Comparison of integrated field programmes for the reduction of fumonisin contamination in maize kernels

Fusarium verticillioides is a common maize pathogen which causes diseases on ears and synthesis of the mycotoxins, fumonisins, in kernels. Fumonisin production is influenced by both environmental conditions and agricultural inputs during growth and maturation of the maize plant. The aim of this research was to evaluate the effect of crop management techniques on fumonisin contamination in maize kernels. Experiments were conducted in Northern Italy during 2006 and 2007 using two maize hybrids with different precocity. Factors evaluated were seed planting time (March versus May), plant density (65,000 plants versus 80,000 plants per ha), N fertilization (200 kg N versus 400 kg N per ha), and chemical treatment to control European maize borer (ECB) (yes versus no). These factors were analyzed were as follows: (T1) May sowing, high plant density and N fertilization, (T2) March sowing time, high plant density and N fertilization, (T3) March sowing time, low plant density and balanced N fertilization, (T4) the same agronomic techniques as T3 plus a chemical treatment to control European maize borer. Ears were analyzed morphologically for ECB incidence and severity. Subsequently, kernels were analyzed chemically for fumonisins. Fumonisin contamination was reduced by 57%, 69% and 86% for T2, T3 and T4, respectively, compared to T1. This study clearly underlines that the application of good agricultural practices (GAP) in crop management strategies can effectively control fumonisin contamination of maize kernels.     

The effects of cultivar and prophylactic fungicide spray for leaf diseases on colonisation of maize ears by fumonisin producing Fusarium spp. and fumonisin synthesis in South Africa

Fumonisins are mycotoxins produced primarily by Fusarium verticillioides and Fusarium proliferatum on maize. These are secondary, carcinogenic metabolites and have been reported on maize worldwide. Field trials were conducted during 2010/2011 and 2011/2012 in six diverse maize production areas of South Africa to study the efficacy of an existing prophylactic fungicide regime for the control of foliar diseases, on the infection of grains of seven cultivars by fumonisin producing Fusarium spp. and fumonisin synthesis. Seven cultivars were selected to include both yellow and white, Bt and non-Bt and regionally adapted varieties. Azoxystrobin + difenoconazole (strobilurin, 200 g/L + triazole, 125 g/L) was applied 40–45 days after planting followed by flusilazole + carbendazim (silicone triazole, 125 g/L + benzimidazole, 250 g/L) with petroleum as adjuvant, 28–30 days later. Fumonisins in harvested kernels were analysed using High Performance Liquid Chromatography (HPLC) and fumonisin producing Fusarium spp. were quantified by means of quantitative Real Time PCR (qPCR). Mean natural colonisation of maize kernels by fumonisin producing Fusarium spp. was highest at Makhathini (33,696 pg/0.5 g of milled maize kernels) and the lowest at Potchefstroom (179 pg/0.5 g of milled maize kernels). Cultivars differed in susceptibility to fungal colonisation and fumonisin synthesis with PAN6P-110, DKC80-10 and CRN3505 proving most susceptible and LS8521B and DKC78-15B most resistant. Mean fumonisin contamination was highest at Makhathini (23.62 ppm) and lowest at Buffelsvlei (1.50 ppm). Analysis of variance showed no significant differences in colonisation of grain by fumonisin producing Fusarium spp. between sprayed and control treatments. Sprayed treatments had significantly higher fumonisin levels compared with unsprayed treatments. A highly significant cultivar × environment interaction was recorded for fungal colonisation. Highly significant environment × fungicide-treatment × cultivar interactions were recorded for fumonisin production. The strong interaction between cultivar and environment may be due to cultivar adaptation/behaviour under different environmental conditions. The use of a prophylactic fungicide spray regime for control of leaf diseases in maize did not reduce Fusarium ear rot in maize, however, significantly elevated fumonisin levels were recorded.     

Effects of fungicide seed treatments on germination, population, and yield of maize grown from seed infected with fungal pathogens

Seedborne fungi can reduce survival, growth, and yield of maize (Zea mays L.). Laboratory, field, and growth chamber experiments were conducted to determine the effects of the seed treatment fungicides fludioxonil, mefenoxam, and azoxystrobin on germination, plant population, and grain yield of maize grown from low-quality hybrid seed infected with seedborne fungal pathogens. Study I used seed of four hybrids infected at 0-54% incidence with Fusarium spp., Stenocarpella maydis, Penicillium spp., Rhizopus spp., and/or Aspergillus spp. Study II used three seed lots for each of two hybrids infected at 7-37% incidence with S. maydis. Warm and cold germination for untreated seed varied among hybrids in both studies. Warm germination of the seed lot with the highest incidence of S. maydis in study II treated with azoxystrobin and fludioxonil was significantly greater (+7%) than the nontreated control. Plant population in study I was significantly affected by seed treatment, hybrid, and their interactions. Populations were greater (≥9%) for fludioxonil, fludioxonil + mefenoxam, and fludioxonil + mefenoxam + azoxystrobin treatments compared to controls. In growth chamber experiments with pasteurized soil, emergence (≥5%) and plant dry weight (≥14%) were both greater than controls only with the triple seed treatment. Plant populations in study II for all seed treatments except mefenoxam and azoxystrobin alone were greater (≥4%) than controls. Yield in study I was significantly affected by hybrid and seed treatment. Yield for one hybrid was higher (≥20%) than the control with all seed treatments except fludioxonil, whereas yield with another hybrid was consistently greater (≥26%) only with the triple seed treatment. Yield in study II was significantly affected by hybrid, seed treatment, and their interactions. Yield was greater (≥8%) than the controls for all seed treatments with one hybrid and with all (≥5%) except azoxystrobin for the other hybrid. Highest yields occurred with the triple seed treatment. Results indicate that fludioxonil and azoxystrobin can increase germination, population, and yield of maize grown from seed infected by S. maydis and other fungi.     

Diallel analysis of fumonisin accumulation in maize

Contamination of maize (Zea mays L.) grain with aflatoxin, produced by the fungus Aspergillus flavus Link: Fries, or fumonisin, produced by the fungus Fusarium verticillioides (Saccardo) Nirenberg (Syn F. moniliforme Sheldon), greatly reduces its value and marketability. Host resistance to fungal infection and mycotoxin accumulation is considered a highly desirable way to reduce losses of both aflatoxin and fumonisin. Maize germplasm lines with resistance to aflatoxin accumulation have been developed in Mississippi. Three of the aflatoxin-resistant lines and five additional lines were used as parents to produce a diallel cross. The diallel cross was evaluated for fumonisin accumulation in field tests conducted in Mississippi in 2007 and 2008. General combining ability (GCA) was a highly significant source of variation in both 2007 and 2008, but specific combining ability (SCA) was not significant. GCA effects for reduced fumonisin levels were highly significant for Mp715, Mp717, and GA209. Mp715 and Mp717 were developed and released as sources of resistance to aflatoxin contamination and exhibit resistance as inbred lines and in hybrid combinations. These lines should be useful in developing maize lines and hybrids with resistance to both fumonisin and aflatoxin accumulation in grain.     

Effect of plant density on toxigenic fungal infection and mycotoxin contamination of maize kernels

Field experiments were set up from 2001 to 2004 in North West Italy to determine the effects of plant density on the susceptibility of medium and medium-late maturity maize hybrids to ear rot and to mycotoxin contamination in natural infection conditions. The ears were rated for the incidence and severity of disease symptoms at harvest and the harvested kernels were analysed for mycotoxin fumonisin B₁, zearalenone, deoxynivalenol, aflatoxin B₁ and ochratoxin A.     

A disease survey of Fusarium wilt and Alternaria blight on sweet potato in South Africa

A disease survey was conducted on sweet potato in the major production areas of South Africa in 2006-2008 to determine the importance of wilt disease (WD) and Alternaria blight (AB) caused by Alternaria bataticola. The disease prevalence, incidence and severity were assessed for both WD and AB in 58 sweet potato fields in seven provinces, and included both commercial and resource-poor growers. The prevalence of WD in commercial fields was significantly higher than in resource-poor fields; while disease incidence and severity were very low in both commercial and resource-poor fields. Soil pH showed a moderate negative linear correlation to WD severity. WD is at present considered a minor disease of sweet potato in South Africa, although local outbreaks can be damaging. AB had very low disease prevalence, incidence and severity levels in both commercial and resource-poor fields countrywide. However, one of the fields had moderately high disease incidence and severity levels, showing that the disease can be destructive if not controlled. AB should be considered a potentially destructive disease of sweet potato in South Africa. Fusarium oxysporum was consistently isolated from WD plants, with F. oxysporum f. sp. batatas identified, but other formae speciales were also associated with the disease.     

Dynamic of water activity in maize hybrids is crucial for fumonisin contamination in kernels

The dynamic of water activity (a_w) and humidity (h) of maize (Zea mays L.) kernels and their relevance for fumonisin (FUM) accumulation in kernels was studied in 10 commercial hybrids grown in 5 locations of North Italy, in 2007 and 2008. The dynamic of both a_w and h in maize kernels was different in diverse hybrids and was accurately described by monomolecular and linear regression, respectively, using degree-days (base 0 °C) accumulated between female flowering and harvest as an independent variable (R² = 0.61-0.96, depending on the hybrid). FUM contamination at harvest was predicted by using a_w as an independent variable in a logistic regression which provided 67% of correct prediction of cases with FUM ≥ 4000 μg/kg of kernel; accuracy of prediction increased to 72% by using both a_w and ECB severity as independent variables. The use of h as independent variable provided 71% correct predictions, but specific correction factors were necessary for each hybrid. Results showed that “slow dry down” hybrids were more prone to FUM accumulation, irrespective of their season length. The identification of factors able to drive a_w dynamic in maize kernels and their genetic bases may then provide a crucial contribution in breeding maize for resistance to FUM contamination.     

Investigation of fungal development in maize kernels using NIR hyperspectral imaging and multivariate data analysis

Near infrared (NIR) hyperspectral imaging and hyperspectral image analysis were evaluated for their potential to track changes in fungal contamination on and fungal activity immediately under the surface of whole maize kernels (Zea mays L.) infected with Fusarium verticillioides. Hyperspectral images of clean and infected kernels were acquired using a SisuChema hyperspectral pushbroom imaging system with a spectral range of 1000–2498 nm at predetermined time intervals after infection. Background, bad pixels and shading of acquired absorbance images were removed using exploratory principal component analysis (PCA). When plotting PC4 against PC5, with percentage sum of squares (%SS) 0.49% and 0.34%, three distinct clusters were apparent in the score plot and this was associated with degree of infection. Loading line plots, with prominent peaks at 1900 nm and 2136 nm, confirmed that the source of variation was due to changes in starch and protein. Partial least squares (PLS) regression models, with time as the Y variable, were calculated and also indicated that changes over time were apparent. Variable importance plots (VIP) confirmed the peaks observed in the PCA loading line plots. More systematic future experiments are needed to confirm this, but it can already be concluded that early detection of fungal contamination and activity is possible.     

Heat stress effects around flowering on kernel set of temperate and tropical maize hybrids

Final kernel number in the uppermost ear of temperate maize (Zea mays L.) hybrids is smaller than the potential represented by the number of florets differentiated in this ear, and than the number of silks exposed from it (i.e., kernel set <1). This trend increases when stressful conditions affect plant growth immediately before (GS₁) or during (GS₂) silking, but the magnitude of change has not been documented for heat stress effects and hybrids of tropical background. In this work we evaluated mentioned traits in field experiments (Exp₁ and Exp₂), including (i) two temperature regimes, control and heated during daytime hours (ca. 33-40 °C at ear level), (ii) two 15-d periods during GS₁ and GS₂, and (iii) three hybrids (Te: temperate; Tr: tropical; TeTr: Te × Tr). We also measured crop anthesis and silking dynamics, silk exposure of individual plants, and the anthesis-silking interval (ASI). Three sources of kernel loss were identified: decreased floret differentiation, pollination failure, and kernel abortion. Heating affected all surveyed traits, but negative effects on flowering dynamics were larger (i) for anthesis than for silking with the concomitant decrease in ASI, and (ii) for GS₁ than for GS₂. Heat also caused a decrease in the number of (i) florets only when performed during GS₁ (−15.5% in Exp₁ and −9.1% in Exp₂), and only among Te and TeTr hybrids, (ii) exposed silks of all GS × Hybrid combinations, and (iii) harvestable kernels (mean of −51.8% in GS₁ and −74.5% in GS₂). Kernel abortion explained 95% of the variation in final kernel numbers (P < 0.001), and negative heat effects were larger on this loss (38.6%) than on other losses (≤11.3%). The tropical genetic background conferred an enhanced capacity for enduring most negative effects of heating.     

Management of fusarium basal rot (Fusarium oxysporum f. sp. cepae) on shallot through fungicidal bulb treatment

Fusarium basal rot caused by Fusarium oxysporum f.sp. cepae is an economic disease of shallot. Field experiments were conducted at Debre Zeit during 2006 and 2007 cropping seasons to determine effective fungicides and their method of application for the management of fusarium basal rot of shallot. The field was naturally infested with F. oxysporum f. sp. cepae and treatments were arranged in randomized complete block design in four replications. Five fungicides, Mirage 50 WP, Folicur 25 EC, Seed plus 30 WS, Penncozeb 80 WP and Ridomil Gold 68 WG were evaluated as seed bulb dressing and bulb dip treatments against basal rot in the field and storage. Bulb dressing with Mirage, and dip treatment in Seed plus reduced the disease incidence by 40% and 43%, respectively over control. These fungicides also resulted in a significant reduction in severity, basal rot affected cull bulbs on shallot. Bulb rot during three months of storage on concrete ground floor and on wire mesh shelves was also reduced by seed bulb treatment over control. The highest increase in yield was obtained from bulb dressing with Mirage (42%) and Seed plus (45%) and from bulb dip treatment in Seed plus (44%) over control. Fusarium basal rot caused 45% loss in yield and 12-30% of bulb loss in the storage. The study showed that basal rot of shallot can be managed effectively by seed bulb dressing or dip treatment in Mirage or Seed plus.     

Evaluation of the Ugandan sorghum accessions for grain mold and anthracnose resistance

Sorghum accessions from Uganda were evaluated for grain mold and anthracnose resistance during the 2005 and 2006 growing seasons at the Texas A&M University Research Farm, near College Station, TX. Accession PI534117 and SC719-11E exhibited the lowest grain mold severities of 2.4, whereas, accessions PI534117, PI534144, PI576337, PI297199, PI533833, and PI297210, with SC748-5 were highly resistant to anthracnose in both years. Accessions PI534117, PI297134, PI297156 exhibited low grain mold severities in 2006. Significant negative correlation was recorded between grain mold and percent germination and high temperature in both years. In 2006, daily precipitation recorded significant positive correlation with grain mold. The seed mycoflora was analyzed across sorghum lines and treatments. In 2005, Curvularia lunata and Fusarium thapsinum were the most frequently recovered fungal species with 31 and 21% incidence, respectively, followed by Alternaria spp. (19%) and F. semitectum (13%). In 2006, predominant colonizers were F. thapsinum (58%), followed by Alternaria and F. semitectum with 15 and 10, percent respectively, while C. lunata had a 6% incidence. In this study, PI534117 holds promise for multiple disease resistance, as it had the lowest disease severity of grain mold and was highly resistant to anthracnose in both years. It also has a high germination rate, a high seed weight, and its short stature is more advantageous for the new A-line conversion program.     

Effects of Fusarium culmorum and water stress on durum wheat in Tunisia

The effects of water stress on Fusarium foot and root rot in durum wheat were investigated in growth chamber, greenhouse and field tests in Tunisia. In the seedling stage, emergence of six durum wheat cultivars in the growth chamber was significantly reduced by inoculation with Fusarium culmorum and water stress (P<0.0001), with more disease under drier conditions. Additionally, the tiller number per mature plant, the 1000 grain weight and disease severity in mature stage were reduced by inoculation in greenhouse studies. In a field test, inoculation with F. culmorum significantly reduced the yield (P<0.001), by more than 17% for Om Rabiaa and 38% for Karim, the two cultivars tested. Yield was also significantly affected by precipitation and irrigation levels. The severity of the disease, estimated by the percentage of white heads, was separately affected by the cultivar (P<0.001) and inoculation (P = 0.0004). Percentage of white heads was 1.5 and 2 × higher in inoculated plants than non-inoculated for Om Rabiaa and Karim cultivars, respectively. Disease severity was highest in treatments with the greatest water stress. This is the first detailed study of water stress and F. culmorum on durum wheat in Tunisia, and indicates that cultivar resistance and irrigation management may be important in the management of Fusarium foot rot.     

Antifungal and antiaflatoxigenic efficacy of Caesulia axillaris Roxb. essential oil against fungi deteriorating some herbal raw materials, and its antioxidant activity

The study deals with evaluation of antifungal and antiaflatoxigenic Caesulia axillaris Roxb. essential oil (EO) against herbal raw materials deteriorating fungi and its free radical scavenging activity. During mycoflora analysis these herbal raw materials were found to be severely contaminated by different fungi and aflatoxins. A total of nine different fungal species were isolated from three herbal raw materials. Aspergillus flavus LHPtc was recorded as the highest aflatoxin B1 producing strain. EOs of some plants were tested for their fungitoxicity against the toxigenic strain A. flavus LHPtc, and C. axillaris EO was found as potent fungitoxicant. C. axillaris EO was chemically characterized through GC-MS analysis which depicted the presence of 18 compounds, dl-limonene and Euasarone being the major components. The EO exhibited broad spectrum of fungitoxicity against fungi causing postharvest deterioration of herbal raw materials. At 1.0 μl ml⁻¹ the oil showed complete inhibition of fungal growth and aflatoxin B₁ production was inhibited at 0.8 μl ml⁻¹. Free radical scavenging activity of the oil was also recorded by 2,2-diphenyl-1-picrylhydrazyl assay, and its IC₅₀ value was found 18 μl ml⁻¹. The safety limit of the EO was determined in terms of LD₅₀ on mice, which was 9166.6 μl kg⁻¹, suggesting its non mammalian toxicity. The EO of C. axillaris may be recommended as a plant based preservative in enhancement of shelf life of herbal raw materials by preventing their lipid peroxidation as well as biodeterioration due to fungal and aflatoxin contamination.     

Effects of leaf scales of different pineapple cultivars on the epiphytic stage of Fusarium guttiforme

The fungus Fusarium guttiforme (Syn. F. subglutinans f. sp. ananas) is responsible for fusariosis, one of the main phytosanitary threats to pineapple (Ananas comosus var. comosus). A structural study comparing epidermal differences in pineapple cultivars resistant and susceptible to fusariosis was performed, relating properties of the epidermis to known susceptibility to the disease. The basal, non-chlorophylled, portions of mature leaves of pineapple plants were analyzed by light and electron microscopy. All cultivars showed common morpho-anatomic aspects characteristic of Bromeliaceae, such as scutiform scales and unstratified epidermis. However, cultivar Vitoria (resistant) had less scales than cultivars Smooth Cayenne (susceptible, intermediate severity) and Perola (susceptible, with extreme severity of fusariosis symptoms). Inoculation of conidia suspension (10⁵ conidia ml⁻¹) of the fungus F. guttiforme to leaves and harvesting 24 h later yielded numbers of viable colonies related to the density of leaf scales. This suggests that scales can act as havens for fungal conidia and favour the epiphytic stage of the fungus on pineapple plants, and are involved in the interaction of plant and pathogen. A reduction in scale numbers was related to lower infection levels and is relevant to the future breeding programme for development of new pineapple cultivars resistant to fusariosis and their involvement in integrated control strategies.     

Maize genotype susceptibility to Rhizoctonia solani and its effect on sugar beet crop rotations

Root and crown rot is the major soil-borne fungal disease in sugar beet. In Europe, the disease is mainly caused by the anastomosis group (AG) 2-2IIIB of the basidiomycete Rhizoctonia solani (Kühn). No chemical fungicide to control the disease has been registered in Europe. Therefore, agronomic measures must be optimized to keep the disease severity below an economic damage threshold and to minimize white sugar yield losses. R. solani AG 2-2IIIB infects many other crops besides sugar beet, including maize, where it causes root rot. Sugar beet and maize are frequently grown in the same crop rotation. The proportion of cultivated maize in several European sugar beet growing areas is expected to rise due to a projected increase in demand for renewable resources over the next few years. Although the susceptibility to and tolerance of the disease varies among cultivars in both crops, little is known about the effects of cultivar susceptibility in the pre-crop on a subsequent susceptible crop. The cultivation of R. solani-resistant maize genotypes in rotation with resistant sugar beet might therefore be a useful tool in an integrated control strategy against R. solani, eliminating the need to restrict the desired crop rotation for phytosanitary reasons. A crop rotation experiment with artificially inoculated R. solani was conducted in the field to investigate the pre-crop effects of maize cultivars which differed in their susceptibility to R. solani on a susceptible sugar beet cultivar. We hypothesized that the maize genotype would influence the inoculum potential and performance of a susceptible sugar beet genotype grown after a maize pre-crop, and that this would correlate with the susceptibility of the maize genotype. The results demonstrate that the susceptibility of maize genotypes is consistent over a period of years and that cultivated maize genotypes influenced the inoculum potential measured as disease severity in sugar beet. However, disease severity in sugar beet did not correlate with the disease susceptibility of the genotype of the maize pre-crop. Possible reasons for this missing relationship might be differences in the quality of maize residues for the saprophytic survival of the pathogen or a genotype-specific alteration of the antagonistic microbial community. However, our findings showed that in the presence of maize- and sugar beet-pathogenic R. solani, the most favourable maize cultivar for a crop rotation cannot be determined solely on the basis of its resistance level against Rhizoctonia root rot.     

Hybrid and environment effects on popcorn kernel physiochemical properties and their relationship to microwave popping performance

The objective of this study was to characterize the effect of hybrid and environment on physical and chemical characteristics of popcorn kernels that have shown importance in predicting end-use quality. Three popcorn hybrids grown in three different environments were tested for physiochemical attributes and popping performance. Hybrid had a significant effect on kernel sphericity, time-to-grind, dietary fiber, sugars, and starch. Environment effect alone affected total mineral content. Hybrid and environment main effects influenced test weight, tangential abrasive dehulling device index, thousand-kernel weight, total carbohydrates, and kernel protein content. Oil adherence to the bag averaged 15.8% and was proportional to oil amount added prior to microwave popping. Unpopped kernels averaged 11.4 ± 5.3%. Most unpopped kernels were observed to successfully pop when heated a second time in microwave tests. Expansion volume was 44.7 ± 3.7 and 47.3 ± 6.4 cm³/g, depending on the method of determination. Expansion volume was correlated (p < 0.05) with several kernel physiochemical parameters that were influenced by hybrid effect. Sphericity, thousand-weight, and total fat are physiochemical characteristics that appear to be good predictors (p < 0.05) of expansion volume.     

Quantification of yield loss due to coffee leaf scorch

Coffee leaf scorch caused by Xylella fastidiosa is widespread in major coffee-growing regions of Brazil. This study was done to quantify the yield loss caused by this disease. The severity data of the disease were collected during the 2006, 2007 and 2008 seasons at commercial plantations growing Coffea arabica ‘Catuaí’ in São Gotardo-MG in 250 plants of three blocks of 7000 coffee plants each. Fifty selected plants per block with different disease severities were determined. The linear regression showed a significant relationship (P < 0.01) between disease severity and bean yield and between disease severity and grain size in all years. The relationship between yield and the disease severity was significant (P < 0.01). For each 1% increase in the disease severity, there was a decrease of 1.22, 1.34 and 2.02 bags of bean yield/ha in 2006, 2007 and 2008, respectively, thus showing the importance of the disease in reducing coffee bean yields.     

Kernel number determination differs among maize hybrids in response to nitrogen

In maize, the effects of nitrogen (N) deficiencies on the determination of kernel number per plant (KNP) have been described only by changes in plant growth rate during the critical period for kernel set (PGRcp). We hypothesize that N availability affects KNP also through variations in biomass allocation to the ear, which determines a stable N concentration in this organ. Six maize hybrids of different breeding origin were evaluated in field experiments at two N levels (0 and 400 kg N ha⁻¹ applied). Traits included were KNP and per apical ear (KN_E1), and the allometric estimation of PGRcp, ear growth rate during the critical period (EGRcp), and N content and N concentration in different plant organs. We demonstrated that (i) N availability promoted differences among genotypes (G) in the response of EGRcp and KNP to PGRcp, (ii) variations in KN_E1 were explained by EGRcp (r² = 0.64) and by ear N content at silking + 12 d (r² = 0.64), and (iii) ear N concentration was a highly conservative trait (range between 10.47 and 15.98 mg N g biomass⁻¹) as compared to N concentration in vegetative tissues (range between 4.94 and 18.04 mg N g biomass⁻¹). Three response patterns were detected among hybrids, one for which the relationship between EGRcp and PGRcp did not vary between N levels and experiments, a second one for which N availability affected this relationship, and a third one for which the response was affected by the year (Y) effect. These results, together with the high correlation between EGRcp and ear N content (r² = 0.88), evidenced the importance of both photo-assimilate and N availability on EGRcp and KNP determination. Values of 1.5–2.3 g ear⁻¹ d⁻¹ during the critical period and 0.49–0.70 g of N ear⁻¹ at silking + 12 d were determined as thresholds for maximizing KN_E1, and both could be easily estimated by means of allometric models.     

Genotype-by-environment interaction of barley DH lines infected with Fusarium culmorum (W.G.Sm.) Sacc.

Infection of plants by pathogens is a biotic environmental stress. Barley plants are infected, among others, by Fusarium culmorum—a pathogen affecting seedling, head, root and stem. The infection can result in reduced yield and grain quality. The aim of the study was to compare the reaction of inoculated and non-inoculated barley doubled haploids (DHs) with F. culmorum in various environments. Thirty-four genotypes were inoculated with an isolate of F. culmorum. The experiment was carried out over 6 years. Kernel weight per spike, 1000-kernel weight and percentage of plump kernels were observed in control and inoculated plants. Genotype-by-environment (GE) interaction and its structure with reference to the environments and genotypes were analysed. Additional information about the sensitivity of healthy and infected genotypes to environments was determined by the regression analysis. Statistical computation was made using the SERGEN software. Lines were considered as unstable when their GE interaction was significant at P = 0.05. Unstable genotypes were classified as intensive or extensive according to the results of the regression analysis. It was found that infection with Fusarium decreased the stability of barley lines in different environments. Interaction of unstable infected genotypes with environments, most often, could not be explained by the regression—their response to various environmental conditions appeared to be unpredictable. Selection of lines less susceptible to biotic and abiotic stresses was possible due to comparison of classification of healthy and infected lines, which was made based on their main effects and GE interaction.     

Swiss Flint maize landraces—A rich pool of variability for early vigour in cool environments

Today's modern Dent × Flint maize (Zea mays L. ssp. mays) hybrids have a high yield potential but often lack satisfying early vigour under typical low spring temperatures of temperate latitudes. Maize was introduced into Europe already in the 16th century and until the 1950s, landraces evolved and adapted well to various geographically restricted and climatically marginal regions in Europe. Therefore, the objective of this study was to assess representatives of the large pool of Swiss Flint maize landraces for their early vigour under cool conditions in the field. A set of 17 landrace accessions were tested for 2 years at sites on the Swiss plateau (450 and 550 m a.s.l.) and in the foothills of the Swiss Alps (830 and 870 m a.s.l.). Plant emergence (PE), emergence index (EI), the efficiency of the photosystem II (F_v/F_m), leaf greenness (SPAD) and plant dry weight at the three- and six-leaf stages (DW3_P, DW6_P) were measured.