Obtenção de progênies de alface crespa resistentes ao míldio

Genetics and Molecular Research, 2019

Lettuce is one of the most consumed leaf vegetables in the world, highlighting itself as a novelty in the market as mini type cultivars. During the winter the downy mildew can lead to severe damage. Thus, the objective of this work was to evaluate the genetic diversity, agronomic potential and downy mildew reaction in biofortified mini lettuce genotypes. The experiment was carried out in the University of Uberlandia, Monte Carmelo Campus. The statistical method used for the field experiment was the randomized complete block design, with 19 treatments (17 genotypes of the generation F3:4 and two cultivars of commercial lettuce) and two repetitions. The following parameters were evaluated: crowndiameter (cm); rod diameter (mm); number of leaves per plant and spad index. The data were submitted to multivariate analyses were performed. The genetic divergence was represented by dendrogram obtained by the hierarchical UPGMA method and by the Tocher optimization method. The laboratory expe...

Scientific Reports, 2013

Many cultivars of lettuce (Lactuca sativa L.), the most popular leafy vegetable, are susceptible to downy mildew disease caused by Bremia lactucae. Cultivars Iceberg and Grand Rapids that were released in the 18 th and 19 th centuries, respectively, have high levels of quantitative resistance to downy mildew. We developed a population of recombinant inbred lines (RILs) originating from a cross between these two legacy cultivars, constructed a linkage map, and identified two QTLs for resistance on linkage groups 2 (qDM2.1) and 5 (qDM5.1) that determined resistance under field conditions in California and the Netherlands. The same QTLs determined delayed sporulation at the seedling stage in laboratory experiments. Alleles conferring elevated resistance at both QTLs originate from cultivar Iceberg. An additional QTL on linkage group 9 (qDM9.1) was detected through simultaneous analysis of all experiments with mixed-model approach. Alleles for elevated resistance at this locus originate from cultivar Grand Rapids. C ultivated lettuce (Lactuca sativa L.) is a diploid, autogamous species with 2n 5 2x 5 18 chromosomes. Lettuce cultivars are classified into horticultural types that differ morphologically. The most popular types produced for leaf consumption are iceberg with a large spherical head, romaine with an elongated head, butterhead with a small spherical head and pliable leaves with oily texture, and non-heading leaf-type lettuces with loose leaves. Analyses with molecular markers identified low genetic variability in iceberg and to lesser extent also in romaine and butterhead types 1-5 . Narrow genetic base may mean that these types are impoverished with respect to genes for resistance to pathogens relative to the lettuce genepools 6 . Consequently, lettuce breeders seek to exploit genetic diversity of wild progenitor species, different horticultural types, landraces, and old cultivars. Downy mildew, caused by the biotrophic oomycete Bremia lactucae Regel, is one of the most economically important diseases of cultivated lettuce worldwide. Lettuce can be infected by this pathogen at any developmental stage, from young seedlings to mature plants. Infected plants develop yellow to pale green lesions that eventually become necrotic due to secondary pathogens following the breakdown of the biotrophic interaction. B. lactucae infection leads to lower marketable yield and to higher harvest-related expenses owing to the need to remove infected leaves. Chemical control of downy mildew with metalaxyl-based fungicides is possible, but ineffective against insensitive pathotypes 7 .

Molecular Plant-Microbe Interactions®, 2009

The nonhost resistance of wild lettuce (Lactuca saligna) to downy mildew (Bremia lactucae) is based on at least 15 quantitative trait loci (QTL), each effective at one or more plant developmental stages. We used QTL pyramiding (stacking) to determine how many of these QTL from L. saligna are sufficient to impart complete resistance towards B. lactucae to cultivated lettuce, L. sativa. The alleles of four of the most promising QTL, rbq4, rbq5, rbq6+11, and rbq7 are effective at both the young and adult plant stages. Lines with these four QTL in all possible combinations were generated by crossing the respective backcross inbred lines (BIL). Using the 11 resulting lines (combiBIL), we determined that combinations of three QTL, rbq4, rbq5, and rbq6+11, led to increased levels of resistance; however, one QTL, rbq7, did not add to the resistance level when combined with the other QTL. One line, tripleBIL268, which contains the three QTL rbq4, rbq5, and rbq6+11, was completely resistant t...

Basic and Applied Ecology, 2007

Zusammenfassung Die Hybridisierung zwischen Pflanzenarten kann ökologische Veränderungen der Arten verursachen, die ihr Potenzial invasiv zu werden vergrößern. Zunehmende Hinweise lassen vermuten, dass die expandierende Verbreitung von Lactuca serriola (teilweise) durch die Hybridisierung mit dem nächsten Verwandten, L. sativa (Kopfsalat), verursacht sein könnte. Die Fitness-Vorteile der Hybriden kann das Ergebnis von Heterosis oder Epistasis sein, aber es könnten auch einzelne zusätzliche Merkmale die Hybridenfitness erhöhen. An dieser Stelle untersuchen wir das Potenzial für die Introgression eines wichtigen Feldfruchtmerkmals, der Resistenz gegen Mehltau (Bremia lactucae), in die L. serriola Hybriden. Wir erfassten die Abundanz von B. lactucae auf wildem L. serriola in den Niederlanden um das Einflusspotenzial zu testen. Wir fanden, dass B. lactucae in den Niederlanden weitverbreitet ist: B. lactucae kam in 33 von 35 untersuchten Populationen von L. serriola vor. Anschließend erfassten wir unter Verwendung von zwei Physiotypen von B. lactucae (BL-16 und BL-18) unter kontrollierten Bedingungen (i) quantitativ die Conidiophoren und (ii) die Entwicklung von Haustorien bei Setzlingen. Darüber hinaus untersuchten wir die Effekte auf die Pflanzenfitness. Basierend auf dem (fehlenden) Vorkommen von Conidiophoren waren in diesen Hybriden seid mindestens zwei Hybridengenerationen genetische Segmente von L. sativa vorhanden und exprimiert, die Bremia Resistenz einschließen. Die Haustoriendichte war jedoch bei allen Hybriden geringer, unabhängig von Physiotyp oder Herkunftssorte. Wir führten dies auf Heterosis zurück. Darüber hinaus verloren alle infizierten Pflanzen Blätter, aber wir konnten keinen Effekt der Infektion auf die Fitness feststellen. Deshalb schlossen wir daraus, dass, wenn L. serriola die Resistenz gegen B. lactucae erhält, die Fitnesseffekte gering sind. Die Hypothese, dass der Erwerb einer B. lactucae. Resistenz ursächlich mit der derzeitigen Ausbreitung von L. serriola in Beziehung steht, ist damit unwahrscheinlicher geworden. Wenn die Hybridisierung überhaupt mit all diesem verbunden ist, dann über Heterosiseffekte. Wir schließen daraus, dass es wichtig ist, die Wirkung von introgressierten Merkmalen auf die Fitness zusammen mit anderen ökologischen Faktoren zu untersuchen.

Theoretical and Applied Genetics, 2014

to their parental BIls and their interactions were additive, 'less-than-additive' epistatic and 'more-than-additive' epistatic, respectively. The additive interaction reduced field infection by 73 %. The double combination with a 'morethan-additive' epistatic effect, derived from a combination between a susceptible and a resistant BIl with 0 and 30 % infection reduction, respectively, showed an average field infection reduction of 52 %. For the latter line, an attempt to genetically dissect its underlying epistatic loci by substitution mapping did not result in smaller mapping intervals as none of the 22 substitution lines reached a similar high resistance level. Implications for breeding and the inheritance of L. saligna's complete resistance are discussed. Abbreviations BIl Backcross inbred line (L. saligna introgression segment, 20-80 cM long, in a lettuce, L. sativa, genetic background) sub-BIl line with a smaller introgression segment than the BIl of which it is derived QTl Quantitative trait locus YDT Young plant disease test ADT F Adult plant disease test in the field ISl Infection severity level rIS relative infection severity level Abstract Key message In a stacking study of eight resistance QTLs in lettuce against downy mildew, only three out of ten double combinations showed an increased resistance effect under field conditions.

Euphytica, 2016

Lettuce downy mildew caused by Bremia lactucae is the most important disease of lettuce worldwide. Breeding for resistance to this disease is a major priority for most lettuce breeding programs. Many genes and factors for resistance to B. lactucae have been reported by multiple researchers over the past ~50 years. Their nomenclature has not been coordinated, resulting in duplications and gaps in nominations. We have reviewed the available information and rationalized it into 51 resistance genes and factors and 15 quantitative trait loci along with supporting documentation as well as genetic and molecular information. This involved multiple rounds of consultation with many of the original authors. This paper provides the foundation for naming additional genes for resistance to B. lactucae in the future as well as for deploying genes to provide more durable resistance.

Indian Journal of Genetics and Plant Breeding, 2020

destructive pathogens of cucurbits (Palti and Cohen, 1980). This disease was first described in Cuba in 1868 (Berkeley and Curtis, 1868). The symptoms of the disease in the susceptible genotypes appear mostly on foliage as small, water soaked lesions on the underside of the leaves which later become angular and turn chlorotic as they are restricted by the small leaf veins. Whereas, the resistant genotypes show hypersensitive response (HR) with small necrotic spots (Call et al. 2012). Since several fungicides, which have earlier provided control, are reported to be ineffective because of evolution of new strains of P. cubensisand resistant varieties substantially reduce or eliminate fungicide requirements (Wan et al. 2010). The development of resistant cultivars is generally considered to be the best approach to control downy mildew (Olczak et al. 2011). So, identification of new sources of resistance to downy mildew is of paramount importance for agriculture and environment. Therefore, this study was undertaken with the objective to find out sources of resistance through artificial screening (pot culture) of cucumber germplasm. Materials and methods In order to identify the sources of resistance in cucumber against downy mildew, the pot experiments were conducted during kharif seasons of 2017 and

South African Journal of Enology & Viticulture, 2017

Different grape cultivars of Vitis species have been cultivated in Turkey since ancient times. A large proportion of these cultivars cannot be cultivated in the humid regions of the country due to downy mildew (Plasmopara viticola) and powdery mildew (Uncinula necator or syn. Erysiphe necator) diseases. Cultivars resistant to these diseases can generally grow without any or fewer fungicide applications. However, there are also differences in the resistance level of cultivars. In particular, Vitis vinifera cultivars, the most widely cultured species, are most affected by these diseases. Thirteen V. vinifera cultivars, eight V. labrusca cultivars and six interspecific cultivars were used in this study, for a total of 27 cultivars. The resistance of cultivars against downy mildew and powdery mildew was determined over two years with natural infection and artificial inoculation applications. Generally, all cultivars showed more resistance to downy mildew, while they also showed lower resistance to powdery mildew. The evaluation based on species found V. vinifera to be the most sensitive. While interspecific cultivars were found to be most resistant to downy mildew, V. labrusca cultivars were the most resistant to powdery mildew. Among cultivars of the same species, however, differences in terms of resistance were observed. These differences can be used in breeding studies in order to obtain new, disease-resistant cultivars, which may be grown commercially to comply with good agricultural practices (GAP) or organic viticulture in the future.

Chilean journal of agricultural research, 2019

Due to the harmful potential and existence of numerous races of lettuce downy mildew (Bremia lactucae Regel), several countries carry out the monitoring of these races through the use of differential cultivars of lettuce (Lactuca sativa L.) The identification of resistance to other important diseases in these cultivars would be of great value for the lettuce's breeding, allowing the simultaneous selection for diseases. Among soil pathogens, the most important are the root-knot nematodes (Meloidogyne spp.) due their damage and difficulty of control. Thus, the present work evaluated the resistance of these differential cultivars (C-Set) against the two most important nematode species for the crop, M. javanica and M. incognita. The experiment was conducted in a completely randomized design, with eight replicates and initial population of 1000 eggs and juveniles. The evaluations were performed by the criteria of reproduction factor and reproduction index, 75 d after inoculation. Data were submitted to ANOVA and averages were compared by the Scott-Knott test (p < 0.05). All cultivars are considered susceptible to M. incognita by the reproduction factor, 'Argelès', 'Bedford', 'Design' and 'Grand Rapids' are considered as slightly resistant by the reproduction index. However, to M. javanica 'Argelès', 'Kibrille', 'Balesta', 'Colorado', 'Design', 'Bartoli', and 'NunDm15' are classified as resistant by the reproduction factor and very resistant by the reproduction index, and can be used as resistance source for simultaneous selection to downy mildew and this species of nematode.