Effect of seed vigor on field performance and yield of grain sorghum (Sorghum bicolor (L) Moench)

Hybrid grain sorghum seed were aged artificially for 0, 3, 5, 7 and 11 days at 42°C and 100% RH, which produced five vigor levels of seed. Among the various laboratory tests performed, standard germination was the least sensitive in discerning the physiological condition of the seed lots. The speed of germination more accurately differentiated the degree of deterioration of the seed lots and was closely correlated to yield. Planting low vigor seed caused reduced plant height, delayed panicle exsertion, and anthesis, less tillering capacity, and reduced yield. These slow growing plants were significantly inferior in panicle exsertion to those produced from more vigorous seeds. Seeds aged for 7 and 11 days had their process of exsertion delayed 2 and 3 days, respectively. Anthesis, consequently, was also significantly retarded. Tillering capacity of plants produced from low vigor seeds was significantly reduced, as well as grain yield. Primary head yield was also significantly reduced 14% for the more deteriorated seeds, and 12% for the mixed treatment, as compared to the control. Yield reductions of 9, 4 and 3% were also detected in seeds aged for 7, 5 and 3 days, respectively, as compared to the control. Seed moisture content was generally higher at harvest time for the lower vigor levels of seed indicating that the process of maturation was delayed due to low vigor. The blended treatment (mixed) was found to be as poor as the most deteriorated seeds in many plant performance characteristics. The drastic reduction in yield in this particular treatment suggests further research using different blending proportions and accurate identification of plants produced from high and low vigor seeds.