Helicoverpa armigera and Helicoverpa zea hybridization: constraints, heterosis, and implications for pest management

Abstract

BACKGROUND: The invasion of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) into the New World has made it possible for this pest to hybridize with a native American species, H. zea (Boddie), under natural conditions. We investigated the viability and development of hybrids of these two Helicoverpa species. We reared the parental species and evaluated crosses between H. armigera males and H. zea females and vice versa, two intercrosses between hybrids, and eight backcrosses between hybrids and parental species. We estimated the length of immature stages, fecundity, survival, sex ratio, and heterosis. RESULTS: Although hybridization occcurred, with heterosis during the development of immatures, reproductive incompatibilities also were observed between the parental species and between hybrids from subsequent crosses. The interspecific crosses between hybrids and backcrosses confirmed the possibility of introgression events and their perpetuation in field populations. The results indicate that hybridization events are favored at high population levels, while at low population levels the 'species identities' will be maintained. CONCLUSIONS:The possibility of interspecific gene flow and its perpetuation through successive crosses and backcrosses suggests several recommenations for management. Populations of both species should be maintained at an equilibrium level to reduce the chance of interspecific crosses, which are presumably more likely to occur during pest outbreaks. The existence of hybridization and resistance to different active pesticide ingredients should be monitored. All practices related to managing the resistance of these pests to chemical and biological insecticides should be systematized to reduce the chance of selecting for resistant individuals.

Helicoverpa genus on the edge of the continental U.S.: Flight phenology, analysis of hybrid presence, and insecticide performance in high-input field crops in Puerto Rico

“…The relevance of analysis to detect hybridization between H. zea and H. armigera is due to the probability of new formations of adaptive genes ( 44 , 47 ), which can have an impact on ecological attributes of the hybrids, such as a wider host range ( 48 , 49 ) and performance of management tools ( 28 , 50 , 51 ). However, a study documenting biological parameters of hybrids between H. armigera and H. zea , under laboratory conditions, indicated that egg viability is a critical factor for the success of the hybridization, with overall egg viability of 14% ( 52 ), when compared with more than 85% egg viability in the parental species. The authors concluded that there are reproductive limitations for hybridization, including barriers from the lock-and-key mechanisms presented in the noctuid genitalia morphology ( 53 , 54 ).…”

The effect of missing data on evolutionary analysis of sequence capture bycatch, with application to an agricultural pest

“…High migratory capacity, the ability to feed on a wide range of shared host plants, and rapidly developed resistance to all of the commonly used groups of insecticide chemistry (Fitt 1989 ; McCaffery 1998 ; Feng et al 2005 ) have facilitated its global spread and impact. H. armigera has recently extended its range into South America which, coupled with its potential to also reach North America (Czepak et al 2013 ; Tay et al 2013 ; Kriticos et al 2015 ), poses a serious problem for invasive pest management (Cordeiro et al 2020 ; Rios et al 2022 ).…”

Performance of cotton expressing Cry1Ac, Cry1F and Vip3Aa19 insecticidal proteins against Helicoverpa armigera, H. zea and their hybrid progeny, and evidence of reduced susceptibility of a field population of H. zea to Cry1 and Vip3Aa in Brazil

“…In the current Brazilian crop production systems, outbreaks of Helicoverpa species are favored by the overlapping and simultaneous cultivation of host plants, including soybean, maize, cotton, tomatoes, and dry bean crops [4]. Studies also reported the occurrence of interspecific hybridization between H. armigera and H. zea under laboratory conditions [5][6][7]. The successful hybridization in a restricted environment suggests that potential for multiple mating events in the field may provide opportunities to select well-adapted hybrid phenotypes [7].…”

“…Studies also reported the occurrence of interspecific hybridization between H. armigera and H. zea under laboratory conditions [5][6][7]. The successful hybridization in a restricted environment suggests that potential for multiple mating events in the field may provide opportunities to select well-adapted hybrid phenotypes [7]. Cases of resistance to Bt proteins in H. zea have been reported in the U.S. and China [8][9][10][11] and decreases in susceptibility to Cry proteins by H. armigera have been reported in U.S., India, and China [12,13].…”