Relationship of Hydroxamic Acid Content in Maize and Resistance to Northern Corn Leaf Blight¹

Abstract

A cyclic hydroxamate (2,4‐dihydroxy‐7‐methoxy‐l,4‐benzoxazin‐3‐one; DIMBOA) recently has been implicated in the resistance of maize (Zea mays L.) to fungi and insects. In our study, a set of 13 inbreds was used to determine the relationship of concentrations of DIMBOA and resistance to northern corn leaf blight (Helminthosporium turcicum Pass).DIMBOA concentration was estimated by the colorimettic procedure of Hamilton in plants 60 to 75 cm in height. Mean concentrations of DIMBOA ranged from 0.06 mg/g to 0.66 mg/g fresh weight. Percent leaf infection on plants at the same height ranged from 7.41 to 19.04%. A significant correlation (r =−0.61) was obtained between these two traits.DIMBOA concentrations also were determined in root, stem, and whorl tissues from five selected inbreds at various stages of growth. At 13‐cm plant height, samples from the inbreds contained uniformly high amounts of DIMBOA. The earliest acceptable separation of high and low DIMBOA lines was obtained using stem or whorl tissue from seedlings 35 to 40 cm in height. Generally those lines highest in DIMBOA at 35 to 40 cm plant height were correspondingly high in DIMBOA at the silking stage. Similarly, lines low in DIMBOA at 35 to 40‐cm plant height were low in DIMBOA at the silking stage.

A deletion in an indole synthase gene is responsible for the DIMBOA-deficient phenotype ofbxbx maize

“…1) of DIMBOA. Our earlier work (20) has demonstrated that maize converts [2][3][4][5][6][7][8][9][10][11][12][13][14] Cindole into 14 C-DIMBOA, and that perdeuterated indole is converted by maize into DIMBOA that is deuterated both in the benzene ring and at the hemiacetal carbon of the heterocyclic ring. These results demonstrate that the DIMBOA biosynthetic pathway utilizes indole as a direct intermediate and raise the question of whether a specific indole synthase exists for this pathway or whether indole is diverted from the tryptophan biosynthetic pathway.…”

Decomposition of 2,4-Dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one in Aqueous Solutions

“…Although the physiological role of DIMBOA is unknown, various workers have postulated its involvement in: (a) detoxification of s-triazine herbicides (21,26); (b) iron transport (25); (c) resistance to fungal infection in corn and wheat (2,7,8,20); and (d) as a factor in insect resistance (17,19). Because of the instability of DIMBOA, Whitney and Mortimore (30) have postulated that its degradation product, MBOA, may be involved in the resistance of corn to bacteria.…”

A Specific β-Glucosidase-Aggregating Factor Is Responsible for the β-Glucosidase Null Phenotype in Maize

“…Physical injury by a biting, chewing, or sucking insect or cell lysis after fungal and bacterial infections disrupts the compartmentalization and brings the enzyme and substrate in contact, releasing the toxic aglycone DIMBOA. Numerous studies show a high correlation between DIMBOA content of maize genotypes and the level of resistance to or inhibitory effect on insects and pathogens (Klun et al, 1967;Long et al, 1975;Argandona et al, 1983;Niemeyer, 1991).…”