Attractiveness of tobacco volatiles induced by Helicoverpa armigera and Helicoverpa assulta to Campoletis chlorideae

The attraction of Helicoverpa armigera- and Helicoverpa assulta-induced and mechanical damage-in- duced tobacco volatiles to Campoletis chlorideae was investi-gated, and the induced volatiles were analyzed. In wind- tunnel, C. chlorideae was strongly attracted by herbivore- induced tobacco volatiles. Mechanically damaged tobacco leaves, whether treated with caterpillar regurgitant or water, were more attractive to the parasitoid than undamaged to-bacco leaves. GC-MS analysis revealed that only 4 com-pounds were released from undamaged tobacco leaves, whereas 13 compounds were commonly emitted from herbi-vore-infested and mechanically damaged tobacco leaves. Compound β-pinene was specifically induced by the infesta- tion of H. armigera, and (Z)-3-hexenal was only induced by the infestation of H. armigera and H. assulta, whereas hexyl acetate was only induced by mechanical damage. Tobacco leaves infested by H. armigera and H. assulta released larger amounts of volatiles than undamaged tobacco leaves did. Tobacco leaves treated with artificial damage plus caterpil- lars regurgitant or water emitted the same levels of volatiles, which were higher than that emitted by undamaged tobacco leaves. The emission amounts of single compounds were also different between differently treated plants. The differences were large between herbivore-induced and mechanical dam-age-induced compounds, and small between H. armigera- and H. assulta-induced compounds, and among compounds emitted from mechanically damaged plants treated with wa-ter or caterpillar regurgitant.

Testes and chromosomes in interspecific hybrids between Helicoverpa armigera(Hübner)and Helicoverpa assulta(Guenée)

The interspecific hybridization between Helicoverpa armigera females and Helicoverpa assulta males yielded F1 hybrids (RS), fertile males and sterile individuals with abnormal genitals. The reverse hybridization between H. assulta females and H. armigera males yielded F1 hybrids (SR)――fertile males and fertile females. The morphology of testes and the karyotype of chromosomes of larvae in the hybrids were investigated. Among the 2d old fifth-instar SR larvae, individuals without testes were fertile females and those with testes were fertile males. The length and breadth of testes between SR and parental species were not significantly different (p>0.05). Among the 2d old fifth-instar RS larvae, the testes were observed in all the individuals, but it could be classified into two types. The length and the breadth of testes in Type 1 larvae were not significantly different from those of their parental species (p>0.05), while those in Type 2 were significantly less than those of their parental species (p<0.01). Mitotic metaphase I of brain cells showed the diploid chromosomes number of both reciprocal hybrids was 2n=62, as many as their parents. The haploid number of 31 was confirmed by counts from spermatocytes at meiotic metaphase from SR male larvae and Type 1 larvae of RS. Meiosis was not observed in spermatocytes of Type 2 larvae of RS. Considering the characteristics of adult hybrids of RS, it was concluded that Type 1 individuals in RS were fertile and those of Type 2 were sterile. The sterility of Type 2 individuals in RS is attributed to the abnormity in development of testes and the failing meiosis of spermatocytes. As a result, the normal spermatozoon could not been produced.