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ARS Home » Midwest Area » Columbia, Missouri » Plant Genetics Research » Research » Publications at this Location » Publication #57274
Title: MAIZE SILK-BROWNING, MAYSIN CONTENT, AND ANTIBIOSIS TO THE CORN EARWORM, HELICOVERPA ZEA (BODDIE)

Author
item Byrne, Patrick
item Darrah, Larry
item SNOOK M E - 6612-24-00
item WISEMAN B R - 6602-20-00
item WIDSTROM N W - 6602-20-00
item MOELLENBECK D J - PIONEER HI-BRED
item Barry, B

Submitted to: Maydica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/14/1995
Publication Date: N/A
Citation: N/A

Interpretive Summary: The corn earworm (CEW), is an important pest of corn, in the southeastern United States and elsewhere in the Americas. Larvae of CEW feed initially on silks and later on developing kernels. After being wounded, silks of some corn plants undergo a browning reaction, while those of other plants do not change color. Our study sought to determine whether selection for browning and nonbrowning silks would result in correlated changes in level of resistance to CEW. The population 10LDD underwent five cycles of divergent selection based solely on the browning reaction to form two populations with nearly all browning or all nonbrowning silks (10LDD-BR and 10LDD-NBR, respectively). A three-location evaluation showed that 10LDD-BR had concentrations of silk maysin (a compound associated with resistance to CEW) significantly higher than 10LDD-NBR. In a laboratory study in which CEW larvae were fed on diets containing dried silks, 10LDD-BR silks resulted in smaller 8-day larval weights and a longer time to pupation than those of 10LDD-NBR. Selection for browning silks was an easily implemented and effective method for increasing silk maysin concentration in 10LDD, but would not necessarily be as effective in all populations segregating for that trait.

Technical Abstract: Silks of some maize (Zea mays L.) genotypes turn brown after wounding, while those of other genotypes do not change color. The browning response involves the oxidation of flavones to quinones, and is believed to be controlled by the p1 locus. A flavone glycoside, known as maysin, occurs in silks of many genotypes. Maysin is a growth retardant to the corn earworm (CEW), Helicoverpa zea (Boddie), and is among the compounds that undergo a browning reaction. Our study sought to determine whether selection for browning and nonbrowning silks would result in correlated changes in levels of antibiosis to CEW and in concentrations of maysin. The population '10LDD Sel. Rec. Cycle 0' underwent five cycles of divergent recurrent selection based solely on the browning reaction to form two populations with nearly all browning or all nonbrowning silks ('10LDD-BR' and '10LDD-NBR', respectively). A three-location evaluation showed highly significant differences (P < 0.001) between 10LDD-BR and 10LDD-NBR, respectively, for concentrations of silk maysin (0.185 vs. 0.000% silk fresh weight) and the related compounds 3'-methoxymaysin (0.029 vs. 0.000% silk fresh weight) and chlorogenic acid (0.046 vs. 0.012% silk fresh weight). In a dried silk bioassay based on CEW growth and development, silks of 10LDD-BR resulted in smaller 8-d larval weights (63 vs. 335 g) and longer time to pupation (18.6 vs. 13.3 d) than those of 10LDD-NBR (P < 0.001 for both traits). Selection for browning silks was an easily implemented and effective method for increasing silk maysin concentration and CEW resistance (antibiosis) in 10LDD, but would not necessarily be as effective in all populations segregating for that trait.