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International audience; Sugarcane variety development programmes are costly and lengthy. It appears important to periodically assess their ability to select competitive genotypes for yield components and provide genetic gains. This article reports a 10-year retrospective analysis of successive variety trials conducted in four regional breeding programmes on Reunion Island in the most advanced regional selection stage. The four variety programmes were dedicated to the humid coastal zone (LM), the per-humid coastal zone (SB), the irrigated dry coastal zone (ES) and the dry high lands (VB) of the local industry. Using mixed linear models, the objective of the study was to (1) assess genetic variabilities available for yield components in this advanced selection stage; and (2) estimate trends of genetic gains achieved over the last decade across the four programmes. Yield components were: cane yield (CY), estimable recoverable sugar (ERS), fibre content (FIB) and economic index (EI). Broad-sense heritabilities were high (0.70-0.91) for all traits in each programme. Mean genetic coefficients of variation were about twice as high for CY (14.1%) and EI (15.5%) compared to ERS (5.7%) and FIB (6.6%). A higher probability of identifying superior varieties was found for CY and EI in two of the four programmes characterized either by thermal and hydric stresses (VB) or by an edaphic stress (SB). Simple linear regression of variety performances versus years of selection revealed trends in genetic gains for EI ranging between 0.53 and 1.81% increase per year that were highly significant (P < 0.001) in the two programmes (LM and VB).

Fiberboards were prepared using phenolic type resins (phenol-formaldehyde) and sugarcane bagasse fibers. Lignin extracted through an organosolv process from sugarcane bagasse was used as substitute of phenol in phenolic resins from 40 (lignin-phenol-formaldehyde) to 100 wt.-% (lignin-formaldehyde) substitution. Some of the fibers were chemically modified by oxidation with chlorine dioxide and treatment with furfuryl alcohol (FA), leading to fibers coated with polyfurfuryl alcohol. Thermal analysis (DSC and TGA) of the prepolymers allowed setting up an efficient curing to prepare fiberboards. Impact strength and water absorption were measured showing the importance of the curing pressure to obtain good performance. When chemically modified fibers were used to prepare board samples, enhanced durability against white root fungi is observed, and to a less degree against brown root fungi. Sugarcane bagasse fiberboards were prepared from prepolymers where lignin substituted phenol up to 100%. This replaces these materials in advantageous position, relating to those prepared from phenol-formaldehyde resins, due to their high content of renewable raw materials. The results obtained are promising for the utilization of sugarcane bagasse as raw materials for preparing fiberboards to be used in tropical areas.

The photochemical behavior of compound 1 was studied as representative of a non-phenolic dibenzodioxocin lignin model, because the presence of both photoreactive α-O-4 and β-O-4 linkages in these structures should bring a high photosensivity of the framework. Fluorescence emission of 1 is situated at shorter wavelength (340 nm) than the emission of the corresponding biphenylbiphenol 5 (380 nm). This observation, which has to be correlated with conjugation between the phenyl rings of the biphenyl chromophore, indicates that dibenzodioxocins are not contributing to the long wavelength emission in lignins (>480 nm). Irradiation of 1 in non-degassed benzene solutions, using Pyrex vessel, which eliminates wavelengths below 290 nm, gives colored solutions. The reaction is very efficient ( Φ R =0.37) and analysis of the photoproducts indicates that the first step of the reaction is a cleavage of the α-O-4 bond followed either by β-O-4 cleavage or formation of rearranged products. The color is due to condensation of biphenyl-oxidized products (quinone type). A mechanism is proposed based on separation and identification of photoproducts. The reactivity of 1 supports the fact that dibenzodioxocins have to be considered as important chromophores in photodegradation of lignocellulosic materials.