Assessing the Response of Diverse Sesame Genotypes to Waterlogging Durations at Different Plant Growth Stages

Sesame is sensitive to waterlogging, and its growth is devastatingly impacted under excess moisture conditions. Thus, waterlogging tolerance is crucial to alleviate yield constraints, particularly under expected climate change. In this study, 119 diverse sesame genotypes were screened for their tolerance to 12, 24, 48, and 72 h of waterlogging relative to non-waterlogged conditions. All plants died under 72 h of waterlogging, while 13.45%, 31.93%, and 45.38% of genotypes survived at 48, 24, and 12 h, respectively. Based on the seedling parameters and waterlogging tolerance coefficients, genotypes BD-7008 and BD-6985 exhibited the highest tolerance to waterlogging, while BD-6996 and JP-01811 were the most sensitive ones. The responses of these four genotypes to waterlogged conditions were assessed at different plant growth stages—30, 40, and 50 days after sowing (DAS)—versus normal conditions. Waterlogging, particularly when it occurred within 30 DAS, destructively affected the physiological and morphological characteristics, which was reflected in the growth and yield attributes. Genotype BD-7008, followed by BD-6985, exhibited the highest chlorophyll and proline contents as well as enzymatic antioxidant activities, including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). These biochemical and physiological adjustments ameliorated the adverse effects of waterlogging, resulting in higher yields for both genotypes. Conversely, JP-01811 presented the lowest chlorophyll and proline contents as well as enzymatic antioxidant activities, resulting in the poorest growth and seed yield.

MORFOFISIOLOGIA DE GENÓTIPOS DE GERGELIM SUBMETIDOS A DIFERENTES ESTRATÉGIAS DE USO DE ÁGUA SALINA

MORFOFISIOLOGIA DE GENÓTIPOS DE GERGELIM SUBMETIDOS A DIFERENTES ESTRATÉGIAS DE USO DE ÁGUA SALINA ANDRÉ ALISSON RODRIGUES DA SILVA1; CASSIANO NOGUEIRA DE LACERDA1; GEOVANI SOARES DE LIMA1; LAURIANE ALMEIDA DOS ANJOS SOARES1; HANS RAJ GHEYI1 E PEDRO DANTAS FERNANDES1 1 Unidade Acadêmica de Engenharia Agrícola, Universidade Federal de Campina Grande, UFCG, Rua Aprígio Veloso, 882 - Universitário, Campina Grande, PB. E-mail: [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]. 1 RESUMO Objetivou-se com este trabalho avaliar as trocas gasosas e o acúmulo de fitomassas de genótipos de gergelim sob estratégias de uso de águas salinas. A pesquisa foi conduzida em casa de vegetação, em delineamento de blocos casualizados em arranjo fatorial 6 x 2, sendo seis estratégias de uso de águas salinas aplicadas nas diferentes fases fenológicas das plantas (SE-irrigação com água de baixa salinidade durante todo ciclo de cultivo; VE - irrigação com água de alta salinidade na fase vegetativa; FL - na fase de floração; FR na fase de frutificação; VE/FL - nas fases vegetativa/floração; VE/FR - nas fases vegetativa/frutificação) e dois genótipos de gergelim (BRS Seda e BRS Anahí), com quatro repetições. Foram aplicadas água com alta salinidade (2,7 dS m-1), em alternância com água com baixa concentração de sais (0,3 dS m-1), em fases diferentes do ciclo. A irrigação com água de 2,7 dS m-1 durante a fase de floração, e nas fases vegetativa/floração, não comprometeu a condutância estomática, transpiração e taxa de assimilação de CO2 dos genótipos de gergelim. A salinidade da água de 2,7 dS m-1 quando aplicada nas fases vegetativa/floração prejudicou o acúmulo de fitomassa pelas plantas de gergelim. Palavras-chave: estresse salino, Sesamum indicum L., qualidade de água. SILVA, A, A, R. da; LACERDA, C. N. de; LIMA, G. S. de; SOARES, L. A. dos A.; GHEYI, H. R.; FERNANDES, P.D. MORPHOPHYSIOLOGY OF SESAME GENOTYPES SUBMITTED TO DIFFERENT STRATEGIES FOR THE USE OF SALINE WATER 2 ABSTRACT The objective of this study was to evaluate gas exchange and phytomass accumulation of sesame genotypes under different strategies for the use of saline water. The research was conducted in a greenhouse, in a randomized block design in a 6 x 2 factorial arrangement, with six strategies for the use of saline water applied in the different phenological phases of the plants (SE - irrigation with low salinity water throughout the cultivation cycle; VE - irrigation with high salinity water in the vegetative phase; FL - in the flowering phase; FR - in the fruiting phase; VE/FL - in the vegetative/flowering phase; VE/FR - in the phases vegetative/fruiting) and two sesame genotypes (BRS Seda and BRS Anahí), with four replicates. Water with high salinity (2.7 dS m-1) was used, alternating with water with low salt concentration (0.3 dS m-1), at different stages of the crop cycle. Irrigation with water of 2.7 dS m-1 during the flowering phase, and in the vegetative/flowering phases, did not compromise the stomatal conductance, transpiration and CO2 assimilation rate of sesame genotypes. The water salinity of 2.7 dS m-1 applied in the vegetative/flowering phases impaired the accumulation of phytomass by sesame plants. Keywords: saline stress, Sesamum indicum L., water quality.

First Report of Sesame Mutants Tolerant to Severe Drought Stress during Germination and Early Seedling Growth Stages

In the context of climate change and water scarcity, there is a need to develop and use drought-tolerant sesame cultivars. This study was conducted to evaluate the response of 13 sesame genotypes, including 11 mutants and their wild-types, to drought during germination and early seedling growth. Moderate and severe drought stress was simulated by applying polyethylene glycol (PEG) at two osmotic potentials, −0.6 MPa and −1.2 MPa, respectively, on seeds of two successive mutant generations, M2 and M3. The parameters measured or calculated were germination percentage (GP), germination rate (GR), mean germination time (MGT), root length (RL), shoot length (SL), root to shoot ratio (RSR), and the seedling vigor index (SVI). Results showed the significant effect of genotype, drought, and drought × genotype interaction on all parameters investigated. Under severe drought, seeds of seven genotypes, including wild types, were not able to germinate. There was a drastic decline of all parameters for the rest, except MGT and RSR, which markedly increased. Interestingly, two mutants, “ML2-5” and “ML2-10”, were identified as the most tolerant to severe drought and the most stable over both generations. The present work is the first report of sesame germplasm with such a high level of tolerance to drought during germination and early seedling growth stages.

Effect of Sodium Azide on Quantitative and Qualitative Stem Traits in the M2 Generation of Ethiopian Sesame (Sesamum indicum L.) Genotypes

The emerging oilseed crop Sesamum indicum, also known as the queen of oilseeds, is being grown globally for its oil content for medicinal and nutritional values. One of the key challenges of sesame cultivation is its low productivity. In the present study, sodium azide (NaN3) was used as a chemical mutagen. The aim of this study was to examine the effect of NaN3 on quantitative and qualitative stem traits in the M2 generation of Ethiopian sesame (Sesamum indicum L.) genotypes. Seeds of fourteen sesame genotypes were used in this study and germinated and grown under greenhouse conditions. Different qualitative and quantitative data were collected and analyzed. Traits such as plant height, ground distance to first distance, and internode length were significantly affected by NaN3 treatment. The highest plant height was recorded in the control on Humera 1 and Baha Necho genotypes, while the lowest was observed on Setit 2 and Hirhir treated with the chemical. The highest ground distance to the first branch was observed in Gumero, while the least ground distance was recorded in Setit 1 in the treated and control genotypes, respectively. The best internode length was recorded on Setit 2 and ADI in the control, while the lowest internode length was observed in Setit 1 genotype treated with sodium azide. Genotypes such as ACC44, ADI, Baha Necho, Borkena, Gonder 1, and Setit 1 treated with NaN3 have showed glabrous type of stem hairiness. All the fourteen genotypes (both treated and control) were clustered into four groups. In conclusion, we observed a highly significant variation among the genotypes due the effect of the chemical and genotypes themselves. Hence, this report would create more genetic diversity for further sesame genetic research improvements.

Characterization of the Genetic Diversity Present in a Diverse Sesame Landrace Collection Based on Phenotypic Traits and EST-SSR Markers Coupled With an HRM Analysis

A selection of sesame (Sesamum indicum L.) landraces of different eco-geographical origin and breeding history have been characterized using 28 qualitative morpho-physiological descriptors and seven expressed sequence tag-simple sequence repeat (EST-SSR) markers coupled with a high-resolution melting (HRM) analysis. The most variable qualitative traits that could efficiently discriminate landraces, as revealed by the correlation analyses, were the plant growth type and position of the branches, leaf blade width, stem pubescence, flowering initiation, capsule traits and seed coat texture. The agglomerative hierarchical clustering analysis based on a dissimilarity matrix highlighted three main groups among the sesame landraces. An EST-SSR marker analysis revealed an average polymorphism information content (PIC) value of 0.82, which indicated that the selected markers were highly polymorphic. A principal coordinate analysis and dendrogram reconstruction based on the molecular data classified the sesame genotypes into four major clades. Both the morpho-physiological and molecular analyses showed that landraces from the same geographical origin were not always grouped in the same cluster, forming heterotic groups; however, clustering patterns were observed for the Greek landraces. The selective breeding of such traits could be employed to unlock the bottleneck of local phenotypic diversity and create new cultivars with desirable traits.

The mechanism of sesame resistance against Macrophomina phaseolina was revealed via a comparison of transcriptomes of resistant and susceptible sesame genotypes

Background Sesame (Sesamum indicum) charcoal rot, a destructive fungal disease caused by Macrophomina phaseolina (Tassi) Goid (MP), is a great threat to the yield and quality of sesame. However, there is a lack of information about the gene-for-gene relationship between sesame and MP, and the molecular mechanism behind the interaction is not yet clear. The aim of this study was to interpret the molecular mechanism of sesame resistance against MP in disease-resistant (DR) and disease-susceptible (DS) genotypes based on transcriptomics. This is the first report of the interaction between sesame and MP using this method. Results A set of core genes that response to MP were revealed by comparative transcriptomics and they were preferentially associated with GO terms such as ribosome-related processes, fruit ripening and regulation of jasmonic acid mediated signalling pathway. It is also exhibited that translational mechanism and transcriptional mechanism could co-activate in DR so that it can initiate the immunity to MP more rapidly. According to weighted gene co-expression network analysis (WGCNA) of differentially expressed gene sets between two genotypes, we found that leucine-rich repeat receptor-like kinase (LRR-RLK) proteins may assume an important job in sesame resistance against MP. Notably, compared with DS, most key genes were induced in DR such as pattern recognition receptors (PRRs) and resistance genes, indicating that DR initiated stronger pattern-triggered immunity (PTI) and effector-triggered immunity (ETI). Finally, the study showed that JA/ET and SA signalling pathways all play an important role in sesame resistance to MP. Conclusions The defence response to MP of sesame, a complex bioprocess involving many phytohormones and disease resistance-related genes, was illustrated at the transcriptional level in our investigation. The findings shed more light on further understanding of different responses to MP in resistant and susceptible sesame.

Efficiency of nitrogen use by sesame genotypes under brazilian semi-arid conditions

Nitrogen (N) is an essential macronutrient for plant growth and rate applications can influence the performance of sesame, and when applied in excess can cause nitrogen loss in the environment, and consequently make the cost of production more costly to the producer. Therefore, the objective of this work was to evaluate the efficiency of nitrogen use by different cultivars of irrigated sesame seeds under the edaphoclimatic conditions of the northeastern semi-arid region in two harvests. The experiments were carried out from February to May (1st harvest) and from July to October (2nd harvest) in 2016. The treatments were arranged in a split plot scheme, in which the plots were the five nitrogen doses (0, 30, 60, 90 and 120 kg ha-1), and in the subplots, the four sesame genotypes (CNPA G2, CNPA G3, CNPA G4 and BRS Seda), the design was in randomized complete blocks with four replications. The nitrogen use efficiency assessments evaluated were: agronomic efficiency (AE), physiological efficiency (PE), agrophysiological efficiency (APE), recovery efficiency (RE) and efficiency of use (EU). The rate that provided the greatest efficiency of use was 30 kg ha-1 of N applied. The cultivar BRS Seda had greater efficiency of use in relation to the other cultivars studied. The crop that had better efficiency of use was the 2nd agricultural harvest.