SEED TESTING FOR QUALITY ASSESMENT 
                                                                                                         J.P.Lakhani 
                                                                                                 Associate Professor 
                                                                                          Plant Breeding & Genetics 
                                                                       
                                                                       
                     Importance of Seed Testing 
                            The importance of seed testing was realized more than 100 years ago for assured 
                             planting  values.  The  adulteration  of  vegetable  seeds  by  stone  dust  which  was 
                             practiced in some parts of the world particularly in Europe 
                            Seed testing has been developed to aid agriculture to avoid some of the hazards of 
                             crop  production  by  furnishing  the  needed  information  about  different  quality 
                             attributes viz., purity, moisture, germination, vigour and health. 
                            Quality  control  of  seed  depends  on  the  different  seed  testing  protocols  which 
                             determine the genuine of cultivar. 
                            Testing of seed evaluate the planting value and the authenticity of the certified lot. 
                            Seed testing is required to assess the seed quality attributes of the seed lots which 
                             have to be offered for sale.  
                            These  quality  attributes  are  seed  moisture  content,  germination  and  vigour, 
                             physical  and  genetic  purity,  freedom  from  seed  borne  diseases  and  insect 
                             infestation. In India, seed testing is done mainly for moisture, germination and 
                             physical purity of seeds are generally determined.  
                            Standard seed testing procedures for the evaluation of the seeds were developed 
                             by ISTA. It is obligatory on the part of the seed analyst to follow rules prescribed 
                             by ISTA (ISTA, 1985) if the seed is moving to the International trade. 
                            The seed testing procedures which are described below are based mostly on the 
                             international rules because most of our rules (Chalam et al., 1967) are based on 
                             their. As per (ISTA, 1996) Economic yield of a crop depends on the quality of 
                             seeds which can be evaluated by seed testing (ISTA, 1996). 
                                                                       
                            The testing of seed quality is carried out on seed samples drawn from seed lot to 
                             be used for cultivation. The quantity of seed sample taken for testing in laboratory 
                             is minute compared to that of seed lot it represent.  
                              
                     Role of Seed Testing Laboratories  
                             Seed testing laboratories are essential organization in seed certification and seed 
                     quality control programmes. The main objective is to serve the producer, the consumer 
                     and the seed industry by providing information on seed quality. Test results may cause 
                     rejection of seed lots or further multiplication or low grade seed in a count of law. 
                      
                                                          Production  
                                                                       
                      
                                        Harvest                                 Certification  
                                                                                                    
                      
                      
                                                          Seed Testing 
                                 Drying                                                    Storage  
                      
                      
                      
                                                                                     Distribution  
                                  Processing  
                      
                      
                                                            Treating  
                      
                      
                     Analysis of Seed in the Laboratory  
                             Seed testing  is  highly  specialized  and  technical  job.  With  a  view  to  maintain 
                     uniformity in quality control the Seed Analysts laboratory includes for distinct sections. 
                     i.      Section for seed purity testing: Purity analysis of seed lot is considered under two 
                                 factors. 
                            Testing the cleanliness of seed lot and  
                            Testing the geneuiness of the cultivar 
                     ii.     Section for moisture testing  
                     iii.    Section for viability , germination and Section for vigour testing 
                                                                       
         
          1.  Seed Sampling 
          2.  Physical Purity Test 
          3.  Germination Test 
          4.  Viability Test  
          5.  Moisture Content  
            
        S.No.1 to 4 has been discussed in practical class with demonstration and students have 
        conducted practical also. So it is not necessary to repeat these lectures here. Now a note 
        on  moisture  content  is  being  discussed  here.  Demonstration  of  Universal  Moisture 
        Meter has also been followed by the students 
         
        Determination of seed moisture content 
           Seed moisture is one of the most important deciding factors of seed viability and 
        quality during storage. Hence, determination of seed moisture content and drying to the 
        safe moisture content is utmost important before transit and storage. According to ISTA 
        (1985), moisture content of the sample is defined as that loss of weight when it is dried in 
        accordance with the rules or the amount of water collected when it is distilled. It  is 
        expressed as percentage of the original weight of sample (wet basis). 
         
        Direct methods 
        Air oven method  
           This is the most practical and basic method prescribed by ISTA (1985). In this 
        method, moisture present in the seed is completely evaporated either after grinding or 
        without grinding by heating in oven (high or low constant) and the amount of moisture 
        loss  by  weight  is  estimated  and  expressed  in  percentage.  The  sample  is  weighed 
        approximately 4-5 g for seeds having less than 8 mm size and 10 g for seeds having more 
        than 8 mm size, in duplicate. The sample should be weighed in 3 decimal places. 
                            
                             
                             
                             
                             
                             
                             
                             
                             
                             
                             
                             
                             
                            Low constant oven method 
                                      Weigh  the  container  and  its  cover  before  and  after  taking  the  sample  in  the 
                            container. Then place the container with seed in an oven maintained at 103 ± 2°C for 17 
                            ± I hour. This method is suitable for oily seeds such as onion, capsicum, brinjal, soybean 
                            radish, groundnut, castor, mustard, sesame, cotton etc. 
                                       
                            High constant oven method 
                                      The sample is dried in an oven at 130 ÷ 3 for about 4 hours for maize, 2 hours for 
                            other cereals and 1 hour for others. This method is suitable for all other species except 
                            those seeds contain volatile oil The containers used for moisture estimation by above 
                            methods should be made up of glass or non corrosive metals with wider mouth. While 
                            drying, spreading seed in uniform layer (not more than 0.3 g cm2) is necessary.  
                                      After drying the seeds either in low or high constant ovens, the seed samples are 
                            placed in desiccators containing calcium chloride (CaCI2) for few minutes and weighed 
                            and the percentage moisture content is calculated using the following formula: 
                                                                           M  - M                       
                                                                         2       3
                            Moisture content (%)  =       -------------  x 100                          
                                                                           M  - M                        
                                                                         2       1