7. Prediction and Standardization of Relative Emergence and Seed Vigour in Rice (Oryza sativa L.) Through Radicle Emergence Analysis

Abstract

An experiment was conducted on fourteen rice varieties to standardize the radicle emergence test for predicting seed germination. Seeds were incubated under a cool white LED’s until the final count of germination at 22 ± 2 °C and 82 ± 2 % relative humidity. Radicle emergence and germination were calculated cumulatively and 72 hours was found to be the most optimal time. The high vigor rice varieties germinated in 4 to 5 days, but required repeated or single counts of maximum radicle emergence (MaxRE), which were consistent with normal seedlings obtained at 216 hours with maximum germination (MaxG). Longer lag periods lengthen the mean radicle emergence time (MRET) in several rice varieties. Seed vigour was divided into six categories based on the MaxRE and MaxG values. The MRET and mean germination time (MGT) distinguish vigour in greater detail i.e., five and six groups than the MaxRE and MaxG, respectively. The variance of germination time was substantial for radicle emergence (RE) and germination time. MaxRET (maximum radicle emergence time) and MaxGT (maximum germination time) had the strongest positive significant association (0.997). Mean germination time (MGT) showed highest negative significant correlation (-0.917) with vigour index (VI) and lowest positive significant correlation (0.296) between MaxRE and VI. Whereas MGT showed lowest negative significant correlation (-0.253) with MaxG. The R 2 values between seed vigour parameters and radicle emergence test were significant for MaxRE, MaxRET, MaxG and MGT. Testing and classifying of seed vigour and radicle emergence of rice varieties from different breeding backgrounds or origins or growing seasons and ecotypes, fifty percent radicle emergence time (t50RE) may have the potential to be used alongside mean radicle emergence time (MRET) rather than MRET alone.