Due to the continuous differentiation of inflorescences throughout the growing season, the day-neutral strawberry cultivars are likely to produce an insufficient number of runners. For the improvement of the runner production, the effects of GA₃ at 50 ppm, BA at 50 ppm, combination of GA₃ at 50 ppm and BA at 50 ppm, and 15N-15P-15K fertilizer levels on runner production, flowering, and growth parameters were evaluated in three cultivars of dayneutral strawberry (Fragaria×ananassa Duch.‘Summer Berry’, ‘Miyoshi’, and‘Enrai’) .
Application of GA₃, BA, and GA₃+BA resulted in a 2-3 fold increase of the number of runners in‘Miyoshi’, whereas GA₃ and GA₃+BA led to an increase of about 8 and 4 times in‘Enrai’and‘Summer Berry’, respectively.
GA₃ significantly increased the petiole length in‘Miyoshi’and‘Enrai’, and all the growth regulators increased the petiole length in‘Summer Berry’. GA₃ increased the number of leaves only in‘Miyoshi’, whereas in‘Summer Berry’BA increased the number of leaves. The number of inflorescences and the leaf area in all the cultivars were not affected by the treatments with growth regulators.
The application of slow release fertilizer NPK (N, P₂O₅, K₂O, 15-15-15) at the rate of 100 mg/pot induced a higher inflorescence production and enhanced the other growth parameters compared with the application at 0 and 50 mg/pot. The runner production was promoted by NPK at 100 mg/pot only in‘Enrai’.
It was suggested that the growth regulator treatments and fertilizer level improved runner production, but the responses varied with cultivars. These data may contribute to the improvement of vegetative propagation of strawberry in the tropics.

View full abstract

In transplanted rice (variety BR 11) grown during July to November in Bangladesh, weed infestation in terms of absolute density, weed dry matter weight and intensity of weed infestation was studied 25 (W₁) and 45 (W₂) days after transplanting at five N levels (0, 40, 60, 80 and 100 kg/ha) and three spacings (20×10 cm, 25×15 cm and 30×20 cm) in a split-plot design with four replications. Nine species of weeds belonging to six families were identified and found to infest the transplanted rice field. Weed growth increased significantly with the increase in spacing and linearly with N level, but the weed growth rate was higher at W₁ than W₂. It was revealed that, with the increase in every kg of N/ha, the absolute density (AD) of weeds increased by 0.422 and 0.200 at W₁ and W₂; the weed dry matter wight (DM) was 0.068 and 0.061 g/m² at W₁ and W₂ and the intensity of infestation (II) was 0.018 and 0.010 at W₁ and W₂. Nitrogen level was correlated with AD, DM and II, and several equations were obtained as follows: AD (AD₁=0.422N+159.602, r²=0.937 and AD₂=0.200N+96.626, r²=0.872), DM (DM₁=0.068N+16.92, r²=0.907 and DM₂=0.061N+16.115, r²=0.968) and II (II₁=0.018N+6.586, r²=0.852 and II₂=0.010N+3.962, r²=0.928), where AD is expressed as no. per m², DM as g per m² and II as no. per rice hill. These results indicate the effect of spacing and N level on weed infestation in transplanted rice field in similar agro-environmental areas. However, depending on the climatic and edaphic factors, the results may vary with the area.

View full abstract

Male sterile cytoplasm and restorer gene of three restorer lines, RT61C, RT98C and RT 102C, in rice were identified and allelic relationships between the restorer genes were studied. Each line was an isogenic line of Taichung 65, cultivar Oryza sativa, developed by the backcrossing method, with a male sterile cytoplasm and a dominant fertility restorer gene derived from the original line of the wild species of O. rufipogon. Male sterile lines, RT61A, RT98A and RT102A, which were used as testers were derived from the restorer lines through two backcrossings with Taichung 65, to replace the dominant restorer gene of the restorer lines with the recessive nonrestorer allele of Taichung 65.
Following crosses were carried out: 1. male sterile line/restorer line -to identify the cytoplasm and restorer gene, 2. restorer line/restorer line//Taichung 65 -to detect the allelism of genes among the restorer lines.
The F₁ hybrids showed a high spikelet fertility in both RT61A/RT98C and RT61A/RT102C. All the F₁ plants derived from the crosses of RT98A/RT61C and RT98A/RT102C showed complete sterility. In the cross of RT102A/RT61C the F₁ plants were sterile, while in RT102A/RT98C the F₁ plants were fertile. Thus, the cytoplasms and the restorer genes of the three restorer lines differed from each other.
In the crosses of RT98C/RT61C//Taichung 65, RT98C/RT102C//Taichung 65 and RT102C/RT61C//Taichung 65, the offsprings segregated into a 1 sterile and 1 fertile plant ratio. From these crosses allelism could not be determined. However, in the other crosses, RT61 C/RT98C//Taichung 65, RT61C/RT102C//Taichung 65 and RT102C/RT98C//Taichung 65, all the F₁ plants produced fertile spikelets. The results suggested that the genes of the three restorer lines were located at the same locus.

View full abstract

The effect of two light intensities (50 and 100%, PAR; 1200μmol⋅m^-1⋅s^-1 at noon) and two air temperatures (33 and 38°C) on the photosynthetic rate (Pr), transpiration rate (E), stomatal conductance (gs), intracellular CO₂ concentration (Ci), fruit yield and fruit sugar content (Brix) of two watermelon (Citrullus lanatus Thunb.) cultivars‘Baoguan’and‘Xinlan’was examined. Plants grown under 100% light showed higher Pr, E and gs values than those under the shade. At the cultivar level, ‘Baoguan’showed higher Pr, E, gs values and yield and a lower Ci concentration than‘Xinlan’under 100% light and at both temperatures. Correlations between photosynthesis and transpiration, stomatal conductance and yield were significantly positive while that between photosynthesis and intracellular CO₂ concentration was significantly negative. Soluble solid content ranged from 12.0-13.5 Brix % and did not differ between cultivars in all the treatments. Although watermelon production is optimum under full sunlight, since cultivation is possible under 50% sunlight, the incorporation of this crop into agroforestry systems in the tropics may be suitable.

View full abstract

The research on Azolla use in Japan has been limited to two indigenous species. We introduced about 50 strains from Azolla Germplasm Collection of the International Rice Research Institute. The growth of these introduced ones was studied at Mie by water and soil cultures. To evaluate growth performance in water culture (from June 1992 to July 1993), fresh biomass increase was measured during consecutive two or three weeks by inoculating a known quantity of Azolla every week. Average daily fresh weight increase during a week was compared. Growth was most active from spring to early summer, followed by its retardation in summer. Growth in autumn did not come back to the level before summer. In winter, the growth almost ceased. Some hybrid (A. microphylla×A. filiculoides) strains gave the highest averages in biomass production (55g fresh weight m^-2day^-1) . The growth was highly related to air temperature. When average daily maximum temperature was above 30°C, the maximum values in biomass production decreased. When this was below 10°C, the growth almost ceased. The optimum temperature of A. filiculoides was lower than that for other species. Nitrogen contents increased as growth rate increased until 50-70g m^-2day^-1. In soil culture, similar seazonal pattern was observed. A. filiculoides was also less tolerant to high temperature. Sporulation was observed in twenty six strains grown in soil culture, being active in Sep.-Dec. and May These results provide useful information for introducing Azolla in Japan.

View full abstract