FEBRUARY 2018 SEEDWORLD.COM / 33 PARTNER CONTENT Right Test, Best Results When doing seed health testing it is important to consider both direct and indirect testing methods to get the most complete and accurate information. A ssurance of seed health is the first step in supplying producers with good quality seed. As seed compa- nies, you work diligently through the seed production process to monitor and control any potential threats – the final step of this being laboratory testing for seed health on your seed lots. Seed health testing meth- ods are a tool for seed-borne disease risk management. Indirect vs Direct “Indirect seed health testing is normally used for prescreening,” says Padma Su- darshana, senior scientist with California Seed and Plant (CSP) Laboratories. “If we see any positive results we generally then recommend moving to the next stage – utilizing direct testing methods.” Indirect testing methods are often very sensitive and rapid. Indirect tests detect proteins (by immono-flourescence (IF) and Enzyme Linked Immuno Sorbent As- say (ELISA)) or nucleic acids (by polymer- ase chain reaction (PCR)) that are specific to the target pathogen. As technology progresses the range of available indirect testing methods continues to expand. “Indirect testing is fast, sensitive and cost effective for screening larger lots of seed,” notes Sudarshana. “The benefits to starting with the indirect testing meth- ods means that we can more quickly rule out any negative results and then these clean lots of seed are able to go market more quickly.” If positive results are detected moving to direct – more confirmatory – methods of testing are recommended. “When we move to the direct method we do a grow out of the seeds to see the symptoms and confirm presence of dis- ease,” Sudarshana explains. “This testing method is more time consuming and often more expensive due to labour required to grow out the seeds. Once we isolate the pathogens and observe the symptoms we are testing for very specific pathogens – for example phytoplasma and viroids – indirect testing methods are your only way confirm their presence,” says Sukhi Pannu, director, of Business and Research Development at CSP Labs. “These viruses can only be tested via PCR or ELISA meth- odologies. Conversely for bacteria testing can be done via direct methods – such as liquid plating – where you can grow them and perform confirmatory tests for bacte- rial fruit blotch in cucurbits and bacterial canker in tomatoes.” “At CSP Labs we strive to be very active in the industry to stay on top of the best testing protocols,” says Pannu. “We are currently collaborating with the Inter- national Seed Health Initiative (ISHI) – branch of the International Seed Federa- tion – on research projects and testing methods for seed health. It is a great learn- ing opportunity for our team.” This is a sentiment echoed by Sudarshana. “By working with research partners in the seed industry we bring or adopt the latest technolo- gies to our testing. Additionally, we can better serve our customers by keeping on top of the latest regulatory changes and threats facing the seed industry. It’s a win-win.” complete a further confirmation on the host plants via PCR testing.” Getting Specific As you work with your laboratory partners it is important to know the best testing methodologies to accurately reflect the po- tential pathogens that may be present in your seed lot. Testing needs to be specific to these target pathogens, which is where the consideration of direct or indirect test- ing methods needs to be discussed. “For certain crop types where you PCR is one method of indirect seed health testing. Growing out seeds is part of direct seed health testing.