河北阳原—蔚县晚上新世兔形类化石

本文记述河北阳原——蔚县晚上新世小哺乳动物群中的兔形类化石共3属5种:Pliopent-alagus nihewanensis sp.nov.,Hypolagus sohreuderi,Ochotona cf.lagrelii,Ochotona minor和Ochotona erythrotis.。对首次发现于亚洲的Pliopentalagus进行了起源和演化方面的探讨;并就华北上新世一早更新世常见的Hypolagus作了一些评述。本文指出:Hypolagus—Plio-pentalagus组合已延至早维拉方期;Ochotona lagrelii—Ochotona minor则为已知的最晚代表。     

黑龙江绥滨地区晚侏罗世东荣组的沟鞭藻类

本文对黑龙江绥滨86-11孔的沟鞭藻类进行了初步研究,共描述化石10属16种(包括2新种,6未定种);其中不少是在我国首次描述的。这些化石分成两个组合,其优势分子分别为Gonyaulacysta jurassica和Amphorula delicata。根据组合内各分子的时代分布,两化石组合的时代分别为Late Oxfordian—Early Kimmeridgian和Portlandian期,并对其产出层位东荣组的时代作了讨论,认为属于晚侏罗世。     

Chromosomal heteromorphism linked to the mating type locus of the oomycetePhytophthora infestans

The mating type locus of the oomycete,Phytophthora infestans, is embedded in a region of DNA that displays distorted and non-Mendelian segregation. By using DNA probes linked to the mating type locus to genetically and physically characterize that region, a large zone of chromosomal heteromorphism was detected. LocusS1 was shown to represent a tandemly repeated array of DNA that was typically present in a hemizygous state in A1 isolates while being absent from A2 isolates. The analysis of the parents and progeny of seven crosses indicated that the tandem array was linked in cis to the A1-determining allele of the mating type locus. A worldwide survey of genotypically diverse field isolates ofP. infestans indicated thatS1 was present in each of 48 isolates of the A1 mating type that were tested, but was absent in 46 of 47 A2 strains. Physical analysis ofS1 indicated that the tandemly repeated DNA sequence spanned about 300 kb and had evolved from a 1.35-kb monomer. Internal deletions occurred withinS1 during sexual propagation. This and other mutations apparently contributed to a high degree of polymorphism within theS1 array.     

A ‘Problematic fossil’ revealed:Pycnoporidium ? eomesozoicum Flügel, 1972 (Late Triassic,Tethys)—not an enigmatic alga but a strophomenid brachiopod (Gosaukammerella n.g.)

Summary The microproblematicumPycnoporidium ? eomesozoicum Flügel, 1972, from Upper Triassic reefs of the Alpine-Mediterranean region, Turkey Oman and Iran (originally interpreted as possible alga) represents the type species of a new strophomenid brachiopod genus (Gosaukammerella n.g.). The genus is characterized by a very small, millimeter-sized plano-convex shell, whose ventral valve is attached to the substratum (mainly sponges) by symmetrically arranged outgrowths developing from a pseudopunctate, lamellose foliated shell wall and composed of densely spaced subparallel ‘tubes’ comparable with productide spines secreted by papillose extensions of the mantle.Gosaukammerella seems to be the only reliable candidate for the existence of post-Paleozoic strophomenid (productid ?) brachiopods. Gosaukammerella eomesozoica is restricted to possibly cryptic, shaded reef environments inhabited predominantly by sponges serving as substrates for micromorphic brachiopods.     

Interspecific hybridization of cultivated rice, Oryza sativa L. with the wild rice, O. minuta Presl.

Crosses were made between four varieties (Mahsuri, Setanjung, MR84 and MR103) of Oryza sativa L. (2n=24, AA) and one accession of O. minuta (2n= 8, BBCC). The seed set obtained ranged between 9.5% and 25.1% depending on the rice variety used. By rescuing 14-day-old embryos and culturing them on 25%-strength MS medium we obtained a total of 414 F₁ hybrids. The F₁s were vigorous, tillered profusely, were perennial and male-sterile. The hybrids were triploid (ABC) with 36 chromosomes and showed irregular meiosis. The average frequency and range of chromosome associations at metaphase I or early anaphase I pollen mother cells of F₁ plants were 29.31(16–36) Is +3.32(0–10) IIs+0.016(0–1) IIIs+0.002(0–1) IVs. Upon backcrossing the original triploid hybrids and colchicine-treated hybrids to their respective recurrent parents, and further embryo rescue, 17 backcross-1 (BC₁) plants were obtained. Of all the crosses using MR84, no BC₁ plant was obtained even after pollinating 13 894 spikelets of the triploid hybrid. The BC₁s were similar in appearence to the F₁s and were male-sterile, their chromosome number ranged from 44 to 48. By backcrossing these BC₁s and nurturing them through embryo rescue, we obtained 32 BC₂ plants. Of these, however, only 18 plants grew vigorously. One of these plants has 24 chromosomes and the other 17 have chromosome numbers ranging between 30 and 37. The 24-chromosome plant was morphologically similar to the O. sativa parent and was partially fertile with a pollen and spikelet fertility of 58.8% and 12.5% respectively. All of the F₁ and BC₁ plants were found to be resistant to five Malaysian isolates (XO66, XO99, XO100, XO257 and XO319) of Xanthomonas campestris pv oryzae. Amongst the BC₂s, the reaction varied from resistant to moderately susceptible. The 24-chromosome BC₂ plant was resistant to the four isolates and moderately resistant to isolate XO100 to which the O. sativa parent was susceptible.Part of PhD thesis submitted by first author to Universiti Kebangsaan Malaysia, Bangi     

Improving chickpea yield by incorporating resistance to ascochyta blight

Ascochyta blight [Ascochyta rabiei (Pass.) Lab.] is the most destructive disease of chickpea (Cicer arietinum L.), but it can be managed effectively by the use of resistant cultivars. Therefore, a breeding programme was initiated during 1977–78 at ICARDA, Syria, to breed blight-resistant, high-yielding chickpeas with other desirable agronomic traits. Crosses were made in main season at Tel Hadya, Syria, and the F₁s were grown in the off season at Terbol, Lebanon. The F₂, F₄ and F₅ generations were grown in a blight nursery in the main season where blight epidemic was artificially created. The plants and progenies were scored for blight resistance and other traits. The F₃ and F₆ generations were grown in the off season under normal day length to eliminate late-maturing plants. The pedigree method of breeding was followed initially, but was later replaced by the F₄-derived family method. The yield assessment began with F₇ lines, first at ICARDA sites and later internationally. A total of 1584 ascochyta blight-resistant chickpea lines were developed with a range of maturity, plant height, and seed size not previously available to growers in the blight-endemic areas in the Mediterranean region. These included 92 lines resistant to six races of the ascochyta pathogen, and 15 large-seeded and 28 early maturity lines. New cultivars produced 33% more seed yield than the original resistant sources. The yield of chickpea declined by 340 kg ha^-1, with an increase in blight severity by one class on a 1–9 scale, reaching zero yield with the 8 and 9 classes. Development of blight-resistant lines made the introduction of winter sowing possible in the Mediterranean region with the prospect of doubling chickpea production. Twenty three cultivars have been released so far in 11 countries.Joint contribution from ICARDA and ICRISAT. ICRISAT Journal Article no. JA 1886.     

Observations on the maintenance and measurement of soil water in simple pot experiments and its effects on seed-borne Fusarium culmorum seedling blight of winter wheat

A simple method for maintaining and measuring soil water and the relationship between soil water and seed-borne Fusarium culmorum seedling blight of wheat was investigated under controlled environmental conditions to develop reproducible assay conditions for epidemiological studies and the testing of fungicide seed treatments. For reproducibility, soil matric potential (ψ_m) was used to define soil water, and a range of watering regimes were tested. Treatments were watered to either a maximum ψ_m or to maintain a mean ψ_m in order to establish which parameter best described the effect that soil water had on the incidence of disease symptoms. The severity of disease symptoms was closely related to the mean soil water status and not the maximum ψ_m value. Watering intervals, ranging from three times a day to once every three days, did not affect this relationship. The percentage of seedlings showing symptoms after emergence (i.e. localised or extensive necrotic lesions) was inversely related to the mean ψ_m. With increasing soil dryness (mean ψ_m from -0.14 MPa to -0.17 MPa) the percentage of seedlings with post-emergence symptoms decreased from 50% to 20%. However, as the mean ψ_m changed from -0.14 MPa to -0.17 MPa the percentage of seedlings dying before emergence increased from 25% to 55% in direct proportion to ψ_m. Overall the incidence of infection as indicated by the total number of seedlings showing symptoms either before or after emergence remained relatively constant, and was not significantly related to mean ψ_m.     

Speculations on carbon dioxide starvation, Late Tertiary evolution of stomatal regulation and floristic modernization

Ambient atmospheric CO₂ concentration ([CO₂]_a) has apparently declined from values above 200μmol mol⁻¹ to values below 200μmol mol⁻¹ within the last several million years. The lower end of this range is marginal for C₃ plants. I hypothesize that: (1) declining [CO₂]_a imposed a physiological strain on plants, and plant taxa evolving under declining [CO₂]_a tended to develop compensating mechanisms, including increased stomatal efficiency; (2) angiosperms were better able to adjust to declining [CO₂]_a than were gymnosperms and pteridophytes; and (3) angiosperm adjustment has been uneven. Fast-evolving taxa (e.g. grasses and herbs) have been better able to adapt to CO₂ starvation. If these propositions are true, stomatal adjustment mechanisms should show patterned variation, and a single pattern of stomatal regulation cannot be assumed.     

Expression of the Phytophthora infestans ipiB and ipi0 genes in planta and in vitro

The ipiB and ipiO genes of the potato late blight fungus Phytophthora infestans (Mont.) de Bary were isolated from a genomic library in a screen for genes induced in planta. Expression of these genes was studied during pathogenesis on various host tissues and different host plants, some of which show specific resistance against P. infestans infection. During pathogenesis on leaves and tubers of the fully susceptible potato cultivar (cv.) Ajax and on leaves of the fully susceptible tomato cv. Moneymaker, the P. infestans ipiB and ipiO genes show a transient expression pattern with highest mRNA levels in the early stages of infection. During the interaction with leaves of the partially resistant potato cv. Pimpernel, the expression is also transient but accumulation and disappearance of the mRNAs is delayed. Also in P. infestans inoculated onto a race-specific resistant potato cultivar and onto the nonhost Solanum nigrum, ipiB and ipiO mRNA is detectable during the initial stages of infection. Apparently, the expression of the ipiB and the ipiO genes is activated in compatible, incompatible and nonhost interactions. In encysted zoospores, ipiB and ipiO mRNA accumulation was not detectable, but during cyst germination and appressorium formation on an artificial surface the genes are highly expressed. Expression studies in mycelium grown in vitro revealed that during nutrient starvation the expression of the ipiB and ipiO genes is induced. For ipiO gene expression, carbon deprivation appeared to be sufficient. The ipiO gene promoters contain a sequence motif that functions as a glucose repression element in yeast and this motif might be involved in the regulation of ipiO gene expression.     

Reversible cytoplasmic rearrangements precede wall apposition,hypersensitive cell death and defense-related gene activation in potato/Phytophthora infestans interactions

We used video microscopy techniques as a tool for live examination of the dynamic aspects of plant/fungus interactions. Early, dynamic responses of epidermal midrib cells of leaves from a potato cultivar (Solanum tuberosum L. cv. Datura) carrying resistance gene R1 to Phytophthora infestans (race 1: compatible interaction, race 4: incompatible interaction) were monitored. Similar responses were observed in both types of interaction, ranging from no visible reaction of invaded plant cells to hypersensitive cell death. The overall defense response of each individual cell exhibited a highly dynamic behavior that appeared to be tightly coordinated with the growth of the fungus. Initial localized reactions, including major rearrangements within the cytoplasm, occurred directly at the fungal penetration site, where rapid apposition of autofluorescent material and callose took place. If fungal invasion stopped at this stage, the host cell restored its normal cytoplasmic activity and survived. Hypersensitive cell death occurred only when fungal growth had proceeded to the formation of a clearly identifiable haustorium. In such cases, cytoplasm and nucleus conglomerated around the intracellular fungal structure, followed by a sudden collapse of the whole conglomerate and an instantaneous collapse of the fungal haustorium. Only small quantitative differences between the compatible and incompatible interactions of the two fungal races were observed for these early responses of epidermal cells. In the incompatible interaction, a slightly larger number of epidermal cells responded to fungal attack. More pronounced quantitative differences between compatible and incompatible interactions occurred upon fungal invasion of the mesophyll. These differences in the number of responding cells were not reflected at the level of gene expression: the spatial and temporal activation patterns of two defense-related genes, encoding phenylalanine ammonia-lyase and pathogenesis-related protein 1, were similar in both types of interaction.Dedicated to Professor Peter Sitte, Freiburg, Germany, on the occasion of his 65th birthday