Drought tolerance of Paspalum notatum subjected to defoliation

La sequía asociada al cambio climático y a la variabilidad climática es el principal factor que afecta la productividad y diversidad de los ecosistemas terrestres. El objetivo de este estudio evaluar la tolerancia a la sequía y el crecimiento compensatorio de dos procedencias de Paspalum notatum sometidas a defoliación y déficit hídrico. El experimento se llevó a cabo en condiciones de invernadero, ubicado en la Estación Experimental para el Estudio del Trópico Seco “El Limón”, adscrita a la UNAN Managua. Se realizó un experimento con arreglo factorial de tratamientos con tres repeticiones. Los individuos de dos procedencias de P. notatum fueron sometidos a dos niveles de defoliación y dos niveles de régimen hídrico. Las variables evaluadas fueron producción de materia seca, tasa de crecimiento relativo y potencial hídrico. Los principales resultados muestran las plantas de P. notatum en condiciones sin estrés hídrico presentaron un aumento en su biomasa aérea en un 15 %, la acumulación de biomasa de rizoma de plantas defoliadas fue menor en relación a las plantas no defoliadas, la biomasa de raíces estuvo en dependencia del régimen hídrico, la biomasa acumulada total aumentó en un 20 % en condiciones no defoliadas y las plantas defoliadas de Muy Muy mostraron una sobrecompensación y las plantas defoliadas de Rivas presentaron una compensación parcial. El potencial hídrico en plantas defoliadas no mostró diferenciación, indistintamente del régimen hídrico al que fueron sometidos. La sequía es un factor determinante que modifica la capacidad compensatoria de gramíneas sometidas a defoliación en biomasa aérea y rizomas.

Performance of growing beef cattle consuming bahiagrass hay treated with calcium oxide and molasses

Two experiments were conducted to evaluate the effects of Pensacola bahiagrass (Paspalum notatum) hay treated with calcium oxide (CaO) and molasses on performance of growing beef cattle supplemented or not with cottonseed meal. In Exp. 1, growing Bos indicus influenced heifers [n = 59; 250 ± 29 kg body weight (BW)] and steers (n = 37; 256 ± 45 kg BW) were used. In Exp. 2, heifers (n = 56; 249 ± 26 kg BW) and steers (n = 8; 249 ± 20 kg BW) from Exp. 1 were used. Both experiments were randomized complete block designs and consisted of 56-d periods in which cattle were weighed every 14 d. On d 0, cattle were weighed after a 16-h water and feed withdrawal, stratified by sex, breed, and BW, and blocked by initial BW. Cattle were allotted to 24 and 16 dormant bahiagrass pastures (1.34 ha each) in Exp. 1 and Exp. 2, respectively. Pastures were located in two different areas within 0.52 km of each other and were stratified by location and randomly assigned (n = 8 pastures/treatment) to treatment. In Exp. 1 treatments were: 1) untreated dry hay (DH); 2) hay treated with 10% molasses [dry matter (DM) basis] + water (to 65% DM; MOL); or 3) hay treated with 5% CaO (DM basis) + 10% molasses (DM basis) + water (to 65% DM; CAO). In Exp. 2 only treatments MOL and CAO were applied, and cottonseed meal was provided at 0.3% of cattle BW/d (as fed basis). In both experiments, data were analyzed using pasture as the experimental unit. The model included the fixed effects of treatment, sex, and their interaction (Exp. 1). Location and block were included as random effects. In both experiments, initial and final BW were not affected by treatment (P ≥ 0.362 and P ≥ 0.283, respectively) or sex (P ≥ 0.512 and P ≥ 0.495, respectively) and no treatment × sex interaction was observed in Exp. 1 (P > 0.05). Additionally, no effects of treatment (P ≥ 0.515), sex (P ≥ 0.285), or treatment × sex interaction (Exp. 1; P = 0.582) were observed on average daily gain (average of -0.03 kg in Exp. 1 and 0.537 kg in Exp.2). Bahiagrass hay treated with molasses alone or in combination with CaO failed to improve performance of growing beef cattle. However, when protein supplementation via cottonseed meal was provided, cattle did not experience weight loss.

High-quality Chromosome-scale De Novo Assembly of the Paspalum Notatum ‘Flugge’ Genome

Background: Paspalum notatum is a diploid multi-purpose subtropical herb native to South America. Its chromosome length is 2n=20XX and has a high ecological significance. It is currently widely planted in tropical and subtropical regions. Despite the gene pool of P. notatum being unearthed to a large extent in the past decade, no details about the genomic information of relevant species in Paspalum have been reported. In this study, the complete genome information of P. notatum was established and annotated through sequencing and de novo assembly of its genome. Results: The latest PacBio third-generation HiFi assembly and sequencing revealed that the genome size of P. notatum is 541M. The assembly result is the highest index among the genomes of the gramineous family published so far, with a contig N50=52Mbp, scaffold N50=49Mbp, and BUSCOs=98.1%, accounting for 98.5% of the estimated genome. Genome annotation revealed 36511 high-confidence gene models, thus providing an important resource for future molecular breeding and evolutionary research. A comparison of the genome annotation results of P. notatum with other closely related species revealed that it had a close relationship with Zea mays. An analysis of the expansion and contraction of gene families suggested that P. notatum contains gene families associated with environmental resistance, increased reproductive ability, and molecular evolution, which explained its excellent agronomic traits. Conclusion: This study is the first to report the high-quality chromosome-scale-based genome of P. notatum assembled using the latest PacBio third-generation HiFi sequencing reads. The study provides an excellent genetic resource bank for gramineous crops and invaluable perspectives regarding the evolution of gramineous plants. Keywords: Paspalum notatum ‘Flugge’, Genome, De novo assembly, Genome annotation

Herbicide Options to Manage Novel Turf-type Bahiagrass (Paspalum notatum)

Herbicide management information is lacking for recently developed turf-type bahiagrass germplasm. The objective of this study was to evaluate the herbicide tolerance of nine experimental bahiagrass genotypes compared to the industry standard ‘Argentine’. The experimental entries included Argentine and ‘Wilmington’ mutants, and wild-type breeding lines. Plants were grown under greenhouse conditions, and twelve herbicides were applied at 1 and 2 times labeled rates. Bentazon, bromoxynil, carfentrazone + 2,4-D + MCPP + dicamba, and carfentrazone were classified as safe. Fluroxypyr, halosulfuron, and triclopyr + clopyralid reduced growth >50% when applied at twice the label rate. Fenoxaprop, sulfentrazone + imazethapyr, and thiencarbazone + iodosulfuron + dicamba reduced growth and caused turfgrass injury above an acceptable threshold (≥20%). In general, the Argentine mutants showed greater herbicide injury compared to the Wilmington-mutants. Although metsulfuron exceeded the acceptable injury threshold and stopped growth in all the genotypes, Argentine and genotype WT6 were the least injured by this herbicide. The experimental genotype WT6 consistently showed the greatest herbicide tolerance. Except for one genotype (WT4), the experimental genotypes responded similarly or better than Argentine to the tested herbicides, except for metsulfuron.

Potential Phytoremediation of Pampa Biome Native And Invasive Grass Species Cohabiting Vineyards Contaminated With Cu In Southern Brazil

The aims of the present study are to evaluate whether the growth of Pampa biome native grass species Axonopus affinis, Paspalum notatum and Paspalum plicatulum, as well as of invasive grass species Cynodon dactylon, is compromised by excessive Cu availability in the soil (0, 35 and 70 mg of Cu kg-1), to determine the impact of excessive Cu on the physiological responses of the investigated species and to assess whether these species have the potential to enable the phytoremediation of soils contaminated with Cu. C. dactylon presented the best performance in soil contaminated with 35 mg of Cu kg-1. In C. dactylon, the concentrations of chlorophyll b and carotenoids increased, as did the photosynthetic rate and plant growth. Phytotoxic effects of Cu in soil contaminated with 70 mg of Cu kg-1 were more severe on A. affinis and led to plant death. The other species presented reduced photosynthetic and growth rates, as well as increased activity of antioxidant enzymes such as SOD and POD. This very same Cu level has decreased photosynthetic pigment concentrations in P. notatum and P. plicatulum. On the other hand, it did not change chlorophyll a and b concentrations in C. dactylon and increased carotenoid concentrations in it. High values recorded for Cu bioaccumulation-in-grass-root factor, mainly in P. plicatulum, have indicated that the investigated plants are potential phytostabilizers. High C. dactylon biomass production - in comparison to other species - compensates for the relatively low metal concentration in its tissues by increasing metal extraction from the soil. This makes C. dactylon more efficient in the phytoremediation process than other species.

Grass pollen sensitization in dogs in Paraná, Brazil: comparison between percutaneous and intradermal testing

ABSTRACT Canine atopic dermatitis is an inflammatory, genetic, pruritic and chronic dermatosis that affects between 10 and 30% of dogs and one of the most important allergens is grass pollen. The objective of this study was to evaluate the sensitization to grass pollen allergens in dogs with canine atopic dermatitis and to compare intradermal skin test (IDT) with percutaneous test (PT). For this study, ten healthy dogs and 39 dogs with atopic dermatitis were tested. Dogs were submitted to IDT and PT for Lolium multiflorum, Cynodon dactylon and Paspalum notatum. The IDT and PT tests were compared using the Proportion Test. All healthy dogs were negative to both tests. Ten atopic dogs (25.6%) responded positively to the PT and none were positive in IDT. C. dactylon, L. multiflorum and P. notatum were responsible for positive reactions in 70%, 70% and 30% of positive dogs, respectively. The number of positive reactions in PT were statistically higher than IDT (P<0.05). In conclusion, grass pollen can be important source of allergens for dogs in Paraná state (Brazil) and the PT showed higher sensitization to grass pollen in dogs with atopic dermatitis than IDT.

Root production in a subtropical pasture is mediated by cultivar identity and defoliation severity

Grasslands occupy significant land area and account for a large proportion of the global soil carbon stocks, yet the direct effects of grazing and genotypic composition on relationships between shoot and root production are poorly resolved. This lack of understanding hinders the development of models for predicting root production in managed grasslands, a critical variable for determining soil carbon stocks. We quantified the effects of season-long defoliation treatments on both shoot and root production across 4 cultivars of a widely planted pasture grass species (Paspalum notatum Flüggé) in a common garden setting in South Florida, USA. We found that infrequently applied (4 weekly) severe defoliation (to 5 cm) substantially enhanced shoot production for all cultivars, while severe defoliation reduced root production across cultivars, regardless of frequency. Overall, there was no significant relationship between shoot and root production. Our results showed that above-ground and below-ground productivity are only weakly coupled, suggesting caution against use of simple above-ground proxies to predict variations in root production in grasslands. More broadly, our results demonstrated that improved modeling and management of grasslands for below-ground ecosystem services, including soil carbon sequestration/stocks, must account for intraspecific genetic variation and responses to defoliation management.