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United States Department of Agriculture

Agricultural Research Service

Research Project: GENETIC IMPROVEMENT OF MAIZE AND PEARL MILLET FOR RESISTANCE TO INSECTS AND AFLATOXIN Title: Physiological basis of fall armyworm (Lepidoptera: Noctuidae) resistance in the seedlings of maize inbred lines with varying levels of silk maysin

Authors
item Ni, Xinzhi
item Da, Kedong - UNIV OF GA
item Buntin, G. David - UNIV OF GA
item Brown, Steve - UNIV OF GA

Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 26, 2008
Publication Date: December 1, 2008
Citation: Ni, X., Da, K., Buntin, G., Brown, S.L. 2008. Physiological basis of fall armyworm (Lepidoptera: Noctuidae) resistance in the seedlings of maize inbred lines with varying levels of silk maysin. Florida Entomologist 91:537-545.

Interpretive Summary: In order to identify new corn genetic resource that is resistant to both leaf- and ear-feeding insects over both seedling and ear-development stages, six maize inbred lines were examined for fall armyworm resistance in corn seedlings. Four corn inbred lines from Mexico (CML333, CML335, CML336, and CML338) have varying levels of corn silk maysin that confers ear-feeding insect (i.e., corn earworm) resistance, while the other two inbred lines (i.e., the fall armyworm-susceptible AB24E, and –resistant Mp708) were used as the controls of the evaluation. The leaf-feeding insect injury ratings on CML333, CML336, and CML338 (with a range of low to high levels of silk maysin) were the same as the resistant control (Mp708), and were significantly lower than the susceptible control AB24E and CML335 (without silk maysin). Plant parameters varied among the six inbred lines, but were not consistently correlated to the FAW resistance at the seedling stage. Physiological basis for insect resistance was assessed by plant photosynthetic rate and photosynthetic capacity. The photosynthetic rate was reduced by the worm injury in AB24E, CML333, CML335, and CML336, but not affected in CML338 and Mp708. The reduction in photosynthetic rate of FAW-susceptible AB24E, and resistant CML333 and CML336 indicated that insect resistance in CML333 and CML336 might not be directly related to photosynthetic rate. No difference in either photosynthetic rate or photosynthetic capacity in CML338 and Mp708 suggests that two inbred lines are tolerant to the FAW feeding injury. This experiment suggests that corn inbred lines with ear-feeding insect resistance could also confer leaf-feeding insect resistance at the seedling stage.

Technical Abstract: To assess both foliage- and ear-feeding insect resistance in the same maize inbred lines, fall armyworm (FAW), Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae) resistance at the seedling stage was examined in six corn inbred lines. The six inbred lines included the four CIMMYT maize inbred lines (i.e., CML333, CML335, CML 336, and CML338) with varying levels of silk maysin that confers corn earworm resistance and the controls (i.e., the FAW-resistant Mp708 and susceptible AB24E). The FAW injury rating and chlorophyll content were examined under greenhouse and field conditions. Plant height, plant stem circumference, and photosynthesis-related measurements were recorded on the un-infested and the infested plants only under the greenhouse conditions. The FAW injury ratings on CML333, CML336, and CML338 (with a range of low to high levels of silk maysin) were the same as the resistant control (Mp708), and were significantly lower than the susceptible control AB24E and CML335 (without silk maysin). Plant height, plant stem circumference, and chlorophyll content also varied among the six inbred lines, but were not consistently correlated to the FAW resistance at the seedling stage. Photosynthetic rate was negatively affected by the FAW injury in AB24E, CML333, CML335, and CML336, but not affected in CML338 and Mp708. The reduction in photosynthetic rate of FAW-susceptible AB24E, and resistant CML333 and CML336 indicated that insect resistance in CML333 and CML336 might not be related to photosynthetic rate. At the same time, the data suggest that CML338 and Mp708 were tolerant to the FAW herbivory, because no difference in either photosynthetic rate or photosynthetic capacity was detected in either inbred line between the un-infested and the FAW-injured corn seedlings. Further examination of photosynthetic capacity using A/Ci and light response curves supported this resistance mechanism categorization. This experiment indicated that corn earworm-resistant corn inbred lines with varying levels of silk maysin also confer resistance to foliage-feeding FAW resistance at its seedling stage.

Last Modified: 11/20/2014
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