Mechanisms underlying the protective effects of beneficial fungi against plant diseases

Biological functions of Trichoderma spp. for agriculture applications

Considerable research has focused on the control of the physiological activity of fruits and vegetables in postharvest conditions as well as microbial decay. The use of edible coatings (ECs) carrying active compounds (e.g., antimicrobials) represents an alternative preservation technology since they can modify the internal gas composition by creating a modified atmosphere through the regulation of the gas exchange (oxygen, carbon dioxide, volatiles) while also limiting water transfer. Of the edible polymers able to form coating films, starch exhibits several advantages, such as its ready availability, low cost and good filmogenic capacity, forming colourless and tasteless films with high oxygen barrier capacity. Nevertheless, starch films are highly water sensitive and exhibit limited water vapour barrier properties and mechanical resistance. Different compounds, such as plasticizers, surfactants, lipids or other polymers, have been incorporated to improve the functional properties of starch-based films/coatings. This paper reviews the starch-based ECs used to preserve the main properties of fruits and vegetables in postharvest conditions as well as the different factors affecting the coating efficiency, such as surface properties or incorporation of antifungal compounds. The great variability in the plant products requires specific studies to optimize the formulation of coating forming products.

https://www.mdpi.com/2079-6412/8/5/152/pdf

Starch-Based Coatings for Preservation of Fruits and Vegetables

Gas exchange responses to irradiance, temperature, air vapor pressure deficit and intercellular CO2 concentration were evaluated in young plants of sweet orange 'Valencia', tangor 'Murcote' and acid lime 'Tahiti' plants, under controlled conditions. Maximum rates of CO2 assimilation were around 9.8, 12.8 and 13.0 µmol m -2 s -1 , respectively, for 'Valencia', 'Murcote' and 'Tahiti', and these differences were related to stomatal conductance and instantaneous carboxylation efficiency. Light saturation of photosynthesis was around 750 µmol m -2 s -1 for 'Valencia', whereas 'Murcote' and 'Tahiti' did not show evident light saturation, exhibiting small increases of CO2 assimilation above 1,000 µmol m -2 s -1 . The CO2 compensation point was 4.8, 5.8 and 5.4 Pa for 'Valencia', 'Murcote' and 'Tahiti', respectively, indicating differences in photorespiration of these citrus species. Leaf temperatures between 25 o C and 30 o C were optimum for photosynthesis of 'Valencia', whereas this optimum was around 30 o C for 'Murcote' and 'Tahiti'. At temperatures above or below the optimum range, CO2 assimilation was reduced by partial decrease of stomatal conductance and instantaneous carboxylation efficiency. Reduced CO2 assimilation rate was also caused by increasing vapor pressure deficit from 1.5 to 3.5 kPa, and this effect enhanced when temperature increased from 28 o C to 35 o C.

/pdf/respostas-da-fotossintese-de-tres-especies-de-citros-a-3wtg89apuf.pdf

Respostas da fotossíntese de três espécies de citros a fatores ambientais

Photosynthetic response of citrus grown under reflective aluminized polypropylene shading nets

The CO2 assimilation rate and leaf water potential were analyzed in 18-months-old `Valencia' orange tree, in pots. The plants were grafted on four different rootstocks: `Rangpur' lime, Trifoliata, `Troyer' citrange and `Cleopatra' mandarin. Plants were submitted to water stress until the CO2 assimilation rate was negligible when they were rehydrated. It was also analysed the hydraulic conductivity of the rootstocks used. Under well watered conditions, CO2 assimilation rate was lower in plants grafted on `Troyer' and `Cleopatra' when compared with plants grafted on `Cravo' which was not different from plants grafted on Trifoliata. Throughout the day the greatest CO2 assimilation rates were observed by 9:00h, with 8mmol/m2.s, followed by a decrease due possibly to the increase in the vapour water deficit and room temperature, from 11:00h through 14:00h. After withholding water, in the decreasing at the leaf water potential was similar to all the plants, regardless of the rootstocks used. Nevertheless, CO2 assimilation rate decreased more rapidly, after withholding water, and it was recovered more slowly after rehydration, in plants grafted on `Cravo'. These plants also presented, during the entire water deficit period, lower CO2 assimilation rate than plants grafted on Trifoliata and `Cleopatra', and similar to `Troyer'. Plants grafted on Trifoliata recovered CO2 assimilation rate in 3 days while those grafted on other rootstocks did not recover entirely in that period. The hydraulic conductivity was higher in `Cravo' lemon tree and there were no differences among the values found in the other rootstocks.

Fotossíntese de laranjeira 'valência' enxertada sobre quatro porta-enxertos e submetida à deficiência hídrica

Biocontrol of melon wilt caused by Fusarium oxysporum Schlect f. sp. melonis using seed treatment with Trichoderma spp. and liquid compost.

This study consisted of one experiment with melon (Cucumis melo L.), carried out in a Vertisol in Juazeiro, BA, Brazil, in 1995, with the objective of evaluating the effects of nitrogen levels through fertirrigation and plant density on fruit yield and quality. The N levels were 0, 80, 130 and 180 kg/ha, combined with row spacings of 2.0 and 1.8 m and 0.20 m between plants within the row, with one or two plants/hole. The source of N was urea applied daily up to 42 days after germination, through drip irrigation. All treatments had a uniform fertilization of 120 kg/ha of P2O5 and 120 kg/ha of K2O. No significant difference was caused by spacing between rows in the studied variables. Eighty kg/ha of N combined with one plant per hole gave a yield of 34.07 ton/ha, being 55,7% of fruit allocated to inside market, not significantly lower than those obtained with the highest N levels in any combination. This same N level gave fruits with 10.22o Brix, significantly higher than the treatment without N and not significantly lower than the other levels. In order to get high number of good fruit for out side market it was necessary to elevate the density to two plants per hole and N level to 130 or 180 kg/ha. Mean weight of fruits increased from 1.008 to 1.705 kg with the increase in the levels of N and the decrease in plant density of two plants per hole to one plant per hole.

/pdf/niveis-de-nitrogenio-por-fertirrigacao-e-densidade-de-4dmelfaiyr.pdf

Níveis de nitrogênio por fertirrigação e densidade de plantio na cultura do melão em um Vertissolo

Realizou-se um estudo no Campo Experimental de Bebedouro, do Centro de Pesquisa Agropecuaria do Tropico Semi-Arido da EMBRAPA, em Petrolina, PE, para avaliar o efeito da aplicacao de nitrogenio e potassio via agua de irrigacao na cultura do melao ( Cucumis melo L.), cultivar Eldorado 300. Adotaram-se duas frequencias de fertirrigacao (diaria e tres vezes por semana) e oito periodos de aplicacao de N ate 55 dias apos a germinacao, via agua de irrigacao. Na testemunha, 55% do N e 100% do K foram aplicados em fundacao, e os 45% restantes do N, em cobertura, 30 dias apos o plantio. Nos demais tratamentos, o K foi aplicado via agua de irrigacao ate 42 dias do ciclo da cultura. O sistema de irrigacao utilizado foi por gotejamento. As maiores producoes foram 26,40 t/ha e 25,89 t/ha com fertirrigacao diaria, para os periodos ate 42 e 55 dias, respectivamente. A aplicacao de N e K via agua de irrigacao nao alterou as caracteristicas quimicas do fruto, o teor de solidos soluveis, a acidez total e o pH. Considerando os resultados obtidos, a frequencia diaria e a aplicacao de N ate 42 dias do ciclo da cultura podem ser recomendados.

Adubacao via agua de irrigacao na cultura do melao.

Realizou-se um estudo no Campo Experimental de Bebedouro, do Centro de Pesquisa Agropecuaria do Tropico Semi-Arido, da EMBRAPA, em Petrolina, PE, para avaliar o efeito de periodos e de frequencias de fertirrigacao com nitrogenio na producao do melao ( Cucumis melo L.), cultivar Eldorado 300. Adotaram-se duas frequencias e seis periodos de fertirrigacao, em um delineamento de blocos ao acaso, em esquema fatorial, com quatro repeticoes. As frequencias de fertirrigacao foram: diarias, e tres vezes por semana. Os periodos de fertirrigacao foram: 1. aplicacao de N ate 55 dias do ciclo do melao; 2. aplicacao de N ate 42 dias; 3. aplicacao de N ate 30 dias; 4. aplicacao de 70% de N ate 42 dias, e os 30% restantes, ate 55 dias; 5. aplicacao de 70% de N ate 30 dias, e os 30% restantes ate 55 dias; e 6. aplicacao de 70% de N ate 30 dias, e os 30% restantes, ate 42 dias. A testemunha recebeu 55% de N aplicado em fundacao, e os 45% restantes, em cobertura, 30 dias apos o plantio. O sistema de irrigacao utilizado foi o de gotejamento. As maiores producoes foram de 20,28 t/ha e 18,87 t/ha com fertirrigacao diaria e periodo de aplicacao de 55 e 42 dias, respectivamente. Considerando os resultados, a frequencia diaria e os periodos ate 55 dias e ate 42 dias poderao ser recomendados para a cultura do melao.

José Maria Pinto

Papers

Fotossíntese de laranjeira 'valência' enxertada sobre quatro porta-enxertos e submetida à deficiência hídrica

Biocontrol of melon wilt caused by Fusarium oxysporum Schlect f. sp. melonis using seed treatment with Trichoderma spp. and liquid compost.

Níveis de nitrogênio por fertirrigação e densidade de plantio na cultura do melão em um Vertissolo

Adubacao via agua de irrigacao na cultura do melao.

Efeitos de períodos e de freqüências da fertirrigação nitrogenada na produção do melão