The hemibiotrophic fungus Colletotrichum kahawae is the causal agent of Coffee Berry Disease - CBD, an economically devastating disease restricted to Arabica coffee production in Africa. Understanding pathogen variability is crucial for the implementation of disease control measures. In this study, six isoenzymatic systems (esterase, acid and alkaline phosphatase, malate dehydrogenase, peroxidase and superoxide dismutase) were used to assess the genetic variation among 12 C. kahawae isolates (from different geographic origins and with different levels of aggressiveness towards coffee) and one Colletotrichum gloeosporioides isolate (not pathogenic to green berries). Cluster analysis of the banding profiles obtained for the six enzymes enabled the differentiation of the two species and revealed the existence of intraspecific variability among C. kahawae isolates. Alkaline phosphatase was the most discriminative enzyme, allowing also the discrimination between the most and least aggressive isolates of C. kahawae.

Genotypes of bread and durum wheat were submitted to heat stress after anthesis and the accumulation of Na, K and P, at booting, grain filling and maturity, were investigated. It was found that, after anthesis, the levels of Na in shoots were considerably higher in durum relatively to bread wheat, being this trend also observed in the total plant accumulation. In these genotypes, heat stress affected significantly Na concentration in shoots. In general, heat stressed plants had significant higher levels of K in the shoots and the proportion of this nutrient translocation from the roots also increased with heat stress. In general, the levels of P didn't show significant differences with heat stress. The effects of heat stress among the wheat genotypes life cycle are characterized and discussed.

In heat stressed genotypes of Triticum aestivum L. (Sever and Golia) and Triticum turgidum subsp. durum (Acalou and TE 9306), chosen according to its genetic background diversity, Ca and Mg accumulations were correlated with its photosynthetic performance. It was found that with high temperatures the concentrations of Ca increased in the shoots, whereas the accumulation of Mg augmented only in bread wheat genotypes. Under heat stress, the pattern of electrolytes release in Golia and Acalou remained similar, but the extrusion rates became higher in Sever. During grain filling, the levels of total chlorophylls decreased in the heat stressed genotypes (excepting in Sever). In all the Triticum genotypes, stomatal conductance and the net carboxilation rate displayed similar trends. After anthesis, the net carboxilation rates did not vary in Acalou and TE 9306 but changed significantly in the heat stressed bread wheat, being found antagonistic patterns in both genotypes. During grain filling, the mean internal CO2 concentration only increased significantly in the heat stressed Golia. In Golia and TE 9306, the transpiration rates didn't vary between the control and heat stress treatments, but in Sever and Acalou, significant increases were found. Our data identified synergistic patterns among Ca, Mg, chlorophylls accumulation, and stomatal conductance, whose implications on photosynthesis are discussed.

The interactions between high temperatures and Cu/Zn accumulation were investigated in bread and durum wheat. Plants were grown in a greenhouse, at two different temperatures regimes (control - 25/14ºC and heat stress - 31/20ºC), and the contents and uptake/translocation of Cu and Zn were evaluated during three developmental stages of plant growth (booting, grain filling and maturity). During grain filling and at maturity it was found that root, shoot and spike concentrations of Cu increased in heat stressed plants of the genotypes Golia and Acalou. The same trend was observed for root and shoot concentrations of Zn in both durum wheat genotypes. It was concluded that plants submitted to high temperatures (during the grain filling period) become more efficient in the Cu translocation to the shoots.

The interactions between Fe/Mn accumulation and the photosynthetic light reactions were investigated in heat stressed bread and durum wheat genotypes (Triticum aestivum L. and Triticum turgidum subsp.durum). Four genotypes were chosen according to its genetic background diversity. Plants were grown in a greenhouse at two different day/night temperatures regimes (control - 25/14ºC and heat stress - 31/20ºC), during the grain filling phase. The contents and uptake/translocation of Fe and Mn were evaluated on booting, grain filling and maturity and correlated with chlorophyll a fluorescence parameters. It was found that, under heat stress, the concentrations of Fe in the culm and leaves diminished in bread wheat, but increased in durum wheat. An opposite trend was found on the contents of Fe in the spike, being this effect higher in Sever. During grain filling, the concentrations of Mn in the heat stressed plants raised significantly in the shoot for all genotypes (excepting Golia). After anthesis, the proportion of Mn translocated also augmented with high temperatures. At maturity, the same trend was found in the translocated proportion of Fe. During grain filling, all the studied fluorescence parameters did not vary significantly except qP and qE that decreased in the heat stressed Golia and F V and Fv/Fm that increases in Acalou. It was concluded that under heat stress, during the grain filling period, Fe and Mn translocation to the shoots accelerates, eventually to overcome the negative effects on several photosynthetic physiological traits.

A produção e a qualidade do grão (incluindo alguns aspectos da qualidade tecnológica) sob estresse térmico, durante o enchimento do grão, foram avaliadas em dois genótipos de trigo mole (Triticum aestivum L.) e trigo rijo (Triticum turgidum subsp. durum) com diferentes tolerâncias às temperaturas elevadas após a antese. O estresse térmico, após a antese, induziu o desenvolvimento de grãos enrugados e com peso reduzido. Observaram-se ainda modificações ultraestruturais em nível da camada de aleurona e nas células do endosperma. Os grãos submetidos a temperaturas mais elevadas mostraram índices de sedimentação SDS menores, tendo estado este efeito associado a um aumento nos teores em proteína do grão e ainda a um decréscimo nos níveis de aminoácidos essenciais. Apesar das respostas às temperaturas elevadas não terem sido diferenciadas entre os genótipos de trigo, os resultados sugerem que o estresse térmico, durante o período de enchimento do grão, pode afectar a força do gluten, diminuindo a qualidade da farinha de trigo.

The yield and grain quality (as well as technological traits) of two heat-stressed genotypes of bread (Triticum aestivum L.) and durum wheat (Triticum turgidum subsp. durum) having different tolerance to high temperatures after anthesis were investigated. Heat stress, during grain filling, triggered grain shrinkage with a reduced weight and ultrastructural changes in the aleurone layer and in the endosperm cells. Heat stress also decreased the sedimentation index SDS, an effect associated with increased protein content in the grain but with decreased levels of essential amino acids. Although the responses to heat stress were similar among the Triticum genotypes, it is further suggested that during grain filling, high temperatures might affect gluten strength, diminishing the wheat flour quality.