Genetics and Biochemistry of Insect Resistance in Maize

Natural Variation in Maize Aphid Resistance Is Associated with 2,4-Dihydroxy-7-Methoxy-1,4-Benzoxazin-3-One Glucoside Methyltransferase Activity

“…For instance, other QTL may function in maize inbred lines that are more resistant to R. maidis than B73 (Figure 2A). Similarly, genetic mapping of resistance to chewing herbivores has identified QTL that are not linked to known benzoxazinoid-related genes (McMullen et al, 2009a;Meihls et al, 2012). Our results demonstrate that newly available maize genetic and genomic resources make it straightforward to proceed from the observation of such natural variation in insect resistance to elucidating the genetic and biochemical basis of this variation.…”

“…QTL mapping is often limited by the relatively high cost of genotyping and the difficulty of repeating experiments with a segregating population. To overcome these limitations, large sets of recombinant inbred lines have been created for several plant species, including Arabidopsis thaliana (Keurentjes et al, 2011) and maize (Zea mays) (Flint-Garcia et al, 2005;Yu et al, 2008;McMullen et al, 2009a). Once such recombinant inbred lines have been genotyped, they represent a permanent resource that can be used to genetically map loci that influence any phenotypic trait that varies in the population.…”

“…A nested association mapping (NAM) population of ;5000 recombinant inbred lines was generated by crossing a genetically diverse population of 25 maize inbred lines to B73 (Flint-Garcia et al, 2005;Yu et al, 2008;McMullen et al, 2009a). The NAM population has been used to map numerous maize traits, including resistance to northern leaf blight (Setosphaeria turcica; Poland et al, 2011) and southern leaf blight (Bipolaris maidis; Kump et al, 2011).…”

“…As chewing herbivores rather than aphids have been the focus of most prior research on natural variation in maize herbivore resistance (McMullen et al, 2009a;Meihls et al, 2012), we initiated experiments using R. maidis and recombinant inbred lines of the NAM population to identify resistance mechanisms. Concerted mapping of loci associated with aphid resistance, benzoxazinoid production, and callose deposition was followed by the molecular and biochemical characterization of candidate genes.…”

Assessment of maize stem borer damage on hybrid maize varieties in Chitwan, Nepal

“…Alternatively, in maize, one of the important herbivore-induced volatiles is terpene synthase TPS10, which is strongly expressed after the damage of lepidopteran pest, and it recruits natural enemies of the pest (Schnee et al, 2006). Furthermore, secondary metabolites in maize such as C-glycosyl flavones maysin and the phenylpropanoid product chlorogenic acid in silk are detrimental to growth and development to certain lepidopteraninsects, Helicoverpa zea and Ostrinia nubilalis respectively (McMullen, Frey & Degenhardt, 2009). Thus, it would be one of the possible reasons that the above mentioned secondary metabolites sufficiently produced by plants in our experimental field to recruit natural enemies of the maize stem borer, as a result of that we were unable to observe the significant variation in plant damage percentage between the tested varieties.…”