Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 2/10/2014
Publication Date: 2/13/2014
Citation: Dowd, P.F., Johnson, E.T., Sattler, S.E. 2014. Popcorn and sorghum studies by the USDA "Ag Lab" in 2013 [abstract]. Central Illinois Irrigated Growers Association.
Technical Abstract: Popcorn ears collected in milk stage from 2010-2012 were used in studies to compare expression of potential insect and ear mold resistance genes in different years, and relate the differences in expression to influences of weather, and levels of mycotoxins at harvest. The same hybrid was evaluated at two different locations. In some cases, the expression of over 12,000 genes was significantly different from one year to the next. The greatest differences were between 2010 (a fairly normal weather year) and 2011 and 2012 (years that had hot and dry periods). The expression of many resistance genes was significantly decreased from 2010 to 2011 and 2012, in some cases over 500 fold. However, the expression of a few resistance genes was increased in 2011 and 2012 compared to 2010. There were some differences between locations, but also some similarities in the changes in expression of the same resistance related genes. Differences in planting dates in some years, which differed by as much as two weeks, influenced periods of time that ears were exposed to high temperatures, and in some cases water stress due to power interruptions that would have affected irrigation, and likely contributed to differences in gene expression the same years for the different locations. The resistance genes that were most highly affected were those responsible for producing inhibitors of protein digestion, which would impact resistance to both insects and ear molds. Additional resistance genes were induced in ears that were damaged by insects compared to those not damaged by insects, and also included those that would impact ear mold resistance. In some cases, changes in resistance gene expression were significantly associated with differences in specific mycotoxin levels in different years. National Institute of Food and Agriculture grant funding permitted a continuation of experiments to evaluate insect damage to low lignin lines of sorghum, which are also being examined for bioenergy production. Results for 2013 were similar to those found in 2012 field tests at the Havana research site location. The incidence of caterpillar leaf damage was often less for the bmr6 compared to bmr12 and normal lignin line. The amount of leaf damage, when it occurred, was significantly less at times for the bmr6 line compared to the other two. European corn borer stalk damage incidence was less for the bmr6 compared to bmr12 and normal lignin lines. The amount of stalk boring was lower in the bmr6 and bmr12 stalks compared to the normal lignin stalks. These results are similar to results for assays where leaves or pith has been removed for lab or small plot grown plants and fed to corn earworm and fall armyworm larvae, as the bmr6 leaves have had less damage and pith has been more toxic to both species.