How do I know CR-7 is actually in the field?

Posted on December 29, 2020

BVT is often asked “how do I know CR-7 is actually in the field?” Sherri Tedford, the company’s Laboratory & Field Testing Manager responsible for quality control of BVT products and for conducting Ontario R&D trials, shares how this is done in her article below.

FAQ: How do I know CR-7 is actually in the field?

BVT’s proprietary Clonostachys rosea strain CR-7, the active ingredient in the company’s natural precision agriculture system, consists of microscopic spores that are not visible to the naked eye and cannot be seen on plant tissue in the field. As C. rosea is an endophytic fungus, you have look for CR-7 inside plant tissues. To determine if the product has been successfully delivered to crop blooms by bees, BVT uses advanced microbial testing techniques.

Microbial testing for CR-7

Flowers from a crop field using BVT’s system are collected and sent to the company’s lab in Canada. At the lab, the flowers are dissected and plated on a special kind of agar in petri plates that encourages the growth of C.rosea. The plates are kept in an incubator and, after a week to ten days, the dissected flowers are examined under a microscope to look for CR-7 colonies.  

Above: CR-7 spores @ 400x magnification under a light microscope.
Below: Macroscopic views of blueberry blooms taken from crop
fields, with the green arrows pointing to CR-7 growing on the flowers.

Collecting just a few flowers from large crop fields can lead to falsely low results. To ensure we achieve representative results, BVT collects flowers from all over a field, not just one spot. We also try to only collect flowers that show signs of pollination, as unpollinated flowers have not come into contact with any bees and therefore will not tell us if CR-7 was vectored successfully by the bees.

Advancing to molecular testing

In the future, BVT’s objective is to move from microbial testing to molecular testing. Rather than dissecting and incubating samples on petri plates, plant tissues would be put through a PCR machine. Molecular testing would be more accurate, require less labor, and would return results faster than BVT’s current microbial tests. PCR testing is used in genealogy tests such as 23 and Me, AncestryDNA, etc., and in medical testing like the COVID-19 detection test.

PCR stands for Polymerase Chain Reaction and works by amplifying specific DNA sequences to detectible levels so that the machine is able to detect the DNA sequence you are looking for. This allows the PCR machine to look for small amounts of DNA, CR-7 for example, in many samples and indicate if CR-7 is present in those samples or not.  

To be able to use molecular testing like PCR, BVT is working to determine the unique genetic sequences in CR-7 that can be used to detect CR-7 in samples with a heavy microbial load (e.g., flowers from a field). It is possible BVT will be able to develop in-field testing kits that would eliminate the need to ship samples and would provide results in a few hours rather than days – right in a grower’s field.

We hope you found this article insightful and look forward to sharing more FAQs with you in the future.

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