Differential tolerance of Hawaiian sugarcane varieties to diuron, 3-(3,4-dichlorophenyl)-1, 1-dimethylurea

Typescript.Thesis (Ph. D.)--University of Hawaii, 1969.Bibliography: leaves 57-58.xii, 75 l illusHawaiian sugarcane varieties, which are interspecific hybrids within the genus Saccharum, were found to differ substantially in their tolerance to diuron, 3-(3,4-dichlorophenyl)- 1,1-dimethylurea, and ametryne, 2-(ethylamino)-4- (isopropylamino)-6-(methylthio)-s-triazine. Metabolism, uptake and distribution of diuron were studied as possible mechanisms of the differential varietal response. In a field experiment diuron and ametryne were applied at 9 lb./acre (4 lb./acre pre-emergence + 5 lb./acre post-emergence) to three varieties of sugarcane which were reported to be either susceptible (H 53-263), intermediately susceptible (H 57-5174), or tolerant (H 50-7209) to herbicides. Using growth in height and diameter as criteria of phytotoxicity, variety H 53-263 was found to be susceptible to both diuron and ametryne, while varieties H 50-7209 and H 57-5174 were found to be tolerant. Tillering was reduced in all varieties; however, reduction was greatest in variety H 53-263. In nutrient solution the concentrations of diuron which brought about a 50% reduction in the fresh weight of variety H 53-263 and H 50-7209 were 0.35 and 1.6 ppm, respectively. Monomethyldiuron, a diuron metabolite, was found to be about 2.5 times less toxic to H 53-263 than diuron. Diuron-14c was found to be degraded in both the resistant variety, H 50-7209, and the susceptible variety, H 53-263. The primary metabolites were monomethyldiuron, 1-(3,4dichlorophenyl)- 3-methylurea, and demethylated diuron, 3,4-dichlorophenylurea. Degradation of diuron was more extensive in the resistant variety, H 50-7209, than in the susceptible variety H 53-263. In an uptake and translocation study, both the tolerant and susceptible varieties removed approximately 8~ of; carbonyl-labeled diuron from nutrient solution within 9 days after treatment. The distribution of radioactivity 14 days after treatment was almost identical in both varieties when calculated on a total activity basis: however, when the distribution data were calculated on the basis of activity per unit of dry weight, there was a greater concentration of radioactivity in the younger leaves of the susceptible variety H 53-263, than in the resistant variety, H 50-7209. Conversely, there was a greater concentration of radioactivity in the roots of H 50-7209 than in H 53-263. The differential varietal response to diuron exhibited by varieties H 53-263 and H 50-7209 is believed to be at least partially explained by differential metabolism and translocation