Effects of simulated and flea beetle injury to cotyledons on growth of drought-stressed oilseed rape, Brassica napus L.

Abstract

Nowatzki, T. M. and Weiss, M. J. 1997. Effects of simulated and flea beetle injury to cotyledons on growth of droughtstressed oilseed rape, Brassica napus L. Can. J. Plant Sci. 77: 475-481. Simulated injury was compared with flea beetle injury on cotyledons of oilseed rape grown at various soil moistures to determine the effects of injury on seedling growth in the greenhouse. The cotyledons of 7-d-old seedlings were injured at 0, 25, 50, and 75% of the total area with a 0.5-mm mechanical pencil or by flea beetles. The soil moisture was maintained at the field capacity, half field capacity, and the permanent wilting point. The growth response of the seedlings was compared for simulated flea beetle injury and soil moisture 7, 14, and 21 d post-injury, and for simulated and flea beetle injury, and soil moisture 7 d post-injury. Simulated injury had the greatest effect on seedlings grown at the field capacity, at 7 d post-injury. At the reduced soil moistures, increased levels of simulated injury were necessary to cause a significant loss in growth. By 14 and 21 d post-injury, compensation to the simulated injury occurred. Simulated injury caused significantly less growth reduction across all injury levels compared with flea beetle injury. However, at injury levels above 25%, both simulated and flea beetle injury had similar trends in growth reduction. The simulated injury tested in these experiments cannot be used in place of flea beetles for resistance screening studies, but may be useful if incorporated as a preliminary tool. Nous avons comparé en serre les effets sur la croissance au dépot d'endommagements artificiels avec ceux des dégàts causés par l'altise des crucifères au cotylédon de plants de colza oléagineux cultivés sous divers régimes hydriques. Les cotylédons de plantules de 7 j étaient endommagés à raison de 0, 25, 50 et 75 % de la surface totale, soit à l'aide d'un stylo à pointe de 0,5 mm, soit par les altises. Le sol était maintenu à la capacité au champ, à la moitié de la capacité au champ et au point de flétrissement permanent. Le comportement des plantules à l'égard des endommagements artificiels et du niveau hydrique était observé 7, 14 et 21 j après les traitements et à l'égard des endommagements artificiels ou par altises et du niveau hydrique, 7 j après les traitements. 7 j après les traitements, l'effet le plus prononcé de l'endommagement artificiel était observé sur les plantules cultivées à la capacité au champ. Au niveau hydrique plus bas, des degrés d'endommagement simulés plus élevés étaient nécessaires pour provoquer une baisse significative de la croissance. Au 14 e et 21 e jours après les traitements, les plantes avaient compensé l'effet des endommagements artificiels. Tous niveaux d'endommagement confondus, le traitement artificiel provoquait une réduction de croissance significativement moins importante que les attaques réelles des altises. Par ailleurs, aux degrés d'endommagement supérieur à 25 %, la réduction de la croissance suivait des tendances semblables quel que soit le mod...

A comparison of artificial defoliation techniques using canola (Brassica napus)

“…The majority of these studies reported detrimental effects on components of plant fitness, such as reduced shoot and root biomass (Knapp 1986;Quinn and Hall 1996;Wirf 2006), decreased flower, fruit, or seed production (Obeso 1993;Domínguez and Dirzo 1994;Koptur et al 1996;Genter et al 1997), and decreased seed size (Sackston 1959;Rockwood 1973;Koptur et al 1996). On the other hand, some studies have demonstrated compensatory or even beneficial, overcompensatory effects of herbivory (McNaughton 1983;Karban and Myers 1989;Paige 1994;Lennartsson et al 1998;Marshall et al 2005; but see Belsky 1986 andBelsky et al 1993) or variable effects, depending on whether defoliation occurred naturally or was achieved artificially (Gedge and Maun 1992;Nowatzki and Weiss 1997). For example, in wild radish, Raphanus raphanistrum, artificial clipping of leaves by scissors resulted in only minimal induced plant resistance (e.g., increased production of defensive chemicals) (Agrawal 1999(Agrawal , 2000a, whereas strong induced resistance, no induced resistance, or even induced susceptibility to herbivory occurred following attack by four lepidopteran herbivores (Agrawal 2000b).…”

Macroevolutionary constraints to tolerance: trade‐offs with drought tolerance and phenology, but not resistance

“…Another commonly limiting resource for plants is water availability, which might also mediate the ability of species to replace tissues lost to herbivores. A few studies have examined tolerance in relation to water as a limiting resource and the results have been mixed (Georgiadis et al 1989, Nowatzki and Weiss 1997, reviewed in Wise and Abrahamson 2007 and all have focused on withinspecies responses.…”

“…A few studies have examined tolerance in relation to water as a limiting resource and the results have been mixed (Georgiadis et al. , Nowatzki and Weiss , reviewed in Wise and Abrahamson ) and all have focused on within‐species responses.…”

Impact ofHalotydeus destructoron Crop Seedlings at Different Plant Developmental Stages and Levels of Moisture Stress

“…Enhanced tolerance to herbivory in moisture stressed plants has been found previously. Nowatzki and Weiss (1997) showed that feeding impacted canola seedlings more when grown in unstressed conditions compared with seedlings that experienced moisture stress. Similarly, Sun et al (2010) found the weed Alternanthera philoxeroides (Martius) Grisebach, had greater tolerance to herbivores when grown under moisture stress.…”