Identification of some major cytokinins in Phaseolus vulgaris and their distribution

The determination of the various endogenous cylokinins and their distribution among organs is important in understanding their role in growth and development in the intact plant. Cytokinins in young plants of Phaseolus vulgaris were purified by immunoaffinity chromatography and HPLC, and characterised by UV spectra. Zeatin nucleotide (zeatin riboside-5'-monophosphate) and isopentenyladenine nucleotide (isopentenyladenosne-5'-monopnosphate) were the most abundant cytokinins in all organs. Their identities were confirmed by GC-MS. The levels of zeatin, zeatin riboside, isopentenyladenine and isopentenyladenosine never exceeded 5% of the nucleotides, as assessed by a methodology that preserves cytokinin nucleotides. Three extraction methods were compared with qualitatively similar results, though differing in their suppression of nucleotidase activity. Cytokinin nucleotide levels were greater in the stems and petioles than in the roots and leaves on a per gram fresh weight basis, and were greater in the stems than in the other organs on a per plant basis. Levels of the zeatin and isopentenyladenine nucleotides were about equal in the stems and leaves, but in the petioles the zeatin nucleotide levels were about twice the level of isopentenyladenine nucleotide, while in the roots they were about half the isopentenyladenine nucleotide level. The importance of considering the cytokinin form is emphasised.     

Identification of RAPD markers linked to a major rust resistance gene block in common bean

Rust in bean (Phaseolus vulgaris L.), caused byUromyces appendiculatus (Pers.) Unger var.appendiculatus [ =U. phaseoli (Reben) Wint.], is a major disease problem and production constraint in many parts of the world. The predominant form of genetic control of the pathogen is a series of major genes which necessitate the development of efficient selection strategies. Our objective was focused on the identification of RAPD (random amplified polymorphic DNA) markers linked to a major bean rust resistance gene block enabling marker-based selection and facilitating resistance gene pyramiding into susceptible bean germplasm. Using pooled DNA samples of genotyped individuals from two segregating populations, we identified two RAPD markers linked to the gene block of interest. One such RAPD, OF10₉₇₀ (generated by a 5-GGAAGCTTGG-3 decamer), was found to be closely linked (2.15±1.50 centi Morgans) in coupling with the resistance gene block. The other identified RAPD, OI19₄₆₀ (generated by a 5-AATGCGGGAG-3 decamer), was shown to be more tightly linked (also in coupling) than OF10₉₇₀ as no recombinants were detected among 97 BC₆F₂ segregating individuals in the mapping population. Analysis of a collection of resistant and susceptible cultivars and experimental lines, of both Mesoamerican and Andean origin, revealed that: (1) recombination between OF10₉₇₀ and the gene block has occurred as evidenced by the presence of the DNA fragment in several susceptible genotypes, (2) recombination between OI19₄₆₀ and the gene block has also occurred indicating that the marker is not located within the gene block itself, and (3) marker-facilitated selection using these RAPD markers, and another previously identified, will enable gene pyramiding in Andean germplasm and certain Mesoamerican bean races in which the resistance gene block does not traditionally exist. Observations of variable recombination among Mesoamerican bean races suggested suppression of recombination between introgressed segments and divergent recurrent backgrounds.Research supported by the Michigan Agricultural Research Station and the USDA-ARS. Mention of a trademark or a proprietary product does not constitute a guarantee or warranty of the product by the USDA and does not imply its approval to the exclusion of other products that may also be suitable     

Assessment of maize and beans storage insect pest in major grain markets,Morogoro-Tanzania

Post-harvest losses for maize and beans are common storage challenges affecting Tanzania's smallholder and large-scale farmers' storage facilities. Consequently, this leads to a reduction of over 50% of harvested grain qualitatively and quantitively per year. Therefore, this experimental study was conducted at the entomological laboratory of the Sokoine University of Agriculture Tanzania, where the research was aimed to assess different common storage insect pests of beans and maize at Morogoro major markets (i.e., Kihonda, Mazimbu and Morogoro Central Market) with similar storage conditions in Morogoro municipality. The complete block design (CBD) with three experimental replications was used. Where locations (Kihonda, Mazimbu and Central market) markets were considered as experimental treatments. The results obtained show that there were no significant differences in number of insect pests (such as maize weevils and bean bruchids) identified between the Kihonda and Central markets (P > 0.05). However, there is a significant difference (P< 0.05) between Mazimbu and other markets regarding the number of insect pest multiplication resulting from the storage condition of those grains in a particular market. Nevertheless, continuous winnowing of stored grains was observed to significantly intensify the infestation of the storage pest in maize and common beans. Therefore, alternatively, to reduce insect pest infestation to maize and common beans in storage facilities, it is important to avoid constant winnowing of stored grains.     

GENETIC AND SOCIAL INHERITANCE OF BODY AND EGG SIZE IN THE BARNACLE GOOSE (BRANTA LEUCOPSIS)

We present heritability estimates for final size of body traits and egg size as well as phenotypic and genetic correlations between body and egg traits in a recently established population of the barnacle goose (Branta leucopsis) in the Baltic area. Body traits as well as egg size were heritable and, hence, could respond evolutionarily to phenotypic selection. Genetic correlations between body size traits were significantly positive and of similar magnitude or higher than the corresponding phenotypic correlations. Heritability estimates for tarsus length obtained from full-sib analyses were higher than those obtained from midoffspring-midparent regressions, and this indicates common environment effects on siblings. Heritabilities for tarsus length obtained from midoffspring-mother regressions were significantly higher than estimates from midoffspring-father regressions. The results suggest that this discrepancy is not caused by maternal effects through egg size, nor by extra-pair fertilizations, but by a socially inherited foraging site fidelity in females.     

豆田刺吸类害虫、天敌自然种群消长规律及其群落结构的研究

在豆田群落中,常见的天敌昆虫及有益生物为12科13种,它们对寄主均有很强的选择性．小花蝽是大豆蚜的主要天敌,系优势种,其次是龟纹瓢虫．大青叶蝉的主要天敌是蜘蛛类,三突花蛛和草间小黑蛛为优势种．在长期不施用农药的环境下,天敌自然种群对控制害虫发生危害的作用明显．经数学分析,建立了12个数学模型,进一步揭示了两种刺吸类害虫与其天敌之间的关系;天敌种群消长、害虫种群消长与时间变动的关系．尤其通过对豆田群落生物的多样性、稳定性动态分析,表明豆田群落在8月9日至8月29日多样性指数和稳定性指数最大;同时亦表明豆田群落的多样性指数愈高,群落的稳定性愈强．     

The palatability of Arctic willow for greater snow geese: the role of nutrients and deterring factors

Temporary feeding on willow buds and leaves by nesting greater snow geese provided us with an opportunity to test the relative importance of nutrients and deterrents in affecting the palatability for geese of a food plant with a high phenol content. Protein, total phenol and fiber (neutral and acid detergent fiber, and lignin) were analyzed in closed and open buds and in rolled and open leaves. Geese feed on willows at the open-buds and rolled-leaf stages but not at the closed-bud and open-leaf stages. Protein content was higher in open buds and rolled leaves (25–27%) than in closed buds and open leaves (19–21%). Phenol content increased during leaf emergence but was already high (14%) in rolled leaves. All plant fibers were very high in closed buds but declined rapidly during leaf emergence. The increase in phenol: protein ratio appeared to be more important than phenol concentration alone in explaining the cessation of feeding by geese on willow leaves whereas the high fiber content of closed buds may explain why they were not eaten. Our results illustrate the value of a multifactorial approach in the study of the food selection process in herbivores.     

应用免疫电镜技术快速检测菜豆黄花叶病毒、马铃薯M病毒和燕麦花叶病毒

应用免疫吸附电流技术(ISEM)可有效地检测腐汁液中的菜豆黄花叶病毒(BYMV)、马铃薯M病毒(PVM)和燕麦花叶病毒(OMV)。BYMV,PVM和OMV三种抗血清的适宜工作浓度和对铜网的适宜包被时间均为1000倍和1小时,对同源病毒的适宜捕获时间分别为4℃下2、2和8小时。PVM和OMV的病汁液检测灵敏度均为稀释4000倍,而BYMV病汁液稀释16000倍时还能检测到少量病毒料子。ISEM捕获法和修饰法的结果表明,这三种病毒之间无血清学交叉反应。     

Changes in water relations and in some physiological functions of bean under very light osmotic shock induced by polyethylene glycol

Bean plantlets ( Phaseolus vulgaris L. cv. Topcrop) were stressed at the age of 16–18 days by gradual (2–8%) or abrupt addition of 6% (w/v) polyethylene glycol Mw 6000 (PEG 6000) to Hoagland solution. Leaf conductance, photosynthesis, internal CO₂ partial pressure (C_i), relative water content (RWC), water content/dry weight (H₂O/DW), apoplastic PEG concentrations and weight of leaves, stems and roots were determined. Leaf conductance, photosynthesis and C_i were determined on non-detached primary leaves, and leaf potentials (water, osmotic and turgor potentials) were investigated in freshly detached (non-rehydrated) primary leaves, both in treated and control plants; RWC and osmotic potential were also assessed at the null turgor point. Low PEG 6000 concentrations induced early and evident decrease in leaf conductance and photosynthesis, whereas C_i decreased only moderately and tended to recover during advanced stress. There were moderate though significant decreases in RWC and H₂O/DW, no change or increases in water potential, no significant changes in osmotic potential and a moderate but significant increase in turgor potential. Even when referred to null turgor point, RWC significantly decreased and osmotic potential was unchanged. It was concluded that apoplastic PEG 6000 accumulation at evaporating sites would account for the early decrease in conductance which would also justify the unchanged or the prevalent increase in water potential and turgor potential. The subsequent PEG diffusion and concentration in the leaf apoplastic water would have induced the RWC and H₂O/DW decrease and the final turgor flexion documented.     

Fitness consequences of egg-size variation in the lesser snow goose

We investigated the relationship between eggsize variation and (a) egg hatching success, (b) chick survival to fledging and recruitment, and (c) adult female survival, over 12 years in the lesser snow goose (Anser caerulescens caerulescens). By comparing the means and variances of egg size for successful and unsuccessful eggs, our aim was to assess the relative fitness of eggs of different sizes and to determine the type of selection operating on egg size in this species. As both egg size and reproductive success vary with age in the lesser snow goose we controlled for the effects of female age. Egg-size variation is very marked in this population, varying by up to 52% for eggs hatching successfully. However, there was no relationship between egg size and post-hatching survival of goslings to fledging or recruitment, either within or between broods, pooling across years. Egg size varied significantly between successful and unsuccessful clutches in only 2 of 33 individual year comparisons. First-laid eggs surviving to onset of incubation, and eggs hatching successfully, were on average larger than unsuccessful eggs, but this was probably due to the confounding effects of female age-specific and sequence-specific egg survival. Variance of egg size differed significantly between successful and unsuccessful eggs in only 3 of 24, and 0 of 21, individual year comparisons for pre- and post-hatching survival respectively. We therefore found little evidence for a relationship between egg-size variation and offspring fitness, or for strong directional, normalising or diversifying selection operating on egg size, in the lesser snow goose. In addition, there was only weak support for the hypothesis that egg-size variation is maintained by temporal variation in selection pressure (sensu Ankney and Bisset 1973). It is likely that egg-size variation represents the pleiotropic expression of alleles affecting more general physiological or metabolic processes. While this does not rule out the existence of alleles with more direct effects on egg size we suggest that their contribution to heritable egg size is small.