Drylands are predicted to become more arid and saline due to increasing global temperature and drought. Although species from the Caatinga, a Brazilian tropical dry forest, are tolerant to these conditions, the capacity for germination to withstand extreme soil temperature and water deficit associated with climate change remains to be quantified. We aimed to evaluate how germination will be affected under future climate change scenarios of limited water and increased temperature. Seeds of three species were germinated at different temperatures and osmotic potentials. Thermal time and hydrotime model parameters were established and thresholds for germination calculated. Germination performance in 2055 was predicted, by combining temperature and osmotic/salt stress thresholds, considering soil temperature and moisture following rainfall events. The most pessimistic climate scenario predicts an increase of 3.9 °C in soil temperature and 30% decrease in rainfall. Under this scenario, soil temperature is never lower than the minimum and seldomly higher than maximum temperature thresholds for germination. As long as the soil moisture (0.139 cm 3 cm 3 ) requirements are met, germination can be achieved in 1 day.According to the base water potential and soil characteristics, the minimum weekly rainfall for germination is estimated to be 17.5 mm. Currently, the required minimum rainfall occurs in 14 weeks of the year but will be reduced to 4 weeks by 2055. This may not be sufficient for seedling recruitment of some species in the natural environment. Thus, in future climate scenarios, rainfall rather than temperature will be extremely limiting for seed germination.

The downy mildew, caused by Plasmopora viticola, is one of the most important grapevine (Vitis vinifera) diseases in Southern Brazil, causing defoliation and economic losses. The evaluation of disease severity is an important decision for adoption of strategies and tactics

ABSTRACT The increase of CO2 concentrations and temperatures may affect the plant development and production. This study aimed to evaluate the impact of the increased temperature and carbon dioxide concentration on the development of cowpea cultivars. The experiment was conducted in growth chambers, with control of CO2 and temperature. A completely randomized design was carried out, in a 4 x 3 x 2 factorial arrangement [cultivar x temperature (day/night) x CO2], with three replicates. The duration of the cowpea vegetative and reproductive phases was evaluated and, at the end of the experiment, the number of pods per plant, number of grains per pod, seed weight, shoot fresh and dry matter weight were quantified. Temperature affects the development of cowpea cultivars, and the temperatures of 29 ºC (day)/23 ºC (night) lead to a higher seed weight. The increase of CO2 leads to a higher number of pods and seeds and seed weight. The BRS Tapaihum cultivar presented the highest number of pods and seeds and seed weight. In addition, the temperatures of 32 ºC (day)/29 ºC (night) lead to a greater flower abortion in the BRS Pujante and BRS Tapaihum cultivars.

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Resumo -O objetivo deste trabalho foi avaliar a resistência à ferrugem causada pelo fungo Phakopsora euvitis, em genótipos de videira, e a efi ciência da infecção de acordo com a idade das folhas e concentração de inóculo. A avaliação foi feita em 15 genótipos, com base nos seguintes componentes de resistência: número de pústulas (urédios) por cm 2 ; tamanho das pústulas; número de esporos produzidos por pústula; e período latente. Os componentes de resistência, com exceção do período latente, apresentaram grande variação quantitativa. A análise multivariada desses componentes diferenciou cinco grupos de genótipos. Os genótipos mais resistentes foram as cultivares porta-enxertos IAC313, IAC572 e IAC766, em que a efi ciência da infecção foi baixa, com pústulas menores e menor produção de urediniósporos, além de reação de hipersensibilidade no tecido em torno das pústulas. O grau de infecção aumenta com o aumento na concentração do inóculo. A ferrugem coloniza, indiscriminadamente, folhas jovens e folhas maduras de videira.Termos para indexação: Phakopsora euvitis, Vitis, análise multivariada, reação de hipersensibilidade, resistência genética. Genetic resistance of grape genotypes to rustAbstract -The objective of this work was to evaluate the genetic resistance of grape genotypes to rust, caused by the fungus Phakopsora euvitis, and the infection effi ciency in relation to leaf age and inoculum concentration. The evaluation was carried out on 15 genotypes, based on the following resistance components: number of pustules (uredia) per cm 2 , size of pustules; number of urediniospores produced per pustules; and latent period. The resistance components, except for the latent period, presented considerable quantitative variation. The multivariate analysis of resistance components discriminated fi ve groups of genotypes. The more resistant genotypes were the rootstocks cultivars IAC313, IAC572, and IAC766, in which the infection effi ciency was low, with small pustule sizes, and less urediniospores production, besides hypersensivity response on tissue surrounding the pustules. The infection increases with increasing of inoculum concentration. The rust colonizes young and mature grape leaves.