Quantifying cardinal temperatures of fenugreek (Trigonella foenum graecum L.) ecotypes using non-linear regression models

Abstract

Seed germination behaviors in addition to genetic factors are affected by ecological parameters and different climate change scenarios. Temporal requirements for seed germination. To understand the effects of different constant temperature levels on the accuracy of different thermal-germination models and germination-rate response of seven Iranian fenugreek (Trigonella foenum-graecum) ecotypes, an experiment was conducted in a completely randomized design with four replications in physiology laboratory of Research Center for Plant Sciences, Ferdowsi University of Mashhad, Iran. In this experiment, different fenugreek ecotypes were Azari, Indica, Shiraz, Ardestan, Mashhad, Shirvan, and Neyshabur along with different temperature levels including 9 constant temperature levels (0, 5, 10, 15, 20, 25, 30, 35, and 40 °C). The results showed that the best explainable models for different fenugreek ecotypes were Intersected-lines and Dent-like models. The germination rate and reciprocal time to median germination (R50) increased by raising the temperature to optimum temperature. The highest ecological temperature range (TR) for germination belonged to Mashhad ecotype at 39.7 °C according to intersected lines and Dent-like models. Also, the mean base temperature (Tb) for fenugreek ecotypes was determined at 1.1, 1.3, and 1.3 °C, the mean optimum temperature (To) was determined at 20.8, 22.4, and 21.0 °C, and the mean maximum temperature (Tm) was also estimated 39.4, 39.2 and 38.6 °C based on the outputs from intersected-lines, quadratic polynomial and five-parameters beta models, respectively. It seems that the adaptation and eco-evolutionary of Mashhad ecotype for higher germination compared to other ecotypes under different environmental conditions occurs to rapid seedling growth and avoid the risks of low productivity and extinction in the presence of abiotic stresses caused by climate change.