Winter and summer performance of potato (Solanum tuberosum) in isohyperthermic regimes

Potato production in isohyperthermic temperature regimes (mean annual soil temperature higher than 22°C) has been considered impractical physiologically and economically. However, recent experiments with potatoes (var. Kennebec) on a clayey, kaolinitic, isohyperthermic Tropeptic Eutrustox of Hawaii during the winters of 1980 and 1981 and the summer of 1980, indicate that although seasonal variation in the tropics is minimal when compared to temperate regions, there is enough of a distinction in temperature that potato production is possible and favored during the cooler winter months. Soil temperatures, measured at 20-cm depth, in irrigated plots range from 18 to 20°C in winter and 24 to 26°C in summer. Tuber initiation in winter and summer began at 40 and 55 days after planting, respectively. Maturity was delayed by 20 days in summer. Yields in irrigated plots were 36,000 in winter and 25,000 kg/ha in summer; in nonirrigated plots, yields were 14,600 in winter and 7,900 kg/ha in summer. Nutrient uptake and water and energy use were less efficient in summer. The results indicated that winter is the most suitable season for potato production in the warm tropics.     

Effect of calcium silicate on growth and dry matter yield of Chloris gayana and Sorghum sudanense under two soil water regimes

The effects of five rates [0 (control), 1, 2, 4 and 6 Mg ha^?1] of calcium silicate on the growth and water consumption by rhodes grass (Chloris gayana Kunth) and sudan grass (Sorghum sudanense Piper) under wet and dry soil water regimes (60 g and 30 g H₂O kg^?1 soil respectively) were evaluated in a pot experiment. The effect of the application of silicate on plant biomass was similar to that of the control. However, the shoot and root dry mass varied significantly (P < 0.001) according to the soil water regime and plant species. During the first cut, the shoot dry mass was 5.7 g per pot under the wet soil moisture regime, significantly exceeding that under the dry soil water regime proportionately by 0.68. For sudan grass, the shoot dry mass varied from 3.6 g per pot in the control to 4.3 g per pot in the treatment that received 6 Mg ha^?1 of calcium silicate. Plant water demand decreased as the rate of calcium silicate application increased, suggesting that an application of calcium silicate could reduce drought stress and enhance water economy. For the soil under study, the reduction in plant water demand represents a water saving ranging from 0.076 to nearly 0.20.     

Diurnal Variations in Photosynthesis,Stomatal Conductance and Leaf Water Relation in Sorghum Grown with or without Silicon under Water Stress

Sorghum [Sorghum bicolor (L.) Moench] was grown hydroponically with or without 50 ppm silicon (Si), and exposed to water stress from 10 days after sowing (DAS). At 15 and 23 DAS, we measured dry weight and diurnal variations in photosynthetic rate (P _N), stomatal conductance (g _s), transpiration rate (T), leaf water potential (ψ _L), and water uptake rate (23 DAS only). The reduction in dry weight at 23 DAS caused by water stress was ameliorated by silicon. Under water stress, silicon-treated seedlings showed higher g _s, P _N, and T than untreated ones. ψ _L remained almost constant within treatments throughout the daytime. Water uptake rate was reduced by water stress, but the reduction was ameliorated by silicon. We conclude that silicon enhanced water uptake and g _s, improving water supply to the leaves. These effects of silicon occurred soon after exposure to water stress.     

Stem productivity in relation to nitrogen concentration and carbon isotopic composition (δ13C) in leaves of hinoki cypress (Chamaecyparis obtusa Endlicher) plantations in Shikoku district,Japan

The stem productivity of the hinoki cypress (Chamaecyparis obtusa Endlicher) in relation to plant nitrogen status and water-use efficiency was investigated in the Okuono (OKU) and Karakawa (KRK) areas in Shikoku district, Japan, where abundant precipitation occurs. The nitrogen concentration and carbon isotopic composition (δ¹³C) in the leaves were used as indexes of plant nitrogen status and water-use efficiency, respectively. The leaf nitrogen concentration increased with decreasing soil carbon/nitrogen (C/N) ratio and with increasing soil pH. There was a marginally significant negative correlation between leaf δ¹³C and soil water content in the KRK area, but leaf δ¹³C in the OKU area did not correlate with the soil water condition, and increased on the upper slope. The results suggest that hinoki trees in the KRK area have higher water-use efficiency (high leaf δ¹³C) under lower soil water conditions. In the OKU area, meanwhile, leaf δ¹³C in the upper slope was higher due to adaptation to adverse conditions. When 12 plots in two areas were included, the mean height and stem increments increased with increasing leaf nitrogen concentration and with decreasing leaf δ¹³C. These findings suggest that nitrogen acquisition is a primary factor for stem productivity in the areas concerned but the productivity of some forests is restricted by the soil water condition or other conditions, as indicated by the high value of leaf δ¹³C. The measurement of nitrogen concentration and δ¹³C in leaves can provide us with valuable insights into the relative importance of nitrogen, water and other conditions on stem productivity in the two areas.     

Multidisciplinary assessment of agricultural innovation and its impact: a case study of lowland rice variety WITA 9 in Côte d’Ivoire

ABSTRACT

Information on comprehensive evaluation of agricultural innovations is often limited. This study provides an overview of multidisciplinary evaluation of a lowland rice variety, WITA 9 (released in Côte d’Ivoire in 1998), with respect to its agronomic performance, grain quality, resistance to diseases, adoption by farmers, impact on productivity and farmers’ income, and marketability. WITA 9 had the highest paddy yield among the tested varieties including an international check (IR 64) and recently developed varieties adapted to this country. WITA 9 had a higher amylose content (26–28%) than others tested. This study confirmed its resistance to bacterial leaf blight, Rice yellow mottle virus (RYMV), and rice blast. A household survey showed that the adoption rate was 24%, its paddy yield advantage was 0.7 t ha^–1, and its adoption increased farmer’s income by US$ 91 ha^–1 per season. A market study showed that consumers’ willingness to pay was higher for WITA 9 than any other locally produced rice variety and comparable to imported rice in one of two markets. We conclude that WITA 9 is an ideal innovation for enhancing productivity and rice import substitution in Côte d’Ivoire. An effective seed delivery system and enhancing farmers’ and consumers’ awareness of this variety are vital for accelerating impact.     

Effects of low protein diet and low protein diet supplemented with synthetic essential amino acids on meat quality of broiler chickens

We investigated the effects of a low crude protein (CP) diet and a low CP diet supplemented with synthetic essential amino acids (EAA) on the meat quality of broiler chickens. Twenty‐one‐day‐old chickens were assigned to one of three diets: control, low CP (LCP), or low CP supplemented with EAA (ELCP). The chickens received these diets for 10 days. The shear force value (SFV) and free glutamate content of the Pectoralis major muscle were measured as indicators of the meat toughness and taste. The collagen and crude fat content of the muscle and the cross‐sectional area of myofibers were measured to evaluate the effects of the LCP and ELCP diets on meat toughness. The SFV of the ELCP group was 47% lower than that of the control group (P < 0.01). However, the LCP diet did not affect the SFV. The collagen and crude fat content were not affected by the dietary treatment. The cross‐sectional area was lower in the LCP and ELCP groups (P < 0.05) than the control group. The free glutamate content of muscle was not affected by the dietary treatment. Thus, a low CP diet supplemented with EAA is an effective means of producing tender meat.     

Resistance to paraquat in Mazus pumilus

Mazus pumilus is an annual self‐pollinating weed that is commonly found in arable land, vegetable gardens and roadsides. This weed harbours insects and pathogens that attack vegetables. The mechanism of resistance to paraquat of M. pumilus found in Ohita, Japan, was studied. Whole plant bioassays revealed that the resistant (R) biotypes were four to six times less susceptible than controls. Chlorophyll destruction of leaf discs by paraquat treatment in R biotypes was 4–20 times lower than those of susceptible (S) biotypes. Ferric reducing antioxidant power (FRAP) values in R biotypes were higher than those of S biotypes before and after paraquat treatments. The activity of superoxide dismutase (SOD) was also higher in R biotypes than those of S biotypes before and after treatment with paraquat, but the activities of ascorbate peroxidase (APX) and catalase (CAT) were not different between R and S biotypes. Change of ascorbate (AsA) contents before and after paraquat treatment was equivalent in both biotypes. These results indicate that the increased SOD activity and antioxidant capacity in R biotypes contribute to the resistance to paraquat of M. pumilus.     

Short photoirradiation induces flavonoid synthesis and increases its production in postharvest vegetables

It is desirable to increase the flavonoid contents of postharvest vegetables since flavonoids play a beneficial role in human health promotion. In the present study, we show that postharvest vegetables increasingly produced flavonoids when irradiated with light near the absorption wavelength of flavonoids in the plant. Three-day exposure to UV-B for 5 min, 98 μmol m?2 s?1 per day, increased the contents of jaceidin in spinach, kaempherol glycoside in radish sprout, apigenin glycosides in parsley, and isovitexin in Indian spinach after 6 days of storage in a refrigerator, compared to the contents in plants without irradiation. Six days of storage of unripe green strawberry under green light for 5 min, 98 μmol m?2 s?1 per day, enabled them to mature and turn red, accompanied by 3.5-fold increased contents of pelargonidin. Elucidation of the mechanism in parsley found the stimulating expression of the flavonoid synthesis gene, PAL, C4H, 4CL, CHS, and FNS, 6 h after exposure to single irradiation with UV-B for 5 min, and the higher expression was maintained for 24 h. After 3 days irradiation during 6 days of storage, parsley did not show adverse changes in the contents of ascorbic acid, β-carotene, chlorophyll, and moisture.     

Novel method to reduce fishy aftertaste in wine and seafood pairing using alcohol-treated yeast cells

"Fishy aftertaste" is sometimes perceived in wine consumed with seafood. Iron in wine has been reported to be a key compound that produces fishy aftertaste. However, cost-effective methods to remove iron from wine have not been developed. Here, we describe a cost-effective and safe iron adsorbent consisting of alcohol-treated yeast (ATY) cells based on the observation that nonviable cells adsorbed iron after completion of fermentation. Treatment of cells with more than 40% (v/v) ethanol killed them without compromising their ability to adsorb iron. Drying the ATY cells did not reduce iron adsorption. Use of ATY cells together with phytic acid had a synergistic effect on iron removal. We term this means of removing iron the "ATY-PA" method. Sensory analysis indicated that fishy aftertaste in wine-seafood pairings was not perceived if the wine had been pretreated with both ATY cells and phytic acid.     

Effect of temperature on survival,growth and malformation of cultured larvae and juveniles of the seven-band grouper Epinephelus septemfasciatus

The effects of rearing temperature (23–29 °C) during the larval and juvenile stage on survival, growth and skeletal malformations in the seven-band grouper Epinephelus septemfasciatus were investigated. The survival rate of juveniles 30–40 mm in total length emerging from eggs was higher at 25 and 26 °C (0.1–1.3 %) than at 23 °C or 27–29 °C (0.004–1.5 %). Growth (increase in total length) was accelerated at higher temperatures. The frequency of malformed individuals was lower at 25–27 °C (36.0–61.5 %) than at 23, 28 or 29 °C (65.3–76.9 %). Specific incidences of spinal curvature and centrum fusion or defects in juveniles were not related to rearing temperature. However, incidences of twisted or compressed vertebrae (6.5–64.0 %) were higher at higher temperatures, while the incidence of bifurcated neural spine was significantly higher at 23 °C (43.6–54.4 %) than at other temperatures (3.3–22.7 %). The incidence rate of spinal curvature (23.3 %) was significantly higher in juveniles with a deflated swim bladder, regardless of rearing temperature. The results of this study suggest that the optimum culture temperature for seven-band grouper is 25–26 °C, collectively considering the survival, growth and incidences of abnormalities. Our results also demonstrate the significance of identifying the conditions for swim bladder inflation to prevent spinal curvature in seven-band grouper.