Three elite tomato (Solanum lycopersicum L., syn. Lycopersicon esculentum Mill.) breeding lines (TOM‐687, TOM‐688, TOM‐689) with high foliar acylsugar (AS) contents were obtained, and used along with two low‐AS lines (TOM‐690, TOM‐684) in hybrid combinations, to obtain six hybrids between one low‐AS line × one high‐AS line (= hybrids with intermediate AS levels), one hybrid between two high‐AS lines (= high‐AS hybrid), and one hybrid between two low‐AS lines (= low‐AS hybrid). These genotypes were tested for resistance to three different tomato pests (spider mites [Tetranychus urticae Koch], silverleaf whitefly [Bemisia argentifolii Bellows & Perring], and the South American tomato pinworm [Tuta absoluta (Meyrick)]) along with hybrid TEX‐154 (low‐AS) and/or Solanum pennellii Correll ‘LA‐716’ (high‐AS wild accession). In all three instances, high‐AS genotypes showed higher levels of pest resistance than low‐AS genotypes. Hybrids with intermediate AS levels showed resistances that were just as high as those of high‐AS genotypes for Bemisia argentifolii and Tuta absoluta, and nearly as good as those for Tetranychus urticae. Acylsugars were confirmed as being a major component of the high levels of pest resistances found in S. pennellii—a component that was successfully introgressed into elite tomato breeding lines. Acylsugar‐mediated pest resistance is effective against a broad spectrum of tomato pests. Because high‐AS breeding lines are scarce, the deployment of hybrids between high‐AS line × low‐AS line would be a quick, viable alternative to obtain commercial pest‐resistant hybrids.

We examined the resistance of improved tomato strains rich in 2-tridecanone (2-TD), zingiberene (ZGB) and acyl sugars (AA) to the tomato moth, Tuta absoluta. We also studied whether selection for strains with higher densities of glandular trichomes, and thus presumably strains with higher concentrations of 2-tridecanone, was effective in promoting greater resistance to the moth. The TOM-584 and TOM-679 strains were used as susceptible controls, which have normal concentrations of the three allelochemicals. The improved strain TOM-687, which has a high AA content, has a widely documented resistance and was used as a standard resistant strain. The wild strain PI134417, which is resistant by means of its high 2-TD content, was also used as a standard resistant strain. The experiment was installed in a greenhouse with a completely randomized design. The wild strain PI 134417 was confirmed as being highly resistant. TOM-622 (rich in 2-TD), ZGB-703 (rich in ZGB), and TOM-687 (rich in AA) showed significant reductions in the oviposition rate of the tomato moth, damage to the plants, injury to the leaflets, and the percentage of leaflets attacked in comparison with the control strains (TOM-584 and TOM-679). The levels of resistance to the moth for the TOM-622, ZGB-703, and TOM-687 strains were similar. In general, the genotypes with higher densities of glandular trichomes had greater resistance than the susceptible controls, with the strain BPX-367D-238-02 being particularly notable in its resistance.Index terms: Solanum lycopersicum, genotypes, breeding, indirect selection. RESUMOComparou-se a efetividade de linhagens melhoradas de tomateiro, ricas em 2-tridecanona (2-TD), zingibereno (ZGB) e acilaçúcares (AA), em relação aos níveis de resistência à traça-do-tomateiro Tuta absoluta. Verificaram-se, também, se linhagens selecionadas para maiores densidades de tricomas glandulares, presumivelmente com maiores níveis de 2-tridecanona, são efetivas em promover maior resistência à traça. Como testemunhas suscetíveis foram utilizadas as linhagens TOM-584 e TOM-679, com nível normal dos três aleloquímicos. A linhagem melhorada TOM-687 (com alto teor de AA) foi utilizada como linhagem resistente padrão, por ter sua resistência amplamente documentada, juntamente com o também resistente acesso selvagem PI134417 (com alto teor de 2-TD). O experimento foi instalado em casa de vegetação, em delineamento inteiramente casualizado. O acesso selvagem PI 134417 confirmou-se como altamente resistente. TOM-622 (rica em 2-TD), ZGB-703 (rica em ZGB) e TOM-687 apresentaram diminuições significativas na ovoposição da traça-do-tomateiro, bem como no dano geral na planta, lesão nos folíolos e porcentagem de folíolos atacados, comparadas às testemunhas TOM-584 e TOM-679. Os níveis de resistência à traça em TOM-622, ZGB-703 e TOM-687 foram similares entre si. Em geral, os genótipos selecionados com maiores densidades de tricomas glandulares apresentaram níveis de resistência também superiores aos das testemunhas suscetíveis, destacando en...

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Acylsugars present in the accession 'LA716' of Lycopersicon pennellii play an important role in the resistance to Tuta absoluta. This paper investigates the possible association between the resistance to T. absoluta and the acylsugar contents in F2 and F2BC1 tomato plants derived from the interspecific crossing between L. esculentum 'TOM-584' and L. pennellii 'LA716'. From the F2 population, four high acylsugars and one low acylsugars plants were selected and tested for Tuta absoluta resistance along with parental lines TOM-584 and LA-716, and with the checks TOM-600 (high 2-tridecanone line with resistance to T. absoluta) and TOM-556 (low acylsugar line). The genotypes were tested under natural field infestation and were evaluated for overall plant damage, leaflet lesion type and percent of attacked leaflet. Four plants from F2BC1 [=(Lycopersicon esculentum 'TOM-584' × F 2 )] were selected for high acylsugars and two for low acylsugars, and tested in greenhouse cages infested with T. absoluta. These genotypes were evaluated with the parental lines and the checks for oviposition ten days after infestation, and for leaflet lesion type and overall plant damage at four different dates. The F2 genotypes BPX-370Bpl#25, BPX370Bpl#30 and BPX-370Bpl#79, the F2BC1 genotypes BPX-370B pl#30-380 and BPX-370B pl#30-271 and the wild accession LA716 had good levels of resistance to Tuta absoluta. The resistance level increased with longer exposition time to the acylsugars, both in the field and in the cage tests. Acylsugar contents seemed to be highly and negatively correlated with the traits related to the pinworm resistance. Key words: Lycopersicon pennellii, Lycopersicon esculentum, allelochemical, plant breeding ACILAÇÚCARES PRESENTES EM FOLÍOLOS DE TOMATEIROCONFEREM RESISTÊNCIA À TRAÇA DO TOMATEIRO, Tuta absoluta Meyr RESUMO: Os acilaçúcares presentes no acesso 'LA716' de Lycopersicon pennellii exercem um papel importante na resistência a Tuta absoluta. Foi avaliada a associação entre níveis de resistência à T. absoluta e o nível de acilaçúcares em plantas das gerações F2 e F2RC1 do cruzamento interespecífico L. esculentum 'TOM-584' × L. pennellii 'LA-716'. Na população F2 foram selecionados 4 genótipos com alto teor de acilaçúcares e um com baixo teor. Esses genótipos seleccionados, juntamente com as linhagens parentais e as testemunhas TOM-600 (linhagem com alto teor de 2-tridecanona e resistente a T. absoluta) e TOM-556 (linhagem com baixo teor de acilaçúcares) foram submetidos à infestação natural da traça no campo e avaliados quanto a danos na planta, lesões nos folíolos e porcentagem de folíolos atacados. Na população F2RC1 [=(Lycopersicon esculentum 'TOM-584' × F 2 )] foram selecionados 4 genótipos com altos teores de acilaçúcares nos folíolos e dois genótipos com baixos teores. Esses genótipos, juntamente com as linhagens parentais e as testemunhas, foram submetidos à infestação em gaiolas, em casa de vegetação. Avaliou-se a ovoposição da traça, os danos na planta e lesões1nos folíolos. Os genótipos F 2 ...

-The objective of this work was to evaluate the feasibility of selection for higher glandular trichome densities, as an indirect criterion of selection for increasing repellence to spider mites Tetranychus urticae, in tomato populations derived from an interspecific cross between Lycopersicon esculentum x L. hirsutum var. glabratum PI 134417. Trichome densities were evaluated in 19 genotypes, including 12 from advanced backcross populations, derived from the original cross L. esculentum x L. hirsutum var. glabratum PI 134417. Counts were made both on the adaxial and abaxial leaf surfaces, and trichomes were classified into glandular types IV and VI, other glandular types (types I+VII), and nonglandular types. Mite repellence was measured by distances walked by mites onto the tomato leaf surface after 20, 40 and 60 min. Spider mite repellence biotests indicated that higher densities of glandular trichomes (especially type VI) decreased the distances walked by the mites onto the tomato leaf surface. Selection of plants with higher densities of glandular trichomes can be an efficient criterion to obtain tomato genotypes with higher resistance (repellence) to spider mites.Index terms: Lycopersicon hirsutum, Tetranychus urticae, 2-tridecanone, methyl-ketone, resistance. Alta densidade de tricomas glandulares em tomateiro e aumento da repelência a ácaros rajadosResumo -O objetivo deste trabalho foi avaliar a eficiência da seleção para maior densidade de tricomas glandulares na resistência (repelência) ao ácaro Tetranychus urticae, em populações de tomate derivadas do cruzamento interespecífico Lycopersicon esculentum x L. hirsutum var. glabratum PI 134417. Foram avaliados 19 genótipos quanto à densidade de tricomas, que incluíram 12 derivados de populações avançadas de retrocruzamentos, obtidos a partir do cruzamento original L. esculentum x L. hirsutum var. glabratum PI 134417. Nas faces abaxial e adaxial dos folíolos, realizaram-se as contagens e os tricomas foram classificados em glandulares tipo IV e VI, outros glandulares (tipo I e VII) e não glandulares. A repelência aos ácaros foi medida pela distância média, percorrida pelo ácaro na superfície do folíolo de tomateiro, após 20, 40 e 60 min. Os biotestes de repelência ao ácaro rajado demonstraram que a alta densidade de tricomas glandulares, especialmente de tipo VI, influencia negativamente a distância média percorrida pelos ácaros na superfície do folíolo. Plantas com número de tricomas glandulares elevado podem ser selecionadas para se obterem genótipos com alto índice de repelência aos ácaros.

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The traditional process of obtaining maize hybrids involves the generation of inbred lines through successive generations of selWng and subsequent testcrosses in order to identify the best combining ability by allelic complementation. A fast alternative to obtain inbred lines is to induce the formation of haploids followed by chromosome doubling. However, even with the aid of haploid-inducing genetic sources, this strategy has not been widely used in maize breeding programs, partly due to diYculties inherent to haploid generation and identiWcation. In order to evaluate the possibility of using dihaploids to generate homozygous maize tropical lines, we used the androgenetic haploid inducer line W23 as a female parent in crosses with the tropical single-cross hybrid BRS1010.Within the progeny of these crosses, 462 seeds were phenotypically selected as putative haploids by the purple-colored endosperm and colorless embryo conditioned by the R1-nj gene. Among these, only four individuals were conWrmed as being haploids using SSR markers, chromosome counting and Xow cytometry, showing that the phenotypic marker was not eYcient in detecting haploids in the tropical maize genotype used. All four haploids as well as some diploid plants presented reduced size, corroborating the diYculties for haploid identiWcation by phenotypic evaluation. Genetic diversity analysis revealed by SSR markers divided the haploids in two groups represented by Xint and dent maize inbred lines, which could be helpful in identifying complementary dihaploid lines. The present article demonstrates that a combination of haploid production and SSR Wngerprinting is a feasible strategy for maize hybrid development in tropical germplasm.