Tiejun Zhang

Path and ridge regression analysis of seed yield and seed yield components of Russian wildrye (Psathyrostachys juncea Nevski) under field conditions.

The correlations among seed yield components, and their direct and indirect effects on the seed yield (Z) of Russina wildrye (Psathyrostachys juncea Nevski) were investigated. The seed yield components: fertile tillers m-2 (Y1), spikelets per fertile tillers (Y2), florets per spikelet- (Y3), seed numbers per spikelet (Y4) and seed weight (Y5) were counted and the Z were determined in field experiments from 2003 to 2006 via big sample size. Y1 was the most important seed yield component describing the Z and Y2 was the least. The total direct effects of the Y1, Y3 and Y5 to the Z were positive while Y4 and Y2 were weakly negative. The total effects (directs plus indirects) of the components were positively contributed to the Z by path analyses. The seed yield components Y1, Y2, Y4 and Y5 were significantly (P<0.001) correlated with the Z for 4 years totally, while in the individual years, Y2 were not significant correlated with Y3, Y4 and Y5 by Peason correlation analyses in the five components in the plant seed production. Therefore, selection for high seed yield through direct selection for large Y1, Y2 and Y3 would be effective for breeding programs in grasses. Furthermore, it is the most important that, via ridge regression, a steady algorithm model between Z and the five yield components was founded, which can be closely estimated the seed yield via the components.

Modelling of seed yield and its components in tall fescue (Festuca arundinacea) based on a large sample

Tall fescue ( Festuca arundinacea Schreb.) is a primary cool-season grass species that is widely used as a cold-season forage and turfgrass throughout the temperate regions of the world. The key seed yield components, namely fertile tillers m -2 (Y 1 ), spikelets fertile tiller -1 (Y 2 ), florets spikelet -1 (Y 3 ), seed number spikelet -1 (Y 4 ), seed weight (Y 5 ), and the seed yield (Z) of tall fescue were determined in field experiments from 2003 to 2005. The experiments produced a large sample for analysis. The correlations among Y 1 to Y 5 and their direct and indirect effects on Z were investigated. All of the direct effects of the Y 1 , Y 3 , Y 4 and Y 5 components on the seed yield were significantly positive. However, the effect of Y 2 was not significant. In decreasing order, the contributions of the five components to seed yield are Y 1 >Y 4 >Y 3 >Y 5 >Y 2 . Y 4 and Y 5 were not significantly correlated with Z. However, the components Y 1 , Y 2 and Y 3 were positively correlated with Z in all the three experimental years and the intercorrelations among the components Y 1 , Y 2 and Y 3 were significant. Ridge regression analysis was used to derive a steady algorithmic model that related Z to the five components; Y 1 to Y 5 . This model can estimate Z precisely from the values of these components. Furthermore, an approach based on the exponents of the algorithmic model could be applied to the selection for high seed yield via direct selection for large Y 2 , Y 3 and Y 5 values in a breeding program for tall fescue. Key words . Modelling, seed yield, components, tall fescue, path and ridge analyses, large sample.

Influence of salinity and temperature on the germination of Hedysarum scoparium Fisch. et Mey.

This study was conducted to determine the effects of temperature and salinity on seed germination and their recovery of germination after being transferred from saline conditions to distilled water. The germination responses of the seeds in complete darkness were determined over a wide range temperatures (10 to 35°C) and salinities (0 to 500 mM NaCl). Germination was inhibited above or below the optimal temperature of 15°C. The highest germination percentages were under non-saline conditions, and increased NaCl concentrations progressively inhibited seed germination. Germination rate decreased with increased salinity at all temperatures, but the highest rates were at 15°C. The interaction between salinity and temperature yielded no germination at 500 mM NaCl (25 and 35°C). After 10 days, seeds were transferred from salt solution to distilled water, and germination recovered at all temperatures with low salinity. At 500 mM NaCl, there was no germination recovery at 25 and 35°C. The results showed that salt stress decreased both the percentage and the rate of germination, exposure to high concentration of NaCl permanently inhibited germination at high temperature.