broccoli `Broc 5'

+

`Purple Sprouting Broccoli'

+

Planting 1

2

+

+ +

`White Sprouting Broccoli' GK 9101/A GK 91001

+ +

Brassica oleracea L . var. gemmifera Zenc. Brussels

`Bedford Selection Classic'

Sprouts

`Bedford Selection 'Darkmar 21' `Cambridge Selection'

+

'Covent Garden' `The Darlington'

+ +

+

+ +

+ +

+

+

+

+ +

+ + +

`Darkmar 21'

+

+

`De Lyon' `Early Half Tall'

+

+ +

`Evesham Special' `Irish Glacier' 'Lunet' 'Noisette' 'Oliver'

+ +

+ + +

+

`Roodnerf Exhibition' 'Roodnerf Opollo' 'Rubine' `Standard'

+ +

`Sultan' `Target' `The Wroxton' 'Zavitka' Brassica oleracea L . var. capitata (L.) Alef. Cabbage 'Bartolo' `Best of All' `Blue Pak'

+ +

+ +

+

+

+ +

+

+ +

+ +

+ + +

+



95 Crop

Accession

Laboratory

Field

1992

1992

1993

Planting 1 2

Planting 1 2

Brassica oleracea var. capitata

`Derby Day'

+

+

`Earliest' `Enfield Market'

+ +

+

+

'Minicole' 'Myatts Offenham Compacta'

+ +

+ +

`NY 10127'

+

+ +

`Polinius' `Red Drumhead'

+

+

`Resistant Danish' 'Rivera'

+

+ +

`Roundup'

+

+

`Ruby Ball' `Savoy King'

+

+

+ +

'Slawdena'

'Zerlina' Brassica oleracea L. var . botrytis L. `Andes' Cauliflower

+

+

`Golden Acre'

'Superette' 'Yates Giant Red'

+

+ + +

+

+ +

+

+

+

+

'Cavalo Broccolo Romanesco Natalino'

+

'Cavalofiore Precoce de Jesi'

+ +

'Cavalofiore Precoce Toscano' 'Cavalofiore Sammartinaro Bianco'

+

'Cavalofiore San Martinisi' `Glossy Andes'

+

'NYR-7802' `Perfection'

+ +

+

+

+

+

`Romanesco Gennarese' `White Rock' 7602-1 7606-2 7606-8 7606-12 7606-13 7606-18

+ +

+

+

+ +

+

+ + + + + + + +



96 Crop

Accession

Laboratory 1992

Field 1992

1993

Planting 1 2

Planting 1 2

Brassica oleracea L . var. capitata (L.) Alef. Collard

`Green Glaze Glossy' `Green Glaze Intermediate'

+ +

+ +

+

`Green Glaze Waxy'

+

+

+

+

+

+ +

+

+

+

+

+ +

Brassica oleracea L . var. acephala DC . Kale

`Extra Curled Kale' `Giant Kale' `Glazed Vates' `Italian Red Kale' 'Pentland Brig' `Purple Leaved Kale'

+ +

+

Brassica campestris L. Chinese

+

`Harmony'

Cabbage Brassica napus L . Swede

`Tina'

+

+