Location: Crop Genetics and Breeding ResearchTitle: Multiple insect resistance in 59 commmerical corn hybrids - 2017
|TOEWS, M - University Of Georgia|
|BUNTIN, G - University Of Georgia|
Submitted to: Agricultural Experiment Station Publication
Publication Type: Experiment Station
Publication Acceptance Date: 10/16/2017
Publication Date: 11/30/2017
Citation: Ni, X., Toews, M.D., Buntin, G.D. 2017. Multiple insect resistance in 59 commmerical corn hybrids - 2017. Agricultural Experiment Station Publication. 101-9, pp. 37-40. http://www.swvt.uga.edu/2017/CN17/AP101-9insect.pdf.
Interpretive Summary: not required.
Technical Abstract: Commercial corn hybrids were screened for ear- and kernel-feeding insect resistance under field conditions at Tifton, GA. Nine hybrids were rated Very Good (VG), the highest rating for multiple insect resistance in 2017 (see following table). Thirteen were Good (G), 19 were Fair (F), and 13 were Poor (P). One hybrid included a blend of 80% transgenic and 20% non-transgenic seeds, known as refuge in a bag (RIB). In cotton growing area and all of Georgia, RIB products are required to have a 20% Non-Bt structured refuge. Three hybrids were developed utilizing YHR traits (also known as Optimum® Intrasect™), 13 hybrids have Genuity VT Double PRO (VT2P) traits, and 1 hybrid has VT Triple PRO (VT3P) traits. The Optimum® Intrasect™ insect protection traits (or YHR) include a combination of two insect protection traits – Herculex® I and YieldGard® Corn Borer, while the VT2P or VT3P traits contain a stack of two or three Bt genes. VT2P hybrids targeted foliar- and ear-feeding lepidopteran pests, while VT3P hybrids have an additional Bt gene for rootworms. Overall insect damage on corn ears was relatively high in the 2017 trial, which is comparable to what we observed in 2016. The six types of ear- and/or kernel-feeding insects in the order of damage severity were: corn earworm and fall armyworm, stink bugs, sap beetles, pink scavenger caterpillar, and maize weevil. Corn earworm and fall armyworm damage was combined because the damage on corn cob is difficult to separate. Feeding penetration by these caterpillar pests of natural infestations in corn ears was between 0.2 and 2.8 cm, which was lower than the damage observed in 2016 (0.2-3.5 cm). Multiple species of sap beetles were recorded in 2017. Stink bug damage in 2017 was relatively low, ranging from 0.1 to 1.6% of the kernels per ear, which was less than that in 2016, 0.1 to 1.4%. Sap beetle damaged kernels were 0.7-4.1%, which is greater than 0.2-2.4% in 2016, as well as pink scavenger caterpillar damaged kernels were < 1% in 2017 and 2016. In addition, flowering time of all entries were similar (between 51 and 57 days after planting), irrespective of categorization of Short (S) or Medium (M) maturity as shown in the table. The relatively early flowering (50-57 days after planting) was observed in 2017, which is similar to what we observed in 2016. Because husk tightness and husk extension are considered important traits for ear- and kernel-feeding insect resistance, the husk features of the sampled ears were examined. Husk tightness was assigned using a scale of 1 to 5, in which 1 = very loose and 5 = very tight. Average ratings for husk tightness were between 3.4 and 4, which were all considered medium for husk tightness. Husk extension ranged between 0.1 and 5.3 cm, and was negatively correlated to worm penetration and percentage of sap beetle-damaged kernels in corn ears, but not to husk tightness. Multiple insect resistance was categorized in four groups according to the insect damage ratings on corn cobs and kernels; they are very good (VG), good (G), fair (F), and poor (P). VG represents the least amount of insect damage, while P represents the greatest amount of insect damage. The rankings of the 59 hybrids for multiple insect resistance in the table was based on the results of the principal component analysis using corn husk extension and tightness along with damage caused by corn earworm and fall armyworm, stink bugs, sap beetles, pink scavenger caterpillar, and maize weevil. The lettered ratings in the table refer only to relative resistance to insects based on a principal component analysis with husk tightness and extension, corn earworm and fall armyworm damage, stink bug, sap beetle, and pink scavenger caterpillar damage kernels. The data in this report are not indicative to yield. For yield data of a hybrid, please refer to other reports provided in this publicati