Common chickweed (Stellaria media (L.) Vill.) has been observed invading forage wheat (Triticum aestivum L.) and triticale (xTriticosecale) fields treated with acetolactate synthase (ALS)-inhibiting herbicides in the southern San Joaquin Valley (SJV) of California. Studies were conducted to verify if these weed populations were resistant to these herbicides and if so, what the mechanism of resistance was. Seeds of common chickweed plants were collected from three locations representing four populations—three suspected resistant and one suspected susceptible to ALS inhibitor herbicides. Plants were grown from these collections, and greenhouse dose–response studies were conducted twice using five common ALS inhibitors: mesosulfuron-methyl, pyroxsulam, imazamox, imazethapyr, and tribenuron-methyl. Results confirmed that three of the populations were resistant to the label rate of all five ALS-inhibitor herbicides tested in this study. Sanger sequencing identified the Trp574Leu substitution, a mutation previously associated with target-site resistance to ALS-inhibiting herbicides. This is the first case of common chickweed populations cross-resistant to ALS herbicides west of the Rocky Mountains in North America.
Synchronizing nitrogen (N) release from cover crop residues with maize N demand is essential for reducing reliance on synthetic fertilizer while maintaining yield in semi-arid, irrigated production systems. Optimizing N fertilizer rates is crucial for sustaining maize yield while reducing production costs and environmental impacts. A three-year study (2023–2025) in Western Colorado evaluated three flex maize hybrids (Zea mays L.) planted into three preceding cover crop species (hairy vetch (Vicia villosa Roth), cereal rye (Secale cereale L.), and a hairy vetch + cereal rye mixture), two tillage systems (strip-till vs. conventional tillage), and two N fertilizer rates (100% vs. 80% of the recommended rate). Grain yield, ear characteristics, and agronomic efficiency varied significantly among hybrids: the high-flex hybrid DKC 105-33 RIB consistently outyielded the low-flex hybrid DKC 48-34 RIB by 1.5–2.5 Mg ha−1 across years and maintained higher productivity. The hybrid × N interaction was not significant, suggesting that yield responses to reduced N were statistically similar across hybrids. Strip-tillage did not significantly affect grain yield in any year, indicating that reduced tillage can be implemented without a yield penalty, although it modestly changed leaf area index, plant population density, and harvest index. Reducing the N rate from 224 to 179 kg N ha−1 decreased grain yield, harvest index, and population density, but did not affect plant height, leaf area index, ear density, or 100-kernel weight; Cover crop N supply ranged from 20.3 to 24.7 kg N ha−1 and was governed primarily by tissue N concentration rather than total biomass; hairy vetch supplied the greatest N credit despite producing only about one-third the biomass of cereal rye. Collectively, these results demonstrate that pairing high-flex maize hybrids with cover crop and reduced-tillage management is a viable strategy for optimizing maize productivity while reducing synthetic N inputs in semi-arid, irrigated cropping systems.
Waterlogging (WL) is a major abiotic stress that restricts eggplant productivity by disrupting plant growth, photosynthesis, cellular homeostasis, and antioxidant defense systems. Although both 6-benzyladenine (BA) and melatonin (MT) have been reported to enhance stress tolerance in plants, their combined effects against WL stress in eggplant (Solanum melongena L.)remain poorly understood. This study investigated the individual and synergistic roles of exogenous BA and MT in mitigating WL-induced damage in two eggplant varieties contrasting in WL tolerance: the tolerant cultivar BHB−6 and the susceptible cultivar BB−8. WL markedly inhibited plant growth and photosynthetic pigment accumulation while intensifying oxidative damage, as evidenced by increased hydrogen peroxide (H2O2) and malondialdehyde (MDA) contents in both varieties. In contrast, combined application of BA and MT significantly alleviated these adverse effects, outperforming the individual treatments by restoring growth, preserving chlorophylls, and suppressing oxidative stress. Under BA + MT treatment, BHB−6 exhibited superior stress adaptation, maintaining higher relative leaf water content (+15%) and accumulating greater levels of soluble sugars (+44%) and free amino acids (+80%) than only WL−stressed plants. This enhanced tolerance was associated with a marked activation of antioxidant defenses, including increases in the activities of catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX). BB−8 showed comparatively lower recovery, but BA + MT substantially improved its tolerance through enhanced osmotic adjustment and antioxidant defense, compared to only WL −stressed plants. Multivariate analyses further confirmed that the combined BA + MT treatment consistently outperformed the individual applications across physiological and biochemical traits. Overall, these findings demonstrate that co-application of BA and MT effectively enhances WL tolerance by strengthening antioxidant capacity, improving osmotic regulation, and maintaining physiological integrity, with more pronounced benefits in the resistant variety while providing substantial protection to the susceptible variety.
Although lowland rice ecosystems play a vital role in meeting the growing demand for rice in sub-Saharan Africa, the performance of New Rice for Africa (NERICA) varieties and their root traits under flooded conditions remain insufficiently characterized. We evaluated seven NERICA varieties (NERICA 1, 2, 3, 4, 7, 10, and 14) and the japonica cultivar ‘Haenuki’ as a regional reference from Japan in a two-year field trial for grain yield and in a tube-culture experiment for shoot and root traits. NERICA 1 had the numerically highest average yield among the NERICA varieties and did not differ significantly from Haenuki in either year, whereas NERICA 14 had the lowest yield in both years. The variety × year interaction was not significant. Compared with Haenuki, NERICA varieties were generally taller but produced fewer tillers and nodal roots, lower root length density (RLD), and coarser root systems, as reflected by a lower specific root length and fine-to-thick root ratio (FTR). Haenuki had greater RLD in upper soil layers, whereas no significant varietal differences were detected in deeper layers (10–20 cm). Exploratory path analysis indicated that shoot dry weight was positively associated with tiller number and RLD and negatively associated with FTR, while tiller number was positively associated with RLD. These results suggest that RLD is associated with shoot growth in tube culture, and that NERICA 1 may be a candidate for further evaluation among the tested NERICA varieties. Since this study is a preliminary screening, validation under actual field conditions in African lowland environments is needed.
Phosphorus (P) management can influence habanero pepper growth and productivity, but crop response may depend on the strategy used to supply this nutrient. This study evaluated five phosphorus fertilization strategies in Capsicum chinense Jacq. grown under shade house conditions: granular diammonium phosphate + urea (T1), soluble diammonium phosphate + urea (T2), soluble orthophosphate with steric protection (T3), phosphoric acid (T4), and a control without additional fertilization after 40 days after transplanting (T5). Four experimental sections per treatment were analyzed, with ten sampled plants distributed among the sections. Vegetative and reproductive traits were evaluated between 72 and 134 days after transplanting. The area under the curve (AUC) was calculated from repeated measurements of plant height, branching, leaf traits, and reproductive variables to assess their cumulative responses over the corresponding evaluation periods. At 134 days after transplanting, T3 and T4 showed greater plant height than T2 and T5, although plant-height AUC did not differ significantly among treatments. T3 had the highest final fruit set (62.0 fruits plant−1) and estimated yield (0.765 kg plant−1 and 0.849 kg m−2), whereas T5 had 35.7 fruits plant−1 and estimated yields of 0.296 kg plant−1 and 0.329 kg m−2. The first two principal components explained 68.93% of the total variation. PC1 (54.71%) was mainly associated with plant height, stem diameter, petiole length, leaves per branch, fruit set, and internode length, whereas PC2 (14.22%) was more closely related to leaf dimensions and branching. T3 and T4 tended toward positive PC1 values, while T5 was positioned toward negative values. Greater vegetative growth did not necessarily result in higher productivity. T3 showed favorable final vegetative growth, the highest numerical final fruit set, and greater estimated yield than T1, T2, and T5, although its yield did not differ significantly from T4. These findings highlight the importance of considering both vegetative growth and reproductive performance when evaluating phosphorus fertilization strategies for habanero pepper.
