Temperature-dependent demography of Chilades pandava peripatria (Lepidoptera: Lycaenidae)

Chilades pandava peripatria Hsu and its host plant Cycas taitungensis Shen, Hill, Tsou & Chen are both endemic species to Taiwan. Ch. pandava peripatria has a specific association with buds and soft leaves of cycad plants. The introduced species, Cy. revoluta, have prolonged budding periods and extensive auxiliary buds that extensively contribute to the outbreak of Ch. pandava peripatria. An in-depth knowledge of the development, survival, and fecundity of Ch. pandava peripatria under different environmental conditions is necessary to understand the population growth of Ch. pandava peripatria. The demography of Ch. pandava peripatria was studied based on the age-stage, two-sex life table at 20, 23, 25, 28, and 31 degrees C, 70% RH, and a photoperiod of 16:8 (L:D) h under laboratory conditions. Ch. pandava peripatria completed its development under tested temperatures but did not produce offsprings at 23 degrees C. Because of the high egg mortality at 20 degrees C, the data at this given temperature were excluded from this study. The intrinsic rate of increase (r) under these tested temperatures was 0.1846, 0.2919, and 0.1412 d(-1), respectively. The net reproductive rate (H(o)) was 165.47, 262.32, and 56.68 offsprings per individual and the mean generation time (T) was 27.72, 19.10, and 28.67 d, respectively. Our results indicated that Ch. pandava peripatria is highly adaptable to environments where temperature ranges from 25 to 31 degrees C.     

Methyl jasmonate induced responses in four plant species and its effect on Spodoptera litura Fab. performance

Defensive proteins, such as polyphenol oxidase (PPO) and trypsin inhibitor (TI), are induced by herbivore wounding and exogenous methyl jasmonate application in various plant species. This study was conducted to measure induction of PPO and TI in radish, sweet pepper, tomato, and water spinach plants following herbivore wounding (I), methyl jasmonate application (M), and a combination of the two treatments (M + I). The effect of induced responses was also examined against third instar Spodoptera litura Fab. PPO activity was induced in radish by treatment I only; in sweet pepper, by treatments I and M; in tomato, by treatments I, M, and M + I; and in water spinach, by treatments M and M + I. The activity of TI was enhanced 1.2–1.4-fold in radish, sweet pepper, and tomato by M and M + I treatments, whereas in water spinach, it was enhanced 1.2-fold by all 3 treatments. The relative growth rate (RGR) of S. litura was reduced by 53% on radish plants following M treatment only. It was reduced by 37% and 42% on sweet paper plants following M and M + I treatment, respectively. RGR was significantly reduced on test tomato plants following I, M, and M + I treatments. The RGR of S. litura was unaffected on water spinach plants following any treatment. Collectively, the results of this study indicated that induction of plant defensive proteins in response to S. litura feeding or exogenous methyl jasmonate application varied among plant species, which further affected the induced plant resistance to the caterpillars.     

Jasmonate-induced defenses in tomato against Helicoverpa armigera depend in part on nutrient availability, but artificial induction via methyl jasmonate does not

The effects of synthetic phytohormones, such as jasmonic acid (JA) and methyl jasmonate (MeJA), on induced plant defenses and protection against herbivores have been well documented. Previous research on tomatoes has shown that exogenous JA and MeJA can elevate the activities of defensive enzymes, like polyphenol oxidases (PPOs) and proteinase inhibitors (PIs), and reduce the performance of herbivores. While such defenses are believed to depend on the availability of resources for the plant, data on the relationship between nutrient availability and tomato JA defenses are scarce. For this study, we grew cultivated tomatoes under different nutrient regimes, that is, high, moderate, or low, and sprayed them with 1.5?mM MeJA or a control solution to assess (1) the oviposition preference of Helicoverpa armigera moths for these plants; (2) the plant??s total nitrogen and protein content; (3) the plant??s PPO and PI activity; and finally (4) the performance of H. armigera larvae on these plants. The results revealed that adult moths selecting an oviposition site did not discriminate between the treatments. Plants had a higher N-content when grown under a high-nutrient regime, but did not differ in total protein, irrespective of the MeJA treatment. Also, PPO activity was the same across treatments, but trypsin inhibitor (TPI) activity was highest in plants grown under a moderate fertilization regime. MeJA-induced TPI activity in all treatments was high but equal. Larvae had the highest weight gain on plants grown under a moderate fertilization regime. Interestingly, they stopped feeding on plants induced with MeJA, resulting in 100?% mortality. Our results indicate that the plant??s normal TPI activity is maximal under moderate-nutrient conditions and that this, surprisingly, coincides with maximal larval weight gain. In contrast, induction of TPI activity via MeJA is much stronger and independent of the plant??s fertilization history yet suffices to make the larvae stop feeding. We speculate that a moderate induction of TPI activity may result in a compensatory feeding response while inducing a high level of TPI activity will lead to enhanced protection.