02865nam a2200265 a 450000100080000000500110000800800410001910000250006024500940008526000510017930000090023050000200023952021340025965000220239365000210241565000120243665000100244865000230245865000180248165000140249965000250251365300220253865300200256065300190258015633241999-04-23       1987    bl uuuu  m   00u1 u    #d1 aCHARCHAR, M. J. d'A.  aReactions of near-isogenic pea cultivars to Fusarium oxysporum f. sp. pisi races 1 and 5.  aWhashington: Washington State Universityc1987  a93p.  aTese Doutorado.  aClosely related pea cultivars (Pisum sativum L.), possessing or lacking a single dominant gene for resistance to Fusarium oxysporum f. sp. pisi race 1 (Vantage = resistant, M410 = susceptible) or race 5 (Sundance II = resistant, Sundance = susceptible), were grown in soil infested with race 1 or 5 at 1,000 or 10,000 cfu/g. Both races colonized surface cells (pathogens able to withstand washing with detergent, but not able to survive surface disinfection) of hypocotyls, tap and lateral roots of both resistant and susceptible cultivars. The surfaces of these organs supported larger numbers of Fusarium colonies per unit length of plant part from susceptible than from resistant cultivars at 20 and 30 days after planting but the differences were inadequate to explain the resistance. Each race was isolated from apices of tap and lateral roots and from excised lateral-root ends, of both resistant and susceptible cultivars, but were isolated more frequently from susceptible than resitant cultivars at all incubation dates and inoculum densities. Internal invasion (pathogens are able to survive surface disinfection) of tap roots and hypocotyls occurred with all cultivars but was less frequent in the resistant than the susceptible cultivars. Lateral roots and stems of resistant cultivars were not invaded internally, in contrast to the equivalent plant parts of susceptible cultivars. Invasion of epicotyls of resistant cultivars was limited as of 20 days after planting, in contrast, epicotyls of susceptible cultivars were extensively invaded by this time. Scanning electron microscopy revealed that vascular plugs sealed off xylem elements in the lateral roots, epicotyl and above ground stems of resistant but not susceptible cultivars. Rather than plugs, xylem of susceptible cultivars was extensively invaded by mycelium of the pathogens. Xylem fluids collected from excised stems, inhibited germtube growth if from resistant cultivars, but stimulated conidial germination and germtube growth if from susceptible cultivars. A resistance response based on physical containment and reduced fungal growth is evident.  aDoença de Planta  aDoença Fúngica  aErvilha  aFungo  aFusarium Oxysporum  aPisum Sativum  aVariedade  aVariedade Resistente  aDisease resistace  aFungal diseases  aPlant diseases