Yukihiro Sugimoto

Impact of pesticide seed treatments on aphid control and yield of wheat in the Sudan.

Abstract Mixtures of imidacloprid and tebuconazole, were evaluated for three consecutive growing seasons, to determine the effects on plant stand, aphid control and wheat grain yield. At rates of 1.05/0.04 and 0.7/0.04xa0g a.i of pesticide, respectively, per kg of seeds, plant stand per unit area increased compared with their respective untreated control. Both rates of imidacloprid efficiently controlled the maize aphid ( Melanaphis maidis ) and suppressed the green bug ( Schizaphis graminum ) for 6–8 weeks after sowing. There were substantial differences among the different treatments in the number of grains/ear and the 1000-grain weight. These differences were reflected in 90% and 30% average increase in the total grain yield of the wheat crop raised from seeds treated with the mixture relative to the corresponding untreated control and a standard mixture of lindane plus thiram, respectively. This strategy of using imidacloprid as seed dressing allowed easy application, gave adequate reliable control of aphids and less hazardous to the environment.

(+)-Strigol, a witchweed seed germination stimulant, from Menispermum dauricum root culture

(+)-Strigol was isolated from Menispermum dauricum root culture filtrate. Its identity was confirmed by HPLC, 1H NMR, UV and MS, and on the basis of its CD spectrum. This is the first report on isolation of strigolactone from aseptic plant culture.

Effect of imidacloprid on incidence of Tomato yellow leaf curl virus

Confidor, an imidacloprid insecticide, was used in two applications at four rates (47.6, 71.4, 95.2, and 119 g a.i./ha) for indirectly controlling Tomato yellow leaf curl virus (TYLCV) in field plantings of tomato. This spray regimen was compared with standard applications of cypermethrins at 10- to 15-day intervals throughout the growing season. In three field trials, a combination of integrated pest management (IPM) practices and two applications of Confidor at the two highest rates immediately after planting and 6 weeks later, protected tomato plants against the disease until 12 weeks after sowing. All rates of Confidor reduced disease incidence compared with standard chemical control applied in an integrated strategy, and quantitative efficacy increased with increase of insecticide rate. In the three seasons, the mean incidence of TYLCV 12 weeks after sowing was 42.7% in plots not adopting IPM compared with 15.7% in those that did. Disease incidence was reduced by Confidor treatments to 2.2 to 17%. Confidor-treated plots consistently had higher yields than control plots, and the yields decreased with the decrease in the rate of Confidor application. Confidor offers several advantages over standard applications of cypermethrins to control TYLCV. When applied immediately after planting, its long-lasting systemic activity protected the crop against the disease during early stages of growth. In addition, it reduced the number of sprays and increased tomato yield.

Growth and Gas Exchange of Three Sorghum Cultivars Under Drought Stress

A field study was conducted to evaluate the drought tolerance of three sorghum [Sorghum bicolor (L.) Moench] cultivars, Gadambalia, Arous elRimal and Tabat, and quantify the physiological bases for differences in their drought tolerance. Water stress reduced shoot dry mass of Gadambalia, Arous elRimal and Tabat by 43, 46 and 58 %, respectively. The respective reduction in leaf area of the three cultivars was 28, 54 and 63 %. The reduction in net photosynthetic rate, stomatal conductance and transpiration rate due to water stress was lowest in Gadambalia and highest in Tabat. The leaf water potentials and relative water contents of Gadambalia under wet and dry treatments were similar, while those of Tabat were significantly reduced by water stress. The lowest and highest liquid water flow conductance was displayed by Tabat and Gadambalia, respectively. Drought tolerance in Gadambalia is associated with its smaller leaf area, higher liquid water flow conductance, and ability to maintain high leaf water potential, relative water content, stomatal conductance, transpiration rate and photosynthetic rate under drought stress.

Response of oilseed rape plant to low root temperature and nitrate: Ammonium ratios

Abstract Oilseed rape (Brassica napus L.) response to root temperature regimes (20/20, 16/8 and 12/12°C day/night) at constant 20°C air temperature was studied. At each regime, three NO3 ‐:NH4 + ratios (10:0, 8:2, or 6:4), at constant 10 mM N, in the irrigation solution were tested. Plant growth, transpiration, ionic composition and level of cytokinins and gibberellins in the xylem exudate were monitored. The two low root temperature regimes, 12/12 and 16/8°C, reduced rape shoot growth by 28 and 22%, and increased the accumulation of soluble carbohydrates by 42 and 26% in the roots, respectively, as compared to the 20/20°C regime. Low root temperatures reduced plants transpiration. The NO3 ‐:NH4 + ratios had no effect on rape growth. At low root temperatures NO3 ‐contents increased in the shoot and decreased in the roots. The sum of cations and that of anions at 12/12 and 16/8°C root temperatures decreased significantly as compared to 20/20°C. The presence of NH4 + in the irrigation solution decreased the...

Effects of low root temperature on sap flow rate, soluble carbohydrates, nitrate contents and on cytokinin and gibberellin levels in root xylem exudate of sand‐grown tomato

Abstract Tomato (Lycopersicon esculuntum Mill.) grown in open fields in dry land areas or in non‐controlled greenhouses are subjected to substantial daily changes in root temperature. In the field, root‐zone temperatures fluctuate both diurnally and during the growing season. The purpose of this study was to monitor root‐zone temperature effects on tomato initial growth, transpiration, sap flow rate, leaf and air temperatures differences, nitrate accumulation, total nitrogen, and soluble carbohydrates in the shoot and roots as well as levels of endogenous cytokinins and gibberellins in xylem exudate. Tomato seedlings were grown in three growth cabinets with variable control of root temperatures. Three day/night root temperature regimes (12/12, 16/8 and 20/20°C) were employed. Low day root temperatures of 12 and 16°C reduced shoot dry weight by 47 and 26%, root dry weight by 36 and 14%, shoot nitrate by 79 and 50%, root nitrate by 49 and 16%, levels of cytokinins in root xylem exudate by 27 and 13% and gib...

SALT TOLERANCE IN TWO SOYBEAN CULTIVARS

Experiments were conducted in an environmentally controlled growth chamber to evaluate the role of the root system in the salt tolerance of two soybean (Glycine max(L.) Merr.) cultivars, Tachiyutaka and Dare, that differ in salt tolerance. Young plants were submitted to 0 (control), 40, 80, and 120u2005mM NaCl treatments for 3, 23, and 30 days in three experiments, respectively. The most significant differences between the two cultivars were obtained in 40u2005mM NaCl. Under this condition, compared with salt sensitive cv. Tachiyutaka, tolerant cv. Dare showed a higher relative shoot and root growth (Dare: 70 and 63%, Tachiyutaka: 42 and 42%, respectively), water extraction ability (Dare: 0.18u2005gu2005cm−2u2005d−1 for transpiration and 0.98u2005gu2005m−1u2005d−1 for water uptake, Tachiyutaka: 0.13u2005gu2005cm−2u2005d−1 and 0.81u2005gu2005m−1u2005d−1 respectively), root pressure (Dare: 5.68u2005mgu2005g−1 for root exudate, Tachiyutaka: 0.32u2005mgu2005g−1), better root osmotic adjustment (Dare: −0.61u2005MPa for osmotic potential, Tachiyutaka: −0.59u2005MPa), and less sodium (Na+) accumulation in plant tissue (Dare: 0.1, 0.4, and 9.2u2005mgu2005g−1 in leaf, stem, and root, respectively, Tachiyutaka: 1.4, 3.5, and 11.6u2005mgu2005g−1). The difference in salt tolerance between the two cultivars is attributed to the root system. The salt tolerance of cv. Dare is associated with high water uptake, and Na+ and chloride (Cl−) exclusion of the roots.

Different Effect of Humidity on Growth and Salt Tolerance of Two Soybean Cultivars

Two soybean (Glycine max (L.) Merr.) cultivars, Tachiyutaka and Dare, were grown in pots at 30 and 70 % relative humidity (RH) and treated with 0 (control), 40 (moderate), 80 and 120 (severe) mM NaCl for 3 weeks. Increasing RH enhanced growth of salt sensitive cultivar, Tachiyutaka, but had no effect on salt tolerant cultivar, Dare, under control and moderate saline conditions. Both cultivars benefited from elevated humidity under severe saline conditions. Cultivar Tachiyutaka had poorer ability for controlling translocation of Na+ to the leaves, lower Na+ exclusion ability in the roots, and lower root activity under NaCl treatment, compared with cv. Dare. The increased growth of cv. Tachiyutaka at high RH was consistent with decreased Na+ accumulation in the leaves, increased stomatal conductance and root activity, while the unchanged growth of cv. Dare was consistent with similar Na+ accumulation in the leaves, and the decreased root activity.

Response of sand‐grown tomato supplied with varying ratios of nitrate/ammonium to constant and variable root temperatures

Abstract Tomato (Lycopersicon esculentum Mill.) is commercially grown in a wide range of climatic conditions. There is a need to understand nutrient uptake by tomato at various climatic conditions in order to devise the specific nutrient supply to this important crop. Tomato seedlings, at the first flower blooming stage, were transplanted into 6‐L pots of washed sand. Four root temperature regimes (day/night, °C) 12/12, 16/08, 17/17, and 30/20, and four temperatures of the shoots 20/20, 25/25, 25/15, and 30/20 were controlled separately for the shoots and roots. All four growth cabinets had the same day length of 13 h and light intensity of 400 μmole/m2/s measured on top of the canopy, The relative humidity was 85%. The nutrient solutions contained 10 mM N in three ratios of nitrate:ammonium (NO3:NH4)—10:0, 8:2, and 6:4 each in three replications in each growth cabinet. The water consumption, fresh and dry weight, water soluble nutrient in the plant, exudate composition at the end of the experiment and to...

Effect of Jasmonates and Related Compounds on Seed Germination of Orobanche minor Smith and Striga hermonthica (Del.) Benth

Jasmonates and related compounds were found to elicit the seed germination of the important root parasites, clover broomrape (Orobanche minor Smith) and witchweed [Striga hermonthica (Del.) Benth]. The stimulation of seed germination by the esters was more effective than by the corresponding free acids, and methyl jasmonate (MJA) was the most active stimulant among the compounds tested.