Effects of waterlogging during grain filling on yield components, nitrogen uptake and grain quality in bread wheat

Waterlogging stress frequently affects wheat production in the current conditions. The aim of this work was to evaluate the effect of waterlogging during grain filling on grain yield components, nitrogen uptake and partitioning and gluten composition and quality in bread wheat. Two greenhouse experiments were conducted under contrasting environmental conditions in Azul, Buenos Aires, in a completely randomized design with three replicates. The cultivar chosen was Klein León and the waterlogging treatment was imposed from 5 days after anthesis to maturity. The effects of waterlogging during grain filling in wheat depended on explored environmental conditions: early sowing vs. late sowing. Waterlogging had not significant effects on the most variables at early sowing conditions. However, the delaying in sowing date (higher temperature and radiation) enhance the effects of waterlogging: i) reducing grain weight by 41% and total nitrogen uptake by 51%; ii) reducing the ratio between the contents of high and low molecular weight glutenin subunits, affecting gluten composition; and iii) increasing the sodium dodecyl sulfate test from 79 to 108 mm, which correlates positively with the gluten strength. Reductions in grain weight due to waterlogging during grain filling affect the milling quality, although changes in protein composition may increase or maintain the gluten strength (SDSS) under particular conditions

Pathogenic ability and saline stress tolerance of two Fusarium isolates from Odontesthes bonariensis eggs

Background Several fungal species represent a potential risk to embryos ofOdontesthes bonariensis(Cuvier and Valenciennes, 1835), a euryhaline freshwater fish that lives in the Pampean inland waters and has potential economic relevance. Aims To identify two fungi isolated fromO. bonariensiseggs exposed to saline conditions and to characterize their pathogenicity and tolerance to sodium chloride solutions. Methods The isolates were identified by morphological features, and a preliminar phylogenetic analysis using sequences of translation elongation factor 1-alpha (EF-1α) and calmodulin (CAM) was performed. Koch's postulates were tested to identify the causative agent of fungal infection. The influence of NaCl on the fungal growth was evaluated in in vitro assays. Results The isolates LPSC 1001 and 1002 were identified as representatives of the genusFusarium, and belonging to theFusarium incarnatum-Fusarium equisetispecies complex (FIESC) and theFusarium solanispecies complex (FSSC), respectively. Histological observations on eggs exposed in vitro to both isolates in infectivity assays confirmed the ability of the fungal isolates to penetrate to egg's chorionic membrane, leading to the death of embryos. Increasing NaCl concentration in the culture medium reduced the growth of the isolates LPSC 1001 and 1002, being completely inhibited at 160 and 120g/l NaCl respectively. Conclusions The isolates LPSC 1001 (FIESC) and 1002 (FSSC) were identified as fungal pathogens toO. bonariensiseggs. The use of NaCl solutions as antifungal treatment was not effective to control the infection with these strains.Antecedentes Diversas especies de hongos pueden representar un riesgo importante para los embriones deOdontesthes bonariensis(Cuvier & Valenciennes 1835), un pez de agua dulce eurihalino que vive en las aguas interiores pampeanas y tiene una relevancia económica potencial. Objetivos Identificar dos especies de hongos de huevos deO. bonariensisexpuestos a condiciones salinas y caracterizar su patogenicidad y tolerancia a las soluciones de cloruro de sodio. Métodos Se identificaron los aislamientos por sus características morfológicas, y se realizó un análisis filogenético preliminar utilizando secuencias de traslación del factor 1 alfa elongación (EF- 1α) y calmodulina (CAM). Se llevaron a cabo los postulados de Koch para identificar el agente causante de la infección fúngica. La influencia de NaCl sobre el crecimiento fúngico se evaluó en ensayos in vitro. Resultados Se identificaron los aislamientos LPSC 1001 y 1002 como representantes del géneroFusarium, y pertenecientes al complejo de especiesFusarium incarnatum-Fusarium equiseti(FIESC) y al complejo de especies deFusarium solani(FSSC), respectivamente. Las observaciones histológicas en los huevos expuestos in vitro a ambos aislamientos en los ensayos de infectividad confirmaron la capacidad de estos para penetrar en la membrana coriónica, lo que condujo a la muerte de los embriones. El aumento de la concentración de NaCl en el medio de cultivo redujo el crecimiento de los aislamientos LPSC 1001 y 1002, quedando completamente inhibidos a 160 y 120g/l de NaCl, respectivamente. Conclusiones Se identificaron los aislamientos LPSC 1001 (FIESC) y 1002 (FSSC) como hongos patógenos para los huevos deO. bonariensis; el uso de soluciones de NaCl como tratamiento antifúngico no resultó eficaz para el control de la infección con estas cepas.dia y mes probable de publicaió

Short communication: Presence of Fusarium graminearum sensu stricto associated with triticale (× Triticosecale Wittmack) in Argentina

Aim of study: To report the occurrence of Fusarium graminearum sensu stricto (s.s.) on triticale grains from field samples in Argentina and the potential mycotoxin production for these isolates.Area of study: Buenos Aires province, ArgentinaMaterial and methods: A total of 40 samples from different crops (barley, rye, triticale, and wheat) showing Fusarium head blight symptoms were taken during 2017/2018 harvest season. Colonies with colour and mycelium similar to Fusarium were taken and were morphologically and molecularly identified. The potential to produce deoxynivalenol, 15-acetyl deoxynivalenol and zearalenones was determined. Also, the Koch´s postulates were used to evaluate the pathogenic capacity of the F. graminearum s.s. isolates in triticale.Main results: Two Fusarium isolates were identified morphologically as F. graminearum, which were confirmed molecularly by PCR using the specific Fg16 F/R primers pair and by sequencing red and tri101 genes. The sequences obtained were compared with those available in the NCBI database using BLAST tools, showing 99-100% homology with those belonging to F. graminearum s.s. The results demonstrated that F. graminearum s.s. isolates were pathogenic when triticale spikes were inoculated by spraying under greenhouse conditions.Research highlights: To our knowledge, this is the first time that the presence of F. graminearum s.s. is reported associated with triticale in Argentina

Occurrence and distribution of soil Fusarium species under wheat crop in zero tillage

The presence of Fusarium species in cultivated soils is commonly associated with plant debris and plant roots. Fusarium species are also soil saprophytes. The aim of this study was to examine the occurrence and distribution of soil Fusarium spp. at different soil depths in a zero tillage system after the wheat was harvested. Soil samples were obtained at three depths (0-5 cm, 5-10 cm and 10-20 cm) from five crop rotations: I, conservationist agriculture (wheatsorghum- soybean); II, mixed agriculture/livestock with pastures, without using winter or summer forages (wheatsorghum- soybean-canola-pastures); III, winter agriculture in depth limited soils (wheat-canola-barley-late soybean); IV, mixed with annual forage (wheat-oat/Vicia-sunflower); V, intensive agriculture (wheat-barley-canola, with alternation of soybean or late soybean). One hundred twenty two isolates of Fusarium were obtained and identified as F. equiseti, F. merismoides, F. oxysporum, F. scirpi and F. solani. The most prevalent species was F. oxysporum, which was observed in all sequences and depths. The Tukey�fs test showed that the relative frequency of F. oxysporum under intensive agricultural management was higher than in mixed traditional ones. The first 5 cm of soil showed statistically significant differences (p = 0.05) with respect to 5-10 cm and 10-20 cm depths. The ANOVA test for the relative frequency of the other species as F. equiseti, F. merismoides, F. scirpi and F. solani, did not show statistically significant differences (p . 0.05). We did not find significant differences (p . 0.05) in the effect of crop rotations and depth on Shannon, Simpson indexes and species richness. Therefore we conclude that the different sequences and the sampling depth did not affect the alpha diversity of Fusarium community in this system