02248naa a2200265 a 450000100080000000500110000800800410001910000220006024500950008226000090017752014330018665000220161965000180164165000220165965300230168165300110170465300460171565300420176170000170180370000220182070000170184270000200185970000240187977300790190310831992010-11-11       2005    bl uuuu     u00u1 u    #d1 aORLANDO, R. C. A.  aRelationship between early - blight epidemic, healthy leaf area and tuber yield in potato.  c2005  aThe field experiments, during the years 2001 and 2002, were carried out to determine the effect of early-blight (Alternaria solani), on potato (Solanum tuberosum) plant growth and tuber yield. Using the disease severity gradient method, plots with five different epidemic intensity levels (D1 to D5 in descending order) were obtained. The objective of this study was to correlate the disease severity (percentage leaf necrosis), the green leaf area index (GLA), duration of healthy leaf area (DHA) or radiation absorption by healthy leaf area (HAA), with tuber production in potato cultivar Bintje. Based on analysis of 100 plants, the tuber yield was linearly related (p&lt=O,O1) to the variables such as AUDPC (area under the disease progress curve), GLA, DHA and HAA. The variables that best explained the tuber yield were DHA (R2= 0.49 and 0.55 in 2001 and 2002, respectively) and HAA (R2= 0.48 and 0.54 in 2001, 2002, respectively). Separate analyses of each epidemic based on 20 plants each showed that the early-blight effect on DHA, HAA, yield and radiation use efficiency was dependent upon the epidemic severity. The highest yields were obtained from plots with least least disease index and highest DHA. In general, the main effect of early-blight epidemic was the reduction of both the leaf area and of the vegetative cycle of the plant, leading to tuber yield loss of 52.5% and 58.2% in 2001 and 2002, respectively.  aAlternaria Solani  aEpidemiologia  aSolanum Tuberosum  aÁrea foliar sadia  aPerdas  aProdução do tubérculo de batata Bintje  aSeveridade da epidemia da pinta-preta1 aZAMBOLIM, L.1 aVALE, F. X. R. do1 aCOSTA, L. C.1 aMARTINEZ, C. A.1 aBERGAMIN FILIHO, A.  tSumma Phytopathologica, Botucatugv. 31, n. 3. p.247-253, July/Sept. 2005.