Tomato Cultivars Research Articles

Physiological and transcriptomic analysis of tomato in response to sub-optimal temperature stress

ABSTRACT Tomato (Solanum lycopersicum L.) is one of the most important economic crops in China. However, its quality and yield are susceptible to the adverse effects of low temperatures. In our study, two tomato cultivars, showing different tolerance to low temperatures, namely the cold-sensitive tomato cultivar (S708) and cold-tolerant tomato cultivar (T722), were grown at optimal (25/18°C) and sub-optimal (15/10°C) temperature conditions for 5 days. Our study aimed to explore the effect of sub-optimal temperature on fresh weight, chlorophyll content and chlorophyll fluorescence, soluble sugars and proline content of two tomato cultivars. Moreover, we employed RNA-Seq to analyze the transcriptomic response of tomato roots to sub-optimal temperature. The results revealed that S708 showed a more significant reduction in fresh weight, chlorophyll content, photochemical efficiency of PSII (YII), maximum quantum yield of PSII (Fv/Fm), photochemical quenching (qP) and electron transport rate (ETR) compared to T722 under the sub-optimal temperature condition. Notably, T722 maintained higher level of soluble sugars and proline in comparison to S708 uner sub-optimal temperature. RNA-seq data showed that up-regulated DEGs in both tomato cultivars were involved in “plant-pathogen interaction”, “MAPK signaling pathway”, “plant hormone signal transduction”, and “phosphatidylinositol signaling system”. Furthermore, “Amino sugar and nucleotide sugar metabolism” pathway was enriched only in T722. Moreover, under sub-optimal temperature, transcription factor genes and osmoregulation genes showed varying degrees of response in both tomato cultivars. Conclusion: In summary, our results offer detailed insights into the response characteristics of tomato to sub-optimal temperature, providing valuable references for the practical management of tomato crops under sub-optimal temperature condition.

Life Table Parameters of the Tomato Leaf Miner Tuta absoluta (Lepidoptera: Gelechiidae) on Five Tomato Cultivars in China.

Tomato is the most preferred host plant for Tuta absoluta, a newly emerged devastating invasive pest in China. However, no study has evaluated the damage risk of T. absoluta on processed tomato worldwide. In the current study, the life table parameters of T. absoluta were systematically investigated on five tomato cultivars (one fresh tomato cultivar, four processed tomato cultivars) to determine their susceptibility to T. absoluta infestation. T. absoluta had a better population growth ability on the fresh tomato, "Dafen", showing shorter duration of the preadult stage, higher lifetime fecundity, and a higher intrinsic rate of increase compared to four processed tomato cultivars. Meanwhile, the life table parameters of T. absoluta among different processed tomato cultivars also showed significant differences. Th9 was the most susceptible to T. absoluta attack, while Th1902, Heinz1015, and Dimen2272 were the least suitable ones for its development and reproduction. In summary, these tomato cultivars are the most recommended for commercial tomato production to reduce the damage caused by T. absoluta and improve the integrated pest management strategy.

Defective mutations in STAY-GREEN 1, PHYTOENE SYNTHASE 1, and MYB12 genes lead to formation of green ripe fruit in tomato.

Modern tomatoes produce colorful mature fruits, but many wild tomato ancestors form green or gray green ripe fruits. Here, tomato cultivar 'Lvbaoshi' (LBS) that produces green ripe fruits was found to contain three recessive loci responsible for fruit development. The colorless peel of LBS fruits was caused by a 603 bp deletion in the promoter of SlMYB12. The candidate genes of the remaining two loci were identified as STAY-GREEN 1 (SlSGR1) and PHYTOENE SYNTHASE 1 (SlPSY1). SGR1 and PSY1 co-suppression by RNAi converted the pink fruits into green ripe fruits in transgenic plants. An amino acid change in PSY1 and a deletion in the promoter of SGR1 were also identified in several wild tomatoes bearing green or gray ripe fruits. Overexpression of PSY1 from green ripe fruit wild tomatoes in LBS plants could only partially rescue the green ripe fruit phenotype of LBS, and transgenic lines expressing ProSGR1::SGR1 from Solanum pennellii also failed to convert purple-flesh into red-flesh fruits. This work uncovers a novel regulatory mechanism by which SlMYB12, SlPSY1, and SlSGR1 control fruit color in cultivated and some wild tomato species.

Effects of Elicitation on Invitro Regeneration of two Tomato (Solanum lycopersicum L.) Cultivars in Tissue Culture

Exploring alternative avenues, in vitro culture emerges as a promising option for potential bioactive compound sources. However, compared to intact plants, only a few cultures demonstrate efficient synthesis of secondary metabolites. Elicitors have gained prominence as stress agents for enhancing in vitro micropropagation in specific tissues, organs, and cells. Recent advancements in plant tissue culture involve elicitors, opening new possibilities for in vitro production of crucial food crops. This research aimed to investigate the impact of three elicitors (Activane®, Micobiol®, and Stemicol®) on germination and in vitro multiplication of two tomato cultivars explants, employing both direct and indirect in vitro organogenesis. Among the texted elicitors, Micobiol® emerged as a successful elicitor, promoting optimal seed germination, survival, and 100% growth compared to the 80% in the control group. Further, Activane® exhibited a favourable induction response and achieved 96%, 95%, and 100% in weight and diameter of callus, yet various elicitor concentrations did not exert significant influence across treatments. In conclusion, an effective disinfection and in vitro implantation of tomato seeds ensured successful germination, promoting seedling survival and growth. Various elicitors positively impacted in vitro organogenesis, particularly in root induction, with higher survival percentages in acclimatized plants. The study guides future research on elicitor treatments for large-scale tomato in vitro propagation, emphasizing the need to identify optimal elicitor concentrations.

A chromosome-level genome assembly of Solanum chilense, a tomato wild relative associated with resistance to salinity and drought.

Solanum chilense is a wild relative of tomato reported to exhibit resistance to biotic and abiotic stresses. There is potential to improve tomato cultivars via breeding with wild relatives, a process greatly accelerated by suitable genomic and genetic resources. In this study we generated a high-quality, chromosome-level, de novo assembly for the S. chilense accession LA1972 using a hybrid assembly strategy with ~180 Gbp of Illumina short reads and ~50 Gbp long PacBio reads. Further scaffolding was performed using Bionano optical maps and 10x Chromium reads. The resulting sequences were arranged into 12 pseudomolecules using Hi-C sequencing. This resulted in a 901 Mbp assembly, with a completeness of 95%, as determined by Benchmarking with Universal Single-Copy Orthologs (BUSCO). Sequencing of RNA from multiple tissues resulting in ~219 Gbp of reads was used to annotate the genome assembly with an RNA-Seq guided gene prediction, and for a de novo transcriptome assembly. This chromosome-level, high-quality reference genome for S. chilense accession LA1972 will support future breeding efforts for more sustainable tomato production. Gene sequences related to drought and salt resistance were compared between S. chilense and S. lycopersicum to identify amino acid variations with high potential for functional impact. These variants were subsequently analysed in 84 resequenced tomato lines across 12 different related species to explore the variant distributions. We identified a set of 7 putative impactful amino acid variants some of which may also impact on fruit development for example the ethylene-responsive transcription factor WIN1 and ethylene-insensitive protein 2. These variants could be tested for their ability to confer functional phenotypes to cultivars that have lost these variants.

Quantifying terpenes in tomato leaf extracts from different species using gas chromatography-mass spectrometry (GC-MS)

Terpenes play a vital role in plant defense; tomato plants produce a diverse range of terpenes within specialized glandular trichomes, influencing interactions with herbivores, predators, and pollinators. This study employed two distinct methods, namely leaf dip and maceration, to extract trichomes from tomato leaves. Terpene quantification was carried out using Gas Chromatography-Mass Spectrometry (GC-MS). The leaf dip method proved effective in selectively targeting trichome content, revealing unique extraction patterns compared to maceration. The GC-MS method demonstrated high linearity, accuracy, sensitivity, and low limits of detection and quantification. Application of the method to different tomato species (Solanum pennellii, Solanum pimpinellifolium, Solanum galapagense, Solanum habrochaites, and Solanum lycopersicum) identified significant variation in terpene content among these species, highlighting the potential of specific accessions for breeding programs. Notably, the terpene α-zingiberene, known for its repellency against whiteflies, was found in high quantities (211.90–9155.13 μg g−1) in Solanum habrochaites accession PI209978. These findings provide valuable insights into terpenoid diversity for plant defense mechanisms, guiding future research on developing pest-resistant tomato cultivars. Additionally, the study underscores the broader applications of terpenes in agriculture.

Partially Substituting Top-light with Intracanopy Light Increases Yield More at Higher LED Light Intensities

This study compared supplemental white light-emitting diode (LED) light provided on top of the canopy (top-light) or partially on top and partially as intracanopy light (ICL) in high-wire cucumber (Cucumis sativus) and tomato (Solanum lycopersicum) crops. The aim was to determine the effects of partially substituting top-light by ICL on fruit yield and its underlying yield components. For each crop, three replicate Venlo glasshouse compartments were used. Two cucumber (HiPower and Skyson) and two tomato cultivars (Brioso and Merlice) were planted in the second half of Oct 2020 and grown on stone wool for a period of 15 weeks (cucumber) or 20 weeks (tomato). Light was supplied at either a light intensity of 250 or 375 µmol⋅m−2⋅s−1, provided either as 100% top-light or as 67% (2/3) top-light and 33% (1/3) ICL. For cucumber at the higher light intensity, 50% more fruits were retained and for tomato at the higher light intensity, planting density was 50% higher to keep the plants balanced in terms of source-to-sink ratio. Substituting 33% of top-light with ICL resulted on average in an increase of 17% in fresh fruit yield for both cucumber and tomato. This increase was twice as high at the higher light intensity (20% to 24%) compared with the lower light intensity (10% to 12%). For both cucumber and tomato, the higher yield for ICL treatments resulted mainly from higher total plant dry weight, whereas partitioning to the fruits was hardly affected. For both crops, the higher plant dry weight resulted from a higher light use efficiency. Increasing light intensity from 250 to 375 µmol⋅m−2⋅s−1 resulted in 38% higher total daily light integral (including solar radiation) and 36% to 37% higher total plant dry weight in cucumber. In tomato, the higher light intensity resulted in 33% higher daily light integral and 36% to 40% total plant dry weight. These values are in agreement with the rule of thumb that 1% increment in light results in 1% increase in plant growth. For cucumber, partially substituting top-light by ICL as well as increasing light intensity resulted in longer and greener fruits, whereas tomato fruit quality (Brix, pH) was unaffected by ICL or light intensity. In conclusion, partially substituting top-light by intracanopy light increased fruit yield and this was even more so at higher than at lower supplemental light intensities.

Host status of melon, carrot, and Meloidogyne incognita-susceptible and -resistant cotton, cowpea, pepper, and tomato for M. floridensis from California.

The host status of carrot, melon, and susceptible and resistant cultivars of tomato, cotton, cowpea, and pepper for a California isolate of the peach root-knot nematode Meloidogyne floridensis was determined in greenhouse pot experiments. It was compared to a race 3 isolate of M. incognita. Melon was an excellent host for both isolates and roots were heavily galled after the 8-week trial. Carrot was a host for M. incognita, but a poor host for M. floridensis, although both isolates caused similar levels of galling. Susceptible cotton was a good host for M. incognita race 3, but a poor host for M. floridensis. Susceptible tomato, cowpea, and pepper were good hosts for both isolates. The M. incognita resistance in tomato and pepper was broken by M. floridensis. Resistant cowpea was a maintenance host as population levels of M. floridensis remained virtually unchanged over the trial period. We conclude that M. floridensis poses a risk to some important vegetable crops in California, as it reproduces on most vegetable crops, including some cultivars that are resistant to M. incognita. On susceptible crops, the reproduction of M. floridensis was always significantly less than that of M. incognita, and we hypothesize that in mixed species field populations, M. incognita will outcompete M. floridensis. This study demonstrates that efforts to limit the spread and prevent further introductions of M. floridensis in California are important to maintain the effectiveness of plant resistance as a nematode management strategy in vegetable crops.

Efficacy of Fluorinated Nematicides for Management of Root-knot Nematodes in California Processing Tomatoes.

California is the primary US producer of processing tomatoes. After decades-long excellent protection against the common tropical Meloidogyne spp. M. incognita, M. javanica, and M. arenaria (root-knot nematode: RKN) by Mi-resistant tomato cultivars, resistance-breaking RKN populations are spreading throughout the San Joaquin Valley. For some time, nematicidal crop management tools have diminished under CA State regulatory pressure. In recent years, new non-volatile compounds have been developed with novel modes of action. In this project with susceptible processing tomato grown on an M. incognita-infested site, the efficacy of three fluorinated nematicides was evaluated in 10 field trials from 2011 to 2021. Seven trials included fluensulfone, six included fluazaindolizine, and five included fluopyram. On average, tomato root-galling (0 - 10 scale) at harvest was reduced by 3.2, 2.3, and 2.5 by fluazaindolizine, fluensulfone, and fluopyram, respectively, compared to the untreated control. These reductions in root-galling corresponded with estimated yield gains of approximately 21%, 14%, and 15%, respectively, over the untreated control. The reproduction of RKN during the tomato crop was not affected by the nematicides. The tested compounds have a very low acute mammalian toxicity and are more target-specific than previous generations of nematicides. However, there is considerable concern about the persistence of synthetic per- and polyfluoroalkyl substances (PFAS) in the environment, including pharmaceuticals and pesticides containing fluorine with the C-F3 functional group.

Binucleate Rhizoctonia induced tomato resistance against Rhizoctonia solani via affecting antioxidants and cell wall reinforcement

Isolates of Rhizoctonia solani (AG-3 PT, AG-4 HG-I, AG-4 HG-II) and one binucleate Rhizoctonia sp. (BNR) belonging to AG-Bb were investigated for pathogenicity on tomato cultivar Mobil. The BNR isolate revealed the lowest virulence and it was used as biocontrol agent against R. solani AG-4 HG-II, which showed the highest virulence on tomato. Inoculation of tomato plants with the hypovirulent BNR isolate reduced the disease symptoms of R. solani and induced resistance. Resistance induction was observed not only on the plants simultaneously inoculated with BNR and R. solani, but also when the plants were inoculated by the BNR and R. solani with time intervals. The peroxidase (POX), superoxide dismutase (SOD) and catalase (CAT) activities and expression levels of the corresponding genes in tomato plants increased after R. solani or BNR inoculation. The highest level of antioxidant activities and expression of their genes, lignin and callose formation were observed in the plants inoculated with the BNR and R. solani, simultaneously. The BNR inoculation reduced H2O2 accumulation. The highest level of priming was observed for the POX among other antioxidants tested via application of the BNR. Treatment with potassium cyanide (as a POX inhibitor) reduced basal resistance and BNR-induced resistance (BNR-IR) via reduction of lignification and callose deposition in tomato plants. These findings demonstrated the role of antioxidant enzymes, mainly the POX, in both basal resistance and BNR-IR. Therefore, redox state and antioxidants are involved in cell wall strengthening via lignin and callose formation, as important defense components which decrease the pathogen progress in plant tissues.

Comparative study on fruit quality of some Romanian tomato cultivars

Comparative study on fruit quality of some Romanian tomato cultivars

Alternaria diseases on potato and tomato.

Kingdom Fungi, Phylum Ascomycota, Class Dothideomycetes, Order Pleosporales, Family Pleosporaceae, Genus Alternaria. Alternaria spp. adopt diverse lifestyles. We specifically review Alternaria spp. that cause disease in the two solanaceous crops potato (Solanum tuberosum) and tomato (Solanum lycopersicum). They are necrotrophic pathogens with no known sexual stage, despite some signatures of recombination. Symptoms of the early blight/brown spot disease complex include foliar lesions that first present as brown spots, depending on the species with characteristic concentric rings, which eventually lead to severe defoliation and considerable yield loss. Good field hygiene can keep the disease pressure low. Some potato and tomato cultivars show differences in susceptibility, but there are no fully resistant varieties known. Therefore, the main control mechanism is treatment with fungicides.

Field Applications of Fluorinated Nematicides for Meloidogyne enterolobii Management on Tomato.

Mexico is the 8th largest producer of tomatoes. Meloidogyne enterolobii is reported in Sinaloa, affecting tomato cultivars with genetic resistance to Meloidogyne spp. We aimed to evaluate field applications of fluopyram, fluensulfone, and fluazaindolizine treatments for managing M. enterolobii on tomatoes. Experiments were set on raised beds in a shade house. Nematicides were applied via drip irrigation. Under fluopyram treatment, M. enterolobii did not reduce the number of extra-large-size fruits. The number of large-size fruits with fluopyram and fluazaindolizine plus fluopyram treatments was also unaffected by M. enterolobii. Yield from the treatments fluopyram, fluazaindolizine plus fluopyram, and fluensulfone plus fluopyram was similar to the control treatment without M. enterolobii. Finally, fluazaindolizine plus fluopyram, fluopyram, and fluensulfone plus fluopyram treatments showed the highest reduction of root galling. We conclude that the fluopyram was more effective as an individual treatment. Pre-plant applications of fluensulfone and fluazaindolizine reduced the damage to the plant and the loss of yield; however, the complementary application of fluorinated nematicides improved the management of M. enterolobii in the tomato crop.

Profitability and efficiency of conduction systems and optimal tomato density for fresh consumption

This study evaluated the productivity and economic profitability of cultivation systems for the table market. A hybrid tomato cultivar, Fascínio was grown in 12 cultivation systems of the “half stake”, “open V”, and “low” types, with four spacings–0.2, 0.3, 0.4, and 0.5 m between plants and 1.5 m between rows. Eleven fruits were harvested at the mature stage, and the productive (total, commercial, and non-commercial productivity, percentage of losses, and types of damage) and economic (production cost, revenue, and profit) parameters were evaluated. The half-stake and low (both with 0.2 m spacing) cropping systems showed the highest total yields (179 t ha-1), differing from the open V (154.4 t ha-1) and half-stake (0.2 m spacing) systems at higher commercial productivity (158.1 t ha-1). With a production cost below 100 thousand R$ per hectare and a profitability index above 58%, the half-stake and low (0.2 m spacing) cultivation systems proved to be more productive and economically efficient than the open V system, fulfilling the requirements of tomato growers. The creeping system (0.2 m spacing) had the highest percentage of losses (22%) due to non-marketable fruits; Based on damage nature, the half-stake system tomatoes showed black backgrounds and the open and creeping systems showed tomato locules affected by pests.

The crosstalk of far-red energy and signaling defines the regulation of photosynthesis, growth, and flowering in tomatoes

This study investigated the effect of light intensity and signaling on the regulation of far-red (FR)-induced alteration in photosynthesis. The low (LL: 440 μmol m−2 s−1) and high (HL: 1135 μmol m−2 s−1) intensity of white light with or without FR (LLFR: 545 μmol m−2 s−1 including 115 μmol m−2 s−1; HLFR: 1254 μmol m−2 s−1 + 140 μmol m−2 s−1) was applied on the tomato cultivar (Solanum Lycopersicon cv. Moneymaker) and mutants of phytochrome A (phyA) and phytochrome B (phyB1, and phyB2). Both light intensity and FR affected plant morphological traits, leaf biomass, and flowering time. Irrespective of genotype, flowering was delayed by LLFR and accelerated by HLFR compared to the corresponding light intensity without FR. In LLFR, a reduced energy flux through the electron transfer chain along with a reduced energy dissipation per reaction center improved the maximum quantum yield of PSII, irrespective of genotype. HLFR increased net photosynthesis and gas exchange properties in a genotype-dependent manner. FR-dependent regulation of hormones was affected by light signaling. It appeared that PHYB affected the levels of abscisic acid and salicylic acid while PHYA took part in the regulation of CK in FR-exposed plants. Overall, light intensity and signaling of FR influenced plants' photosynthesis and growth by altering electron transport, gas exchange, and changes in the level of endogenous hormones.

Evaluation of Tomato Germplasm against Tomato Brown Rugose Fruit Virus and Identification of Resistance in Solanum pimpinellifolium.

The tomato is one of the most important vegetable crops grown worldwide. Tomato brown rugose fruit virus (ToBRFV), a seed-borne tobamovirus, poses a serious threat to tomato production due to its ability to break the resistant genes (Tm-1, Tm-2, Tm-22) in tomatoes. The objective of this work was to identify new resistant source(s) of tomato germplasm against ToBRFV. To achieve this aim, a total of 476 accessions from 12 Solanum species were tested with the ToBRFV US isolate for their resistance and susceptibility. As a result, a total of 44 asymptomatic accessions were identified as resistant/tolerant, including thirty-one accessions of S. pimpinellifolium, one accession of S. corneliomulleri, four accessions of S. habrochaites, three accessions of S. peruvianum, and five accessions of S. subsection lycopersicon hybrid. Further analyses using serological tests identified four highly resistant S. pimpinellifolium lines, PI 390713, PI 390714, PI 390716, and PI 390717. The inheritance of resistance in the selected lines was verified in the next generation and confirmed using RT-qPCR. To our knowledge, this is a first report of high resistance to ToBRFV in S. pimpinellifolium. These new genetic resources will expand the genetic pool available for breeders to develop new resistant cultivars of tomato against ToBRFV.

Integrated transcriptome and DNA methylome analysis reveal the biological base of increased resistance to gray leaf spot and growth inhibition in interspecific grafted tomato scions.

Grafting is widely used as an important agronomic approach to deal with environmental stresses. However, the molecular mechanism of grafted tomato scions in response to biotic stress and growth regulation has yet to be fully understood. This study investigated the resistance and growth performance of tomato scions grafted onto various rootstocks. A scion from a gray leaf spot-susceptible tomato cultivar was grafted onto tomato, eggplant, and pepper rootstocks, creating three grafting combinations: one self-grafting of tomato/tomato (TT), and two interspecific graftings, namely tomato/eggplant (TE) and tomato/pepper (TP). The study utilized transcriptome and DNA methylome analyses to explore the regulatory mechanisms behind the resistance and growth traits in the interspecific graftings. Results indicated that interspecific grafting significantly enhanced resistance to gray leaf spot and improved fruit quality, though fruit yield was decreased compared to self-grafting. Transcriptome analysis demonstrated that, compared to self-grafting, interspecific graftings triggered stronger wounding response and endogenous immune pathways, while restricting genes related to cell cycle pathways, especially in the TP grafting. Methylome data revealed that the TP grafting had more hypermethylated regions at CHG (H = A, C, or T) and CHH sites than the TT grafting. Furthermore, the TP grafting exhibited increased methylation levels in cell cycle related genes, such as DNA primase and ligase, while several genes related to defense kinases showed decreased methylation levels. Notably, several kinase transcripts were also confirmed among the rootstock-specific mobile transcripts. The study concludes that interspecific grafting alters gene methylation patterns, thereby activating defense responses and inhibiting the cell cycle in tomato scions. This mechanism is crucial in enhancing resistance to gray leaf spot and reducing growth in grafted tomato scions. These findings offer new insights into the genetic and epigenetic contributions to agronomic trait improvements through interspecific grafting.

Application of ethanol alleviates heat damage to leaf growth and yield in tomato.

Chemical priming has emerged as a promising area in agricultural research. Our previous studies have demonstrated that pretreatment with a low concentration of ethanol enhances abiotic stress tolerance in Arabidopsis and cassava. Here, we show that ethanol treatment induces heat stress tolerance in tomato (Solanum lycopersicon L.) plants. Seedlings of the tomato cultivar 'Micro-Tom' were pretreated with ethanol solution and then subjected to heat stress. The survival rates of the ethanol-pretreated plants were significantly higher than those of the water-treated control plants. Similarly, the fruit numbers of the ethanol-pretreated plants were greater than those of the water-treated ones. Transcriptome analysis identified sets of genes that were differentially expressed in shoots and roots of seedlings and in mature green fruits of ethanol-pretreated plants compared with those in water-treated plants. Gene ontology analysis using these genes showed that stress-related gene ontology terms were found in the set of ethanol-induced genes. Metabolome analysis revealed that the contents of a wide range of metabolites differed between water- and ethanol-treated samples. They included sugars such as trehalose, sucrose, glucose, and fructose. From our results, we speculate that ethanol-induced heat stress tolerance in tomato is mainly the result of increased expression of stress-related genes encoding late embryogenesis abundant (LEA) proteins, reactive oxygen species (ROS) elimination enzymes, and activated gluconeogenesis. Our results will be useful for establishing ethanol-based chemical priming technology to reduce heat stress damage in crops, especially in Solanaceae.

Phenylalanine Ammonia-Lyase-Mediated Differential Response of Tomato (Solanum lycopersicum L.) Cultivars with Different Stress Tolerance to Treatment with Low-Molecular-Weight Chitosan

The latest research has shown that chitosan acts as a growth stimulator and elicitor in plants, including resistance to biotic and abiotic factors. However, increasing concentrations could possibly make chitosan a source of stress for plants. In this study, we investigated the effect of low-molecular-weight chitosan hydrolysate on the root development of tomato (Solanum lycoperscum) cultivars Red Cherry, Lel, and Tytan. The growth rate change, together with total phenolic content, phenylalanine ammonia-lyase (PAL) activity, and gene expression, were studied in relation to tomatoes. High concentrations of chitosan negatively affect the growth of tomato seedlings and contribute to changes in the tropism of the seedling roots. After the addition of chitosan hydrolysate, the PAL activity and the total phenolic content decreased 24 h later. PAL is a key enzyme in the biosynthesis of many plant stress factors. An analysis of the tomato PAL gene family was carried out. The SlPAL gene expression in the seedlings of cv. Cherry increased 1.5 times after 48 h, while in cv. Lel, the expression stably decreased in the presence of chitosan. The obtained results are supposed to aid our understanding of the mechanisms underlying the effects of chitosan on plant development and further its successful application in agriculture as well as in research on plant stress.

Reaction of Brazilian genotypes of pulses (pea, chickpea and lentil) to the root-knot nematode Meloidogyne enterolobii

Summary The root-knot nematode, Meloidogyne enterolobii, is an important pathogen of numerous crops, including the so-called pulses. Hence, it is necessary to identify genetic resistance, as it is the most efficient, cost-effective, and environmentally sound way to manage nematodes in the field. The objective of this study was to screen a Brazilian germplasm collection of pulse crops (peas, chickpeas, and lentils) comprising accessions from the Embrapa Germplasm Bank and commercial cultivars against M. enterolobii under glasshouse conditions. The experiment was conducted with 23 treatments (genotypes), i.e., 14 pea, six chickpea and one lentil genotype, and two tomato cultivars, ‘Rutgers’ (susceptible) and ‘Nemadoro’ (resistant). Each plant (replication) was inoculated with 5000 eggs and second-stage juveniles (J2) of M. enterolobii and evaluated 65 days after inoculation, considering the following variables: gall index, egg mass index, number of eggs per g of roots, and reproduction factor. The experiments were conducted at two independent time points (summer and autumn/winter). Results showed that all 23 plant genotypes were susceptible to the nematode, with pea genotype ‘Itapuã’ being intolerant to infection. Cultivation of pulse crops has been steadily increasing both in Brazil and worldwide. Our research findings make a valuable contribution to the ongoing efforts to identify genetic resistance to nematode pathogens that can significantly affect the productivity of these crops. By identifying and developing resistant genotypes, pulse crop yields can be safeguarded, and sustainable agricultural practices can be supported.