Phytoene synthase 1 (Psy-1) and lipoxygenase 1 (Lpx-1) Genes Influence on Semolina Yellowness in Wheat Mediterranean Germplasm

Phytoene synthase 1 (Psy1) and lipoxygenase 1 (Lpx-1) are key genes involved in the synthesis and catalysis of carotenoid pigments in durum wheat, regulating the increase and decrease in these compounds, respectively, resulting in the distinct yellow color of semolina and pasta. Here, we reported new haplotype variants and/or allele combinations of these two genes significantly affecting yellow pigment content in grain and semolina through their effect on carotenoid pigments. To reach the purpose of this work, three complementary approaches were undertaken: the identification of QTLs associated to carotenoid content on a recombinant inbred line (RIL) population, the characterization of a Mediterranean panel of accessions for Psy1 and Lpx-1 genes, and monitoring the expression of Psy1 and Lpx-1 genes during grain filling on two genotypes with contrasting yellow pigments. Our data suggest that Psy1 plays a major role during grain development, contributing to semolina yellowness, and Lpx-1 appears to be more predominant at post-harvest stages and during pasta making.info:eu-repo/semantics/publishedVersio

Quantitative trait loci associated with longevity of lettuce seeds under conventional and controlled deterioration storage conditions

Lettuce (Lactuca sativa L.) seeds have poor shelf life and exhibit thermoinhibition (fail to germinate) above ∼25°C. Seed priming (controlled hydration followed by drying) alleviates thermoinhibition by increasing the maximum germination temperature, but reduces lettuce seed longevity. Controlled deterioration (CD) or accelerated ageing storage conditions (i.e. elevated temperature and relative humidity) are used to study seed longevity and to predict potential seed lifetimes under conventional storage conditions. Seeds produced in 2002 and 2006 of a recombinant inbred line (RIL) population derived from a cross between L. sativa cv. Salinas×L. serriola accession UC96US23 were utilized to identify quantitative trait loci (QTLs) associated with seed longevity under CD and conventional storage conditions. Multiple longevity-associated QTLs were identified under both conventional and CD storage conditions for control (non-primed) and primed seeds. However, seed longevity was poorly correlated between the two storage conditions, suggesting that deterioration processes under CD conditions are not predictive of ageing in conventional storage conditions. Additionally, the same QTLs were not identified when RIL populations were grown in different years, indicating that lettuce seed longevity is strongly affected by production environment. Nonetheless, a major QTL on chromosome 4 [Seed longevity 4.1 (Slg4.1)] was responsible for almost 23% of the phenotypic variation in viability of the conventionally stored control seeds of the 2006 RIL population, with improved longevity conferred by the Salinas allele. QTL analyses may enable identification of mechanisms responsible for the sensitivity of primed seeds to CD conditions and breeding for improved seed longevity

A genetic locus and gene expression patterns associated with the priming effect on lettuce seed germination at elevated temperatures

Seeds of most cultivated varieties of lettuce (Lactuca sativa L.) fail to germinate at warm temperatures (i.e., above 25–30°C). Seed priming (controlled hydration followed by drying) alleviates this thermoinhibition by increasing the maximum germination temperature. We conducted a quantitative trait locus (QTL) analysis of seed germination responses to priming using a recombinant inbred line (RIL) population derived from a cross between L. sativa cv. Salinas and L. serriola accession UC96US23. Priming significantly increased the maximum germination temperature of the RIL population, and a single major QTL was responsible for 47% of the phenotypic variation due to priming. This QTL collocated with Htg6.1, a major QTL from UC96US23 associated with high temperature germination capacity. Seeds of three near-isogenic lines (NILs) carrying an Htg6.1 introgression from UC96US23 in a Salinas genetic background exhibited synergistic increases in maximum germination temperature in response to priming. LsNCED4, a gene encoding a key enzyme (9-cis-epoxycarotinoid dioxygenase) in the abscisic acid biosynthetic pathway, maps precisely with Htg6.1. Expression of LsNCED4 after imbibition for 24 h at high temperature was greater in non-primed seeds of Salinas, of a second cultivar (Titan) and of NILs containing Htg6.1 compared to primed seeds of the same genotypes. In contrast, expression of genes encoding regulated enzymes in the gibberellin and ethylene biosynthetic pathways (LsGA3ox1 and LsACS1, respectively) was enhanced by priming and suppressed by imbibition at elevated temperatures. Developmental and temperature regulation of hormonal biosynthetic pathways is associated with seed priming effects on germination temperature sensitivity

An update on genetically modified crops

A. R. Schwember. 2008. An update on genetically modified crops. Cien. Inv. Agr. 35(3):231-250. Genetically modified (GM) crops were introduced in the mid 1990s and two principal transgenic technologies currently domínate the market, herbicide-tolerant (HT) crops and insect-resistant crops (Bacillus thuringiensis (Bt) crops). HT crops have simplified weed management practices, reduced crop production costs, and have had positive effects on the environment. However, there are concerns about the potential development of weeds resistant to glyphosate, the main herbicide employed with HT crops. A second major worry associated with the use of HT crops is the potential introgression of genes from GM crops into wild relatives (i.e. gene flow) and its potential impact on natural ecosystems. Bt crops have increased yields and reduced the use of insecticides, providing benefits for human health and the environment. However, the potential development of resistance to the Bt toxin by insect pests and the indirect damage of Bt toxins to non-target species are major concerns related to their use. Different strategies to mitígate and elimínate the problems associated with the use of GM crops are discussed in the paper. The next step in plant biotechnology is the reléase of nutrí ti onally-enhanced components in seeds that will benefit humans directly.Los cultivos genéticamente modificados (GM) fueron introducidos a mediados de los noventa y hay actualmente dos tecnologías principales de transgénicos en el mercado,los cultivos tolerantes a los herbicidas (HT) y los cultivos resistentes a insectos (cultivos Bacillus thuringiensis (Bt)). Los cultivos HT han simplificado y reducido los costos de manejo de malezas a los productores y han favorecido el medio ambiente. Sin embargo, existe inquietud por el desarrollo potencial de malezas resistentes al glifosato, el principal herbicida empleado en cultivos HT. Una segunda trascendental preocupación asociada al uso de cultivos HT es la introgresión potencial de genes desde los cultivos GM a las especies cercanas nativas (flujo génico) y su impacto en los ecosistemas. Los cultivos Bt han incrementado los rendimientos, reducido el uso de insecticidas, lo que ha consiguientemente beneficiado la salud de los productores y el ambiente. Sin embargo, el desarrollo potencial de resistencia de los insectos a las toxinas Bt y el daño indirecto de las toxinas Bt a especies no albo a éstas constituyen problemas relevantes relacionados al uso de cultivos Bt. Diferentes estrategias para mitigar y eliminar los problemas asociados al uso de transgénicos son discutidas en el artículo. La próxima etapa en biotecnología vegetal es la introducción de semillas mejoradas en su composición nutritiva, lo que va a beneficiar a los consumidores directamente

Improving durum wheat (Triticum turgidum L. var durum) grain yellow pigment content through plant breeding

A. Schulthess, and A.R. Schwember. 2013. Improving durum wheat (Triticum turgidum L. var durum) grain yellow pigment content through plant breeding. Cien Inv. 40(3): 475-490. Wheat grain yellow pigment content (GYPC) is an important trait that determines pasta quality. The main objective of this review is to examine the genetics regulating GYPC to enhance it through breeding, leading to improved pasta quality. Although GYPC is a polygenic trait, its high heritability has facilitated breeding internationally. GYPC is influenced by one or two major loci with additive effects plus several minor genes, and there is evidence showing that the phytoene synthase loci PSY1A and PSY1B are strong candidate genes that regulate GYPC. Nine Chilean durum wheat (Triticum turgidum L. var. durum) genotypes showed intermediate to low levels of GYPC based upon both phenotypic and genotypic data. The next step is to improve GYPC in those materials by introgressing the high-yellowness PSY1 allelic variants (i.e., the PSY1Ao allele and the PSY1Bb allele) using plant breeding strategies such as backcrossing and marker-assisted selection.A. Schulthess y A.R. Schwember. 2013. Mejora del contenido de pigmentos amarillos del grano de trigo candeal (Triticum turgidum L. var durum) a través de fitomejoramiento. Cien Inv. Agr. 40(3): 475-490. El contenido de pigmentos amarillos del grano de trigo (GYPC) es un rasgo de calidad importante que determina la calidad de la pasta. El objetivo principal de esta revisión de literatura es examinar la regulación genética de la amarillez endospermática para mejorar el GYPC a través del fitomejoramiento, lo que finalmente se traduciría en una mejor calidad de la pasta. Aunque el GYPC es un rasgo poligénico, es un carácter altamente heredable, aspecto que ha facilitado el trabajo de mejoramiento a nivel internacional. El GYPC está controlado por uno o dos loci principales de efectos aditivos, además de varios genes menores, y existe evidencia que demuestra que los loci de la fitoeno sintasa PSY1A y PSY1B son los principales genes candidatos que regulan el GYPC. Nueve genotipos chilenos de trigo candeal (Triticum turgidum L. var. durum) mostraron niveles intermedio a bajos de GYPC basado en datos fenotípicos y genotípicos. El siguiente paso consistirá en incrementar el GYPC de estos materiales, introgresando las variantes alélicas de PSY1 de alta amarillez (es decir, el alelo PSY1Ao y el alelo PSY1Bb) a través de estrategias de fitomejoramiento como el retrocruzamiento y la selección asistida por marcadores moleculares

Quantitative trait loci associated with longevity of lettuce seeds under conventional and controlled deterioration storage conditions.

Lettuce (Lactuca sativa L.) seeds have poor shelf life and exhibit thermoinhibition (fail to germinate) above ∼25°C. Seed priming (controlled hydration followed by drying) alleviates thermoinhibition by increasing the maximum germination temperature, but reduces lettuce seed longevity. Controlled deterioration (CD) or accelerated ageing storage conditions (i.e. elevated temperature and relative humidity) are used to study seed longevity and to predict potential seed lifetimes under conventional storage conditions. Seeds produced in 2002 and 2006 of a recombinant inbred line (RIL) population derived from a cross between L. sativa cv. Salinas×L. serriola accession UC96US23 were utilized to identify quantitative trait loci (QTLs) associated with seed longevity under CD and conventional storage conditions. Multiple longevity-associated QTLs were identified under both conventional and CD storage conditions for control (non-primed) and primed seeds. However, seed longevity was poorly correlated between the two storage conditions, suggesting that deterioration processes under CD conditions are not predictive of ageing in conventional storage conditions. Additionally, the same QTLs were not identified when RIL populations were grown in different years, indicating that lettuce seed longevity is strongly affected by production environment. Nonetheless, a major QTL on chromosome 4 [Seed longevity 4.1 (Slg4.1)] was responsible for almost 23% of the phenotypic variation in viability of the conventionally stored control seeds of the 2006 RIL population, with improved longevity conferred by the Salinas allele. QTL analyses may enable identification of mechanisms responsible for the sensitivity of primed seeds to CD conditions and breeding for improved seed longevity

Regulation of Symbiotic Nitrogen Fixation in Legume Root Nodules

In most legume nodules, the di-nitrogen (N2)-fixing rhizobia are present as organelle-like structures inside their root host cells. Many processes operate and interact within the symbiotic relationship between plants and nodules, including nitrogen (N)/carbon (C) metabolisms, oxygen flow through nodules, oxidative stress, and phosphorous (P) levels. These processes, which influence the regulation of N2 fixation and are finely tuned on a whole-plant basis, are extensively reviewed in this paper. The carbonic anhydrase (CA)-phosphoenolpyruvate carboxylase (PEPC)-malate dehydrogenase (MDH) is a key pathway inside nodules involved in this regulation, and malate seems to play a crucial role in many aspects of symbiotic N2 fixation control. How legumes specifically sense N-status and how this stimulates all of the regulatory factors are key issues for understanding N2 fixation regulation on a whole-plant basis. This must be thoroughly studied in the future since there is no unifying theory that explains all of the aspects involved in regulating N2 fixation rates to date. Finally, high-throughput functional genomics and molecular tools (i.e., miRNAs) are currently very valuable for the identification of many regulatory elements that are good candidates for accurately dissecting the particular N2 fixation control mechanisms associated with physiological responses to abiotic stresses. In combination with existing information, utilizing these abundant genetic molecular tools will enable us to identify the specific mechanisms underlying the regulation of N2 fixation

A Comprehensive Review on Chickpea (Cicer arietinum L.) Breeding for Abiotic Stress Tolerance and Climate Change Resilience

Chickpea is one of the most important pulse crops worldwide, being an excellent source of protein. It is grown under rain-fed conditions averaging yields of 1 t/ha, far from its potential of 6 t/ha under optimum conditions. The combined effects of heat, cold, drought, and salinity affect species productivity. In this regard, several physiological, biochemical, and molecular mechanisms are reviewed to confer tolerance to abiotic stress. A large collection of nearly 100,000 chickpea accessions is the basis of breeding programs, and important advances have been achieved through conventional breeding, such as germplasm introduction, gene/allele introgression, and mutagenesis. In parallel, advances in molecular biology and high-throughput sequencing have allowed the development of specific molecular markers for the genus Cicer, facilitating marker-assisted selection for yield components and abiotic tolerance. Further, transcriptomics, proteomics, and metabolomics have permitted the identification of specific genes, proteins, and metabolites associated with tolerance to abiotic stress of chickpea. Furthermore, some promising results have been obtained in studies with transgenic plants and with the use of gene editing to obtain drought-tolerant chickpea. Finally, we propose some future lines of research that may be useful to obtain chickpea genotypes tolerant to abiotic stress in a scenario of climate change