BACKGROUND: The widespread occurrence of ALS inhibitor-and glyphosate-resistant Amaranthus palmeri has led to increasing use of protoporphyrinogen oxidase (PPO)-inhibiting herbicides in cotton and soybean. Studies were conducted to... more
BACKGROUND: The widespread occurrence of ALS inhibitor-and glyphosate-resistant Amaranthus palmeri has led to increasing use of protoporphyrinogen oxidase (PPO)-inhibiting herbicides in cotton and soybean. Studies were conducted to confirm resistance to fomesafen (a PPO inhibitor), determine the resistance frequency, examine the resistance profile to other foliar-applied herbicides and investigate the resistance mechanism of resistant plants in a population collected in 2011 (AR11-LAW B) and its progenies from two cycles of fomesafen selection (C1 and C2). RESULTS: The frequency of fomesafen-resistant plants increased from 5% in the original AR11-LAW-B to 17% in the C2 population. The amounts of fomesafen that caused 50% growth reduction were 6-, 13-and 21-fold greater in AR11-LAW-B, C1 and C2 populations, respectively, than in the sensitive ecotype. The AR11-LAW-B population was sensitive to atrazine, dicamba, glufosinate, glyphosate and mesotrione but resistant to ALS-inhibiting herbicides pyrithiobac and trifloxysulfuron. Fomesafen survivors from C1 and C2 populations tested positive for the PPO glycine 210 deletion previously reported in waterhemp (Amaranthus tuberculatus). CONCLUSION: These studies confirmed that Palmer amaranth in Arkansas has evolved resistance to foliar-applied PPO-inhibiting herbicide.
The dairy activity, based on pastures, represents the main source of income for the rural population of the Andes of northern Peru. The objective was to evaluate biomass yield, growth rate, plant height, Crude Protein (CP), Neutral... more
The dairy activity, based on pastures, represents the main source of income for the rural population of the Andes of northern Peru. The objective was to evaluate biomass yield, growth rate, plant height, Crude Protein (CP), Neutral Detergent Fiber (NDF), in vitro digestibility of dry matter (IVDDM) and metabolizable energy (ME) of 22 genotypes of Lolium spp. in three Andean floors (AF) (AF I: 2300 - 2800, AF II: 2801 - 3300 and AF III: 3301 - 3800 masl) in northern Peru. Better biomass (7662 kg dry material (DM) ha-1 year-1) and growth rate (21.0 kg DM ha-1 day-1) showed AF I for Lolium perenne L., however AF III stood out in yield (9,041 kg MS ha-1 year-1) and growth rate (24.8 kg DM ha-1 day-1) for Lolium multiflorum L. The mean ME was 2.61 Mcal kg-1 MS and 2.43 Mcal kg-1 MS for L. perenne and L. multiflorum, respectively. The nutritional values of both varieties are adequate for feeding cattle to grazing in the mountains. Likewise, the genotypes that showed better performance should be used in a pasture improvement plan.
