Evaluation of Greenbug and Yellow Sugarcane Aphid Feeding Behavior on Resistant and Susceptible Switchgrass Cultivars

Switchgrass (Panicum virgatum L.) is an emerging biofuel crop that serves as host for aphids. To discern the effects of plant age and possible resistance mechanisms, the feeding behavior of greenbugs (Schizaphis graminum Rondani.) and the yellow sugarcane aphid (Sipha flava Forbes.) was monitored on three diverse switchgrasses by the electrical penetration graph (EPG) technique. Callose deposition and genes associated with callose metabolism were also analyzed to discern their association with plant resistance. There was a strong host effect on greenbugs feeding on lowland cultivar Kanlow at the V3 stage of development, as compared to the greenbug-susceptible upland cultivar Summer and plants derived from Kanlow (♂) × Summer (♀) (K×S) crosses. These data confirmed that Kanlow at the V3 stage had antibiosis to greenbugs, which was absent in the Summer and K×S plants. In contrast, similar effects were not observed for yellow sugarcane aphids, excluding significant differences in the time to first probe on Kanlow plants at the V1 stage and reduction in time spent on pathway processes on Kanlow plants at the V3 stage. These data demonstrated that Kanlow plants may have multiple sources of resistance to the two aphids, and possibly some were phloem based. Microscopy of leaf sections stained with aniline blue for callose was suggestive of increased callose deposition in the sieve elements in Kanlow plants relative to Summer and K×S plants. RT-qPCR analysis of several genes associated with callose metabolism in infested plants was equivocal. Overall, these studies suggest the presence of multiple defense mechanisms against aphids in Kanlow plants, relative to Summer and K×S plants.     

Influence of Six Vegetable Cultivars on Reproduction of Meloidogyne javanica

Replicated field and greenhouse experiments were used to evaluate the effect of tomato, cabbage, cucumber, carrot, Amaranthus hybridus, and pepper on growth and fecundity of Meloidogyne spp., particularly M. javanica. In the field tests, tomato, cucumber, and carrot favored population increases of Meloidogyne spp., while Amaranthus, pepper, and cabbage limited them. Some cropping sequences that included crops from the latter group had a suppressive effect on population growth. Thus, of the 36 cropping sequences that were investigated, the following kept the pests in check: tomato-pepper; tomato-Amaranthus; cabbage-pepper; Amaranthus-pepper; carrot-cabbage; pepper-pepper; pepper-Amaranthus; and Amaranthus-pepper. In the greenhouse tests, tomato, cucumber, and carrot had a high number of galls per 50 cm of root, large, conspicuous galls and egg masses, and a high number of larvae per egg mass. Thus, they were highly susceptible. Cabbage and Amaranthus were unsuitable hosts as reflected in the absence of galls or a low number per 50 cm of root. small size of galls and egg masses, and few progeny on the subsequent crop of pepper. The length of time required for eggs to hatch on different hosts varied considerably and is thought to be a significant factor in infection of hosts.     

Factors Affecting Egg Hatch of Heterodera mediterranea and Differential Responses of Olive Cultivars to Infestation

The influence of temperature and olive root exudates on Heterodera mediterranea egg hatch and the effects of H. mediterranea on the growth of two olive cultivars (Arbequina and Picual) were investigated. Egg hatch occurred over a temperature range of 10 to 30°C and was optimal at 20 to 25°C. There were no differences in egg hatch between sterile deionized distilled water or root exudate dilutions (undiluted, diluted 1:1, and 1:2) of Arbequina and Picual at 20°C. Heterodera mediterranea reproduced on both olive cultivars in growth chambers at 25°C. Soil and root final nematode populations, as well as total number of cysts per plant and reproduction rate, were significantly higher in Arbequina than in Picual. Shoot dry and root fresh weights as well as increases of shoot height, trunk diameter, and numbers of nodes were significantly suppressed by infection with 10,000 eggs + second-stage juveniles/pot in Arbequina but not in Picual.     

Spatial and Temporal Effects on Switchgrass Stands and Yield in the Great Plains

Switchgrass (Panicum virgatum L.) is being developed into a perennial, herbaceous, cellulosic feedstock crop for use in temperate regions of the USA. Information on spatial and temporal variation for stands and biomass yield among and within fields in large agroecoregions is not available. Spatial and temporal variation information is needed to model feedstock availability for biorefineries. In this 5-yr study, the spatial and temporal variation for biomass yield and stands was determined among and within 10 fields located in North Dakota, South Dakota, and Nebraska. Switchgrass fields were managed for bioenergy from 2000 to 2004 for the Nebraska locations and 2001 to 2005 for the South Dakota and North Dakota locations. A global positioning system (GPS) receiver was used to repeatedly measure within field quadrat sites for switchgrass stands using frequency grid (2.25 m²) measurements in June for five growing seasons. Sixteen quadrat (≥1 m²) yield samples were taken post-killing frost in the establishment year and in August in subsequent years at each location. Topographic within field effects on switchgrass stand frequency and biomass yields were largely insignificant. Stands tended to increase from establishment year to year 3 and then begin to plateau. Weather factors, which were the principal source of temporal variation, were more important in switchgrass yield variation than on switchgrass stand frequencies. Temporal standard deviations for yield were higher on quadrat sites with higher than average field means while temporal standard deviations were smaller in quadrat sites that had lower than average field means at six locations. In the Northern Great Plains agroecoregion, there is greater temporal and spatial variation for switchgrass biomass yields among fields than within fields. Results indicate that modeling feedstock availability for a biorefinery can be based on field scale yields.     

Effects of Light Quality on Tiller Production in Lolium spp

Variations in phytochrome status in grasses were provoked by end of day red and far-red treatments and above canopy irradiations. Lolium perenne L. and Lolium multiflorum Lam. plants developed more tillers when illuminated with higher red/far-red ratios. These results show that branching of grasses is controlled by phytochrome activity in a way similar to that in dicotyledon plants.     

A Novel Tiller Angle Gene,TAC3, together with TAC1 and D2 Largely Determine the Natural Variation of Tiller Angle in Rice Cultivars

Tiller angle is one of the most important components of the ideal plant architecture that can greatly enhance rice grain yield. Understanding the genetic basis of tiller angle and mining favorable alleles will be helpful for breeding new plant-type varieties. Here, we performed genome-wide association studies (GWAS) to identify genes controlling tiller angle using 529 diverse accessions of Oryza sativa including 295 indica and 156 japonica accessions in two environments. We identified 7 common quantitative trait loci (QTLs), including the previously reported major gene Tiller Angle Control 1 (TAC1), in the two environments, 10 and 13 unique QTLs in Hainan and Wuhan, respectively. More QTLs were identified in indica than in japonica, and three major QTLs (qTA3, qTA1b/DWARF2 (D2) and qTA9c/TAC1) were fixed in japonica but segregating in indica, which explained the wider variation observed in indica compared with that in japonica. No common QTLs were identified between the indica and japonica subpopulations. Mutant analysis for the candidate gene of qTA3 on chromosome 3 indicated a novel gene, Tiller Angle Control 3 (TAC3), encoding a conserved hypothetical protein controlling tiller angle. TAC3 is preferentially expressed in the tiller base. The ebisu dwarf (d2) mutant exhibited a decreased tiller angle, in addition to its previously described abnormal phenotype. A nucleotide diversity analysis revealed that TAC3, D2 and TAC1 have been subjected to selection during japonica domestication. A haplotype analysis identified favorable alleles of TAC3, D2 and TAC1, which may be used for breeding plants with an ideal architecture. In conclusion, there is a diverse genetic basis for tiller angle between the two subpopulations, and it is the novel gene TAC3 together with TAC1, D2, and other newly identified genes in this study that controls tiller angle in rice cultivars.     

A Comparison of Main-stem and Tiller Growth in Barley; Apical Development and Leaf-unfolding Rates

Information is presented on the hierarchical relationship betweenthe stems of Proctor barley grown under controlled conditions.Rates of production of foliar and floral primordia and ratesof leaf unfolding were found to follow the order main-stem >primary tillers > secondary tillers. Apical dome size wasinitially substantially greater for the main-stem than for thetillers due principally to the slower transition of the latterto the reproductive condition; by the time that double ridgesare formed on the tiller apices apical dome sizes are similarto that of the main-stem. Transition to the reproductive conditionoccurs at about the same time for the primary tillers. Thisnear-synchrony results in a smaller number of leaves borne onsuccessive tillers, since these have had less time to initiatefoliar primordia, and a measure of synchrony in awn appearance,since rates of car development are similar for these stems. The nature of the hierarchical relationship between main-stemand tillers is discussed.     

Pathogenicity of the Lesion Nematode,Pratylenchus brachyurus,on Six Soybean Cultivars

Pathogenicity tests of Pratylenchus brachyurus on selected greenhouse-grown soybean cultivars indicated the nematode reduced seed yield of ''Hood'' but not that of ''Custer'', ''Bragg'', ''Dyer'', or ''Pickett''. Root weights of all cultivars were reduced. Damage and numbers of nematodes within soybean roots growing at 13, 21, and 29 C were greater at higher temperatures. At 29 C, root pruning was prominent in ''Hood'' and ''Pickett'' but limited in ''Custer'' and ''Hill''. Root pruning was not observed at 13 C and only ''Pickett'' showed pruning at 21 C. Plant height and foliage weight were not affected. P. brachyurus had no effect on the emergence of ''Pickett'' or ''Bragg'' soybeans. Nematode counts from roots of ''Pickett'' at intervals after inoculation indicated that hatching of second generation second-stage larvae occurred about 15 days after egg laying. An average of 68% of the initial inoculum penetrated the roots within five days of inoculation, the highest observed was 81% in five days. Details of structural damage in penetrated tissues were studied in sectioned roots. In soybean roots infected by P. brachyurus and/or Rhizoctonia solani greater damage occurred with nematode and fungus combined than with either acting alone.     

交配对小地老虎成虫寿命和繁殖的影响

通过室内饲养小地老虎,研究了交配对其成虫寿命和繁殖的影响.结果 表明,小地老虎成虫的寿命随其交配状况而有所变化,无论雌蛾还是雄蛾,未能得到及时交配时,则寿命稍长些,交配过的雌蛾产卵前期缩短、产卵期延长、产卵量增大.小地老虎的交配次数对其产卵量和幼虫孵化率有明显的影响,0次交配的产卵量最低,并且产的是不育卵,均不能孵化;随着交配次数的增加,其产卵量和幼虫孵化率都显著增大.     

Effects of Tiller Separation and Root Pruning on the Growth of Lolium perenne L.

Experiments have been carried out to assess the role of inter-tillerinteractions within plants of Lolium perenne L. cv. S24 as factorswhich could play a part in determining the growth-rate of thewhole plant. In order to do this, the effect of tiller separationon plant growth was studied as well as the influence of theremoval of different parts of the root and shoot system. Wheneverplants were supplied with nutrients by means of culture solutions,separation of tillers brought about a marked increase in theamount of dry matter produced. Root pruning and in particularthe removal of root apices brought about similar increases ingrowth. Separation of tillers in soil-grown plants did not bringabout increased growth. These results are interpreted as indicatingthat separation of tillers or the initial removal of root apicesin plants supplied with nutrients by means of culture solution,promotes root branching which brings about an increased netassimilation rate arising from an increase supply of a growth-promotingsubstance, probably a cytokinin, from the root apices. The resultsare not taken as indicative of an intertiller interaction whichrestricts the growth of intact plants.     

Honey Bee Colonies Headed by Hyperpolyandrous Queens Have Improved Brood Rearing Efficiency and Lower Infestation Rates of Parasitic Varroa Mites

A honey bee queen mates on wing with an average of 12 males and stores their sperm to produce progeny of mixed paternity. The degree of a queen’s polyandry is positively associated with measures of her colony’s fitness, and observed distributions of mating number are evolutionary optima balancing risks of mating flights against benefits to the colony. Effective mating numbers as high as 40 have been documented, begging the question of the upper bounds of this behavior that can be expected to confer colony benefit. In this study we used instrumental insemination to create three classes of queens with exaggerated range of polyandry– 15, 30, or 60 drones. Colonies headed by queens inseminated with 30 or 60 drones produced more brood per bee and had a lower proportion of samples positive for Varroa destructor mites than colonies whose queens were inseminated with 15 drones, suggesting benefits of polyandry at rates higher than those normally obtaining in nature. Our results are consistent with two hypotheses that posit conditions that reward such high expressions of polyandry: (1) a queen may mate with many males in order to promote beneficial non-additive genetic interactions among subfamilies, and (2) a queen may mate with many males in order to capture a large number of rare alleles that regulate resistance to pathogens and parasites in a breeding population. Our results are unique for identifying the highest levels of polyandry yet detected that confer colony-level benefit and for showing a benefit of polyandry in particular toward the parasitic mite V. destructor.     

Confounding Effects of Soil Moisture on the Relationship Between Ecosystem Respiration and Soil Temperature in Switchgrass

Understanding the response of ecosystem respiration (ER) to major environmental drivers is critical for estimating carbon sequestration and large-scale modeling research. Temperature effect on ER is modified by other environmental factors, mainly soil moisture, and such information is lacking for switchgrass (Panicum virgatum L.) ecosystems. The objective of this study was to examine seasonal variation in ER and its relationship with soil temperature (T _s) and moisture in a switchgrass field. ER from the nighttime net ecosystem CO₂ exchange measurements by eddy covariance system during the 2011 and 2012 growing seasons was analyzed. Nighttime ER ranged from about 2 (early growing season) to as high as 13 μmol m^?2 s^?1 (peak growing period) and showed a clear seasonality, with low rates during warm (>30 °C) and dry periods (<0.20 m³ m^?3 of soil water content). No single temperature or moisture function described variability in ER on the seasonal scale. However, an exponential temperature–respiration function explained over 50 % of seasonal variation in ER at adequate soil moisture (>0.20 m³ m^?3), indicating that soil moisture <0.20 m³ m^?3 started to limit ER. Due to the limitation of soil–atmosphere gas exchange, ER rates declined markedly in wet soil conditions (>0.35 m³ m^?3) as well. Consequently, both dry and wet conditions lowered temperature sensitivity of respiration (Q ₁₀). Stronger ER–T _s relationships were observed at higher soil moisture levels. These results demonstrate that soil moisture greatly influences the dynamics of ER and its relationship with T _s in drought prone switchgrass ecosystems.     

Comparison of Growth Rates and Sugar and Protein Concentrations of the Extension Zone of Main Shoot and Tiller Leaves of Wheat

The objective of this study was to determine, for wheat plantsgrowing in an irrigated, well fertilized crop, whether therewere any differences in leaf growth rates and sugar and proteinconcentrations of the extension zone between leaves on the mainshoot and those on the first two primary tillers. High nitrogensupply was used to accentuate any basic differences that mayexist and to ensure minimum carbohydrate concentrations. Final leaf length, leaf extension rates, the responsivenessof leaf extension to temperature, and the sugar and proteinconcentrations of the extension zone did differ between successiveleaves on a shoot but the values for these parameters were similarfor leaves growing on separate shoots at the same time. Theseresults were consistent with the assumptions that the growthof tiller leaves was integrated with the activity of the mainshoot and that there were no basic physiological differencesbetween the leaves on the separate shoots. The differences ingrowth rates between leaves with time were not related to hexoseconcentrations. The variation in protein concentrations wasless than recorded previously and insufficient to establisha significant relationship with leaf growth rates.     

Isolation and Comparison of Eight SWEET17 Genes from Six Loquat Cultivars

Russian Journal of Plant Physiology - The plant SWEET (Sugars Will Eventually be Exported Transporters) proteins, as newly discovered sugar transporters, play various important roles during plant...     

激素对水稻分蘖芽生长和分蘖相关基因表达的调控效应

以水稻品种‘南粳44＇为材料,研究了植物激素对水稻分蘖芽生长及OsTB1、OsD3、OsD10和OsD27等基因表达的调控。结果表明,水稻分蘖芽生长的调控至少存在两条途径,一条通过调控分蘖芽中CTK含量进而调控OsTB1等基因表达来实现,另一条通过调控OsD3、OsD10和OsD27等系列基因表达来实现。外源IAA和GA_3对水稻分蘖芽生长的调控是通过这两条途径共同实现的。     

Variability in Reproduction of Four Populations of Meloidogyne incognita on Six Cultivars of Cotton

A range of virulence levels was found in four populations of Meloidogyne incognita collected from cotton fields of the Punjab region of Pakistan. The most virulent population was associated with development of larger gall size, larger giant cell formation and improved success of juveniles transitioning into reproducing adults. The most virulent nematode population, MI-78, emanated from cotton cultivar NIAB-78. This cotton cultivar also possessed the greatest level of resistance to the three other nematode populations evaluated in this study. The source of plant resistance was not evident during root penetration by second-stage juveniles (J2), but became apparent as nematode feeding was attempted. Although one other cotton cultivar, CIM-506, could also be designated as showing a level of resistance, none of the other cultivars reduced any nematode stage by more than 75% of that achieved on the best host. These data provide an example of a single cotton cultivar that could have short-term utility in field settings. The data also provide insight for future cotton breeding programs.