Non-destructive assessment of mango vegetative growth during a growing season. Application to four cultivars

The non-destructive measure of annual vegetative growth is of particular interest in mango to study the relationships between vegetative growth and flowering. Allometric relationships are powerful tools to infer vegetative growth from the basal cross-sectional area ot a branch. The objectives of this study were fIrst to develop a method to estimate allometrically the total biomass and leaf area of a I-year-old branch from its basal cross-sectional area, and second to examine whether these relationships were cultivar-specifIc. Dry biomass, leaf area and basal diameter were measured during three consecutive years on a sample of I-year-old branches belonging to four cultivars: Cogshall, Irwin, Jose and Kensington Pride. Allometric relationships were computed using the ordinary least square method on log-transformed data. Year and cultivar effects on the slope and y-intercept of the relationships were tested using appropriate statistical tests. For each variable, a relationship per cultivar and a relationship common to the four cultivars were computed. A dataset of basal diameters of I-year-old branches measured on fIve trees per cultivar was used to compare these relationships. The mean dry biomass and leaf area produced per tree were calculated with the cultivar-specific relationship and the common relationship. These data we~e compared statistically for each cultivar, and among cultivars. . Slopes of the relationships were similar among years and cultivars. Y-intercepts were generally not affected by year, but varied among cultivars. Consequently, mean dry biomass and leaf area per tree calculated with cultivar-specific and common relationships were mostly signifIcantly different. The comparison of vegetative growth among cultivars gave the same ranking with the cultivar-specifIc and the common relationships, with however differences in the multiple means comparison test. In conclusion, allometric relationships appeared as a simple non-destructive method to assess vegetative growth in mango. Cultivar-specific relationships should be preferred to relationships common to several cultivars. (Texte intégral