PLANT RESISTANCE Digestive Enzymatic Activity and Nutritional Responses of Helicoverpa armigera(Lepidoptera: Noctuidae) Larvae Fed Various Tomato Cultivars B. NASERI, 1 D. KOUHI, J. RAZMJOU AND A. GOLIZADEH Department of Plant Protection, Faculty of Agricultural Sciences, University of Mohaghegh Ardabili, Ardabil, Iran J. Econ. Entomol. 107(4): 1655Ð1661 (2014); DOI: http://dx.doi.org/10.1603/EC13284 ABSTRACT Digestive enzymatic activity and nutritional responses of sixth-instar larvae of the tomato fruit borer, Helicoverpa armigera (Hu ¨ bner), were studied on eight tomato cultivars commonly cultivated in Iran. Among various tomato cultivars, the larvae fed on ÔCal JN3Õ (4.860  0.092 U/mg) signiÞcantly showed the highest level of proteolytic activity. However, proteolytic activity of the larvae reared on ÔSun 6108 f1Õ (2.182  0.161 U/mg) was signiÞcantly lower than those reared on Cal JN3, ÔKorral,Õ ÔRio grande UG,Õ ÔSuper crystal,Õ and ÔCH falatÕ. Also, the larvae fed on Korral (0.170  0.007 mU/mg) signiÞcantly had higher amylolytic activity than the other tomato cultivars. The pupal weight of H. armigera was signiÞcantly lower on Rio grande UG (0.208  0.014 g), Sun 6108 f1 (0.216  0.008 g), and Super strain B (0.229  0.014 g) than Cal JN3 and CH falat. Because the larvae and pupae reared on Rio grande UG were lighter than those fed on the others, this cultivar can be suggested as the least suitable host for feeding of H. armigera. However, because the mean weight gain of the larvae, food consumption, and larval weight during feeding period were signiÞcantly highest on CH falat, it can be selected as suitable cultivar for feeding of the pest. KEY WORDS tomato fruit borer, Helicoverpa armigera, digestive physiology, tomato The tomato fruit borer, Helicoverpa armigera (Hu ¨ b- ner) (Lepidoptera: Noctuidae), is a serious and eco- nomically destructive pest, which causes severe quan- titative and qualitative damage to host crops, including cotton, tomato, maize, and bean (Liu et al. 2004, Moral Garcia 2006). In tomato (Lycopersicon esculentum Miller), which is a preferred host plant (Jallow and Matsumura 2001), H. armigera results in 5Ð55% yield loss as the young larvae feed on tender foliage and ßowers, and the older larvae eat the fruits (Berlinger 1986, Selvanarayanan and Narayanasamy 2004). Be- cause control of H. armigera using chemical insecti- cides has negative effects, including the development of insecticide resistance in the pest (Kranthi et al. 2002), pest outbreaks, and environmental pollution (Javed et al. 2009), there is now a trend toward the use of eco-friendly approaches (Sharma and Oritz 2002), such as developing host plant resistance for the man- agement of this pest (Selvanarayanan and Narayana- samy 2004, Jallow et al. 2004). Although the insects can synthesize some of their nutritional requirements, they obtain the majority of them through their food (Chapman 1998). The pri- mary component of the herbivorous lepidopteran diet is protein, which can be broken down into amino acids by proteases. Furthermore, many lepidopteran spe- cies live on a polysaccharide-rich diet, and amylases play an important role in starch breakdown (Valencia- Jimenez et al. 2008, Zibaee et al. 2008). It is noteworthy that the secondary biochemicals of host plants can affect the activity of digestive enzymes in the insectsÕ gut (Wang et al. 2006). However, insect growth is directly attributable to nutrient input (Hwang et al. 2008), and maintaining a balance of digestive enzymes is crucial for the availability of the main nutrients (Kotkar et al. 2009). Plant protease and amylase inhibitors act as anti- metabolic proteins that interfere with the digestive process (Lawerence and Koundal 2002). Moreover, inactivation of insect digestive enzymes by plant in- hibitors can result in poor nutrient consumption and delayed development (Hosseininaveh et al. 2007, Amirhusin et al. 2007). As the insect alimentary canal is the main interface between the insect and its en- vironment, understanding the function of digestive enzymes is imperative in the development of insect pest control, and this includes the use of enzyme inhibitors and transgenic plants (Ghoshal et al. 2001, Maqbool et al. 2001, Mansouri et al. 2013). Despite the economic importance of H. armigera on the tomato, little information is available regarding the digestive enzymatic activity and nutritional responses of this pest on commonly grown tomato cultivars. However, Nemati Kalkhoran et al. (2012) considered life table parameters of H. armigera on different to- mato cultivars, and Kotkar et al. (2009) studied the 1 Corresponding author, e-mail: bnaseri@uma.ac.ir. 0022-0493/14/1655Ð1661$04.00/0  2014 Entomological Society of America Downloaded from https://academic.oup.com/jee/article/107/4/1655/814387 by guest on 13 August 2022