Rate of photosynthesis seems to be a significiant component of yield at least in restrictive environmental conditions, and it could be used as an additional parameter of selection. More data, however, are needed. We have analyzed the variability of this physiological trait in a set of 104 full sib families extracted from a synthetic population developed for second cropping in North Italian climate. Measurements were made at flowering time on single leaves of 6 plants per plot with 2 replications of a completely randomized block design. The portable system of ADC Ltd. (Hoddesdon-England) (consisting of an IRGA, a leaf cuvette, an air supply unit and a data logger) was used. Photosynthesis rate was estimated as C02 exchange rate (µ mol m-2 s-1) in an open system. Data range from 5.93 to 32.77 with an average value of 24.498. As regards the genetic component of the trait the estimate of intraclass correlation coefficient was 0.43. The frequency distribution of the family mean values is reported in the Figure.
These preliminary data seem encouraging to start a two way intrapopulation selection procedure in order to assess the correlated response to selection of the main morphological and physiological components of yield in environmentally restrictive conditions.
A. Camussi, F Stefanini and M. Bozza
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