生物炭和其他有机土壤改良剂对Ustoxic Quartzipsamment土壤上植物养分有效性的影响

A sandy soil, Nampong soil(classified as Ustoxic Quartzipsamment), was incubated under controlled condition i) to compare the mineralization of major plant nutrients derived from different types of biochars and other organic soil amendments; ii) to examine their effects on soil properties and plant nutrient availability; and iii) to evaluate the plant nutrient losses in leachate from the rooting zone of soil incorporated with the different amendments. The experiment was arranged in a completely randomized design with 3 replications.Five treatments of soil amendments used were cassava stem base biochar(CSB), rice husk biochar(RHB), chicken manure(CM),compost(CP), and no amendment application(control). The RHB treatment released the highest amounts of mineralized NO-3-N,available P and K(2.30–17.26, 5.50–42.90 and 43.00–187.63 mg kg-1, respectively) while the CM treatment releasing the highest NH+4-N in the range of 1.86–53.67 mg kg-1. The CSB and RHB treatments showed better continuity of mineralization of nutrients than the treatments of CM and CP, particularly in the case of the CSB treatment. In the soil column incubation experiment, the amounts of NH+4-N and NO-3-N in all treatments barely changed on Day 1 to Day 30 of incubation and then the amounts increased markedly on Day 60. On Day 60, the RHB treatment contained a very high amount of NO-3-N( 250 mg kg-1). This suggests that N would become more available 30 d after the incorporation. The CM treatment gave the highest amounts of organic matter and available P in the ranges of 4.64–8.94 g kg-1and 14.41–36.33 mg kg-1, respectively, during the 60-d column incubation. The CSB treatment tended to have higher available K throughout the measuring period. The NO-3-N was leached from the soil column quite quickly on Day 1 of incubation while the loss of NH+4-N decreased slightly from Day 1 until the end of the measurement. The amounts of P and K losses varied with the type of soil amendments, and the pattern of the loss was irregular.     

小麦抗秆锈突变系龙辐03D51的筛选及其抗病性的遗传分析与RAPD标记

以龙6239幼胚为外植体,利用辐射诱变和组织培养相结合的方法,选育出突变系龙辐03D51,经秆锈接种鉴定,发现其对优势小种21C3CPH免疫,而亲本龙6239对21C3CPH高度感染。遗传分析表明,抗病性由显性单基因控制。该突变系还具有其亲本的优质、高产特点,已成为优异的后备品系。在RAPD检测中,所用的60个随机引物中有3个引物在龙辐03D51和其亲本龙6239中具有多态性,引物E07、E11、E17在龙辐03D51中分别扩增出380bp、700bp和600bp的特异带,初步认为这些谱带可能与秆锈抗性有关。     

榨菜叶还田对水稻养分吸收的影响

利用盆栽试验研究了榨菜叶还田对水稻养分吸收的影响,结果表明,水稻的吸肥规律与其整个生育期的三个生长中心相适应,对氮的吸收在整个生育期出现两个高峰,第一个在水稻移栽后2￣4周,第二个在移栽后8￣10周;对磷和钾的吸收高峰出现在移栽后8￣10周。各施肥处理水稻对氮磷钾的吸收累积量均大于对照,榨菜叶配施化肥处理对氮磷钾的吸收积累量和收获指数都高于等NPK养分含量的其它处理。水稻吸收的氮和磷大部分储存于籽粒中,而钾主要存在于秸秆中,同时,氮磷钾的收获指数随着施肥量的增加而降低,多吸收的养分主要存在于秸秆中,因此秸秆还田对于维持土壤肥力,尤其对缓解中国磷钾肥不足意义重大。     

Karyotype Analysis of Sesbania rostrata Brem.

The karyotype of Sesbania rostrata, a species endemic to West Africa, which produces nitrogen fixing, nodules on stem and branches, was analysed. The somatic chromosome number was 12 with two pairs of long, submetacentric and four pairs of short, metacentric chromosomes. The chromosome number in another species S. aculeata, which is well adapted as a green manure crop in India but not capable of stem nodulation, was also 2n = 12. The similarity between the chromosome complements of the two species indicates that they may be cross compatible.     

Genetics of stem elongation ability in rice (Oryza sativa L.)

Summary The genetics of stem elongation ability in rice was studied in parents, F₁, F₂ and backcross generations of six crosses. Segregation analysis indicated dominance for stem elongation ability. Estimation of genetic parameters under epistatic model indicated more than one locus control stem elongation ability and both additive and nonadditive gene effects were important. Epistatic effects were predominant over additive and dominance effects with an important role of duplicate type of epistasis. The occurrence of significant additive and additive x additive types of genetic variation and the moderately high broad sense heritability indicated the possibility of selection for an increased manifestation of stem elongation ability.     

Ear:stem ratios in breeding populations of wheat: significance for yield improvement

Earlier studies showed that the ratio of the weight of the wheat ear to stem at anthesis (ear:stem ratio) may give a better indication of potential yield than harvest index because it is determined early in the life cycle and is not affected by post anthesis stress. These studies concluded that selection for high ear:stem ratio at anthesis may lead to further improvement in grain yield of wheat. The present work was undertaken in the field to identify lines varying in ear:stem ratio in breeding populations and to study its implications for yield improvement.At anthesis stem length, ear length, tiller number, dry weight of stem and ear and ear:stem ratio were measured in 14 crosses on F₂ single plants and F₂ derived lines grown in the F₃, F₄, and F₅ at three locations in Western Australia over four seasons. In addition, biomass, grain yield and yield components were measured on selected crosses at two locations on F₂ derived lines grown in the F₄ and F₅. There was a considerable range of ear:stem ratio between and within the crosses studied. Although ear:stem ratio was strongly correlated with stem length, there was substantial variation within stem length classes. Ear:stem ratio had a high mean broad sense heritability (82%), whereas HI, grain yield and above ground biomass had lower heritabilities, 68, 55 and 35% respectively. Ear:stem ratio was strongly correlated between generations and sites indicating stability of this character. Ear:stem ratio had a significant positive correlation with grain yield, HI, grains per ear and per m². The correlation of grain yield with HI was equal or slightly higher than that of grain yield with ear:stem ratio.Ear:stem ratio offers promise as a predictor of HI and yield potential where post-anthesis moisture stress can influence HI. Ear:stem ratio measurement is unlikely to be adopted for selection purposes in routine breeding programs, as it is laborious and time consuming. However, ear:stem ratio could be used to identify superior parental genotypes and early generation selections from special crosses in terms of its ability to partition assimilate.     

Genetic and environmental variability in wheat characteristics reported to be involved in morphological resistance to wheat stem rust

Summary Four morphological characteristics of wheat peduncles were evaluated for genetic and environmental variability. The thickness of the epidermis and the amount and distribution of chlorenchyma tissue in the peduncle were measured. The genetic variability was estimated to be large, whereas the environmental variability was small. It was also concluded that cultivars could be screened for morphological characteristics of the peduncle that contributed to non-specific resistance to stem rust with a minimum sample size of about 10 plants per replication from a single location.Paper No 9328, Scientific Journal Series, Minnesota Agricultural Experiment Station. University of Minnesota. St. Paul. MN 55108.     

A comparison of apple and pear seedlings with reference to the juvenile period I. Seedling growth and yield

Summary Several thousand apple and pear seedlings of many progenies were studied in connection with their juvenile period (J.P.). The initially significant inverse relation between the vigour (stem diameter) and the J.P. of the seedlings became insignificant as the trees grew older, due to a retardation of growth occurring when the seedlings become generative. This relation can be used effectively in pre-selecting for vigour in the nursery. Cumulative yields were higher when the J.P. was shorter, but there was no evident link between the J.P. and annual yield in full bearing, that is to say, precocity and preductivity are not directly connected. Better growing conditions and pre-selection have shortened the mean progeny J.P. of either crop by three years since the 1950's. Generally, the pear seedlings appear to grow faster, to become generative slower and to yield lower than comparable apple seedlings. The mean J.P. of apple and pear progenies averaged 4.2 and 6.0 years respectively. The difference between apple and pear may be attributable to a greater selection pressure on both precocity and productivity with apple than with pear.This possibly also led to a smaller tree in the productive phase on the assumption that tree size at first flowering-small at a short, large at a long J.P.-expresses reproductive efficiency and as such is reflected in the size of the adult tree.Also presented at the Juvenility Symposium held at West-Berlin, November 1976.     

Induced mutagenesis for the development of multiline cultivars in bread wheat

Summary Variation for resistance toPuccinia graminis f.sp.tritici, P. recondita f.sp.tritici andP. striiformis was induced in theTriticum aestivum cultivar Lalbahadur using nitrosomethyl urea. Variations were isolated from the M₂ population in the post-seedling stage in the field when infected with a mixture of races of each of the three rusts. Plants exhibiting simultaneous resistance to stem rust, leaf rust and yellow rust were indentified. Repeated screening in the subsequent generations confirmed the resistance of the mutant lines that are morphologically similar to the parental cultivar. The rust resistance of 20 mutant lines was also confirmed at the seedling stage using individual races of stem rust and leaf rust. The different patterns observed in the mutant lines tested against a wide range of races show that these lines can be used as components of a multiline. The patterns of variation compared with those of the known genes for resistance against the Indian races of the pathogens suggest that the mutations for rust resistance are due to factor different from those already known in bread wheat, providing a broadened genetic base for future breeding programmes.     

Stem solidness and its relationship to grain yield in 17 spring wheat crosses

Summary Stem solidness in the wheat plant provides resistance to the wheat stem sawfly, a pest of wheat in Montana and North Dakota, but some agronomists have been concerned that stem solidness might be related to low grain yields. We evaluated 17 spring wheat crosses for stem solidness, grain yield, and other agronomic traits in F₂ through F₄ generations from 1972 to 1975.Highly significant correlation (0.735) and regression (0.731) coefficients between F₂ and F₃ generations verify previous studies showing that stem solidness is highly heritable and that selection in F₂ should be successful. Solid-stemmed F₄ composites yielded more than hollow stemmed composites at Bozeman and equal yields were obtained at Huntley, indicating that stem solidness is not a deterrent to high grain yield.Joint contribution of Federal Research, Science and Education Administration, U.S. Department of Agriculture and the Montana Agricultural Experiment Station, Bozeman, MT 59717. Published with approval of the Director of the Montana Agricultural Experiment Station as Paper No. 815, Journal Series.