Screening of Melons for Sweetpotato Whitefly Resistance: 1993

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Cucurbit Genetics Cooperative Report 17:83-85 (article 24) 1994

James D. McCreight
U.S. Department of Agriculture, Agricultural Research Service, U.S. Agricultural Research Station, 1636 East Alisal Street, Salinas, CA 93905, USA

Sweetpotato whitefly, Bemisa tabaci Genn., type B virtually destroyed the Fall 1991 melon crop in the lower desert valleys of Arizona and California (7). It does not appear to be and important vector of lettuce infectious yellows virus (LIYV) (3). This whitefly type was recently re-named the silverleaf whitefly (8,9,10), but not without controversy (1,2,11). This whitefly has recently been found in the San Joaquin Valley of California (4).

In 1991, 17 of 150 PIs from India appeared to have some level of resistance to B. tabaci, type B (5). In 1992, these 17 PIs were re-tested for B. tabaci, type B resistance along with 108previously untested PIs from India plus 27 standard varieties, breeding lines, and F1 F2 and backcross families from crosses of susceptible parents with lines identified as potentially resistant to LIVY or B. tabaci, type B (6). None of the entries was superior for whitefly resistance.

In 1993, 276 melons from Afghanistan and Pakistan were evaluated for whitefly resistance in a naturally infested field test. Also included in the 9193 test were three cultivars (PMR 45, Top Mark, GF Honeydew), breeding line WMR 29, Snakemelon from the Middle East, and progenies 28479 an F1 from the cross Top Mark FR x top Mark FR (Snakemelon [Freeman Cucumber x Snakemelon]), and 28481 and 28482 which are backcrosses from the series PMR Honeydew (Snakemelon [Freeman Cucumber x Snakemelon]). Plots were planted on 80 inch centers and consisted of five two-plant hills spaced 30 inches apart. There were two replications. the test was evaluated on a plot basis 4 weeks (September 22) and 8 weeks (October 20) post-planting for number of live plants, plant size, plant condition, yellowing, leaf necrosis (burn) and flowering. Plots were not treated with any pesticides or herbicides.

Of the 276 PIs planted, four failed to germinate in either one replication (three entries) or both replications (one entry). Four weeks post planting, 63 entries were dead in one replication and an additional 17 PI were dead in both replications. Eight weeks post-planting, all but 15 entries were dead. Of those 15, only one had live plants in both replications. This is in sharp contrast with the 1991 test when most of the entries were alive and 1992 when approximately 70% of the entries were alive after 8 weeks. Severity of the test is also indicated by differences in mean ratings of plant condition 4 weeks post-planting for Top Mark in 1992 and 1993, 7.0 and 2.0, respectively.

Table 1 summarizes the mean ratings of plant condition 4 weeks post-planting. At that time, nine entries showed promise as sources of whitefly resistance; they are the entries with means ranging 3.75 to 5.50. By 8 weeks post-planting, only one (28481) of those nine entries had any (one) live plants. Entry 28481 is a backcross progeny with the following pedigree: PMR HD (Snakemelon [Freeman Cucumber x Snakemelon]). Snakemelon appeared to be a potential source of B. tabaci, type B resistance in 1991, but in this test it had a mean rating of 20 at 4 weeks and was dead at 8 weeks. Of the remaining eight best entries 4 weeks post-planting, PI 125918, PI 125890, PI 116915, and PI 125951 are of most interest for further study for the following reason. Each of these four entries had plant condition ratings of 2 or 3 in one replication, but was rated 6 or better in the other replication. Especially interesting are PI 125918, PI 125890 which were rated 9 in one replication. They appeared to have as many adults and immatures as other entries in the test, but the plants were normal in appearance, were flowering, and were the largest in the field. A greenhouse test of these nine entries is in progress.

Table 1. Mean plant condition on 22 September 1993 (four weeks post-planting) in response to whitelfy feeding.

Meanz

Entries
5.5 125918 125890 — — — — — — — —
4.5 28481 116915 — — — — — — — —
4.0 125951 125996 125997 126165 — — — — — —
3.0-3.5 WMR 29 116917 125928 126017 126091 126154 127565 220786 — —
28478 125860 125964 126050 126131 126174 211588 223768 — —
28479 125879 125989 126057 126146 126199 220170 324525 — —
28482 125886 126000 126076 126151 127564 220655 — — —
2.0-2.5 GF Honeydew 125901 125952 125996 126056 126097 126164 127546 212291 300956
PMR 45 125903 125953 126004 126059 126098 126166 127547 217515 323937
Snakemelon 125905 125955 126006 126060 126101 126167 127548 217526 355051
Top Mark 125906 125956 126008 126062 126105 126168 127550 219945 418766
116916 125907 125957 126012 126064 126113 126170 127560 218070 420152
125862 125910 125958 126013 126068 126116 126172 127567 218071 426628
125865 125914 125961 126016 126074 126117 126178 127570 220515 532929
125868 125919 125969 126018 126075 126126 126185 127572 220651 —
125870 125921 125970 126024 126078 126133 126195 127575 22-654 —
125872 125922 125972 126027 126080 126140 126197 127576 220787 —
125876 125923 125974 126030 126083 126141 126198 127578 221439 —
125880 125925 125979 126032 126084 126142 127524 135315 222097 —
125885 125931 125981 126036 126086 126143 127528 204304 222098 —
125891 125932 125984 126040 126088 126145 127531 107478 242907 —
125892 125935 125986 126042 126089 126147 127534 210016 260651 —
125893 125943 125991 126044 126090 126150 127536 211726 261750 —
125895 125944 125992 126047 126093 126152 127538 212087 269367 —
125896 125946 125993 126052 126095 126160 127539 212089 269368 —
125897 125947 125994 126054 126096 126162 127545 212090 300955 —
—
1.0-1.5 125863 125913 125938 125973 126037 126077 126110 126156 207477
125866 125920 125942 125976 126051 126079 126111 126159 223770 —
125881 125924 125948 125987 126053 126081 126112 126171 269474 —
125883 125927 125962 125990 126069 126082 126114 126180 269478 —
125900 125930 125963 126005 126070 126099 126125 127535 401646 —
125904 125933 125967 126020 126072 126106 126127 127551 410768 —
125911 125937 125971 126033 127073 126108 126134 135319 426627 —

zCondition was rated on a 1 (dead) to 9 (vigorous, flowers) scale

Literature Cited

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  2. Campbell, B.C., J.E. Duffus, and P. Baumann, 1993. Determining whitefly species. Science 261:1333.
  3. Cohen, S., J.E. Duffus, and H.Y. Liu. 1991. A new Bemisia tabaci biotype in the Southwestern United States and its role in silverleaf of squash and transmission of lettuce infectious yellows virus. Phytopathology 82:86-90.
  4. Gruenhagen, N.M., T.M. Perring, L.G. Bezark, D.M. Daoud, and T.F. Leigh. 1993. Silverleaf whitefly present in the San Joaquin Valley. Calif. Agr. 47(1):4-6.
  5. McCreight, J.D. 1992. Preliminary screening of melons for sweetpotato whitefly resistance. Cucurbit Genet. Coop. Rpt. 15:59-61.
  6. McCreight, J.D. 1993. Screening of Melons for Sweetpotato Whitefly Resistance: 1992. Cucurbit Genet. Coop. Rpt. 16:49-52.
  7. Perring, T.M., A. Cooper, D.J. Kazmer, C. Shields, and J. Shields. 1991. New strain of sweetpotato whitefly invades California vegetables. Calif. Agr. 45(6):10-12.
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  9. Perring, T.M., C.A. Farrar, T.S. Bellows, A. D. Cooper, and R.J. Rodriguez. 1993. Evidence for a new species of whitefly: UCR findings and implications. Calif. Agr. 4(1):7-8.
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  11. Perring, T.M.., C.A. Farrar, A.D. Cooper, T.S. Bellows, and R.J. Rodriguez. 1993. Determining whitefly species – response. Science 261:1334-1335.