Canola cultivars affect nutrition and cold hardiness of Plutella xylostella (L.) (Lepidoptera: Plutellidae)
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ORIGINAL RESEARCH ARTICLE
Canola cultivars affect nutrition and cold hardiness of Plutella xylostella (L.) (Lepidoptera: Plutellidae) Gadir Nouri-Ganbalani 1
&
Bahram Naseri 1 & Shadi Majd-Marani 1 & Ehsan Borzoui 1
Received: 29 March 2019 / Accepted: 11 February 2020 # African Association of Insect Scientists 2020
Abstract The diamondback moth, Plutella xylostella (L.), has become the most destructive insect pest of Brassica crop plants, such as B. napus throughout the world including Iran. In this study, nutritional indices, digestive enzyme activity and cold hardiness of P. xylostella on seven canola cultivars including Delgan, H19, Modena, Okapi, Opera, RGS003, and SLM046 were studied under laboratory conditions (25 ± 1 °C, 65 ± 5% RH, 16:8 L:D). Fourth instar larvae fed on cultivar SLM046 had the highest efficiency of conversion of ingested and digested food (4.35 ± 0.24% and 4.99 ± 0.31%, respectively). Relative consumption rate (RCR) of P. xylostella 4th instar was higher when fed on Opera cultivar (5.62 ± 0.15 mg/mg/day) while it was lower on Okapi (3.33 ± 0.15 mg/mg/day). The larvae fed on cultivars SLM046 and Okapi had the highest (0.194 ± 0.007 mg/mg/day) and the lowest (0.088 ± 0.003 mg/mg/day) relative growth rate (RGR), respectively. We found a significantly higher amylolytic and proteolytic activity in the midgut of the larvae fed cultivar SLM046. Our findings showed that the activity of enzyme inhibitors and polyphenol oxidase, as antidigestive compounds, are major reasons for the low nutritional efficiency of P. xylostella larvae on some cultivars. The results of the present study indicate that cultivar Okapi is an unsuitable host for the feeding of P. xylostella. These results develop our knowledge of the negative effects of plant defenses on P. xylostella. Keywords The diamondback moth . Nutritional indices . Plant inhibitors . Polyphenol oxidase
Introduction Canola (Brassica napus L.; Brassicaceae) is a major arable crop throughout the world (FAO 2011). In Iran, this crop is often attacked by several insect pests that often require control by growers to protect yield. The diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), a serious pest of brassicaceous crops including the canola, are responsible for heavy economic losses worldwide (Brown et al. 1999; Furlong et al. 2013). Plutella xylostella larvae may feed on different parts of Brassica plants and is often difficult to control if it feeds internally on covered areas of crops (Justus et al. 2000). Conventional approaches based on synthetic insecticides to control this pest have failed due to the development of resistance against many insecticides (Shelton et al. 1993; Kegley et al. 2007). While developing strategies to control * Gadir Nouri-Ganbalani [email protected] 1
Department of Plant Protection, Faculty of Agriculture and Natural Resources, University of Mohaghegh Ardabili, Ardabil, Iran
economically important herbivorous insects, it is necessary to have a thorough understanding of nutritional response and midgu
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