Fusao Mizutani

Genetic characterization of cultivated bananas and plantains in Kenya by RAPD markers

Abstract A polymerase chain reaction (PCR)-based approach, namely, random amplified polymorphic DNA (RAPD) was used to estimate the genetic relationships among 20 selected banana cultivars from different regions of Kenya. Nineteen random primers were used. The polymorphisms in PCR amplification products were subjected to the unweighted pair group method for arithmetic averages (UPGMA) and plotted in a phenogram. The dendogram constructed from the similarity data showed that all the 20 cultivars analysed were related. The highly related cultivars included Ng’ombe, Nusu Ng’ombe, Ntobe, Sialamule, Kimuga, Kibuzi, Sibusi, Bukamba, Mfupi and Gitigi whose genome was AAA. The cultivars Manyatta, Mokoya, Murure and Horn plantain whose genome was AAB were less similar while Pekera, Muraru, Spambia, Matumbo, Nyar Sausett and Mtama formed the least related group.

Effect of root-zone flooding on mycorrhizal and non-mycorrhizal peach (Prunus persica Batsch) seedlings.

The effect of root-zone flooding on mycorrhizal and non-mycorrhizal peach seedlings growing in a low P medium was examined. Mycorrhizal seedlings showed relatively faster development prior to flooding and recorded significantly higher concentrations of shoot P, K and Zn and biomass yield. Ethanol accumulation was significantly higher in the taproots of non-mycorrhizal as compared to mycorrhizal plants after 3 days of flooding. A more rapid decline in plant health was also observed in non-mycorrhizal as compared to mycorrhizal seedlings. The presence or absence of the fungal partner led to significant difference in the ratio of roots that remained viable after extended flooding. Therefore, it is clear that arbuscular mycorrhizal (AM) infection confers limited tolerance to flooding on peach seedlings. This could be due to improved plant nutrition, the suppression of ethanol accumulation in roots and the extension of the duration of root activity in a flooded environment.

Effects of Partial Ringing and Heating of Trunk on Shoot Growth and Fruit Quality of Peach Trees

Small-sized peach (Prunus persica [L.] Batsch.) trees for commercial fruit production have not been available due to the lack of suitable dwarfing rootstocks that have a wide range of compatibility among cultivars. Effects of partial girdling and trunk heating on the growth, yield, and fruit quality of peach were studied. A 4 cm wide partial ring of bark was removed at a height of 25 cm from the ground leaving a connecting strip of 5 mm. Furthermore, the dc-barked spot was heated at 150℃ for fifteen minutes using an electric heater. The partial girdling was effective in reducing shoot growth and improving fruit quality. The total soluble solids content of fruit in treatment trees was higher than that of control. The heating had little additive effects over partial ringing.

Cyanide metabolism linked with ethylene biosynthesis in ripening processes of climacteric and non-climacteric fruits

Abstract The cyanide metabolism linked with the ethylene biosynthesis was compared with fruits of apple (climacteric type), satsuma mandarin (non-climacteric type) and grape (non-climacteric type) during their development and in storage after harvest. In apple, the rate of ethylene production and β-cyanoalanine synthase activity were very low in young immature fruit, but increased markedly with the onset of ripening. At the same time corresponding increases in the ACC content were observed, whereas the cyanide content was slightly increased. In satsuma mandarin and grape, ethylene production was low during development and maturation, but increased slightly during senescing processes. The β-cyanoalanine synthase activities were extremely low compared with that of apple, although slight increases were observed during maturation through senescing processes. It seems that no bulk induction of β-cyanoalanine synthase is needed for non-climacteric fruits with the onset of ripening. The ACC content in grape was consistently higher than in apple, although the rate of ethylene production was quite low. The cyanide content in grape considerably increased during maturation and ripening processes. The causes of these specificities of grape are not clear at present.

Effects of ethylene and hydrogen cyanide on β-cyanoalanine synthase activity in satsuma mandarin (Citrus unshiu Marc.) fruit

Abstract Exogenous ethylene increased β-cyanoalanine synthase activity in satsuma mandarin fruit. An inward decreasing gradient in the activity was found in ethylene-treated fruit; the highest activity was in the flavedo and the lowest in the juice sacs. β-Cyanoalanine synthase activity in the peel (flavedo and albedo) increased in parallel with increasing ethylene concentrations up to 500 ppm and then leveled off. Green mature fruit were less responsive to ethylene in the induction of β-cyanoalanine synthase activity than more mature fruit. Regardless of ripening stage, the latter group of fruit responded to ethylene to reach similar maximum enzyme activities, which were approximately two-fold greater than those of green mature fruit. 2,5-Norbornadiene, a specific inhibitor of ethylene action, repressed the ethylene-induced increase in β-cyanoalanine synthase activity. Hydrogen cyanide did not induce β-cyanoalanine synthase but rather reduced the activity at high concentrations.

Inhibition of ethylene production and 1-aminocyclopropane-1-carboxylate oxidase activity by tropolones

Abstract The effect of tropolone and hinokitiol on C 2 H 4 production and in vitro ACC oxidase activity was examined by using apple fruit plugs. Application of aqueous tropolone and hinokitiol solution inhibited C 2 H 4 production, but the addition of Fe 2+ in the solution alleviated the inhibition. Gaseous tropolone and hinokitiol were also effective in suppressing C 2 H 4 production, but the suppression was annulled when apple plugs were pretreated with Fe 2+ . Tropolone and hinokitiol inhibited in vitro ACC oxidase activity, which was recovered by adding Fe 2+ in the assay medium. Therefore part of inhibition of C 2 H 4 production by these tropolones was due to their chelating action of Fe 2+ , which is essential for the activation of ACC oxidase.

Cyanide metabolism linked with ethylene biosynthesis in satsuma mandarin (Citrus unshiu Marc.) fruit

Abstract The cyanide metabolism linked with ethylene biosynthesis was examined with detached satsuma mandarin fruit at different stages of ontogeny. Young immature fruit showed a rapid rise in ethylene production after detaching. Concomitant increases were observed in the β-cyanoalanine synthase activity, ACC and cyanide content with the rise of ethylene production. Moreover, partially yellowing, abscising young fruit on the tree also showed an increased rate of ethylene production, as well as high ACC content and β-cyanoalanine synthase activity. However, the conspicuous increase in ethylene production disappeared as the fruit became larger. Similarly, there was no marked increase in β-cyanoalanine synthase activity. The mechanism of how citrus fruit lose the ability to produce ethylene as they develop remains to be elucidated.

Influence of different temperatures on bud break and 1-aminocyclopropane-1-carboxylic acid content of young peach trees

Effects of different temperatures on bud break and 1-aminocyclopropane-1-carboxylic acid (ACC) content were determined by using potted two-year-old ‘Akatsuki’ peach trees. One group of trees were subjected to 1°C for four weeks and then transferred to a growth chamber at 24°C, while the other was kept at 24 °C throughout the experiment. After four-week temperature treatments floral and vegetative bud break were evaluated weekly and bud break percentage was calculated. Bud break was greater under 1 °C than 24 °C in both November and December. The time required to release buds from dormancy was shorter in December than November. In November ACC content in peach buds increased after one and two weeks, then decreased in the forth week under both treatments. However, in December ACC content after two and four weeks showed a similar trend under 1 °C and a reverse trend under 24 °C. It was higher under low temperature treatment. These data indicate that chilling requirements for bud break of peach seems to be associated with the promotion of ethylene biosynthesis caused by low temperature stress.