INFIVE   05416
Unidad Ejecutora - UE
congresos y reuniones científicas
Impact of poplar rust on leaf dynamics and photosynthesis
Buenos Aires
Congreso; XIII Congreso Forestal Mundial; 2009
Institución organizadora:
In Paraná River Delta, an excellent region to produce softwood for the industry, there are 14,000 hectares of poplars. The first plantations were made with P. deltoides subesp. angulata cv. carolinensis at the end of the 19th century. This clone was heavily infected by Melampsora medusae and had to be replaced during the ’20s with P. nigra cv. italica, which was decimated by M. larici-populina in 1935. Thereafter poplars were only infected towards the end of the growing season. However, in 1994, P. deltoides ‘Catfish 2’ was attacked in the middle of the growing season by M. medusae. To assess the effects of this disease on poplar foliage and photosynthesis in stool-beds, we established a factorial experiment, with two clones of P. deltoides ‘Australiano 106/60’ and ‘Onda’ and two levels of disease (without rust, sprayed with 25,8 g ai/ha of tebuconazole; and with rust, not sprayed). The disease progress was monitored every fifteen days by counting the number of uredia per square centimeter on a random sample of ten heavily infected leaves per plot. The leaf dynamics was also evaluated every fifteen days by counting the number of new and fallen leaves. Leaf area was estimated using a model based on the length and maximum width of the leaves. Photosynthesis at light saturation (Asat) was measured during the peak of the rust attack with a PP System IRGA in both clones and the respiration in dark (R) was measured in ‘Onda’. Electron transport rate (ETR) was measured with a FMS2 (Hansatech). Leaf dynamics was affected in ‘Onda’, but only the amount of leaves developed at the beginning of a new growing season was reduced in ‘Australiano 106/60’. In ‘Onda’ Asat and Agross were lower in leaves with uredia but R was higher. So, the decrease in Asat was not due only to a higher respiration cost,  indicating that the photosynthetic system was damaged as it was shown by the drop in ETR. Asat in leaves with uredia was not affected in ‘Australiano 106/60’. Both leaf dynamics and photosynthesis indicate that the damage produced by the disease is related to the genotype, and that growth reduction reported for the disease is explained by a reduction in leaf area and also by a decrease in photosynthesis in the remnant leaves. The implications of the efficiency of photosynthesis and the structure of the genotypes in the development of the disease are discussed.