Resistance to Western Spotted and Striped Cucumber Beetle in Melon

A.N. Kishaba,1 S.J. Castle,2 and D.L. Coudriet3

U.S. Department of Agriculture Agricultural Research Service,
Boyden Entomological Laboratory, University of California Riverside, CA 92521

J.D. McCreight4

U.S. Department of Agriculture, Agricultural Research Service,
U.S. Agricultural Research Station, 1636 East Alisal St. Salinas, CA 93905

G.W. Bohn5

U.S. Department of Agriculture, Irrigated Desert Research Station,
4151 Highway 86, Brawley, CA 93905

Additional index words. Cucumis melo, cantaloupe, Acalymma trivittatum, Diabrotica undecimpunctata undecimpunctata, insect resistance

Abstract. While breeding for resistance to a particular pest, one may inadvertently introduce susceptibility to one or more other pests. Damage by the western spotted (Acalymma trivittatum (Mannerheim)) and striped (Diabrotica undecimpunctata undecimpunctata (Mannerheim) cucumber beetles (CB) to some of our advanced melon (Cucumis melo L.) breeding lines in field plots alerted us to the necessity of assessing these lines for their susceptibility to feeding damage by CB. The damaged lines had been bred for resistance to melon aphid (Aphis gossypii Glover) using several different melon aphid-susceptible (MAS) recurrent parents from an initial cross of 'PMR 45' with PI 414723. Fifteen advanced melon breeding lines with different levels of melon aphid resistance (MAR), their recurrent parents and PI 414723 were compared in a naturally infested field test for susceptibility to feeding damage by CB. PI 222187 and breeding line WMR 29 were also included in the test. Two of the 15 MAR breeding lines were less damaged, and five of the 15 were more damaged at the seedling stage than their respective recurrent parent. None of the MAR entries were more susceptible than their recurrent parents were for fruit damage by CB. PI 414723 was found to have a low level of resistance to seedling damage, and a high level of resistance to fruit damage from feeding by CB.

 

 

There was extensive feeding damage in our field plots from 1975 to 1981 by CB to fruit of MAR breeding lines that had 'Hale's Best Jumbo' (HBJ) as the recurrent parent (unpublished). In contrast, two MAR breeding lines that had 'PMR 45' and 'PMR 5' as recurrent parents sustained little feeding damage on peduncles from CB feeding in a field test in 1976 (Coudriet et al., 1980). We were, therefore, concerned about the possibility of increased susceptibility to CB in some of our MAR breeding lines while we improved their fruit quality. The MAR lines were derived from an initial cross of MAS 'PMR 45' with MAR PI 414723 (McCreight et al., 1984).

Michelbacher et al. (1953) reported extensive damage of melon seedlings and fruit by adults and larvae of the Western striped and the Western spotted CBs in northern California. They described the formation of fruit epidermal corky areas that

Research performed in cooperation with University of California, Riverside. We thank R. Keim and his staff at the University of California South Coast Field Station, Santa Ana, for maintaining our plots for many years to make this work possible. We thank T. Gibson, L. Moerman, and J.A. Principe for their technical assistance. Mention of a proprietary product in this paper does not constitute endorsement of the product by the USDA.

1Research entomologist, retired. Current address: 1640 Sawpeck Way, Paradise, CA 95969.

2Formerly agricultural research technician, currently Research entomologist, USDA, ARS, Western Cotton Research Laboratory, 4135 East Broadway Road, Phoenix, AZ 85040.

3Research entomologist, retired. Current address: 17522 E. Grande Blvd., Fountain Hills, AZ 85268.

4Research horticulturist.

5Research geneticist, retired. Current address: 1094 Klish Way, Del Mar, CA 92014.

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formed in response to feeding by adult CB on immature fruit. They observed larval feeding scars on the smooth epidermis of 'Honeydew' and on the net (lenticle) and epidermis of a netted melon cultivar where their fruit came into contact with the soil (ground spot). Overman and MacCarter (1972) reported that 'Hale's Best Jumbo' (HBJ) seedlings were resistant to CB feeding in Florida relative to other melon cultigens. Nugent et al. (1984) showed that 'Hale's Best 36', a selection of HBJ, was nonbitter (Lee and Janick, 1978), and that 'Hale's Best 36' was comparable to other nonbitter cultivars in nonchoice feeding tests on leaf disks.

We compared advanced MAR breeding lines with their MAS recurrent parents and PI 414723 for susceptibility to seedling and fruit damage by the CB complex to determine whether ARHBJ and other MAR lines were more susceptible than their recurrent parents to feeding damage by CB. A preliminary analysis of this research was previously reported (Kishaba et al., 1983).

Materials and methods

We followed Quisumbing and Lower's (1978) plot design for evaluating CB resistance in cucumber. Fifteen MAR breeding lines, derived from F1('PMR 45' x 90234) via backcrossing and selection for MAR, and their six recurrent parents were included in this experiment (Table 1). Progeny 91213, derived from PI 371795 (McCreight et al., 1992), the source of MAR in the MAR breeding lines (McCreight et al., 1984), was included in order to assess its level of susceptibility or resistance to CB. Progeny 91213 is essentially equivalent to PI 414723 and will be referred to as such (Figure 1; McCreight et al., 1992). PI 222187 was included because its cut fruit were reportedly not as attractive to CB as other cucurbits (Sharma and Hall, 1973). Breeding line WMR 29 was included because of the thick and dense netting on its fruit (Bohn et al., 1980).

 

Table 1. Mean feeding damage by Western spotted and striped cucumber beetles on melon seedlings and fruit of melon cultivars and their respective melon aphid-resistant breeding lines, University of California South Coast Field Station, Santa Ana, Calif., 1981.

Seedlingz Fruity

Entry n Mean ± se CIx n Mean ± se CI

PMR 45 75 5.89 ± 0.097 5.70­6.08 98 33.98 ± 3.084 26.43­41.53

31264 167 6.53 ± 0.073 6.39­6.68 125 32.72 ± 3.017 26.75­38.69

31275 185 6.14 ± 0.073 5.99­6.28 151 33.84 ± 3.065 27.78­39.90

18072 102 5.49 ± 0.112 5.27­5.71 89 37.19 ± 4.842 27.57­46.81

Hale's Best Jumbo 147 5.71 ± 0.091 5.54­5.89 118 48.14 ± 4.761 38.71­57.57

17884 157 5.95 ± 0.085 5.78­6.12 141 34.33 ± 3.214 27.97­40.68

AR Hale's Best Jumbo 161 6.32 ± 0.082 6.16­6.48 147 33.67 ± 3.235 27.28­40.07

18031 188 6.66 ± 0.281 6.11­7.21 183 45.46 ± 3.763 38.04­52.89

Perlita 133 5.96 ± 0.083 5.80­6.13 106 41.51 ± 3.372 34.82­48.20

31175 164 6.06 ± 0.070 5.92­6.20 113 47.17 ± 4.072 39.10­55.24

31197 171 6.14 ± 0.075 5.99­6.28 160 49.64 ± 3.299 43.13­56.16

31205 169 5.98 ± 0.080 5.83­6.14 90 44.56 ± 4.081 36.45­52.67

Gulfstream 127 5.53 ± 0.101 5.33­5.73 120 34.50 ± 3.320 27.93­41.07

31346-47 163 6.23 ± 0.066 6.10­6.36 133 36.84 ± 3.518 29.88­43.80

31348 169 6.20 ± 0.076 6.06­6.36 098 46.74 ± 6.047 36.72­56.75

Top Mark 174 6.24 ± 0.290 5.67­6.81 81 40.99 ± 14.373 32.28­49.69

AR Topmark 62 5.40 ± 0.109 5.18­5.62 078 30.26 ± 2.937 24.41­36.11

18063 172 6.59 ± 0.310 5.98­7.21 090 29.44 ± 3.020 23.44­35.45

PMR 5 138 5.91 ± O.099 5.72­6.11 84 37.50 ± 14.445 28.66­46.34

AR 5 117 5.56 ± 0.081 5.40­5.72 075 27.33 ± 12.955 21.45­33.22

18052 174 5.50 ± 0.070 5.36­5.64 078 28.46 ± 13.414 21.66­35.26

PI 414723 72 4.88 ± 0.091 4.70­5.05 73 2.74 ± 10.878 0.99­4.49

PI 222187 177 6.63 ± 0.067 6.50­6.77 71 19.58 ± 2.572 14.45­24.71

WMR 29 179 6.15 ± 0.075 6.00­6.31 114 27.66 ± 2.606 22.49­32.82

zSum of three separate damage ratings in a scale of 1 to 3, from trace to severe: 1) cotyledon, 2) stem, 3) leaf.

ySum of percent area of ground spot with 1) net damage, 2) extended into the epidermis proper, and 3) covered by cork.

xCI = 95% confidence interval.

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The test was planted on 9 June 1981 at the University of California, South Coast Field Station, Santa Ana. We relied upon feeding damage from natural infestation by CB to be sufficient for assessing feeding damage based upon previous experience with CB at this location. We used three hills per plot and planted enough seeds (estimated by germination tests) to have 15 seedlings per hill. There were six replications arranged in a randomized complete block design; each block was six plots wide and four plots deep. Hills were spaced 0.9 m apart with 1.5 m spacing between plots, and rows were on 2.3-m centers. When PI 222187 plants were at the three to seven leaf stage of growth (the other entries had fewer leaves), hills were thinned to two plants. Seedlings removed during thinning were assessed for beetle damage. We used a 1 to 9 scale to estimate the feeding damage on: cotyledons, 1 to 3; hypocotyl, 4 to 6; and true leaves and stems, 7 to 9. Higher and/or lower values were assigned within each group, depending on the intensity of the damage. These three values were summed for each seedling to give a single rating value used to calculate the mean, se and 95% confidence interval for each entry (Sokal and Rohlf, 1981). This composite score gave greater weight to feeding damage on the hypocotyl and true leaves than on the cotyledons.

After thinning, plots were maintained without insecticide treatment until one week before harvest when Malathion and Benomyl were applied at recommended rates to control melon aphid and powdery mildew. Fruit were harvested and graded from 26 Aug. through 10 Sept.

Ten fruit (minimum) per plot were evaluated; the mean number of fruit per plot was 18. The area of the ground-spot (that portion of fruit surface in contact with the soil) that was scarred and/or corky as a result of CB feeding was assessed using three criteria: 1) damage restricted to the net, 2) damage extending into the epidermis, and 3) area covered by cork.

These three values (estimated to the nearest 10% in 10% increments) were summed to give a single feeding damage score for each fruit. These values were used to calculate mean fruit damage per plot, which were then used to calculate the treatment-wise mean, se and 95% confidence interval. Mean seedling damage and fruit damage values per plot were used for ANOVA. Treatment-wise standard errors were calculated for seedling and fruit damage. Because of the large and variable number of observations per entry, statistics based on all observations rather than the means per plot are presented.

Results and discussion

Damage varied among entries for seedlings and fruit (Table 1). At the seedling stage, PI 414723 was the least damaged (=4.89); the most damaged were PI 222187 and 18031 (=6.58 and 6.66, respectively). The recurrent parents ranked as follows from the least to the most damaged: 'Gulfstream', HBJ, 'PMR 5', 'PMR 45', 'Perlita', and 'Top Mark'. Of the 15 AR breeding lines, five were significantly more damaged than their respective recurrent parent: 31264 ('PMR 45'), ARHBJ and 18031 (HBJ), and 31346, 31347, and 31348 ('Gulfstream'). ARTM and 18072 were less damaged than their recurrent parents ('Top Mark' and 'PMR 45', respectively).

The difference in the performance of HBJ in this study (susceptible) and that reported by Overman and MacCarter (1972) (relatively resistant) could be due to several factors. One of the factors may have been host availability. Overman and MacCarter (1972) stated that antixenosis-type resistance varies with the available choices, and Wiseman et al. (1961) noted that CB behavior differs on cucurbits in a single-variety block compared with a multiple-variety block. A second factor may have been differential response of the CB species. Resistance to CB may, therefore, depend upon the proportion of each species in a

Figure 1. Pedigree of 91213 and PI 414723. PI 371795 was assigned to the single melon contaminant of cucumber (Cucumis sativus L.) PI 175111. PI 371795 is variable for MAR; 91060, 91213 and PI 414723 were selected from PI 371795 for more uniform MAR.

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given population. A third factor may have been that the presence of different resistance genes in a given test could affect resistance of a given cultigen (Nugent et al., 1984). Fourth, we did not include highly susceptible melons in the test. 'Deserta Naja' was not included in this test; it is highly susceptible to feeding damage by CB (Coudriet et al., 1980). In addition, four of the six recurrent parents in this test were reported to be nonbitter (Lee and Janick, 1978), and it is likely that the other two recurrent parent are also nonbitter (Pitrat, 1998). Nonbitter seedlings have a moderate level of resistance to feeding damage by CB (Nugent et al., 1984).

PI 414723 was the most resistant to fruit damage (Table 1). Its fruit damage rating was 2.61, which was significantly lower than the other 23 entries whose mean fruit ratings ranged from a low of 19.67 (PI 222181) to a high of 49.64 (31197). The breeding lines and recurrent parents did not significantly differ from PI 222181 for mean fruit damage. The most damaged recurrent parent was HBJ, followed in decreasing order by 'Top Mark,' 'Perlita,' 'PMR 5,' 'PMR 45,' and 'Gulfstream'. WMR 29 showed less fruit damage than the recurrent parents, and also was not significantly different from PI 222181. Among the MAR breeding lines, the most damaged was 31197 ('Perlita') with a mean damage rating of 50.2, the least damaged was AR 5 ('PMR 5') with a mean of 27.5. None of the MAR lines had significantly more damage to the fruit than their respective recurrent parent.

These results indicate that we did not inadvertently increase susceptibility to the CB complex while transferring MAR from PI 414723 to the five recurrent parents.

An unexpected result was the observation that PI 414723 was resistant to seedling and fruit damage by CB. This was especially surprising because PI 414723 fruit are virtually free of netting. PI 414723 fruit have a bland flavor and low soluble solids. It is a kakri or phut type melon (C. melo ssp. melo L. Group Momordica) from India, the fruit of which are characterized by soft, mealy flesh that cracks and splits open upon maturation. 'Honeydew', a smooth-skinned melon not included in this test, was found to be highly susceptible to seedling damage by CB (Overman and MacCarter, 1972). In contrast, all of the recurrent parents and

WMR 29 are netted types. WMR 29 has an especially thick net and hard rind.

PI 414723 is also resistant to cucurbit aphid borne yellowing virus (Pitrat et al., 1996), papaya ringspot virus watermelon strain (Anagnostou and Kyle, 1996; McCreight, 1996), watermelon mosaic virus (Munger, 1991), zucchini mosaic virus (Pitrat and Lecoq, 1984), virus transmission by melon aphid (Gray et al., 1988; Pitrat and Lecoq, 1980; Kishaba et al., 1992), and powdery mildew (McCreight et al., 1987).

Susceptibility to feeding damage on melon peduncles was found to be conditioned by a single dominant gene in 'Deserta Naja', a casaba type melon (Coudriet et al., 1980). Resistance to hypocotyl and cotyledon damage by CB in the seedling stage of growth was demonstrated by Nugent et al. (1984) to be conditioned by two recessive genes, bi (Lee and Janick, 1978) and cb (Nugent et al., 1984) in breeding line C922-174-B. Nonbitter seedlings (bibi) had a level of resistance to CB whereby resistant plants had no hypocotyl damage and up to 30 feeding bites on cotyledons (Nugent et al., 1984). In the presence of both genes (bibicbcb), seedlings had no hypocotyl damage and five or fewer feeding bites on cotyledons (Nugent et al., 1984).

Overman and MacCarter (1972) and Nugent et al. (1984) did not report evaluation of fruit damage by CB. The contrasting difference in the levels of resistance to CB between seedling and fruit damage in PI 414723 shown in this test suggests that the two responses may be independently conditioned, but further research is needed in order to clarify this relationship. Correlations of fruit and seedling damage were significant, but very low; r0.05 = 0.17.

The inheritance of resistance to feeding damage by CB on the stem and foliage, and fruit of PI 414723 is not known. Further studies are needed to determine if the genes conditioning CB resistance in PI 414723 are allelic to those in C922-174-B (bi or cb).

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