The Predictive Potential of X-ray Imaging for Determining Seed Viability and Seedling Quality Prior to Germination

Seed is the basis of every crop, forestry, and horticultural practice, such that if a seed quality issue is not detected early on, significant loss in conservation and restoration efforts or in crop yield potential and in re-seeding another crop will have already been introduced.

Traditional Seed Testing Methods

Evaluation of seed quality is critical for seed production, conservation breeding programs, and agricultural optimization, ensuring that high-quality seeds are used for planting and propagating. Traditionally, seed quality has been assessed through testing methods that require the seed to be destroyed or otherwise rendered unusable as a result of the testing process. These methods include embryo excision (cut test), germination test, or chemical tetrazolium (TZ) staining. Though each method can provide valuable information, their considerable drawbacks must be weighed.

The embryo excision test, or cut test, involves removing the seed coat to directly examine the embryo’s morphological development. While the value of direct examination is obvious, the test is both time-consuming and destructive, rendering the seed unusable after testing.

Similarly, germination testing has value as a direct assessment of seed germination potential and health of the resulting seedling. Germination testing involves sprouting the seeds under controlled conditions to observe their ability to germinate and develop into seedlings. One can then extrapolate the results to determine what percentage of seeds are likely to germinate under ideal conditions, as well as the percentage of the resulting seedlings that can be expected to be classified as normal (i.e. well-formed, healthy seedlings) vs. abnormal (i.e. seedlings exhibiting physical damage or absence of structures). However, depending on the species of plant, the process can take several days to weeks for seeds to germinate before conclusions may be drawn about their quality and fitness for use. If the goal is seed banking, the method does consume seeds. Additionally, apart from observing surface blemishes, no instant assessment can be made regarding the presence of seed-borne pests, nor can the impact of mechanical damage on the internal anatomy of the seed be quickly determined. Germination testing is also the most expensive of the methods, as it can require germination chambers and/or professional lab services.

Tetrazolium chloride (TZ) staining is another method that is frequently used to assess seed viability. TZ works by exposing seeds to a chemical that stains the outside of the seed shell in correlation to live seed tissue underneath, allowing the viability of a seed to be evaluated based on the stain pattern. However, interpreting the patterns requires a high degree of expertise. Also, the test can be tedious to perform, and the time required can be significant. Furthermore, the technique renders the tested seeds unusable, and little to no information about the potential health of the seedlings is gained.

Other commonly performed seed testing methods include vigor and thousand kernel weight (TKW) assessments. Unlike the germination test, vigor testing assesses a seed’s ability to germinate under challenging conditions, such as cold temperatures. TKW measures the seed’s weight in bulk to determine seeding rates, which is crucial for optimizing plant density, but can only provide a very rough estimate of expected seed quality.

Though these methods have been proven to provide useful information, they are slow, labor-intensive, incomplete, and all, apart from TKW, are destructive or otherwise diminish the seed reserves. These limitations highlight the need for more efficient, non-destructive, more complete alternatives that allow researchers and seed producers to assess seed quality without compromising seed viability. This becomes even more crucial when the seeds being evaluated are valuable, rare, or endangered.

The Emergence of X-ray Imaging as a Tool for Seed Quality Assessment

Recent advancements in high-resolution X-ray imaging have introduced a non-destructive, fast, and highly accurate method for assessing seed quality. Unlike the traditional methods previously discussed, X-ray imaging allows for the visualization of internal seed structures in seconds without harming the seed. The use of X-ray systems can reveal key information about the seed’s internal anatomy, such as the integrity of the embryo and the distribution of endosperm. The ability to visualize detailed morphological development in a fully intact seed is one of the most significant advantages of X-ray imaging. Early detection of morphological abnormalities—such as poorly developed embryos or inadequate endosperms—can provide crucial insights into how the seedling is likely to perform. Given that X-ray imaging has been shown to be conducive to predicting germination potential and overall seedling vigor¹, early and accurate identification of seeds likely to fail to germinate or to result in damaged or unusable seedlings can save time, labor, and resources, as well as increase yields.

Furthermore, X-ray imaging can detect various seed defects, such as mechanical damage, which could occur during harvesting, handling, or storage processes. By visualizing these defects, proactive measures can be taken to address seed quality issues before they affect crop yields or breeding programs. In addition, X-ray imaging can identify insect infestations to help prevent the spread of pest-related diseases and reduce overall seed loss.

The XSEED® Family of X-ray Imaging Systems

XSEED® is a range of high-resolution X-ray imaging systems and software solutions designed specifically for use in seed and agricultural analysis applications. Each of the XSEED systems is capable of high-resolution imaging for detailed analysis of internal seed morphology in fully intact seeds, enabling non-destructive assessment of seed quality in dramatically less time than traditional methods.

All systems are equipped with DIGISEED® seed analysis software that provides the tools needed for precise, customizable, and repeatable seed analysis. With DIGISEED, all XSEED systems can quantify critical factors of seed characterization, including count, size, density, and fill percentage, in seconds.

The Next Benchmark Solution for Agriculture and Beyond

With mounting long-term challenges such as climate change, food insecurity, pest management, deforestation, illegal logging, and loss of biodiversity, the ability to assess seed quality with high precision becomes ever more critical. The XSEED systems offer powerful tools for improving seed testing procedures which can enhance seed production for healthier, more robust crops in the future, and help restore, maintain, or preserve threatened plant populations, while reducing the time and resources needed.

The predictive power of X-ray imaging is poised to revolutionize the way seed quality is assessed, clearing the way for XSEED systems to become the next benchmark solution in modern methods for determining seed viability and seedling quality prior to germination.

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1. Campos, T.S.; Pereira, V.M.; El Merzougui, S.; Beleski, D.; Pérez, H.E.; Pivetta, K.F.L.; Vendrame, W.A. Cryopreservation of Lavender Trumpet Tree (Handroanthus impetiginosus) Seeds. Horticulturae 2024, 10, 1256.