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

30th Congress of the International-Society-of-Sugar-Cane-Technologists (ISSCT)

International audience

anglais. In Reunion Island, new sugarcane commercial varieties 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 growth 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 for R570 and R577. Does the variety R583 selected under temperature constrained environment performs 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 obtained 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. Taking into account the germination threshold temperature obtained, a simulation of the germination times was carried out per zone, on the west coast of Reunion Island, based on climatic 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 parallel was drawn between the geographical limits obtained, where the establishment of the variety R583 is possible regarding the time required for germination (in days) from the simulation and the actual spreading of this variety.