Germination potential and methods for overcoming seed dormancy for domesticated and wild annatto populations after two years of storage

ABSTRACT: Annatto (Bixa orellana L.) is an arboreal species domesticated in Amazonia from its wild ancestor (B. orellana var. urucurana). Bixin extracted from its orthodox seeds is a natural dye widely used in the food industry. This study evaluated methods to overcome seed dormancy and determine the germination potential, comparing domesticated and wild annatto populations. Seeds from two domesticated-type populations and two families of a wild-type population, stored for two years after field collection, were submitted to five treatments to overcome dormancy: T1 - control; T2 - mechanical scarification (with sandpaper); T3 - mechanical scarification (with sandpaper) + immersion in water at 36 ºC overnight (12 hours); T4 - immersion in water at room temperature (23 ºC, on average) for 24 h; T5 - immersion in concentrated sulfuric acid (95 - 98%) for 15 min + running water for 3 min. Highly significant differences (P < 0.001) were observed in the germination percentage of annatto seeds between wild and domesticated types, and among the treatments tested. Domesticated types showed higher germination percentage (10 - 58%) over all treatments when compared to the wild type (0 - 44%). The best treatments were those performed with mechanical scarification. Given the simplicity, we concluded that mechanical scarification with sandpaper is a good alternative to overcome dormancy of annatto seeds.

Genome-Wide Association Analysis of Salt-Tolerant Traits in Terrestrial Cotton at Seedling Stage

Soil salinization is the main abiotic stress factor affecting agricultural production worldwide, and salt stress has a significant impact on plant growth and development. Cotton is one of the most salt-tolerant crops. Therefore, the selection and utilization of salt-tolerant germplasm resources and the excavation of salt resistance genes play important roles in improving cotton production in saline–alkali soils. In this study, we analysed the population structure and genetic diversity of a total 149 cotton plant materials including 137 elite Gossypium hirsutum cultivar accessions collected from China and 12 elite Gossypium hirsutum cultivar accessions collected from around the world. Illumina Cotton SNP 70 K was used to obtain genome-wide single-nucleotide polymorphism (SNP) data for 149 elite Gossypium hirsutum cultivar accessions, and 18,430 highly consistent SNP loci were obtained by filtering. It was assessed by using PCA principal component analysis so that the 149 elite Gossypium hirsutum cultivar accessions could be divided into two subgroups, including subgroup 1 with 78 materials and subgroup 2 with 71 materials. Using the obtained SNP and other marker genotype test results, under salt stress, the salt tolerance traits 3d Germination potential, 3d Radicle length drop rate, 7d Germination rate, 7d Radicle length drop rate, 7d Germination weight, 3d Radicle length, 7d Radicle length, Relative Germination potential, Relative Germination rate, 7d Radicle weight drop rate, Salt tolerance index 3d Germination potential index, 3d Radicle length index, 7d Radicle length index, 7d Radicle weight index and 7d Germination rate index were evaluated by GWAS (genome-wide association analysis). A total of 27 SNP markers closely related to the salt tolerance traits and 15 SNP markers closely related to the salt tolerance index were detected. At the SNP locus associated with phenotyping, Gh_D01G0943, Gh_D01G0945, Gh_A01G0906, Gh_A01G0908, Gh_D08G1308 and Gh_D08G1309 related to plant salt tolerance were detected, and they were found to be involved in intracellular transport, sucrose synthesis, osmotic pressure balance, transmembrane transport, N-glycosylation, auxin response and cell amplification. This study provides a theoretical basis for the selection and breeding of salt-tolerant upland cotton varieties.

Determining Seed Viability During Fruit Maturation to Improve Seed Production and Availability of New Citrus Rootstocks

In recent years, the pressure for replanting and resetting huanglongbing (HLB or citrus greening) affected citrus groves has led to an inadequate seed supply for the most popular rootstock cultivars in the State of Florida, United States. Early fruit harvesting of citrus rootstock source trees might reduce fruit losses and enhance seed availability, especially in HLB-endemic and hurricane susceptible areas, if the physiological quality of the seeds is adequate. The effects of fruit maturity on seed quality and seedling performance of US-802, US-897, and US-942 citrus rootstocks were investigated for two consecutive growing seasons. The study included the evaluation of seed germination and nursery performance of the citrus rootstock seedlings. The germination test was performed in vitro, where seeds were hand-peeled, surface-sterilized and placed in culture tubes containing basal Murashige and Skoog medium. For the emergence test, seeds were sown in seedling trays containing sterilized growing substrate in a greenhouse with controlled-environment conditions. Rootstock fruits from all three varieties harvested in August and September had seeds with higher germination potential, as more than 90% of the seeds generated seedlings. US-942 had more % of emergence than US-802 and US-897, resulting in faster seed germination; in contrast, US-802 had the faster shoot growth rate. Assays on fruit abscission response showed that by August, fruit from all three varieties were responsive to ethylene and abscised, although response varied and was higher in US-942, suggesting the seeds were mature enough. Taken together, our findings indicate that fruits these three rootstocks can be harvested as early as August in contrast to the current procedures without losing germination potential. This will result in an increase in available seeds for nurseries in Florida.

Germination potential of Hymenaea courbaril L. in different maturation stages

The production of quality forest seedlings in large quantities is essential for the restoration of environments that have been deforested and degraded. However, obtaining seeds with high vigor is a challenge for several tree species native to Brazil. The objective of this work was to verify the germination potential of jatobá-da-mata seeds at different stages of maturation, in order to favor the production of seedlings of this species in nurseries. The seeds were extracted from green and ripe fruits detached from the mother plant and ripe fruits collected from the ground. The germination percentage, average germination time, emergence speed index, average speed, relative frequency, leaf area of the seedling, and length of the aerial part and root were measured. The planting was carried out with mechanically scarified and intact seeds from each maturation group. The results indicated that non-scarified green seeds can be used for planting and seedling production, as they do not require pre-germination treatment and have a favorable germination percentage (79%). Fruit seeds harvested from the ground, on the other hand, needed a method to overcome integumentary dormancy, such as mechanical scarification, obtaining a germination rate of 85%. The seeds of ripe fruits harvested in the matrix showed greater vigor, with a higher percentage of germination (96 to 100%), a higher emergence speed index, shorter average germination time, and seedlings with greater leaf area and greater length of shoot.

A comparative study on seed physiology and germination requirements for 15 species of Eucalyptus

Seed physiology of 15 Eucalyptus species of interest for cut foliage plantations was unknown and therefore evaluated. The viability and vigour of seeds and germination potential of 15 Eucalyptus species was determined by using a tetrazolium (TZ) staining test, and the results were compared to a germination test. In a separate experiment, seeds of each lot were subjected to either 0 or 4-week cold stratification at 4 ± 1 °C to investigate their potential stratification requirement. After stratification, seeds were then allowed to germinate at 22 ± 1 °C with 16 h lighting per day for 36 days. Seed viability and vigour were checked by evaluating % root, cotyledon and first true leaves emergence, and the speed of emergence, in the germination test. The germination percentages varied with the species. Seed stratification with the interaction of seed species lots significantly affected both viability and vigour. The seed viability of the different species ranged from 9 to 100% and 2 to 100%, for the TZ test and germination test, respectively, with a high correlation (R2 = 0.89) between the two. Physiology tests revealed that cold stratification of seed was not required for the 15 species to maximise their germination potential and growth in Irish and British climate.

The GmXTH1 Gene Improves Drought Stress Resistance of Soybean Seedlings

To study the role of GmXTH1 gene in alleviating drought stress. T4 transgenic soybean seeds with GmXTH1 gene were treated with PEG6000 at 0%, 5%, 10% and 15%, respectively. Germination potential, germination rate and germination index were measured. The results showed that the germination potential, germination rate and germination index of OEA1 and OEA2 strains overexpressed in T4 generation were significantly higher than that of control material M18. After 0d, 7d and 15d drought stress, the analysis of seedling phenotypes and root-shoot of different T4 generation transgenic soybean lines showed that under stress conditions, the growth of GmXTH1 overexpression material was generally better than that of control material M18, and the growth of GmXTH1 interference expression material was generally worse than that of control material M18, with significant differences in plant phenotypes.The root system of GmXTH1 overexpressed material was significantly developed compared with that of control material M18. The analysis of physiological and biochemical indexes showed that the relative water content and the activity of antioxidant enzymes (superoxide dismutase and peroxidase) of GmXTH1 transgenic soybean material were significantly higher than that of control material M18, and the accumulation of malondialdehyde was lower under the same stress conditions at seedling stage. Fluorescence quantitative PCR assay showed that the relative expression of GmXTH1 gene in transgenic soybean was significantly increased after drought stress.The results showed that the overexpression of GmXTH1 could increase the total root length, surface area, total projection area, root volume, average diameter, total cross number and total root tip number, thereby increasing the water intake and reducing the transpiration of water content in leaves, thus reducing the accumulation of MDA and producing more protective enzymes in a more effective and prompt way.Reducing cell membrane damage to improve drought resistance of soybean.

Accelerated Ageing Mediated Seed Longevity Prediction and Assessment of Seed Deterioration Pattern through 2D-Gel Electrophoresis in Chickpea (Cicer arietinum L.)

Background: Accelerated ageing is a method to assess seed storage performance by exposing the seeds to higher temperature and relative humidity to make seeds lose its vigour and viability quickly. The seed physiological parameters are then compared with the natural ageing to derive certain conclusions. But, the molecular pattern of seed deterioration under accelerated ageing varies compared to that of natural ageing.Methods: Chickpea, seed lots of variety JG-11 and Annigeri-1 were subjected to natural ageing in cloth bag with nine per cent initial seed moisture under ambient conditions. Simultaneously, representative sample of same seed lot were also aged at 41oC and 95±2% humidity up to 120 hours.Result: Both the ageing methods had significant negative effect on seed physiological and biochemical quality parameters. The germination potential of seeds tested after 48 hours of accelerated ageing (83.5%) was equal 10 months of natural ageing (85%) in JG-11, while also in Annigeri-1, 48 hours of accelerated ageing (78%) was nearly equal to 10 months of natural ageing (80%). The protein expression analyzed through 2D-PAGE at similar germination potential brought out by two independent ageing methods showed higher protein down regulation ratio (3.4) in accelerated ageing than in natural ageing (3.2) unveiling its rapidity in the seed deterioration process. Therefore, accelerated ageing can be used for predicting chickpea seed longevity.

Effect of Radiation Processing on Water Absorption and Germination of Kodo and Kutki Millets

Background: In pursuit of exploring gamma irradiation as a technology-intervention for de-husking of Kodo and Kutki millets grown widely, authors of this paper observed that irradiation leads to easy de-husking of hardest Kodo grains. Calibration for appropriate dose of irradiation is needed and hence, this study was planned. This technology, if established, may check millet farmers shifting to other crops.Methods: Kodo and Kutki millets were irradiated by gamma radiations for doses of 0 kGy to 10 kGy. Water absorption capacity and germination potential of irradiated grains were measured to determine the dose for desired results.Result: Water absorption and germination potential of Kodo and Kutki grains improved on irradiation; dose of 2.5 kGy and above resulted in an increase in the quantity of water absorbed and rate of water absorption. The germination also increased but registering maxima at 7.5 kGy for Kodo and 5.0 kGy for Kutki. Irradiation at doses higher than maxima caused decline. Thus, appropriate dose of irradiation was found to be 7.5 kGy for Kodo and 5 kGy for Kutki.