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Eenink, A. Groenwold, H.R. Dieleman, F.L. 1982 Resistance of lettuce ( Lactuca ) to the leaf aphid Nasanovia ribisnigri . 1. Transfer of resistance from L. virosa to L. sativa by interspecific crosses and selection of

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Big vein (BV) disease of lettuce is caused by soil borne fungal vectored viruses, and reduces marketability through head deformation. Tolerant cultivars reduce BV frequency, but no resistant cultivars exist. L. virosa L. is highly resistance. The objectives were to 1) determine if L. virosa P.I.s exhibit variation for resistance, and 2) determine if resistance is transferable to lettuce. Seedlings were inoculated with root macerate of BV infected plants, transplanted to BV infested soil, and greenhouse grown for 3 months. Twelve plants in each of 1,2, or 3 reps of Great Lakes 65 (GL65-susceptible), Pavane (Pav-tolerant), L. virosa (11 accessions), and BC1 F2 through F5 families of lettuce cultivars x L. virosa accession IVT280 were tested. The percentage of BV afflicted plants was recorded. In hybrid families, BV free plants from tolerant families were selected and advanced. No BV was found in L. virosa. Variation for tolerance was observed in BC1 F2 and F3 families; 33% had greater tolerance than Pav (17% afflicted). Additional tests identified 11 BC1 F3 families (14%) with greater tolerance than Pav (42% afflicted). Subsequent BC1 F4 and F5 generations however, were more susceptible than Pav. Lactuca virosa is highly resistant, but resistance did not transfer to hybrid progeny. Variation for tolerance was observed in BC1 F2 and F3 families, but later generations were susceptible. Interactions or linkage of genes for developmental processes and BV resistance may hinder introgression. Introgression will continue using congruity backcrossing and a greater diversity of L. virosa.

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Beet western yellows virus (BWYV), a member of the Luteovirus group, causes severe losses in many lettuce-growing areas. Attempts to identify complete resistance to BWYV in lettuce cultivars (Lactuca sativa L.) or in L. serriola L. and L. saligna L. were unsuccessful. Among three accessions of L. virosa tested, one, IVT 280, appeared to be extremely resistant to BWYV. Heredity of this resistance was studied in crosses with susceptible L. virosa IVT 1398. The results were compatible with the hypothesis of one gene, with resistance being dominant. The symbol Bw for Beet western is proposed for this gene.

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environmentally desirable means for controlling lettuce aphid infestation of lettuce ( Painter, 1980 ). Complete and partial types of resistance to lettuce aphid have been described in Lactuca virosa L., a wild, distant relative of cultivated lettuce ( Eenink

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known worldwide, and biotype Nr:1 is, thus far, known only in Europe. Complete and partial types of resistance to Nr:0 were described in Lactuca virosa L., a wild, distant relative of cultivated lettuce ( Eenink and Dieleman, 1983 ). Complete

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York, NY Eenink, A. Groenwold, H.R. Dieleman, F.L. 1982 Resistance of lettuce ( Lactuca ) to the leaf aphid Nasanovia ribisnigri . 1. Transfer of resistance from L. virosa to L. sativa by interspecific

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Abstract

Lactuca saligna L., Lactuca serriola L., and Lactuca virosa L., which are cross-fertile with cultivated lettuce (L. sativa L.) were tested for resistance to lettuce infectious yellows virus in greenhouse and field tests. Fifteen of 25 L. saligna accessions were resistant, whereas 50 accessions of L. serriola and seven accessions of L. virosa were susceptible.

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three wild species ( L. serriola , L. saligna , and L. virosa ) and primitive lettuce have thermoinsensitive genotypes. The observed thermotolerance in UC96US23 ( Lactuca serriola ) was consistent with previous results of Argyris et al. (2008a , 2008

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Abstract

A 6-year (1975-1980) survey established that broad bean wilt virus (BBWV) was second only to cucumber mosaic virus (CMV) in causing destructive diseases in leading lettuce cultivars grown in New York State. Conversely, the widespread usage of certified seed had drastically reduced the occurrence of lettuce mosaic virus (LMV). Screening for resistance revealed that a number of accessions of Lactuca sativa and a few of L. virosa were tolerant to BBWV. Tolerant plants, although infected with the virus, remained symptomless or responded with a mild and often transient chlorotic mottle.

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Leafminer (Liriomyza langei Frick) is a major insect pest of many important agricultural crops including lettuce (Lactuca sativa L.). The goals of this study were to evaluate lettuce genotypes for resistance to leafminer and to estimate heritabilities of three leafminer-resistant traits. Forty-six lettuce genotypes were evaluated in two tests in insect cages. Wild species (Lactuca serriola L., Lactuca saligna L., and Lactuca virosa L.) had significantly fewer leafminer stings than cultivated lettuce (L. sativa) in both tests. PI 509525 (L. saligna) had few leafminer stings and no flies emerged. Leaf (leaf and romaine) lettuce also showed significantly less stings than head (crisphead and butterhead) types, while differences between leaf and romaine lettuces, and between crisphead and butterhead types were nonsignificant. Broad-sense heritability for number of stings per unit leaf area was relatively high, averaging 65% over the two tests. Heritabilities for egg-hatching period and flies per plant were 10% and 15%, respectively. Stings per unit leaf area from the two tests were highly correlated (r = 0.828), suggesting that resistance was stable over different plant ages and against different pressures of leafminer. These results suggest that genetic improvement of cultivated lettuce for leafminer resistance is feasible.

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