Truffle Microscope Specification Guide
This guide seeks to provide recommendations for truffle growers wishing to analyze root tips collected from their orchards to better understand the mycorrhizal relationship within their soil. Information on two types of microscopes, the USB microscope and the stereo/dissecting microscope, and our recommendations for their use with respect to truffle growing is provided. Both microscopes utilize light (top light) that is reflected off the surface of object for low magnification observation. Stereoscopes can also use bottom lighting, which projects light through thin specimens; however, it is not required or practical for observing root tips. The USB microscope is more compact and less expensive, while the stereoscope is easier to use and has better optics, but at a higher cost and can require more space.
For observation of root tip samples for evidence of truffle colonization, a stereoscope should have magnification up to at least 40X, but 50X is ideal. At this magnification, basic morphological characteristics of root tips can be observed and allows the observer to estimate the percentage of mycorrhization for each root tip sample. Using root tip morphology to distinguish Tuber species from other ectomycorrhizal fungi is not absolute. This tool can be used only to increase your confidence of Tuber species colonization. Only morphological and DNA analysis performed by a skilled technician allows for conclusive differentiation.
Stereoscope
The stereoscope (otherwise known as a dissecting microscope) uses two eyepieces (also called oculars) that provide different viewing angles from both the left and right eye simultaneously that allows for 3D visualization of samples between approximately 10X and 50X. Dissecting scopes with a single ocular are available, but are not ideal. Most stereoscopes are binocular, meaning they have two eyepieces – one for each eye. Trinoculars are also available where the third eyepiece/ocular can be equipped with a microscope camera allowing for pictures to be saved for future reference. However, microscope cameras may be cost prohibitive for your budget. There are two main types of optical designs for stereoscopes; common main objective (CMO; also known as Galilean or parallel optic design), that tend to be very expensive, but have greater light-gathering capabilities, resolution, and field of view, and Greenough microscopes that produce a lower quality stereo effect for routine tasks and daily use, but can be many times cheaper. Greenough microscopes are perfectly adequate for observing root tips. When determining magnification for stereoscopes, multiply the magnification of the eyepiece lens (typically 10X) by the magnification of the objective lenses (lens closest to the specimen) (typically between the range of 0.5X-6X). For example, a stereoscope with a 10X eyepiece and 0.7X-4.5X objective lenses has a magnification range of 7X-45X. Zoom ratio is the maximum magnification of the objective lens divided by the minimum magnification. Microscopes with large zoom rations have greater magnification ranges. Depth of field is the ability to see at multiple depths at the same time. A smaller depth of field is ok, but larger is better. Below are the minimum specifications for a stereoscope.
- Zoom range: must be able to reach 40X magnification, but 50X is optimum
- Illumination: Top lighting. (Bottom lighting is not required)
- Resolution: 2 Megapixel camera – (Trinocular Microscope only)
Microscope recommendations are listed below. Higher quality microscopes have better optics and may come with a warranty.
Amscope 20X-40X Binocular Stereo Microscope
Amscope 10X-80X Binocular Stereo Microscope
AmScope 10X-45X Binocular Stereo Microscope
AmScope 5X-80X Binocular Stereo Microscope
AmScope 8X-50X Trinocular Stereo Microscope
AmScope 3.5X-90X Trinocular Stereo Microscope (Camera Included)
Olympus SZ51 8X-40X Binocular Stereo Microscope
Olympus SZ-6145TR 6.7X-45X Trinocular Stereo Microscope
Nikon SMZ-745T 6.7X-50X Trinocular Stereo Microscope (Camera Included)
USB Microscope
A USB-microscope at its core is a small camera combined with a high-powered lens that allows for low magnification observation of samples that connects and displays images onto a computer or laptop. They are inexpensive and allow for the ability to observe and capture pictures. However, their lower price point reflects some drawbacks. Most models will come with chunky software, lack optical zoom (the ability to focus on particular depth of the sample), and come with low resolution cameras. We do not recommend cameras less the 2 Megapixels (1080p) as the resolution is too low to be effective. Higher quality models typically come with a stand, have higher resolution quality, better software, and allow for optical zoom. However, at those prices it may be better to purchase a stereoscope. The USB microscope can still be useful and is ideal if space is limited because of its compact nature, but it is important to understand its disadvantages before purchasing. At high zoom, the camera must be very close to the sample roots in order to get a clear image and can be cumbersome to use.
Dino-Lite has a large range of USB microscopes and although they may be more expensive, it is a reputable company with high quality specifications. There are also many lower cost alternatives available on the internet, so we have listed the minimum specifications below. Check the specifications to ensure compatibility with your computer such as the software and USB connectivity (USB 2.0, 3.0 or other). Frame rate is the frequency at which your USB microscope refreshes the image: the higher the number, the quicker the refresh. Working distance is the distance your microscope is from the object. A standard working distance is adequate and should reach within ½ in of your specimen).
- 2 Megapixel camera is ideal, 1.3 MP or greater may also be satisfactory
- Be able to reach 40X magnification, at minimum, but 50X is optimum
- Minimum working distance within or around ½ in (4 to 5 mm), at minimum
- Sample stand (optional – your preference)
- Compatible with your computer
Other sources of microscopes:
Some universities, states, and federal agencies have surplus sales and basic, but functional microscopes can be found at these sales for very low prices. However, be careful when shopping for used microscopes as they may be damaged or missing parts.
Supplemental Materials and Resources
Petri dishes or other clear trays are useful to place root samples in when using the microscopes.
Metal specialty probes like automotive or dental tools are useful for sorting out root tips and can be found on Amazon or in budget tool shops. Here is one example.
Learning the parts of your microscope will be helpful in understanding these specifications and many websites and videos are available online. Here are a couple examples: