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List of crisphead cultivars selected for heat tolerance trials from an initial screening of lettuce germplasm.
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Lettuce ( Lactuca sativa L.) is a cool season crop that is vulnerable to high temperature stress, which promotes bolting and decreases yield and quality. It is anticipated that climate change may lead to higher temperatures in current lettuce growing areas in the United States, thereby negatively affecting lettuce production and possibly resulting...
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Context 1
... materials. Twenty-five crisphead lettuce cultivars (Table 1) were selected to test their responses to high temperature stress in five different environments based on their performances in preliminary growth chamber tests of more than 700 lettuce cultivars each with 16 3-week-old seedlings exposed to 43 °C 12 h day/35 °C 12 h night, 450 mmol · m -2 · s -1 photosynthetic photon flux density for 7 d, and then evaluated for leaf injury (rated on a 0-6 scale: 0, no injury; 1, <1/2 leaf edge injured; 2, >1/2 leaf edge injured; 3, <1/3 leaf area injured; 4, <2/3 leaf area injured; 5, >2/3 leaf area injured; 6, plant dead), reduction in leaf fresh weight, and percent seedling survival compared with controls at 25 °C day/ 17 °C night (Lafta and Mou, unpublished data). Several of the cultivars were developed outside the United States (e.g., 'Reine des Glaces'). ...Context 2
... maturity Percent bolted heads D313 D512 W313 W512 S612 Mean (G) D313 D512 W313 W512 ...Context 3
... (°C) Wind velocity (km·h -1 ) Day length Precipitation (cm ) Maximum Mean Minimum 2012 2013 2012 2013 2012 2013 2012 2013 2012-13 2012 2013 WSREC March 20 24 13 16 7 7 13 5 11h 57m 0.08 0.84 April 24 28 16 19 8 9 13 7 13h 08m 0.08 0.02 May 31 31 21 22 11 12 15 9 14h 07m 0.01 0.05 June 33 36 23 26 13 15 16 9 14h 37m 0.00 0.00 July 36 39 26 29 16 18 11 7 14h 23m 0.00 0.00 August 38 38 27 27 17 17 13 8 (Table 7). Warmer temperatures were registered at DREC during these experiments, where mean daily temperatures ranged from 18 to 35 °C in 2012 and 20 to 36 °C in 2013 with a maximum of 41 °C. ...Similar publications
Background
The projected increase in global temperature is expected to negatively impact food production in many regions. Rice exposure to heat stress can limit plant growth in different stages, especially at the seedling stage. In this experiment, two Indica parental lines N22 (heat tolerant) and BIM (heat sensitive) along with their F 2 hybrid we...
Citations
... In suboptimal temperature conditions, mainly when the temperature is above 30 °C, the leaves become sharpened and have longer internodes, which decreases their commercial value [4]. In addition, high temperatures cause rib discoloration, tip burning, premature bolting, and ribbiness [5,6]. Investigating the effects of heat stress on lettuce, Zhao et al. [7] found changes in the plant biomass and leaf shape. ...
... The experimental design involved completely randomized blocks with four replications, and the experimental plot was represented by ten 5L pots containing the genotypes mentioned above. As stated by Lafta et al. [6], the time lapse to anthesis can indirectly assess heat tolerance in lettuce. Hence, the heat tolerance of the lettuce genotypes was evaluated by counting the number of days until the first anthesis. ...
Lettuce is an important cool-temperature crop, and its principal abiotic stress is low heat tolerance. Lettuce production has become more challenging in the context of global warming changes. Hence, the main objective of this research was to investigate the relationship between stability and lettuce heat tolerance. Field and greenhouse trials were run in 2015 (summer) and 2016 (fall and spring). The environments were composed of a combination of season and place (field, glass, and plastic greenhouse), and the assessed genotypes were BRS Leila and Mediterrânea, Elisa, Everglades, Simpson, and Vanda. Statistical analysis showed a significant effect (p < 0.05) of environments (E), genotypes (G), and the GEI. BRS Leila, Elisa, and BRS Mediterrânea showed the greatest means to the first anthesis in suitable environments (milder temperatures). Among these cultivars, BRS Mediterrânea was the most stable and adapted to hot environments. The environmental conditions studied in this research, mainly high temperatures, could become a reality in many lettuce-producing areas. Therefore, the results can help indicate and develop lettuce varieties with greater heat tolerance.
... The genetic variability among genotypes could be used as an important source for drought stress screening. Plant breeders have traditionally addressed the issue of environmental stress by selecting for performance adaptability to a range of environmental conditions using rigorous testing and biometric methods (Blum 1988, Meena et al. 2014, Lafta et al. 2020, Roeber et al. 2020, Formisano et al. 2021. However, the genetic pathways that enable these traits are largely unknown because drought tolerance is the result of a complex interaction of morphological, physiological, and biochemical traits, and these traits could be used to screen for acceptable plant ideotypes. ...
... Thus, characterising accessions/germplasm for diversity is essential for germplasm utilization. This further reiterates that morpho-agronomic characterization and phenotyping, though basic, are pivotal for trait selection for crop improvement, in particular for stress tolerance (Lafta et al. 2020, Formisano et al. 2021. ...
This study characterized 33 pearl millet accessions for drought tolerance and expression patterns of drought-related genes (P5CS and DREB1A) at the pre-fruiting stage. The accessions were evaluated for variability and screened for drought tolerance. Five weeks after sowing, we screened the pearl millet accessions for morpho-agronomic variability and to determine their tolerance to water stress over 14 days. From these screenings, we identified the most and least tolerant accessions (NGB00886 and NGB00885, respectively) for gene expression studies. To determine the expression pattern of the DREB1A and P5CS genes, RNA was extracted from leaf samples and converted to cDNA for analysis via quantitative real-time polymerase chain reaction. The study found significant variation (p > 0.05) in morphological traits among the pearl millet accessions. The principal component analysis showed three components accounted for over 90% of the variance. Additionally, there were significant (p < 0.01, p > 0.05) correlations among the plant growth attributes of the accessions. At genetic index 15, the accessions were grouped into five distinct clusters corresponding to their genetic similarities. Gene expression studies showed differences in the Ct values of the reference gene (ACT1) against the target genes. The expression pattern showed that DREB1A was up-regulated in the most tolerant and down-regulated in the least tolerant, while P5CS was up-regulated in both accessions. The study concluded that there are morphological variations among the accessions in response to water stress at the pre-fruiting stage, and the up- and down-regulation of DREB1A and P5CS genes are involved in the mechanism of regulation of water stress modulations in pearl millet.
Key words
germplasm; drought tolerance; pearl millet; quantitative real-time polymerase chain reaction; reference genes
... Instead, Mou [19] proposed a classifcation system comprising six primary lettuce types, categorized based on distinct characteristics such as had formation, leaf shape, size, stem type, and texture as follows: butterhead lettuce, crisphead lettuce, Latin lettuce, leaf or cutting lettuce, romaine or cos lettuce, and stem or stalk lettuce. A cultivar is a variety selected for desirable traits for cultivation, and several researchers have tried to select a pure line for their own purposes: higher yield, appearances [20], heat resistance [21], etc. ...
Heukharang (Lactuca sativa L.), the artificially developed lettuce cultivar for enhancement of lactucin content, exhibits antioxidant activities and sleep-promoting effects. However, potential of Heukharang as a raw material for the skin-whitening agent has not been investigated yet. This study evaluated the effects of Heukharang extract (HHE) on α-melanocyte-stimulating hormone (α-MSH)-induced melanogenesis in vitro and in vivo models. Our findings revealed that HHE (25–100 μg/mL) effectively inhibited α-MSH-induced melanin synthesis in both 2D and 3D cell culture environments without compromising the viability of the B16F10 murine melanoma cell line. Furthermore, HHE suppressed intracellular tyrosinase activity, along with both gene and protein expression of tyrosinase (TYR) and tyrosinase-related protein (TRP)-1 and TRP-2. HHE downregulated the mRNA level of microphthalmia-associated transcription factor (MITF) and the phosphorylation of cAMP response element-binding (CREB) protein. The antimelanogenic activity of HHE (50 and 100 μg/mL) was also confirmed using a zebrafish embryo model, highlighting its efficacy in inhibiting α-MSH-induced melanogenesis through the downregulating CREB/MITF/TYR signaling pathways. Moreover, our study demonstrated that a corresponding amount of lactucin (5–20 μM) to the HHE inhibited and regulated melanogenesis. These results collectively suggest that HHE, enriched with lactucin, holds promise as a potential skin-whitening agent for nutricosmetic industries.
... A unique approach to overcome the difficulty of producing lettuce during warmer temperature is to develop heat-tolerant lettuce cultivars using classic breeding approaches. Leaf and iceberg lettuce varieties have been identified to have a tolerance for warmer temperatures when planted in warmer conditions (Holmes et al. 2019;Lafta et al. 2017Lafta et al. , 2021. Some of the identified heat-tolerant accessions have less tipburn, bolting, and other physiological damage when cultivated in harmful conditions (Lafta et al. 2017(Lafta et al. , 2021. ...
... Leaf and iceberg lettuce varieties have been identified to have a tolerance for warmer temperatures when planted in warmer conditions (Holmes et al. 2019;Lafta et al. 2017Lafta et al. , 2021. Some of the identified heat-tolerant accessions have less tipburn, bolting, and other physiological damage when cultivated in harmful conditions (Lafta et al. 2017(Lafta et al. , 2021. Identifying additional heat tolerance in all types of lettuce is needed because breeders will have to improve tolerance in all horticultural types to meet market demands. ...
... Heat tolerance was observed in leaf and crisphead lettuce germplasm planted in field locations with warm temperatures (Lafta et al. 2017(Lafta et al. , 2021. These lettuce accessions produced an acceptable head weight (HW) and had less tipburn and bolting. ...
Warmer temperatures during crop production are not desirable for a cool-season crop such as lettuce ( Lactuca sativa L.). Lettuce is among the top 10 most consumed vegetables in the United States. Production of this vegetable is concentrated mostly in temperate areas of California, and during the wintertime in Arizona and Florida as a result of their mild climatic conditions. Heat-tolerant cultivars are needed for the leafy vegetable industry to continue thriving. However, there is very little information on heat-tolerant germplasms of lettuce that can be used as a source to improve heat tolerance in lettuce. This is particularly important in romaine and butterhead lettuce, which are two morphological types with increasing demand in the market. Therefore, research was conducted to identify germplasm that performs acceptably in warmer regions in the western United States. This investigation also aimed to understand the reaction of varieties to different environments, which could help plant breeders select and evaluate lettuce plants during the breeding process. Twenty-three and 25 accessions of romaine and butterhead lettuce, respectively, were planted in five trials near Holtville, CA, USA: Five Points, CA, USA, under warmer temperatures and Salinas, CA, USA, under cooler temperatures. Romaine genotypes Bambi, Blonde Lente a Monter, Medallion MT, and Red Eye Cos; and butterhead genotypes Butter King and Margarita had no bolting, an acceptable head weight, short cores, and acceptable head height. Head weight and related traits (including core length, height, width, etc.) and heat-related disorders were significantly different across multiple experiments, indicating genetic variation. The major component of the phenotypic variation in these experiments was a result of environmental factors. Therefore, plant breeders may still need to evaluate progeny in multiple trials and multiple locations to select heat-tolerant romaine and butterhead lettuce effectively.
... Also, a long photoperiod can cause premature stem elongation and initiate the flowering phase . Consequently, plants lose marketable value and quality for processing, resulting in a poor head density, and bitter taste (Lafta et al., 2021). ...
... The demand for vegetables available year-round has driven the horticultural sector to deseasonalize lettuce production by extending its cultivation into summer (Fu et al., 2012). As a species well-adapted to winter and spring microclimatic conditions, the high temperatures and light intensity typical of Mediterranean summers could reduce yield, especially in protected cultivation (Ilić et al., 2017;Lafta et al., 2021). In this scenario, plant biostimulants could be considered a practical tool to improve productivity, especially under unfavorable growing conditions (Di Mola et al., 2021;Du Jardin, 2015). ...
... Similar to findings in previous studies on lettuce (Cristofano et al., 2021;Sabatino et al., 2021), arugula (Caruso et al., 2019), and celery (Consentino et al., 2020), the application of V-PH, regardless of cultivar, significantly increased fresh yield (+4.5%), emphasizing the advantage of using biostimulants under suboptimal growing conditions (Figure 2). Considering that optimal temperatures for lettuce growth range from 18 to 28°C, in our experiment, the average temperature was 33,4°C, a condition that, as observed by Al-Said et al. (2018) and Lafta et al. (2021), induces alterations in water relations, photosynthetic activity, osmolyte accumulation and hormone production. This improvement could be explained as an effect of modulation of biometric parameters, consistent with increases in fresh leaf weight (5.4%) and leaf area (5.77%), which increased total dry weight (19.23 g plant -1 ). ...
... Plants with adequate capacity to move Ca through transpiration can produce biomass effectively to support the plant growth rate without tipburn risk. A cultivar's capacity to transport Ca relies on the genetics of that cultivar as well as the environmental conditions, reflecting the results of tipburn susceptibility of different cultivars in different geographic locations as reported by Lafta et al. (2021) and Jenni and Hayes (2010). For each cultivar, the transpiration rate to supply Ca must be adequate to support leaf expansion, which may vary among the genetics of each cultivar. ...
... However, because outer leaf Ca has no correlation with inner leaf Ca concentration (data not shown), we do not think this analysis is representative of Ca requirements to prevent tipburn. The ability of each cultivar to drive xylem transport of Ca is linked to genotype, environment, and genotype × environment interactions when comparing cultivars across multiple open-field locations (Jenni and Hayes 2010;Lafta et al. 2021). In our experiment, leaf tissue Ca concentration for inner and outer leaves varied among and within cultivars, but the inner-to-outer Ca ratio was similar. ...
Low evaporative conditions in indoor (vertical) farms reduce mass-flow-driven transport of calcium (Ca), resulting in tipburn of lettuce. Lettuce tipburn symptoms develop along the margins of young leaves and the growing shoot tip, where necrotic tissue forms as a result of Ca deficiency. For indoor farms, lettuce tipburn poses a major economic risk because the crop becomes unmarketable as a result of its appearance. Difference in tipburn sensitivity among cultivars has been thought to be related to differences in growth rate, morphology, or anthocyanin production, whereas most commercial lettuce cultivars have been known to express tipburn symptoms in the indoor farm setting. We created a tipburn-inducing growing condition in walk-in growth chambers that limits plant potential transpiration rate while achieving relatively high growth rates, and examined 10 commercial cultivars selected for tipburn sensitivity. Selected cultivars differ in morphology (butterhead, romaine, and leafy type) and color (red or green; resulting from anthocya-nin production). All cultivars expressed visually detectable tipburn symptoms 22 ± 2.6 days after transplanting, and varied tipburn rates of 7% to 41% of all leaves at the time of harvest (28 days after transplanting). Despite cultivar-specific variation, neither lettuce morphology nor anthocyanin content were significantly correlated with the incidence or severity of tipburn. However, cultivars recommended for "indoor" production by seed suppliers had less tipburn severity than those recommended for outdoor or both indoor and outdoor production systems. Although tipburn risk may vary under other environmental conditions, low evaporative conditions in this experiment caused tipburn symptoms in all tested cultivars at varying degrees of severity. Cultivar-specific average yield and tipburn severity were not correlated with the Ca concentrations in the inner leaves, suggesting that the amount of tissue Ca required to prevent tipburn is cultivar specific and not related to yield. Our selected tipburn-inducing condition was found to be effective in comparing tip-burn sensitivity of lettuce cultivars for indoor farm settings, and similar fast-growing but low-evaporative conditions should be used to assess cultivars for indoor farm production.
... This process is referred as bolting and is characterized by the elongation of plant stem followed by flowering, which drastically reduces yield and marketability of heads ( Fig. 1-2) (Silva et al., 1999). Genetic variability for yield under warmer conditions and heat-related traits, such as bolting and tipburn in lettuce, has been previously identified through screening experiments (Kreutz et al., 2021;Lafta and Mou, 2013;Lafta et al., 2017;Lafta et al., 2021). As certain lettuce producing regions are becoming warmer with climate change, currently lettuce breeding programs are focused on the development of cultivars tolerant to warmer temperatures. ...
... Most of the G×E studies in lettuce focused on several traits such as tipburn, rib discoloration, stem length, yield, and heat tolerance, in which G×E was an important component of the genetic variation (Eenink and Smeets, 1978;Jenni and Hayes, 2010;Jenni and Yan, 2009;Lafta et al. 2017;Lafta et al., 2021). For such traits, G×E interactions were influenced by macro and microenvironmental factors, including photoperiod and light intensity, temperature, growing seasons; in most cases G×E interactions were identified as a crossover type (Jenni and Yan, 2009;Kreutz et al. 2021), meaning that breeders must conduct evaluations in multi-location or in occasions in multi-year trials. ...
... These results are in accordance with previous studies in which adaptability of lettuce accessions to certain locations influenced the performance of plants. Lettuce cultivars bred for warmer environments did not produce marketable heads when planted under mild temperatures in California (Lafta et al., 2021). Similarly, lettuce accessions locally adapted to Florida conditions showed reduced weight loss during postharvest storage when compared to non-adapted germplasm (Belisle et al., 2021). ...
... Although nutrient solution concentration of Ca is adequate and no deficiency symptoms appear in the roots , best assessments suggest that Ca is not translocated to young tissues at a rate commensurate with the demand for growth . Tipburn can limit leaf expansion, reducing yield and marketable quality due to the poor visual appearance Lafta et al., 2021). The issue is most highly reported in lettuce types for morphology that encloses the meristem and young leaves with larger, expanded, or mature leaves. ...
... This QTL was determined to be a useful candidate for breeding tipburn resistance using marker assisted selection (MAS). Lafta et al. (2021) studied lettuce heat-tolerance, finding that genotype, environment, and the interaction of genotype × environment all have significant effects on tipburn sensitivity. Therefore, environmental variation and genetic susceptibility are highly linked to tipburn phenotypes seen in production. ...
... The biggest limiting factors for breeding improvement of tipburn-resistant lettuce for CEA are a) time requirements of breeding programs and b) the number of cultivars that are being bred for tipburn resistance. The studies mentioned previously (Jenni et al., 2013, Lafta et al., 2021, Macias-González, 2019 focus mainly on crisphead lettuce, but IFs often grow multiple types of lettuce (and cultivars within these types) at once, or over the course of the year, to cater to market niches (high anthocyanin content, nutritional content, flavor, appearance, high yield, lettuce type, e.g., Romaine, butterhead, leaf, etc.). In just one seed company website, 139 cultivars of lettuce are offered, of which dozens are recommended for hydroponic use specifically in greenhouses and indoor farms (https://www.rijkzwaanusa.com/crop/lettuce, ...
Indoor vertical farming has become increasingly popular in the United States due to the ability to grow fresh produce year-round. However, among other challenges to indoor farmers, is the issue of lettuce (Lactuca sativa) tipburn, a localized calcium deficiency disorder that causes marginal necrosis of leaves. Tipburn can cause significant economic losses and decrease the quality of the crop. Indoor farms generally encounter tipburn due to environmental conditions limiting transpiration that reduces supply of calcium to young, expanding leaves. During fast growth of lettuce, calcium supply is unable to meet the demand of growth, resulting in the deficiency. Therefore, evaluated tipburn risk under selected environmental conditions to induce tipburn and then examined two different lighting methods to reduce the risk of tipburn. We found that tipburn severity of ten commercial lettuce cultivars varied widely. However, those cultivars that had been developed specifically for indoor production had lower rates of tipburn than those recommended for outdoor cultivation or both indoor and outdoor production. Morphology or leaf color had no relationship with tipburn risk. Further, we found that average tissue calcium concentrations of inner leaves were not associated with shoot fresh mass or tipburn severity between cultivars. Therefore, shoot biomass or leaf calcium concentration is not indicative of tipburn risk. To develop alternative strategies that reduce tipburn of lettuce, we applied a reduced daily light integral (DLI) during the fast-growing stage of lettuce at the end of cultivation (final 12 d of 28-d production). This strategy resulted in less tipburn due to
lower light limiting the yield of lettuce. For one highly tipburn-sensitive cultivar, we found that limiting yield under the lowest end-of-production DLI treatment reduced tipburn severity enough to increase marketable biomass. Therefore, reduced end-of-production DLI has the potential to increase revenue contribution for some lettuce cultivars in indoor farms. In another experiment, we examined the application of dim nighttime (8 h) lighting of blue or 4:1 blue: red light to increase stomatal conductance and enhance transpiration to increase the supply of calcium. It has been reported that the stomata of plants can be opened to increase stomatal conductance by blue or blue and red light at low intensities without contributing to plant growth. However, although nighttime lighting was able to increase nighttime stomatal conductance of lettuce, calcium concentration in leaves was not increased and tipburn severity was the same as with nighttime darkness. In a follow-up experiment, we confirmed that nighttime dim blue light did not offer a benefit in reducing tipburn of lettuce, but increasing airflow using fans eliminated the deficiency. Results from these several experiments suggest that lettuce tipburn risk seems inherent to the genetics of individual cultivars and not morphological categorizations. To mitigate tipburn of lettuce in indoor farms, end-of-production reduced DLI lighting can be applied to increase marketable yield of highly tipburn-sensitive lettuce, but increasing downward airflow remain the most effective method to reduce tipburn risk.
... One of the main methods of overcoming temperature limitations for lettuce production is cultivar selection (Wien 1997). Seed companies have many listed heat-tolerant lettuce cultivars, some of which have been evaluated in different locations (Dufault et al. 2009;Kolbe et al. 2019;Lafta et al. 2021) and many cultivars have been found to be heat tolerant in specific locations. Heat tolerance is the capacity of plants to function and remain productive under high temperature stress (Lafta et al. 2017). ...
Lettuce ( Lactuca sativa ) is a high-value crop cultivated worldwide. Harvested lettuce acreage in New Mexico, USA, trails the leading lettuce production states (California, Arizona), but growers in New Mexico are interested in expanding their production. For New Mexico farmers to increase lettuce production to reach new markets, information on heat-tolerant cultivar performance is needed. This study was conducted to evaluate six lettuce cultivars described as heat tolerant by seed suppliers or other sources. In 2020 and 2021, we assessed two butterhead types, ‘Anuenue’ and ‘Mikola RG10’; two green leaf types, ‘Muir’ and ‘Tropicana’; and two romaine types, ‘Parris Island Cos’ and ‘Sparx’, in the Jose Fernandez Garden at the New Mexico State University Heritage Farm in Las Cruces, NM. To determine which cultivars and types of lettuce are better suited for southern New Mexico, we measured these variables: marketable harvest weight, number of days from transplant to first bolt, and number of days from transplant to 50% bolted. In 2020, ‘Sparx’, a romaine-type lettuce, had, on average, 32% higher yield compared with the other lettuce types. In 2021 both romaine-type cultivars, Sparx and Parris Island Cos, produced 19% more marketable yield than the other lettuce cultivars. In 2020, ‘Sparx’ was the last to bolt and to reach the 50% bolted stage, whereas in 2021 ‘Mikola RG10’ and ‘Muir’ were the last cultivars to bolt and reach the 50% bolted stage. These results suggest that ‘Sparx’ would be a good potential candidate for farmers in southern New Mexico. ‘Mikola RG10’ and ‘Muir’, butterhead and green leaf type, respectively, demonstrated slower bolting in 2021, indicating they may be useful cultivars for extending lettuce harvest in New Mexico.
