The Molecular Determination of Hybridity and Homozygosity Estimates in Breeding Populations of Lettuce (Lactuca sativa L.)

Abstract

The development of new varieties of horticultural crops benefits from the integration of conventional and molecular marker-assisted breeding schemes in order to combine phenotyping and genotyping information. In this study, a selected panel of 16 microsatellite markers were used in different steps of a breeding programme of lettuce (Lactuca sativa L., 2 n = 18). Molecular markers were first used to genotype 71 putative parental lines and to plan 89 controlled crosses designed to maximise recombination potentials. The resulting 871 progeny plants were then molecularly screened, and their marker allele profiles were compared with the profiles expected based on the parental lines. The average cross-pollination success rate was 68 ± 33%, so 602 F1 hybrids were completely identified. Unexpected genotypes were detected in 5% of cases, consistent with this species’ spontaneous out-pollination rate. Finally, in a later step of the breeding programme, 47 different F3 progenies, selected by phenotyping for a number of morphological descriptors, were characterised in terms of their observed homozygosity and within-population genetic uniformity and stability. Ten of these populations had a median homozygosity above 90% and a median genetic similarity above 95% and are, therefore, particularly suitable for pre-commercial trials. In conclusion, this study shows the synergistic effects and advantages of conventional and molecular methods of selection applied in different steps of a breeding programme aimed at developing new varieties of lettuce.

Bioactive compounds and antioxidant activity of crisphead lettuce (Lactuca sativa L.) of three different cultivation systems

“…The crisphead lettuce (Lactuca sativa L.) is the most consumed vegetable in Brazil, being considered a horticultural culture of great consumption (Fernandes et al, 2002). In the world it is one of the most important green leafy vegetables (Campos et al, 2019) and consumed on a large scale (Patella et al, 2019), being produced around 27 million tons per year (Food and Agriculture Organization of the United Nations, 2019). It is a vegetable that deserves special interest, not only for its food importance but also for its nutritional and functional value (Chiconato et al, 2014).…”

“…Curly lettuce is a fresh vegetable consumed alone or in combination with other vegetables ready for consumption, usually consumed in mixed and fresh-cut salads. Depending on the leaf type and growing conditions, its edible leaves present high demand for nutrients (El-Nakhel et al, 2019;Oliveira et al, 2018;Patella et al, 2019).…”

Potentials and Challenges of Genomics for Breeding Cannabis Cultivars

“…Lastly, owing to the lack of a robust panel of SNP markers based on a standardized set of genes and considering the urgent need to develop a reference method for genotyping plant varieties with ease to detect markers, as well as reliable and transferable protocols, a discriminant panel of SSR markers was selected from polymorphic microsatellite regions of Cannabis spp. Recent signs of progress in the development of multiplex assays have been made in several crops (Palumbo et al, 2018;Patella et al, 2019a;Patella et al, 2019b), suggesting that these markers, especially when finely mapped and scattered throughout the genome, remain as relevant and cost-effective molecular tools at least for characterizing genetic resources and breeding new varieties. On the whole, this information is reported in Section 6.…”

Genetic Diversity Assessment and Marker-Assisted Selection in Crops

“…Informative molecular markers such as SSR were adopted also for detecting hybridity and homozygosity in breeding segregant populations in lettuce ( Lactuca sativa L.). In this study, a panel of 16 SSR was used to genotype 71 putative parental lines and to plan 89 controlled crosses designed to maximize the genetic recombination [ 12 ]. Unexpected genotypes were detected (5%), consistent with this species’ spontaneous out-pollination rate.…”

“…Unexpected genotypes were detected (5%), consistent with this species’ spontaneous out-pollination rate. Overall, the synergistic advantages of conventional and molecular selection applied in different steps of a breeding programs aimed at developing new varieties were demonstrated [ 12 ].…”