Effect of the germination threshold temperature on the geographical distribution of the variety R583 in Réunion

In Réunion, new sugarcane commercial cultivars selected for constrained environments, particularly with regard to low temperatures, have demonstrated their better adaptability by producing more biomass in the high-lying parts of the island. The germination dynamics of populations of single-bud setts were studied and characterized in climate chambers for three contrasting varieties at different constant temperatures. The emergence of setts as a function of time is faster and more complete for the variety R583, which is known to be better adapted to low temperatures than R570 and R577. Does the variety R583 selected under temperature-constrained environment perform better under such conditions as a result of its lower threshold temperature for germination? The objectives of our study were (i) to characterize the germination performance of three varieties under different temperature regimes, and (ii) to illustrate in the field the important simulated results developed with the help of mapping tools. A germination non-linear mixed model with random effects was developed from the degree-days data. This Weibull equation made it possible to determine a threshold temperature for the germination process for each variety. Using this germination threshold temperature, a simulation of the germination times was carried out for each zone on the west coast of Réunion based on weather data over 10 years. The two-degree difference between the base temperatures of varieties R583 and R570 shows the relative importance of this parameter on germination date, suggesting that the plant is able to establish more quickly. A comparison was made between the geographical limits obtained from the simulation of where the establishment of the variety R583 is possible given the time required for germination (in days), and the actual distribution of this variety