Fiorella Franco

A fin de ayudar a tomar decisiones sobre el control de enfermedades en trigo en la presente campaña, en un informe anterior (Abbate et al. 2021) se dio a conocer el estado sanitario de los cultivares de ciclo largo evaluados en la Red de evaluación de cultivares de trigo (RET-INASE) conducida en INTA Balcarce, al inicio de encañazón (12-oct-2021). En esta oportunidad se presenta el estado sanitario de los cultivares de ciclo largo y corto, luego de la expansión de la hoja bandera.EEA BalcarceFil: Abbate, Pablo Eduardo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce; Argentina.Fil: Franco, María Fiorella. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Cabral Farias, Carlos Alejandro. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce; Argentina

Abstract The identification of sources of resistance to Fusarium head blight (FHB) in bread wheat is key to the sustainable management of the disease. An accurate characterization of resistance is critical; however, the experimental designs commonly used disregard germplasm variability in anthesis date (moment of highest disease susceptibility). Here, an accurate methodology for assessing type II resistance to FHB in the field was developed. Individual spikes of 126 RILs were point-inoculated at their optimum moment. The effect of anthesis date and environmental conditions on the prediction of bread wheat lines' performance was established. Anthesis date explained 26% of the total phenotypic variation for Severity at 21 days post-inoculation (dpi). Including this factor in the model increased the accuracy of the best linear unbiased predictors through a reduction of the residual and genotype by environment interaction variances. In addition, the genotypic variance and heritability of FHB severity at 21 dpi were increased. In summary, including the anthesis date effect in the model lead to a more precise and objective characterization of the level of genetic type II resistance to FHB under field conditions.

Systemic fungal endophytes may increase the adaptive potential of their hosts to different environmental conditions. However, the mechanisms involved in the adjustment are still an area of active inquiry. Considering that anatomical features in plants are the result of adaptation to different environments, this aspect of plants response to the symbionts deserves further research. In this work we investigated whether an asexual Epichloë endophyte modifies the foliar anatomy of symbiotic plants (E+) of its host grass with respect to endophyte-free plants (E-), using the Epichloë occultans – Lolium multiflorum system. The experiment was carried out in a greenhouse and plants were grown under benign, non-stressful (controlled) conditions. Symbiotic plants showed thinner leaf blades and lower mesophyll thickness. Likewise, the endophyte is associated with a greater number of vascular bundles. The stomatal density on the lower epidermis was higher in symbiotic plants than non-symbiotic plants. Our study reveals that Epichloë occultans modifies the foliar anatomy of Lolium multiflorum . Considering that leaf anatomy exhibits characters that were selected as a result of evolution in relation to specific environmental conditions, these results are promising since they can offer information about the mechanisms involved in the adaptive adjustment of symbiotic plants.

Many C3 grasses establish mutualistic associations with endophytic fungi Neotyphodium spp. Lolium multiflorum Lam. natural diploid populations of the Pampa region present high levels of infection whereas commercial cultivars, mainly tetraploid, exhibit low or no infection. In the genus Bromus, no information is available about this association in polyploid populations. The incidence of Neotyphodium spp. endophytes in diploid and tetraploid commercial cultivars of L. multiflorum, as well as in natural hexaploid populations of genus Bromus, was analysed. Observed infection was higher in diploid populations of L. multiflorum than in tetraploid populations. No infection was detected in Bromus spp. Various factors such as the production and handling of commercial seeds, the interaction of endophytes with ploidy level, and the genetic manipulation of seeds are discussed as the possible causes for the differences observed between natural and improved annual ryegrass and brome populations, and between diploid and tetraploid annual ryegrass.

Spike fertility index (SF) has been proposed as a promising selection criterion for increasing grain yield (GY) in bread wheat. Here, changes in GY and related traits after simulated selection (10% intensity) for high SF or high GY per se were assessed in two RIL populations: (I) Avalon/Glupro and (II) Baguette 10/Klein Chajá, and in (III) advanced lines from a breeding program. Grain yield, SF, grain number per unit area (GN), grain weight (GW), test weight (TW) and grain protein content (GPC) were determined. Regardless of the environmental conditions, simulated selection for high SF always resulted in GN increases (between 1.6 and 27.4%). Average GY increase observed after selection for high SF (11.5%; N=10; SEM=5.8) did not differ (p=0.92) from the average GY increase observed after selection for GY per se (11.8%; N=10; SEM=4.9). Grain weight, GPC and TW tended to decrease with selection for high SF; however, these trade-offs might be avoided by concurrent selection. Our finding...