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  • Author or Editor: H. H. Toba x
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Abstract

When free choice was available in the Geld, build up of melon aphid (Aphis gossypii Glover, Western Biotype) was extremely low on Cucumis melo L. breeding line U 90234 derived from PI 175111, even if it was next to heavily infested suscepts. LJ 90234 infested with large no. of aphids which were given no choice for food survived with little injury while treated susceptible hosts were killed. Melon aphid nymphs confined on young mature leaves of LJ 90234 often died and survivors grew slowly to small body size and their fecundity was reduced. LJ 90234 is attacked by other insects, however. LJ 90234 appears to exhibit nonpreference, apparent tolerance, and apparent antibiosis to the melon aphid.

Open Access

Abstract

Reproduction of the melon aphid, Aphis gossypii Glover, varied on different plants of Cucumis melo L., PI 371795, and its inbreds. Successive generations of selection and inbreeding increased uniformity and potency of antibiosis. Aphid reproduction on F1, F2, and backcross hybrids from a resistant × susceptible cross indicated that a single, dominant major gene conferred some antibiosis; but variation within resistant and susceptible classes indicated that additional, minor genes caused effects similar to those found in resistant inbreds.

Open Access

Abstract

A collection of Lactuca saligna (P.I. 261653), although heterozygous, contained individuals that retard the development of cabbage loopers (Trichoplusia ni Hubner) compared with preferred hosts such as cultivars of lettuce and broccoli. Development of 1st instar to adult required 5 to 6 days longer on L. saligna than on broccoli. Comparable development of lst-instar larvae to 2nd instar required 32 hours more for larvae fed exclusively on leaves of L. saligna than for those confined to L. sativa cv. Hanson. Also, more significantly, in this test 26% of the larvae died before the 2nd-instar stage compared to 0% in the control.

Interspecific hybrids between L. saligna and L. sativa were produced. The F1 plants were fertile to a limited extent. These interspecific crosses will allow an exchange of genes between the 2 species and make possible the development of lettuce cultivars resistant to the cabbage looper.

Five collections of L. saligna (other than P.I. 261653) were evaluated for their effect on looper development from 1st to 2nd instar. A significant delay in larval development was established for 2 entries (P.I. 253299 and P.I. 281876). However, they were more preferred than P.I. 261653 in a preference test. A collection of Lactuca species, consisting of 19 entries were tested for antibiosis. Two entries listed as L. perennis L. were uncovered where development from 1st instar to 2nd instar was suppressed. This result suggests that antibiosis for cabbage looper is not widespread in the genus, but probably fairly common in L. saligna as evidenced by plant to plant variation among numerous collections.

Open Access

Abstract

When given a choice, the cabbage looper, Trichoplusia ni (Hübner), preferred lettuce for oviposition over chard [Beta vulgaris L. (Cicla group)], cabbage [Brassica oleracea (Capitata group)], broccoli (Brassica oleracea L. [Italica group)], and spinach (Spinacia oleracea L.). Preference did not appear to be related to leaf area or to any factor that enhances the survival of progeny of a particular plant species. A 20- to 29-fold difference in oviposition was noted on lettuce grown under 2 environmental conditions.

Open Access

Abstract

Resistance to the western biotypes of Aphis gossypii Glover in Cucumis melo L. breeding line LJ 90234 (inbred of P.I. 371395 from India) included tolerance expressed as freedom from curling of leaves following aphid infestation. The flat and curled phenotypes in progenies from a cross of this line with cv. PMR 45 were differentiated by a single gene, melon aphid tolerance (Ag, Aphis gossypii tolerance) with flat leaves dominant. Tolerance expressed as nearly normal ht of F1 and some F2 plants following mass infestation appeared to be less simply inherited. Its measurement was masked by inherent variation in growth rate and environmental factors including variation in insect attack.

LJ 90230, selected from P.I. 161375 from Korea, was stunted by the aphid but its leaves remained free from curl. F2 hybrids from the cross 90234 × 90230 were free from curl but they varied in stunting after aphid attack. Single-peaked distribution curves for ht suggested complex inheritance of tolerance. LJ 90254, selected from P.I. 255478 from Korea, possessed tolerance to aphids expressed as freedom from stunting and curling. F2 plants from the cross 90234 × 90254 were free from curl but varied in ht after aphid attack. The single-peaked distribution curves suggested complex inheritance of tolerance.

Open Access

Abstract

When moths of the cabbage looper, Trichoplusia ni (Hubner), were exposed to 208 entries of lettuce, significant reduction in oviposition occurred on 8 cultivars, 4 breeding lines, and 17 Plant Introductions. Preference for any 1 cultivar varied depending on the host choice offered. Looper moths preferred younger lettuce plants when plantings of 1 host entry were made as little as 1 week apart. One introduction, each, of Lactuca serriola L. and L. saligna L. were less attractive to looper moths than any entry of L. sativa, and may be valuable sources of resistance to that insect pest.

Open Access