[Ammonia volatilization and nitrogen use efficiency in the field of fresh edible maize as affec-ted by different band fertilization depths of controlled-release urea]. / æŽ§é‡Šå°¿ç´ æ¡æ–½æ·±åº¦å¯¹é²œé£ŸçŽ‰ç±³ç”°é—´æ°¨æŒ¥å‘å’Œæ°®è‚¥åˆ©ç”¨çŽ‡çš„å½±å“.

A field experiment was conducted to examine the effects of controlled-release urea (CRU) application on ammonia (NH3) volatilization, nitrogen (N) use efficiency and fresh ear yield of fresh edible maize. The treatments included one control (CK: no N fertilizer application) and four different band fertilization depths (0, 5, 10, 15 and 20 cm). Results showed that NH3 volatilization from non-fertilization band and planting band mainly occurred in the first two weeks after the fertilization, which lasted for almost a month in the fertilization band. Compared to CK, surface broadcasted CRU (0 cm) significantly increased NH3 volatilization from wide-row non-fertilization band or planting band in field. Soil NH3 volatilization amounts ranged from 3.1 to 25.5 kg N·hm-2 with the different depths of CRU application treatments, accounting for 1.7%-14.2% of total N applied. The cumulative NH3 volatilizations were comparable among the depths of 10, 15 and 20 cm of CRU fertilization treatments, which were significantly decreased by 85.9%-87.8% and 67.0%-71.6% as compared with surface broadcasted CRU and 5 cm of CRU fertilization, respectively. The increases of CRU application depth within a certain extent could increase fresh ear yield, total nitrogen accumulation of plants during milking stage, partial factor productivity, agronomic efficiency and apparent recovery efficiency of nitrogenous fertilizer, and the maximum values of these indices were recorded for 15 cm depth. We concluded that CRU application at 15 cm depth would be the optimal practice in terms of reducing NH3 volatilization and improving N use efficiency of fresh edible maize.

A novel Brassica-rhizotron system to unravel the dynamic changes in root system architecture of oilseed rape under phosphorus deficiency.

BACKGROUND AND AIMS: An important adaptation of plants to phosphorus (P) deficiency is to alter root system architecture (RSA) to increase P acquisition from the soil, but soil-based observations of RSA are technically challenging, especially in mature plants. The aim of this study was to investigate the root development and RSA of oilseed rape (Brassica napus L.) under low and high soil P conditions during an entire growth cycle. METHODS: A new large Brassica-rhizotron system (approx. 118-litre volume) was developed to study the RSA dynamics of B. napus 'Zhongshuang11' in soils, using top-soils supplemented with low P (LP) or high P (HP) for a full plant growth period. Total root length (TRL), root tip number (RTN), root length density (RLD), biomass and seed yield traits were measured. KEY RESULTS: TRL and RTN increased more rapidly in HP than LP plants from seedling to flowering stages. Both traits declined from flowering to silique stages, and then increased slightly in HP plants; in contrast, root senescence was observed in LP plants. RSA parameters measured from the polycarbonate plates were empirically consistent with analyses of excavated roots. Seed yield and shoot dry weights were closely associated positively with root dry weights, TRL, RLD and RTN at both HP and LP. CONCLUSIONS: The Brassica-rhizotron system is an effective method for soil-based root phenotyping across an entire growth cycle. Given that root senescence is likely to occur earlier under low P conditions, crop P deficiency is likely to affect late water and nitrogen uptake, which is critical for efficient resource use and optimal crop yields.

[Effects of soil moisture and boron supply on the plant growth and leaf water content and boron forms of oilseed rape cultivars with different boron use efficiency at their seedling stage].

The study with pot experiment showed that under the stress of low soil moisture content, the oilseed rape cultivars with high and low boron (B) use efficiency had a higher fresh mass per plant at their seedling stage under high B supply, compared with those under low B supply. The increment was 43.1% and 31.7%, respectively, but no significant difference was observed between the cultivars. Under two B supply levels, the bound water content and semi-bound B distribution proportion in the leaves of the cultivar with high B use efficiency were 11.4% and 1.7%, and 6.9% and 23.8% higher than those of the cultivar with low B use efficiency, respectively. Under normal soil moisture condition, high B supply induced an increase of fresh mass per plant by 11.1% for the cultivar with high B use efficiency and by 27.4% for the cultivar with low B use efficiency, compared with low B supply. Under these two B supply levels, the cultivar with high B use efficiency had a higher content of free water in its leaves, and its leaf free B content was 2 times as much as that of the cultivar with low B use efficiency, which would benefit the B transportation in plant.

[How long the way from QTL to QTGS?].

Most of the important economic traits in higher plants are quantitative traits. Genetic basic researches for quantitative traits were strongly promoted. This article fully elaborated the complicated relationship between quantitative phenotype and its genotype, introduced the recently developed strategy of fine mapping. discussed the current difficulty and hardness among the process of dissect the genetic basis of target traits, then brought forward several research direction that remained to be improved , and finally gave a view of such prospect. Generally speaking,, however, a QTL is still a considerable DNA fragment frequently containing multiplex genes. We also provided some ways and means from QTL coarse locus research to the variation at quantitative trait gene (QTG) level and from QTG to quantitative trait nucleotides (QTN) corresponding to alleles resulted from the intragenetic polymorphism. This is a major challenge for quantitative genetics in the post-genome era.

[Integration of DNA clones related to important economic traits of Brassica napus onto Arabidopsis genetic map].

Arbidopsis thaliana and Brassica oilcrops are closely related species in Brassicae, Cruciferae, and show highly homologous genomes. After a serial important agronomic characteristics of Brassica napus being mapped with probes from EST clones of Arabidopsis and DNA clones of rapeseed, DNA segment sequencing was performed with 25 clones which were found to be closely linked to the CMS restore gene, the boron efficiency gene (BE1), the Sclerotinia resistant QTLs and the characteristic of interspecific biomass heterosis in rapeseed respectively. Highly homologous sequences were found in Arabidopsis genome by searching the relative databases. According to the position of homologous sequences on the chromosomes of Arabidopsis, the 25 clones were integrated into the genetic map of Arabidopsis. Two markers flanking BE1 in B. napus were integrated into a narrow region at the short arm of chromosome 1 of Arabidopsis. One of EST clones, pA24, from this region was used as a probe to map B. napus and consequently been integrated in a position between the two flanking markers of BE1. This event increased the confident for one to map the important characteristics of cultured Brassica species via reciprocal comparative mapping between Arabidopsis and target Brassica crops.