Ear Damage of Sweet Corn Inbreds and Their Hybrids under Multiple Corn Borer Infestation

Abstract

In Mediterranean countries, the principal corn (Zea mays L.) pest is the pink stem borer (PSB) (Sesamia nonagrioides Lef.), followed in importance by the European corn borer (ECB) [Ostrinia nubilalis (Hübner)]. Our objective was to quantify injury by these pests in a set of inbreds that showed different levels of ear damage by the PSB in a previous study and in their hybrids. A diallel among seven sweet corn inbreds that varied for ear damage by PSB was evaluated in three environments under PSB and ECB infestations. The importance of general combining ability (GCA) and specific combining ability (SCA) for ear damage by corn borer was determined. Inbred parents were also tested under manual infestation conditions with both borers. There was variability for ear damage traits among sweet corn inbred lines, but none of them were completely resistant. General combining ability effects were significant for the general appearance of the ear, ears with damaged grain, and ears with damaged shanks under PSB infestation. Under PSB infestation, SCA was not significant for any trait. Most traits showed significant GCA effects under ECB infestation, although SCA effects were also important for some damage traits. The inbred EP61 could supply some favorable alleles because it showed negative and significant GCA effects for ear damage under infestation by both species. Inbreds EP59 and V7726 showed negative and significant GCA effects for ear damage by ECB. These inbreds could be included in a sweet corn synthetic population that would be improved to decrease ear damage by corn borers.

On-farm evaluation of inundative biological control of Ostrinia nubilalis (Lepidoptera: Crambidae) by Trichogramma brassicae (Hymenoptera: Trichogrammatidae) in three European maize-producing regions

“…Corn borers represent the main biotic stressor for maize crops in Europe . The European corn borer (ECB), Ostrinia nubilalis (Hübner), is the most important maize pest in most parts of Europe, while the Mediterranean corn borer (MCB), Sesamia nonagrioides Lef., is predominant in warmer areas of southern Europe . ECB damage is mostly caused by larvae that enter the maize stalk after hatching and feed on the pith.…”

“…A key element for reaching this goal is to promote the implementation of integrated pest management (IPM), which has been compulsory in the EU since the beginning of 2014. Several alternatives have been suggested to reduce the dependence on insecticides for ECB control in maize crops, for example the breeding of maize cultivars with increased tolerance to insects, the use of pheromone mating disruption, and the use of Bt maize expressing the insecticidal protein Cry1Ab from Bacillus thuringiensis . However, owing to the rather conservative EU policies on genetically modified crops, in concert with the strong opposition of European consumers both to their cultivation and to the extensive application of pesticides, a more acceptable way to control ECB, in line with the Directive 2009/128/EC, is by means of biological control, which was the focus of the present study.…”

Searching for New Sources of Pink Stem Borer Resistance in Maize (Zea mays L.)

“…Until now, only one popcorn population, ESP0070441, has been evaluated for resistance to stem and ear damage by the pink stem borer along with many field corn populations . ESP0070441 was as resistant to stem and ear attack as the most resistant field corn populations.Resistance to pink stem borer, measured as less tunnel length and/or damage on the ear, is mainly under additive gene control , Cartea et al.1999, 2001, Velasco et al 2002. Nevertheless, yield under infestation conditions has been defined as the best trait for evaluating the level of defense against pink stem borer attack and general combining ability as well as specific combining ability effects are significant for this trait .…”

“…Resistance to pink stem borer, measured as less tunnel length and/or damage on the ear, is mainly under additive gene control , Cartea et al1999, 2001, Velasco et al 2002. Nevertheless, yield under infestation conditions has been defined as the best trait for evaluating the level of defense against pink stem borer attack and general combining ability as well as specific combining ability effects are significant for this trait .…”

Spatial distribution and losses by grain destroying insects in transgenic corn expressing the toxin Cry1Ab

“…However, while the initial generations of S . frugiperda occurs in young corn plants, subsequent generations of this species infest older plants and at higher levels in subsequent cultivation cycles [ 44 ], damaging leaves, tassels, stems and ears, causing substantial loss of productivity [ 45 , 46 ].…”