Lowland arabica coffee can be affected by leaf rust and its decrease the coffee production up to 80%. The resistance level of the plant can be determined by the content of cellulose, lignin, calcium pectate, and polyphenols in leaf tissue. Many publications reported that the mineral element could increase the content of the metabolites. This study aimed to determine the effect of Si, B, I, Ca, and K on the incidence of leaf rust attack. The experiment was carried out at 400 m a.s.l. in 2018. The experimental subjects were KT variety, which was six years old. The experiment used a randomized block design with seven treatments. The results showed that there were 1) decrease the number of leaves affected by rust between first and second observation, and 2) compared to controls, all treatments has decreased the incidence of attacks leaf rust disease. Conclusion: There is a tendency of differences in the incidence rate of attack of leaf rust disease in each treatment. Control plants showed the highest incidence rate of 1.25%, while the lowest incidence was affected by Silica, iodine, and potassium, which were 0.63%. The treatment of silica and iodine was able to reduce the highest number of colonies Leaf Rust.

The production of arabica coffee in Indonesia is still low because of leaf rust disease suppression caused by Hemileia vastatrix. Basically, it can produce well in the overlapping zone (1000-1500 masl). This potential can be used as basic for intensifying arabica coffee cultivation to the lowland. For anticipation steps to reduce the spread of leaf rust can be done by increasing the production of polyphenol as plant resistance. The addition of mineral element such as silica, boron, iodine, calcium, and potassium can stimulate the synthesis of plant polyphenol. In this research, five minerals above were tested into 7 treatment with single factor RCBD, that is without additional of the mineral element, 150 mg L-1 Si, 300 mg L-1 B, 3000 mg L-1 Ca, 20.000 mg L-1 K, 300 mg L-1 I, and the combination/mix of five mineral elements. The laboratory analysis shows that calcium able to produce the highest polyphenol, but it is not a real difference with silica. The polyphenol that synthesized by Si, I, and K was able to reduce the leaf rust incidence until 78,13%, while Ca can reduce the incidence up to 71,88%.

Cocoa (Theobroma cacao L.) like most tropical trees is recalcitrant in tissue culture. Somatic embryogenesis is generally efficient micropropagation technique to multiply elite material. However, Somatic embryogenesis in cocoa is difficult and this species is considered as recalcitrant. One of the factors often considered as a component of in vitro recalsitrance is a high phenolic content and oxidation of these compounds. In cocoa tissue culture accumulate large amounts of poliphenolics compounds which probably impair further development. This study was conducted to investigate the composition of phenolic compounds in cocoa flower and leaves, and their changes troughout the somatic embryogenesis process. Calli were induced in cacao floral and leaves explants on a half-strenght Murashige and Skoog medium containing 30 g/L Glucose and combination of 2,4 dichlorophenoxyacetic acid (2,4 D) with kinetin (kin). Total polyphenol content was observed on Sulawesi 1 cocoa clone. Embryogenic and non-embryogenic callus were also compared. The percentage of callus production from flower tissue is 85%, percentage of embryogenic callus 40 %, although  the percentage of somatic embryo production from embryogenic callus callus is 70%. The conservation of callus into somatic embryos followed by decline in phenol content and an increase in peroxidase. The synthesis kinetics for these compounds in calli, under different somatic embryogenesis conditions, revealed a higher concentration under non-embryogenic conditions. So that, phenolic compound can influence the production of calli and an absence the phenolic compound can enhance production of somatic embryo.Kata kunci: Theobroma cacao L., polifenol, embrio somatik, kalus, flavonoid, katekin, in vitro recalcitance

Tomato has the characteristics natural to damage. Damage fruits are caused by destitute of fruit quality and sensory attributes. The loss of tomato production on harvest in developing countries reached 50% due to the long duration of tomato distribution. Servo varieties of tomatoes are in demand by farmers because of their genetic advantages, high productivity, and abundant fruit weights. The shortage of servo varieties of tomatoes is the short shelf life of fruit, which is seven days after harvest. Short shelf life is influenced by fruit thickness and fruit hardness. In improving the quality and shelf life of tomatoes, potassium (K) nutrition plays a role in photosynthetic translocation, strengthens the cell wall, and involved in the lignification process of sclerenchyma tissue. Tomatoes, as climacteric fruits have a high respiration rate influenced by ethylene. Ethylene production can be inhibited by calcium chloride (CaCl2) application by strengthening the cell wall mechanism, cross-link with pectin, and increase the cell wall regeneration can change the texture of the fruit become harder, and it reduces sensitivity to physiological damage. Based on the treatment of this research, the quality and shelf life of servo varieties of tomato is increased.

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