A rapid reliable test for screening aryloxyphenoxy- propionic acid resistance within Alopecurus myosuroides and Lolium spp. populations

A reliable seedling bioassay was developed and tested for the rapid screening for resistance to aryloxyphenoxypropionic (APP) herbicides in Alopecurus myosuroides and Lolium spp. populations. It is based upon the difference in coleoptile length of resistant and susceptible A. myosuroides and Lolium seedlings, respectively, exposed to fenoxaprop-P acid and diclofop acid solution for 6 days in a plastic box. A 6 mg L⁻¹ fenoxaprop-P acid solution was selected as the best concentration for a reliable screening of resistant biotypes within A. myosuroides populations. At this concentration, coleoptile lengths of susceptible and resistant seedlings were shorter and longer than 10 mm respectively. Similarly, resistant seedlings within Lolium populations were easily detected at 10 mg L⁻¹ diclofop acid. At this concentration, coleoptile lengths of susceptible and resistant seedlings were shorter and longer than 20 mm respectively. For both populations, the coleoptile length distributions appear to discriminate between two kinds of APP-resistant biotypes (highly and slightly resistant).     

The Relationship Between Wheat Seed Weight, Infection by Fusarium culmorum or Microdochium nivale, Germination and Seedling Disease

The distribution of seeds by weight for three lots of winter wheat cv. Avalon infected by Fusarium culmorum and three lots of winter wheat cv. Riband infected by Microdochium nivale was determined. The distribution of infected seeds within each seed lot was then determined by isolating F. culmorum from seeds on moist filter paper and M. nivale from seeds on potato dextrose agar. The distribution of M. nivale infected seeds between seeds of different weight was similar to that of the seed lot as a whole, whereas the distribution of F. culmorum was greater in light seeds than heavy seeds. The percentage germination of infected seeds decreased with seed weight. A similar situation was found with respect to seedling emergence in compost for F. culmorum infected seeds. However, with M. nivale infection, similar numbers of seedlings emerged from both light and heavy infected seeds. Seed treatment with guazatine increased seedling emergence for both light and heavy seed infected by M. nivale. However, seedling emergence from F. culmorum infected seed was poor even following treatment with guazatine. Poor emergence was most evident from light seed.     

Variation in Virulence of Plasmodiophora brassicae in Japan Tested with Clubroot-resistant Cultivars of Chinese Cabbage (Brassica rapa L. ssp. pekinensis)

The differential hosts of Williams (1966) and the European Clubroot Differential (ECD) (Buczacki et al., 1975) have been used commonly to identify populations of Plasmodiophora brassicae, which causes clubroot disease in Brassica crops. However, some of these hosts showed intermediate and fluctuating scores to most populations from Japan. Therefore, these hosts could not be used to provide a clear classification in Japan. We have tried to clarify the genetic diversity in pathogenicity of P. brassicae in Japan using Japanese clubroot-resistant (CR) F₁ hybrid (F₁) cultivars and lines of Brassica rapa. The responses of some CR F₁ cultivars were very clear. Four groups of field populations in Japan were recognized using the CR F₁ cultivars. The clear response obtained here may depend largely on the genetic purity of the F₁ cultivars. Moreover, it is possible to classify some of these Japanese populations into the same race using the Williams set and ECD 01 to ECD 05. The present differential hosts may be useful in the study of European populations of P. brassicae. The response of the differential hosts suggests that there are several major CR genes in B. rapa. It is suggested that pyramiding CR genes would be useful in breeding CR cultivars that can overcome the breakdown of the present CR cultivars of Chinese cabbage.     

Isolation of Microdochium oryzae and Pinatubo oryzae from Rice Seeds and their Survival on Stored Seeds

The aim of these studies was to develop a semi-selective medium to differentiate Microdochium oryzae and Pinatubo oryzae, determine the frequency of seed infection of M. oryzae, study survival of the pathogen in stored seeds, and determine the frequency of infection of seed components. To simulate epidemics of differing intensities, panicles of rice cultivars that are susceptible (IR36) and resistant (IR42 and IR46) to M. oryzae were either non-inoculated, inoculated once, twice, or three times with a conidial suspension of M. oryzae. Both M. oryzae and P. oryzae colonies were recovered from seeds and were similar in culture. A semi-selective medium developed to detect M. oryzae seed infection rates aided in differentiating M. oryzae and P. oryzae by stimulating aerial conidiogenesis of P. oryzae. The conclusions taken from these results were: (a) seeds of IR36 had higher infection of M. oryzae than of IR42 and IR46 from plants grown in the dry season, but had lower infection of M. oryzae than of IR42 and IR46 from plants grown in the wet season; (b) M. oryzae infected seeds increased with an increase in the epidemic intensity with the highest occurring after three inoculations, the least occurring with non-inoculation, and intermediate with one, or two inoculations; (c) survival of M. oryzae decreased over time in seed lots stored at 10°C and 40% relative humidity and (d) all components of the rice seeds of IR36, IR42 and IR46 lots were infected with M. oryzae with the highest frequency in the endosperm and lemma, intermediate in the basal glumes and palea, and the least in the embryo.     

Mechanizsed microsite preparation and direct seeding of Pinus sylvestris in boreal forests — a way to create desired spacing at low cost

The main objective of this study was to examine the cost, flexibility, and appropriate scale of mechanized microsite preparation (MP), in combination with mechanical direct seeding of Pinus sylvestris L. with orchard seed. This technique was tested at four boreal forest sites in Northern Sweden. Orchard and stand seeds were sown with and without MP. The use of orchard seed increased seedling establishment by 41% and the use of MP increased seedling establishment by 47%, respectively, after two years. The best substrates for sowing when using MP were OA_h-, E- and BC-horizon, in ranked order. The use of orchard seed compared to stand seed increased mean seedling height by 25% after four years. These trials suggest that to obtain a density of 5,000 stems ha^-1 four years after seeding, 61,000 viable stand seeds or 41,000 orchard seeds ha^-1 should be sown if MP is not used. If MP is used, seeding rate could be reduced by about 32%. By using MP, and by further improving scarification technique so that all scarified area is thin OA_h-horizon, we predict that only 32,000 stand seeds or 22,000 orchard seeds ha^-1, i.e., half the dosage, should be needed. Under these optimal conditions, it would be necessary to sow about six and four germinable stand and orchard seeds, respectively, to ensure one seedling after four years. Furthermore, regeneration cost would be less than a third that of planting.     

樟树种源/家系苗期性状变异分析

为了解樟树遗传变异的来源和规律,进行了樟 树苗期种源／家系两水平试验研究。结果表明,樟树的遗传变异存在于种源和家系两个层次。樟树苗高,枝下高,冻害性状在种源层次的变异远大于家系层次的变异,地径则相反。     

厚朴苗木质量与幼树生长关系的研究

为提高厚朴造林质量,开展了苗木地径、亩高与厚朴幼树生长关系的研究,结果表明：厚朴苗木高度对幼树生长无明显的影响,苗木过高反而会降低造林成活率;苗木地径大于0．9cm时,地径对幼树生长也无显著的影响。因此,厚朴苗木不宜以苗高为分级依据。厚朴苗木的适宜高度可从便于起苗、运输、栽种等生产环节来确定。厚朴苗木地径的分级,优质苗的下限也不应大于0.9cm。     

石榴硬枝扦插技术

石榴扦插于春季采用粗壮的１年生枝条扦插,不经处理,其成活率可达到９５％以上,苗木当年即可出圃栽培。     

磁处理土壤对作物生长影响的初步研究

磁处理土壤可以促进番茄、黄瓜和水稻的苗期生长,提高作物对氮磷钾主要养分的吸收能力,影响最大的是氮。在磁处理的土壤上黄瓜和小麦叶面积与叶绿素含量增加,黄瓜的品质提高。对油菜、小麦和黄瓜的研究证明磁处理土壤对作物的产量有一定的影响。     

杂交稻低播量精准条播育秧机插提高群体均匀度和产量的效应分析

[目的]明确杂交稻低播种量下精准条播(precision drill sowing,PS)育秧提高机插群体均匀度和产量的效应,创建杂交稻毯苗稀播少本机插理论与技术.[方法]选用籼粳杂交稻甬优1540为供试品种,在余杭区崇化村和富阳区中国水稻研究所试验基地开展试验.以传统撒播(broadcast sowing,BS)育秧...