Reaction of sugarcane genotypes to brown and to orange rust by leaf whorl inoculation

ABSTRACT: In this research eleven sugarcane genotypes were classified in relation to their resistance to brown rust, and eleven to their resistance to orange rust. Artificial inoculation was carried out in the leaf whorl of 165-day-old plants in the city of Paranavaí, Paraná State, Brazil, in 2017. The evaluation was performed 30 days after inoculation, using a rating scale. Among the genotypes tested for brown rust, four were classified as susceptible, six as moderately susceptible and one presented moderate resistance. For orange rust, three genotypes were classified as susceptible, seven as moderately susceptible and one as moderately resistant. The evaluation and classification of the reaction of sugarcane genotypes to the rusts is an important tool that assist in preliminary trials and selection of promising genotypes for more advanced stages of breeding programs and provides information to producers on the choice of cultivars to be planted.

New data on systematic position and paleoecology of the Permian equisetophyte Annulina neuburgiana (Radczenko) Neuburg

The paper deals with the morphology, systematic position and paleoecological preferences of the species Annulina neuburgiana (Radczenko) Neuburg assigned to equisetophytes. The species Annulina neuburgiana is characteristic of the Permian deposits of Angaraland (i.e. north-eastern part of Eurasia in recent geographical situation), especially for the deposits of Kungurian, Ufimian (Roadian), and Kazanian (Wordian) stages. A. neuburgiana had long segmentated stems consisting of nodes and internodes. Long lanceolate leaves of this plant bear a single axial vein, the leaves were aggregated into leaf whorls. Basal parts of the leaves were connected by their margins forming well-defined narrow leaf sheath. Reproductive organs are fertile zones disposed on the stems just below the leaf whorl. The fertile zones consist of the numerous peltate sporangiophores. Ecologically A. neuburgiana most probably preferred well-watered mostly near-water environments.

Plant Growth Regulator Drenches Suppress Foliage and Inflorescence Height of ‘Leia’ Pineapple Lily

Plant growth regulators (PGRs) are used to control excessive plant growth in potted crops to improve quality and compactness for shipping and display. Pineapple lily (Eucomis sp.), a recent introduction to the potted crop market, can have excessive foliage growth and inflorescence height making the use of PGRs desirable. Bulbs of ‘Leia’ pineapple lily were forced in the greenhouse and drenched at leaf whorl emergence with three PGRs at five different concentrations: 1) flurprimidol (0.25, 0.5, 1.0, 2.0, and 4.0 mg per 6.5-inch pot), 2) uniconazole (0.25, 0.5, 1.0, 2.0, and 4.0 mg/pot), or 3) paclobutrazol (0.5, 1.0, 2.0, 4.0 and 8.0 mg/pot) and an untreated control. As concentration increased, days to anthesis increased and foliage height decreased for each PGR. Paclobutrazol (4.0 and 8.0 mg/pot), uniconazole (4.0 mg/pot), and flurprimidol (2.0 and 4.0 mg/pot) treatments resulted in excessive stunting with none of the plants being marketable. Flurprimidol had the greatest influence on plant growth among all the PGRs. Acceptable concentrations for each PGR are paclobutrazol at 0.5 to 2.0 mg/pot, uniconazole at 0.25 to 2.0 mg/pot, and flurprimidol at 0.5 to 1.0 mg/pot based on percentage of marketable plants and foliage and inflorescence height suppression without excessively increasing the number of days to anthesis.

Leaf Whorl Inoculation Method for Screening Sugarcane Rust Resistance

Brown rust, caused by Puccinia melanocephala, and orange rust, caused by P. kuehnii, are agronomically important diseases of sugarcane in Florida. Cultivar resistance is the best means of controlling these diseases. Natural infection has been the primary means of assessing resistance in sugarcane cultivars against rusts; unfortunately, natural infection is not always efficient in identifying resistant cultivars due to variable environmental conditions. Therefore, a more reliable screening method is needed to effectively select resistant genotypes. An inoculation technique was evaluated for identification of brown and orange rust resistance in sugarcane cultivars. Inoculations were performed in the field by placing a 0.5-ml urediniospore suspension in the leaf whorl of three individual sugarcane stalks per plant using a pipette. Symptoms developed on leaves of all the susceptible cultivars after 4 weeks, and appeared as a band of pustules. Plants were rated for their reaction to rust 4 weeks after inoculation. The optimum concentrations of inoculum for expression of brown and orange rust symptoms were determined. The most severe brown rust and orange rust symptoms were observed using inoculum containing 105 and 104 urediniospores/ml, respectively. Clones in several stages of the Canal Point breeding program were screened for their rust reaction by leaf whorl inoculation. The technique enabled rapid screening of a large number of cultivars in field plantings using a small amount of inoculum and limited man hours.

SELECTIVE CONTROL OF FALSE CLEAVERS IN RAPESEED WITH BENAZOLIN

Under field conditions, control of false cleavers (Galium spurium L.) in rapeseed (Brassica campestris L.) with three formulations (dimethylamine solution, ethyl ester emulsifiable concentrate, or ethyl ester wettable powder) of benazolin at 0.5 kg/ha was good. The ester formulations provided better control of false cleavers than the dimethylamine. There were no differences in degree of control following application of the dimethylamine formulation at the one-, three- or five-leaf whorl in the field. Under greenhouse conditions control of false cleavers and tolerance of rapeseed to benazolin dimethylamine at 0.25–0.75 kg/ha at the one-, two- or three-leaf whorl was good. Slight to moderate rapeseed injury in the form of stunting or thinning was observed 2 wk following application of benazolin under field conditions. The dimethylamine and emulsifiable concentrate formulations caused more injury than the wettable powder formulation. At harvest, these injury symptoms had disappeared. Control of false cleavers with benazolin did not result in an increase in yields of rapeseed over a weedy control.Key words: False cleavers, rapeseed, benazolin

DEVELOPMENTAL STUDIES OF ELODEA CANADENSIS MICHX.: I. MORPHOLOGICAL DEVELOPMENT AT THE SHOOT APEX

The shoot apex consists of a few initial cells at the tip of a thimble devoid of leaf initials for at least 100 μ. Leaf primorida are initiated from the superficial layer of cells, whereas branch buds arising among the; very youngest leaf primordia are produced deeper in the apex. Chinks occur where three or more cell walls come together. The tissue of the stem for the first 200 μ has no internodes. Two squamulae intervaginales lie on the adaxial surface of each leaf with which their development is associated. Internodes are initiated by the longitudinal growth and division of cells from the bottom of the leaf insertion disks. Cells of the young node divide longitudinally to increase the diameter of the nodal disk and to split the intercalary meristem into segments. Internodes are thus initiated with lacunae. Cells destined to become wood vacuolate at the seventh leaf whorl. Scalariform thickenings are produced but quickly disintegrate along with the rest of the xylem cells leaving a lacuna in the center of the stem. The bast surrounding the central xylem differentiates only slightly, beginning at the 20th leaf whorl, whereas the leaf traces and vertical cortical strands are apparent in younger tissue.