The Effects of Intercrop Spacing Patterns on the Silage Yield of Maize and Soybean

The effects of intercrop spacing patterns on the silage yields of both maize (lea mays L.) and soybean (Glycine max [L.] Merr.) were examined from 1985 to 1987. Dwarf maize was intercropped with nonnodulatmg or nodulating soybean in the spacing patterns, S_40same (two crops in the same row, 40 cm row width) and S_20ait or S_40ak (two crops in alternate rows, 20 cm or 40 cm row width, respectively). Tall maize was intercropped with nodulating soybean in S_40sames S_40alt and S_40pair (maize in 40 cm paired rows, soybean rows 20 cm outside each maize row and 80 cm from the next set of four rows) at 0 or 60 kg N ha⁻¹ and at population densities of 67% maize: 67% soybean or 50 % maize: 50% soybean. Maize and soybean were also intercropped and stripcropped on a farm-scale. The only difference between intercrops arranged in the same rows versus those in alternate rows was that the average soybean protein yields were higher in S_40same than in S_40alt. In 1986, the S_40alt maize-soybean intercrops produced higher maize yields, total biomass yields and Land Equivalent Ratios (LERs) than in S_40pirs, and in 1987, these responses were higher in intercrops than in stripcrops. In 1986, at 0 kg N ha⁻¹, the soybean biomass and protein yields were lower in S_40alt, than in S_40pairs and in 1987, these responses were lower in intercrops than in stripcrops.     

中国地毯草野生种质资源耐旱性变异的初步研究

对我国不同来源地毯草野生种质资源抗旱性的研究结果表明,各供试地毯草的抗旱性与生境有着直接的关系,基本表现为分布于山坡地和路边等旱生环境中的地毯草,其抗旱性也相对较好,而那些在综合评判中表现为抗旱性较差的地毯草,大多是从河滩等湿生环境中采集到的材料。通过对土壤含水量、水分饱和亏缺指数、叶片保水力、游离脯氨酸含量和可溶性糖等与草坪抗旱有关的几个生理生化指标值的试验分析以及综合评判,将饶平地毯草初步确定为耐旱生态型。该生态型具有植株比较低矮,匍匐茎长短轴的差异不明显,叶片相对较小,匍匐茎生长速度和分蘖能力中等特点。     

The effect of quality of grass and maize silage on the intake and performance of beef cattle

A study was undertaken to evaluate the effects of incorporating high (HMS) and low (LMS) maturity maize silages into diets based on low (LGS) and high (HGS) feed value grass silages offered to beef cattle. Seventy-two continental cross-bred steers were used in a 14-week continuous design, randomised block experiment. The six treatments were arranged as a 2 × 3 factorial design incorporating the LGS and HGS offered as the sole forage, along with each of the two grass silages offered in a 60:40 ratio (DM basis) with the HMS and LMS. All diets were supplemented with 3 kg/head/day concentrates. Total daily DM and metabolisable energy intakes were higher (P < 0.001) for diets based on HGS compared to those based on LGS. Intakes were similar (P > 0.05) between diets containing LMS and HMS, both of which were higher (P < 0.001) than diets containing grass silage as the sole forage. Highest DM intakes were recorded with a mixture of HGS and HMS (P < 0.05 or greater). Cattle offered diets containing HGS had higher live-weight gain (P < 0.05), final live weight, carcass gain and carcass weight (P < 0.001) than those offered diets containing LGS. Feed conversion efficiency, assessed on a carcass gain basis, was poorer (P < 0.05) with diets containing LGS compared with those containing HGS, though differences between diets containing either LMS or HMS and GS as the sole forage were not significant (P > 0.05).     

A high-throughput glasshouse bioassay to detect crown rot resistance in wheat germplasm

A high-throughput and reliable seedling bioassay to screen wheat germplasm for crown rot resistance was developed. Single wheat seedlings were grown in square seedling punnets in a glasshouse and inoculated with a monoconidial Fusarium pseudograminearum isolate 10 days after emergence. The punnets were laid horizontally on their side and a 10- µ L inoculum droplet placed on the stem base. Seedlings were incubated at near-saturated relative humidity, and crown rot severity was assessed 35 days after inoculation. Studies on the duration of incubation period, inoculum concentration and temperature were carried out to optimize these parameters. Seedling growth at 25/15(±5)°C in a glasshouse and 48-h incubation at near-saturated RH in darkness gave the best results. When crown rot resistance rankings of 16 Australian cultivars from the bioassay were compared with their field performance, Spearman's rank correlation coefficient was highly significant. This indicated that the seedling bioassay mimicked field resistance to crown rot in adult plants. A bootstrap resampling analysis showed little or no improvement in the coefficient of variation with an increasing number of replications, indicating a high level of precision and reproducibility. By detecting small but consistent differences in crown rot severity, the bioassay proved effective in large-scale screening for partial resistance: already over 1400 wheat genotypes have been screened. The high degree of precision makes this an invaluable tool in the understanding of pathogen aggressiveness, host specialization and parasitic fitness.     

Comparing rice germplasm groups for growth, grain yield and weed-suppressive ability under aerobic soil conditions

Germplasm and cultivars need to be selected as parents for breeding weed‐competitive aerobic rice in the tropics. Forty rice (Oryza sativa) cultivars belonging to the aus, indica and tropical japonica germplasm groups, or derived from crosses among them, were evaluated in adjacent weed‐free and weedy trials in aerobic soil conditions during the wet seasons of 2001–2003. The objectives of this study were to assess vegetative growth, grain yield under weed‐free (Y_F) and weedy (Y_W) conditions, and weed‐suppressive ability (WSA) of different germplasm groups. In the first 4 weeks after sowing, indica cultivars had faster growth in height, tillering and crop biomass than other groups. They also had high Y_F, Y_W and strong WSA. Aus cultivars were similar to the indica types in early growth and WSA, but were poor in Y_F. Tropical japonica groups and the group derived from indica/tropical japonica crosses were generally inferior to aus and indica groups in early growth and WSA. Both of their Y_F and Y_W were lower than that of the indica group. Therefore, indica germplasm seemed to be most suitable for breeding high‐yielding and weed‐suppressive aerobic rice for the tropics. The relationship of WSA with various traits within tropical japonica germplasm revealed that fast early growth, rather than plant erectness, is crucial to WSA.     

陕西线辣椒育种研究进展与展望

本文概述了陕西线辣椒的发展历史,及其种质资源、育种目标、育种方法的研究进展;同时提出了对未来育种研究的展望。     

Distribution and relative importance of lepidopteran cereal stemborers and their parasitoids in Uganda

Infestation levels and parasitism of lepidopteran stemborers on maize were assessed in four agroecological zones (AEZ) in Uganda. The indigenous noctuidBusseola fusca Fuller (Noctuidae) and the invasiveChilo partellus Swinhoe (Crambidae) were the most important stemborers recorded.C. partellus represented 77% of the stemborers in the Eastern AEZ whileB. fusca was dominant in the other AEZs, accounting for 60–79%. The proportion of infested plants was between 16% and 45% and borer density between 0.2 and 1.0 borers per plant. There was no clear relationship between damage and stem tunneling, which is often used to estimate yield loss.Telenomus busseolae Gahan (Scelionidae), the only egg parasitoid recovered, caused parasitism of up to 46% onB. fusca eggs. Several larval and pupal parasitoid species were recorded. The most common were the indigenous braconidCotesia sesamiae and the introducedCotesia flavipes, which are larval parasitoids ofB. fusca andC. partellus, respectively. Mean parasitism by the indigenousC. sesamiae ranged between 2.0% and 29.4% onB. fusca and from 0 to 13% onC. partellus. C. flavipes was recovered at most locations with parasitism of 0–30.5% onC. partellus and 0–12% onB. fusca; the latter was probably the result of multiparasitism as laboratory studies have shown that it was not a suitable host forC. partellus. Results indicated further that the parasitoid has not attained equilibrium 5 years after its introduction. http://www.phytoparasitica.org posting Nov. 20, 2006. Teddy Matama-Kauma died suddenly in an accident on Dec. 10, 2006, while this paper was in press.     

扁穗牛鞭草种质遗传多样性的ISSR分析

用ISSR标记对来自中国西南地区(四川、重庆、贵州)的28份扁穗牛鞭草材料的遗传多样性进行了检测。从96个ISSR引物中共筛选出13个多态性明显、反应稳定的引物。28份材料的DNA共扩增出129条谱带,平均每个引物扩增出9.9条带,多态性条带比率达84.2%。材料间遗传相似系数为0.466~0.980,表现出丰富的遗传多样性。通过聚类分析和主成分分析,将28份扁穗牛鞭草分为两大类,同一地区的扁穗牛鞭草品种(系)基本聚在同一类,呈现出一定的地域性分布规律。     

Host status and reaction of <Emphasis Type="Italic">Medicago truncatula</Emphasis> accessions to infection by three major pathogens of pea (<Emphasis Type="Italic">Pisum sativum</Emphasis>) and alfalfa (<Emphasis Type="Italic">Medicago sativa</Emphasis>)

Ditylenchus dipsaci, the stem nematode of alfalfa (Medicago sativa), Mycosphaerella pinodes, cause of Ascochyta blight in pea (Pisum sativum) and Aphanomyces euteiches, cause of pea root rot, result in major yield losses in French alfalfa and pea crops. These diseases are difficult to control and the partial resistances currently available are not effective enough. Medicago truncatula, the barrel medic, is the legume model for genetic studies, which should lead to the identification and characterization of new resistance genes for pathogens. We evaluated a collection of 34 accessions of M. truncatula and nine accessions from three other species (two from M. italica, six from M. littoralis and one from M. polymorpha) for resistance to these three major diseases. We developed screening tests, including standard host references, for each pathogen. Most of the accessions tested were resistant to D. dipsaci, with only three accessions classified as susceptible. A very high level of resistance to M. pinodes was observed among the accessions, none of which was susceptible to this pathogen. Conversely, a high level of variation, from resistant to susceptible accessions, was identified in response to infection by A. euteiches.