Biology, Ecology, Distribution and Control of the Invasive Weed, Lactuca serriola L. (Wild Lettuce): A Global Review

Lactuca serriola L. (wild lettuce) is a highly invasive C3 weed in many countries, including Australia, Canada, and the USA. This weed is a severe threat to agricultural systems, especially in crops grown with reduced or no-tillage approaches, which commonly include wheat, cereals and pulses. Owing to the vertical orientation of its leaves in the north-south plane and its root architecture, L. serriola can maintain high water use efficiency under drought conditions, giving it the ability to expand its range under a drying climate. Each plant can produce up to 100,000 seeds which have no primary dormancy and form a short-term seedbank lasting up to three years. Most seedlings emerge in autumn and overwinter as a rosette, with a small flush of emergence in spring depicting staggered germination. Research into control methods for this weed has been performed, and these methods include chemical herbicides applied alone and in combination, the establishment of plant competition, tillage, mowing and bioherbicide. Herbicides can provide effective control when applied in the seedling or rosette stage; however, spring germination is difficult to control, as it skips the rosette stage. Some biotypes are now resistant to ALS inhibitor and synthetic auxins, causing concern regarding using herbicides. A dedicated integrated management plan for 3–4 years is recommended for the control of this troublesome species. This review will explore the biology, ecology, distribution, current control techniques and previous research on this weed, allowing us to make recommendations for its future research and management.

Results of the vir collecting mission in Adygea and Kuban in september 2018

Twenty-six habitats in the Western Caucasus have been examined. Fifty-nine samples of seeds of cultivated plants, their wild relatives, and 77 herbarium specimens have been collected. Some of the samples are landraces of Phaseolus beans (Phaseolus vulgaris L.), spring garlic (Allium sativum L.), shallots (Allium ascalonicum L.), hot pepper (Capsicum annuum L. var. longum (DC.) Sendtn.), chickpea (Cicer arietinum L.), grass pea (Lathyrus sativus L.), etc. Another part of the samples are cultivated plants forms of folk breeding, e.g., cucumber (Cucumis sativus L.), tomato (Lycopersicon esculentum L.), etc. Samples of such wild relatives of cultivated plants as Lactuca serriola L., Prunus spinosa L., Cicerbita racemosa (Willd.) Beauverd, Asclepias syriaca L., Lathyrus sylvestris L., etc. were included in the VIR collections.

Sequence of the Mitochondrial Genome of Lactuca virosa Suggests an Unexpected Role in Lactuca sativa’s Evolution

The involvement of the different Lactuca species in the domestication and diversification of cultivated lettuce is not totally understood. Lactuca serriola is considered as the direct ancestor and the closest relative to Lactuca sativa, while the other wild species that can be crossed with L. sativa, Lactuca virosa, and Lactuca saligna, would have just contributed to the latter diversification of cultivated typologies. To contribute to the study of Lactuca evolution, we assembled the mtDNA genomes of nine Lactuca spp. accessions, among them three from L. virosa, whose mtDNA had not been studied so far. Our results unveiled little to no intraspecies variation among Lactuca species, with the exception of L. serriola where the accessions we sequenced diverge significantly from the mtDNA of a L. serriola accession already reported. Furthermore, we found a remarkable phylogenetic closeness between the mtDNA of L. sativa and the mtDNA of L. virosa, contrasting to the L. serriola origin of the nuclear and plastidial genomes. These results suggest that a cross between L. virosa and the ancestor of cultivated lettuce is at the origin of the actual mitochondrial genome of L. sativa.

Quantitative Trait Loci and Candidate Genes Associated with Photoperiod Sensitivity in Lettuce (Lactuca spp.)

Key message A population of lettuce that segregated for photoperiod sensitivity was planted under long-day and short-day conditions. Genetic mapping revealed two distinct sets of QTLs controlling daylength-independent and photoperiod-sensitive flowering time. Abstract The molecular mechanism of flowering time regulation in lettuce is of interest to both geneticists and breeders because of the extensive impact of this trait on agricultural production. Lettuce is a facultative long-day plant which changes in flowering time in response to photoperiod. Variations exist in both flowering time and the degree of photoperiod sensitivity among accessions of wild (Lactuca serriola) and cultivated (L. sativa) lettuce. An F6 population of 236 recombinant inbred lines (RILs) was previously developed from a cross between a late-flowering, photoperiod-sensitive L. serriola accession and an early-flowering, photoperiod-insensitive L. sativa accession. This population was planted under long-day (LD) and short-day (SD) conditions in a total of four field and screenhouse trials; the developmental phenotype was scored weekly in each trial. Using genotyping-by-sequencing (GBS) data of the RILs, quantitative trait loci (QTL) mapping revealed five flowering time QTLs that together explained more than 20% of the variation in flowering time under LD conditions. Using two independent statistical models to extract the photoperiod sensitivity phenotype from the LD and SD flowering time data, we identified an additional five QTLs that together explained more than 30% of the variation in photoperiod sensitivity in the population. Orthology and sequence analysis of genes within the nine QTLs revealed potential functional equivalents in the lettuce genome to the key regulators of flowering time and photoperiodism, FD and CONSTANS, respectively, in Arabidopsis.

New records of adventive vascular plants in the Ulan-Ude city and its neighborhood (Western Transbaikalia)

New data on 10 adventive plant species are given. Two species and one subspecies (Atriplex hortensis, Solanum nigrum subsp. schultesii, Nepeta cataria) are new for the Republic of Buryatia. Five species and two interspecies hybrids (Arctium × mixtum, Galinsoga parviflora, Hesperis pycnotricha, Lactuca serriola, Medicago × varia, Onobrychis viciifolia, Viola tricolor) are recorded for the first time in the Ulan-Ude city and its neighborhood.

Invasive Lactuca serriola seeds contain endophytic bacteria that contribute to drought tolerance

The mutualistic relationship between alien plant species and microorganisms is proposed to facilitate or hinder invasive success, depending on whether plants can form novel associations with microorganisms in the introduced habitats. However, this hypothesis has not considered seed endophytes that would move together with plant propagules. Little information is available on the seed endophytic bacteria of invasive species and their effects on plant performance. We isolated the seed endophytic bacteria of a xerophytic invasive plant, Lactuca serriola, and examined their plant growth-promoting traits. In addition, we assessed whether these seed endophytes contributed to plant drought tolerance. Forty-two bacterial species were isolated from seeds, and all of them exhibited at least one plant growth-promoting trait. Kosakonia cowanii occurred in all four tested plant populations and produced a high concentration of exopolysaccharides in media with a highly negative water potential. Notably, applying K. cowanii GG1 to Arabidopsis thaliana stimulated plant growth under drought conditions. It also reduced soil water loss under drought conditions, suggesting bacterial production of exopolysaccharides might contribute to the maintenance of soil water content. These results imply that invasive plants can disperse along with beneficial bacterial symbionts, which potentially improve plant fitness and help to establish alien plant species.

The carcass and meat quality characteristics of Japanese quail fed a diet supplemented with powdered Lactuca seriola leaves

The present study was aimed to evaluate the effect of dietary supplementation with Lactuca serriola leaves on growth performance, carcass characteristics, meat quality, and its antioxidant stability of Japanese quails. A total of eighty growing quails (1-week old) were distributed into 2 equal groups consisting of 40 birds (5 replicates of 8 birds each). The first group was fed a basal diet without Lactuca serriola leaves (0 g.kg-1 diet) and the second group received diets containing 20 g.kg-1 Lactuca serriola leaves. At age of 6 weeks, quails were slaughtered for meat and carcass examinations. The growth performance for the quails fed with Lactuca serriola leaves diet was similar to that of a control group. Carcass measurements, physical properties, and chemical composition of quail breast meat did not differ between the control and experimental group. However, the inclusion of Lactuca serriola leaves significantly increased the omega-3 polyunsaturated fatty acid content and improved breast meat lipid stability during postmortem refrigerated storage compared to the control diet. In conclusion, dietary supplementation of Lactuca serriola leaves can improve the performance of Japanese quail enrich its meat with an omega-3 polyunsaturated fatty acid, and reduce lipid oxidation during storage.

Quantitative trait loci and candidate genes associated with photoperiod sensitivity in lettuce (Lactuca spp.)

The molecular mechanism of flowering time regulation in lettuce is of interest to both geneticists and breeders because of the extensive impact of this trait on agricultural production. Lettuce is a facultative long-day plant which changes in flowering time in response to photoperiod. Variations exist in both flowering time and the degree of photoperiod sensitivity among accessions of wild (Lactuca serriola) and cultivated (L. sativa) lettuce. An F6 population of 236 recombinant inbred lines (RILs) was previously developed from a cross between a late-flowering, photoperiod-sensitive L. serriola accession and an early-flowering, photoperiod-insensitive L. sativa accession. This population was planted under long-day (LD) and short-day (SD) conditions in a total of four field and screenhouse trials; the developmental phenotype was scored weekly in each trial. Using genotyping-by-sequencing (GBS) data of the RILs, quantitative trait loci (QTL) mapping revealed five flowering time QTLs that together explained more than 20% of the variation in flowering time under LD conditions. Using two independent statistical models to extract the photoperiod sensitivity phenotype from the LD and SD flowering time data, we identified an additional five QTLs that together explained more than 30% of the variation in photoperiod sensitivity in the population. Orthology and sequence analysis of genes within the nine QTLs revealed potential functional equivalents in the lettuce genome to the key regulators of flowering time and photoperiodism, FD and CONSTANS respectively, in Arabidopsis.