Interaction Between Heficoverpa zea Damage with Corncob Diseases on Genetically Modified Corn in Sinaloa, México

GM （genetically modified） corn with the CrylAb, mCry3A and Vip3Aa20 protein of Bt （Bacillus thuringiensis） and its respective isoline as control with and without chemical control for corn earworm were used in this research. Fusarium corncob damage was lower on GM corn with （12.5%） and without （25.7%） insecticide treatment as compared with the isoline that had 48.3% and 83.1% of damaged corncobs with and without chemical control, respectively. Corn smut cob damage was also lower on GM corn with （3.2%） and without （6.3%） insect control compared with 15.5% and 49.7% damage with and without insecticide treatment, respectively. Fusarium sp. corncob rot was also lower on GM corn with 5.7% and 9.5% whereas a 24.6% and 63% rot was observed on the isoline with and without insecticide control, respectively. Ustilago maydis severity was also lower on Bt corn finding 0.07% and 0.25% damage on treatments with and without insect control as compared with the isoline that showed an 11.6% and a 41.4% smut rot with and without insecticide treatment, respectively. The authors conclude that GM corn resistant to Helicoverpa zea prevents damage by the pest, eliminating the entrance pathway for Fusarium sp. and Ustilago maydis.

TOPLESS promotes plant immunity by repressing auxin signaling and is targeted by the fungal effector Naked1

In plants,the antagonism between growth and defense is hardwired by hormonal signaling.The perception of pathogen-associatedmolecularpatterns(PAMPs)frominvadingmicroorganismsinhibits auxin signalingand plant growth.Conversely,pathogens manipulate auxin signaling to promote disease,but how this hormone inhibits immunity is not fully understood.Ustilago maydis is a maize pathogen that induces auxin signaling in its host.We characterized a U.maydis effector protein,Naked1(Nkd1),that is translocated into the host nucleus.Through its native ethylene-responsive element binding factor-associated amphiphilic repression(EAR)motif,Nkd1 binds to the transcriptional co-repressors TOPLESS/TOPLESS-related(TPL/TPRs)and prevents the recruitment of a transcriptional repressor involved in hormonal signaling,leading to the derepression of auxin and jasmonate signaling and thereby promoting susceptibility to(hemi)biotrophic pathogens.A moderate upregulation of auxin signaling inhibits the PAMP-triggered reactive oxygen species(ROS)burst,an early defense response.Thus,our findings establish a clear mechanism for auxin-induced pathogen susceptibility.Engineered Nkd1 variants with increased expression or increased EAR-mediated TPL/TPR binding trigger typical salicylic-acid-mediated defense reactions,leading to pathogen resistance.This implies that moderate binding of Nkd1 to TPL is a result of a balancing evolutionary selection process to enable TPL manipulation while avoiding host recognition.

Influence of brown stink bug feeding, planting date and sampling time on common smut infection of maize

Phytopathogen infections are frequently influenced by both biotic and abiotic factors in a crop field. The effect of brown stink bug, Euschistus servus （Hemiptera： Pentatomidae）, feeding and planting date and sampling time on common smut （Ustilago maydis） infection percentage of maize plants was examined in 2005 and 2006, and 2010 and 2011, respectively. Brown stink bug adult feeding on maize hybrid ＂DKC6971＂ at flowering in 2005 and 2006 did not influence smut infection percentage when examined using 3 treatments （i.e., 0 adult, 5 adults, and 5 adults mixed with the smut spores）. The smut infection percentages were 〈 3% （n =12） in the 3 treatments. The smut infection percentage among the 4 weekly samplings was the same, so was natural aflatoxin contamination at harvest among the treatments. The 2nd experiment showed that planting date did not affect the smut infection percentage in either 2010 or 2011. But, the smut infection percentage from the postflowering sampling was greater than preflowering sampling in both years. The smut infection percentage varied among the germplasm lines in 2010, but not in 2011. This study demonstrated that brown stink bug feeding at flowering had no effect on smut infection in maize, and the best time for smut evaluation would be after flowering. The temperature and precipitation might have also influenced the percentage of smut-infected maize plants during the 4 years when the experiments were conducted. The similarity between kernel-colonizing U. maydis and Aspergillus flavus infections and genotype × environment interaction were also discussed.