Effect Of Plant Genotype Research Articles

GENOTYPIC VARIATION IN LEAF DAMAGE IN PIPER ARIEIANUM (PIPERACEAE) BY A MULTISPECIES ASSEMBLAGE OF HERBIVORES.

The shrub Piper arieianum (Piperaceae) has a diverse herbivore fauna (95 species total) in Costa Rican rain forest. The effect of plant genotype on leaf damage by individual herbivore species and total leaf area removed was studied in P. arieianum through a cloning experiment. Damage patterns were measured over 3.5 years for two plots, four genotypes per plot, in the understory of lowland rain forest. In both plots, there were significant differences among genotypes in total leaf area missing throughout the study period. Rankings of genotypes based on overall damage remained constant over time in plot 1 but changed in plot 2. Certain individual herbivore species caused significantly higher damage in some genotypes than in others; the change in genotype rankings in plot 2 was associated with increased damage to particular genotypes by specific herbivore groups. The genotype most heavily damaged by a given insect species varied depending on the herbivore species; thus, resistance to one herbivore species did not necessarily confer resistance against all species. Those herbivore species causing the greatest proportion of damage for a given plant changed over time. Because total damage resulted from the summation of losses to individual herbivore species, whether an individual plant lost more leaf area than its neighbors depended on the relative abundance of the herbivore species at any one time. Finally, for a portion of the study period in each plot, more heavily damaged clones grew less than lesser damaged clones. Together with previous reports that naturally growing plants differ significantly in damage and that these differences are sufficient to cause fitness differences, the results presented here suggest that the herbivores of P. arieianum represent a selective force for changes in resistance but that this selective force changes both in intensity and quality over time.

Growth enhancement of maize (Zea mays L) through Azospirillum lipoferum inoculation : effect of plant genotype and bacterial concentration

Des essais de germinaton et des essais en pots ont ete utilises pour etudier la specificite de l'association entre une souche d'Azospirillum lipoferum et diverses varietes hybrides de mais ainsi que la dose d'inoculum. L'influence du genotype de la plante hote est clairement montree dans les 2 types d'essais comme le montrent la figure 1 et le tableau V. Le niveau optimal de l'inoculation a ete estime a 10 7 bacteries par plante et l'importance d'une inoculation precoce est demontree (tableaux I, II, III). Les essais en pots sont moins selectifs que les tests de germination (tableau IV) (...)

Transformation ofVicia fabaCotyledon and Stem Tissues7Agrobacterium rhizogenes: Infectivity and Cytological Studies

Transformation of Vicia faba cotyledon and stem tissues by Agrobacterium rhizogenes has been demonstrated. Hormone autotrophy and NPTII dot blot assays were used to confirm the transgenic nature of root clones, and to show the co-transfer of the T-DNA from the Ri plasmid and the NPTII gene from pBIN 19. An effect of plant genotype on susceptibility to A. rhizogenes was observed. The response to infection depended on tissue type in addition to plant genotype. Cytological analysis of transformed root clones uncovered variation in ploidy up to the octoploid level and structural rearrangements of chromosomes. The possible origins of these karyotype changes and their implications are discussed.

Differential Cadmium Accumulation and Phytotoxicity in Sixteen Tobacco Cultivars

A greenhouse experiment was conducted to determine the effect of plant genotype on cadmium accumulation and phytotoxicity in tobacco. When low levels of CdCl{sub 2} were added to the nutrient solution of 16 tobacco cultivars growing in sand culture, the heavy metal was partitioned in the following order: leaves > roots > stems. Because leaves are the commercial product, this pattern of partitioning is highly undersirable. The concentration of Cd accumulated in the tissues varied with plant genotype and level of Cd treatment. At the 0.25 ppm Cd treatment, a maximum of 127.6 ppm Cd was found in foliage of the Coker-48 variety, and at the 1.0 ppm Cd treatment, a maximum of 382.6 ppm Cd was detected in the foliage of NC-232. None of the Cd-treated tobacco plants exhibited visual foliar symptoms commonly observed in other plant species. A concentration of 0.25 ppm Cd stimulated shoot height, internode length and leaf number but inhibited total dry weight and percent dry weight. Cd phytotoxicity was found to vary with plant genotype and level of Cd treatment but not with the amount of Cd accumulated by the plant.

Development of the Xylem Ureide Assay for the Measurement of Nitrogen Fixation by Pigeonpea (Cajanus cajan(L.) Millsp.)

Quantification of N2 fixation by pigeonpea (Cajanus cajan (L.) Millsp.) in the field has proved difficult using techniques such as 15N isotope dilution, acetylene reduction and N difference. We report experiments to develop the ureide assay of N2 fixation based on extraction and analysis of xylem exudate. Plants of pigeonpea cv. Quantum, inoculated with effective Rhizobium spp. CB756, were grown in a temperature-controlled glasshouse in large pots filled with a sand: vermiculite mixture, in water culture and in a slightly acidic, red-brown earth in replicated field plots. Xylem exudate was collected as bleeding sap from both nodulated and unnodulated roots, and from detached nodules. Exudate was extracted also from detached shoots and stems of pigeonpea using a mild vacuum (60–70 kN m−2). Large differences in the composition of N solutes exported from roots of N2-dependent and nitrate-dependent plants suggested that shifts in plant dependence on N2 fixation may be reflected by concomitant changes in N solutes. Thus, nodulated plants were supplied throughout growth with either N-free nutrients or nutrients supplemented with 1, 2, 5, 5, 10, or 20 mol m−315NO3-⁠. Plants were harvested at regular intervals for dry matter and vacuum-extracted exudate. The relative abundance of ureides ([ureide-N/ureide-N + nitrate-N + α-amino-N] × 100) in the exudate was highly correlated with the proportion of plant N (calculated using a 15N isotope dilution technique) derived from N2 fixation. Two distinct phases of plant growth were recognized and standard curves were prepared for each. The relationship between proportional dependence of plants on N2 and xylem relative ureides was unaffected by mineral-N source, i.e. nitrate or ammonium. This result is discussed in relation to interpretation of material from field-grown plants. The effects of plant genotype, strain of rhizobia, section of stem extracted, removal of leaves, time delay between shoot detachment and extraction, and diurnal characteristics were examined in order to identify potential sources of error and to optimize sampling procedures.

Effects of auxin concentration on induction and growth of embryogenic callus from young inflorescence explants of Old World bluestem (Bothriochloa spp.) and bermuda (Cynodon spp.) grasses

Objectives of this research were to test the effects of plant genotypes and auxin 2,4-D (2,4-dichlorophenoxyacetic acid) medium concentrations on embryogenic (E) callus production of two grass species. Two Old World bluestem,Bothriochloa ischaemum, accessions (A-8793 and A-8911c) and three bermudagrass,Cynodon dactylon (L.) Pers., accessions (A-10978b, A12164, and ‘Brazos’) supplied the explant material. Immature inflorescences ≤9 mm in length were placed on modified Murashige-Skoog (MS) agar medium containing 0, 1, 3, or 5 mg L-1 of 2,4-D. Explants of all genotypes produced callus by the end of a 4-week dark incubation period at 25°C. When subcultured onto fresh media and maintained at 25°C with a 16 hr photoperiod, calli became embryogenic within 8 weeks of inoculation. Three mg L-1 of 2,4-D in the media maximized E callus production in both bluestem genotypes and in A-10978b and A-12164 bermudagrass genotypes. Maximum E callus production from Brazos bermudagrass resulted from the 1 mg L-1 treatment. Somatic embryos developed after subculture under light. Embryos showed scutellum-like structures and coleoptile-coleorhiza bipolar organization. Plantlets were regenerated from all genotypes except Brazos, whose embryoids failed to germinate. All callus from Brazos eventually senesced. Light and scanning electron microscopy confirmed regeneration through somatic embryogenesis.

Diversity within two serogroups of Rhizobium leguminosamm native to soils in the Palouse of eastern Washington*

SUMMARYThe effect of plant genotype, soil temperature, and moisture on recovery of Rhizobium leguminosamm serogroups WA01 and WA02 from soil, was evaluated in the greenhouse using three plant genotypes (Pisum sativum cv. Alaska, Pisum sativum cv. Paloma and Lens culinaris cv. Rechief), three temperatures (12, 20 and 24°C) and soil from two different slope positions. The impact of moisture was followed by assessing pea nodulation after incubation of soil at different preplanting moisture levels. Isolates were also evaluated for serogroup, response to low levels of antibiotics and efficacy of symbiotic characters.Of the 33 antibiotic‐strain combinations showing growth, 10 permitted 50% or more of the isolates to grow. Of the 24 clusters obtained, all except one were dominated by isolates in either serogroup. WA01 or WA02. There was no relation between either serogroup or cluster groupings and N2 fixation. Serogroup recovery was influenced by plant genotype and temperature. At root temperatures of 12 and 24°C, serogroup WA02 occurred in a significantly lower fraction of the lentil nodules as compared to the pea species. At 12°C, recovery of WA02 was higher for the Paloma than Alaska pea. Recovery of WA02 in pea nodules generally increased as the soil moisture was preconditioned to drier levels of ‐0.5 and ‐1.5 MPa water potential.

Effect of plant genotype and nitrogen fertilizer on symbiotic nitrogen fixation by soybean cultivars

Isotopic as well as non-isotopic methods were used to assess symbiotic nitrogen fixation within eight soybean [Glycine max (L.) Merr.] cultivars grown at 20 and 100 kg N/ha levels of nitrogen fertilizer under field conditions.

Genetics of nitrogen metabolism and physiological/biochemical selection for increased grain crop productivity

It is necessary to increase protein productivity of grain crops to meet present and future world protein requirements. Conventional plant breeding methodology has been to select genotypes with enhanced yield or grain protein concentration. In addition to this determination of end product, we suggest measurements of a number of physiological and biochemical processes of nitrogen (N) metabolism which precede plant maturity as selection criteria for enhanced N metabolism and grain crop productivity. The measurement across the growing season of genotypic variation in components of N metabolism would constitute a physiological/biochemical selection program to be incorporated with the determination of harvestable end product. A properly designed physiological/biochemical selection program would integrate the effects of plant genotype, environment, and their interactions allowing identification of the factors limiting productivity of particular genotypes, and would also estimate end product. Our review of literature pertinent to whole plant N metabolism suggests that such a selection program initially include NO 3 (-) uptake, N2 fixation, N accumulation, N remobilization, seed protein synthesis, and Nitrogen Harvest Index.

VARIABILITY IN POD FILLING CHARACTERISTICS OF PEAS (Pisum sativum L.) UNDER FIELD CONDITIONS

The average rates of pod dry weight increase, final pod weights and durations of pod growth were estimated for peas (Pisum sativum L.) growing in the field. The effects of plant genotype, field location and the time of season on these characters were studied in several populations of pea genotypes. Rate of pod filling and final pod weight were both affected by genotype, year and initiation time during the season. Effective duration of pod filling was not affected by any of these factors and final pod weight was always strongly related to the rate of filling. For 46 genotypes, the rate of pod filling ranged from 16 to 75 mg∙day−1 in a single location. Despite the large environmental and seasonal variation, the interactions with genotype were small and estimates of broad sense heritability were high. Across genotypes, rate of pod filling was correlated with weight per 100 seeds and final seed yields. The large changes in rate of pod filling during the season were similar in pattern in 2 yr. However, because this pattern was similar in populations with different flowering times, and because of the significant relationship to the changes in irradiance during both seasons, it is suggested that these seasonal changes in pod filling are of environmental rather than developmental origin.Key words: Pod bulking, seed development, pod development, seasonal changes, growth rate, duration

Effects of Plant Genotypes and Root Nodulation on Growth and Survival of Sitona spp. Larvae 12

The feasibility of locating resistance to Sitona spp. larvae and effects of root nodules on growth and survival of larvae was studied by using a slant board plant culture technique. No resistance to larvae of S. hispidulus (F.) was found in diverse genotypes of alfalfa, Medicago sativa L., red clover, Trifolium pratense L., and white clover, T. repens L. No resistance to S. flavescens (Marsham) was found in red or white clover; however, three cultivars of birdsfoot trefoil, Lotus corniculatus L., two cultivars of crownvetch, Coronilla varia L., and bigflower vetch, Vicia grandiflora var. kitaibeliana W. Koch, were resistant to S. hispidulus larvae. S. flavescens did not survive on alfalfa or crownvetch roots. Growth but not survival of larvae of S. hispidulus was less on red clover plants without root nodules than on those with nodules. Growth and survival of larvae was less on alfalfa roots without nodules than on roots with nodules. The slant board culture system should be useful to evaluate plant germplasm for antibiosis to Sitona spp. larvae.

Plant genotype effects on nitrogen fixation in grasses.

Potentials for nitrogen fixation of economic importance have been shown now for a number of tropical forage grasses, sorghum, maize, rice, and perhaps even wheat. The exploitation of this potential, however, will be dependent on the identification of the limiting factors and agronomically feasible practices to eliminate them. Environmental effects are pronounced but rather difficult to manipulate. Whenever possible, preference should be given to plant-breeding practices.