Chen Yigen, Ni Xinzhi, Cottrell Ted E, Wood Bruce W, Buntin G David
Department of Entomology, University of Georgia, Griffin, GA 30223, USA.
J Econ Entomol. 2009 Jun;102(3):1262-9. doi: 10.1603/029.102.0353.
The black pecan aphid, Melanocallis caryaefoliae (Davis) (Hemiptera: Aphididae), is a foliar feeder of pecan, Carya illinoinensis (Wangenh.) K. Koch (Juglandaceae). The pest causes chlorosis of leaflet lamina, physiological damage to foliage and trees, and commonly limits the profitability of commercial pecan orchard enterprises. However, key aspects of this host-pest interaction are poorly understood. We report here the effects of M. caryaefoliae feeding on the foliar activity of oxidative (i.e., catalase, lipoxygenase [LOX]-1 and 3, and peroxidase) and hydrolytic (i.e., esterase) enzymes in relation to the degree of aphid resistance among pecan varieties. The 2-yr study showed that M. caryaefoliae-infested foliage exhibited elevated peroxidase activity only in susceptible ('Desirable', 'Sumner', and 'Schley'), but not in resistant ('Cape Fear', 'Gloria Grande', and 'Money Maker') genotypes. Susceptible genotypes also exhibited more severe leaf chlorosis in response to M. caryaefoliae feeding than the resistant genotypes; however, the aphid feeding did not influence catalase or esterase activity in all varieties, except the increase of esterase activity in Desirable and Gloria Grande. Melanocallis caryaefoliae feeding also influences activity of two lipoxygenase isozymes, with LOX3 being more frequently induced than LOX1. Foliar LOX3 activity was more frequently induced by M. caryaefoliae feeding in the moderately resistant 'Oconee' and highly resistant Money Maker and Cape Fear than in the susceptible genotypes. Therefore, the elevation of peroxidase is likely to be associated with aphid susceptibility and contributed to the severe leaf chlorosis, whereas the increase of LOX3 activity might be associated with aphid resistance in pecan. These findings contribute to our understanding of the etiology of M. caryaefoliae-elicited leaf chlorosis on pecan foliage. Such information may also be used to develop enzyme markers for identifying black pecan aphid resistance and/or susceptibility in pecan germplasm.
黑核桃蚜（Melanocallis caryaefoliae (Davis)，半翅目：蚜科）是核桃（Carya illinoinensis (Wangenh.) K. Koch，胡桃科）的一种叶部取食害虫。该害虫会导致小叶叶片黄化，对叶片和树木造成生理损害，通常会降低商业核桃园企业的盈利能力。然而，这种寄主 - 害虫相互作用的关键方面却知之甚少。我们在此报告黑核桃蚜取食对氧化酶（即过氧化氢酶、脂氧合酶[LOX]-1和3以及过氧化物酶）和水解酶（即酯酶）叶部活性的影响，以及这些影响与核桃品种间抗蚜程度的关系。这项为期两年的研究表明，受黑核桃蚜侵害的叶片仅在易感品种（‘Desirable’、‘Sumner’和‘Schley’）中过氧化物酶活性升高，而在抗性品种（‘Cape Fear’、‘Gloria Grande’和‘Money Maker’）中则没有。与抗性品种相比，易感品种在黑核桃蚜取食后叶片黄化也更严重；然而，除了‘Desirable’和‘Gloria Grande’中酯酶活性增加外，蚜虫取食对所有品种的过氧化氢酶或酯酶活性均无影响。黑核桃蚜取食还会影响两种脂氧合酶同工酶的活性，其中LOX3比LOX1更常被诱导。在中度抗性的‘Oconee’以及高抗性的‘Money Maker’和‘Cape Fear’中，黑核桃蚜取食比在易感品种中更常诱导叶部LOX3活性。因此，过氧化物酶的升高可能与蚜虫易感性相关，并导致严重的叶片黄化，而LOX3活性的增加可能与核桃的蚜虫抗性相关。这些发现有助于我们理解黑核桃蚜引发核桃叶片黄化的病因。此类信息还可用于开发酶标记物，以鉴定核桃种质中对黑核桃蚜的抗性和/或易感性。
