Influence of Growth Stage on Spring Barley (Hordeum vulgare) Tolerance to Chlorsulfuron

Abstract

Tolerance of barley to chlorsulfuron at various stages of crop development was studied in weed-free field and pot experiments. Five barley crops were sown between mid-May and mid-July in the field in 1988 and sprayed simultaneously with four rates of chlorsulfuron when the corresponding stages of crop development ranged from growth stage 7 (GS 7) to GS 31. Early-sown barley yielded more than late-sown barley, but percent grain yield reduction from chlorsulfuron was similar for all planting dates. In a field experiment in 1989, barley was sown at three dates (May, June, and July) and each was treated with chlorsulfuron at 0, 15, 30, and 60 g ai ha−1 at either GS 12 or GS 15. Grain yield of barley sown in May and treated with 15 g ha−1 chlorsulfuron at GS 12 was reduced 35%, compared with no effect when applied at GS 15; this yield reduction was related to spike size and number. Application of chlorsulfuron at GS 12 and GS 15 to barley sown in June caused yield reductions of 20 and 11%, respectively. In contrast, barley sown in mid-July was not affected by chlorsulfuron. Applications of chlorsulfuron at GS 12,13,14, and 15 led to reductions of 75,35,15, and 5% shoot dry matter (DM) of plants grown in pots and measured at GS 33. Root DM was more sensitive to chlorsulfuron than shoot DM. Tolerance of barley to chlorsulfuron increased with age of the plant at the time of application.

Glyphosate tolerance in maize (Zea mays L.). 2. Selection and characterization of a tolerant somaclone

“…The families able to tolerate this treatment, derived from seven somaclones, also showed tolerance to the herbicide at a 2 .4 mM concentration when tested at the three-leaf stage . Such a result is consistent with a progressive decrease in herbicide sensitivity during seedling development recently reported in the case of barley for sulfonylureas (Lemerle & Cousens, 1993) . The dose employed for selection is relatively low with respect to those usually described in field usage (0.2 to 4 kg ha 1 ; Turner, 1985), but the application of a moderate selective pressure in R2 generation should be appropriate for retaining a higher amount of germplasm with potential useful traits .…”