The genetic control of highly restricted branching in narrow-leafed lupin (Lupinus angustifolius L.)

Most current cultivars of narrow-leafed lupin have an indeterminate growth habit such that vegetative growth continues while the pods are being filled, causing strong intra-plant competition for assimilates. Restricted-branching (RB) genotypes can reduce this tendency and raise the proportion of the plant's biomass going into grain. Studies on the inheritance of the RB trait showed that two spontaneous mutants, P25598 and P21227, each carried a single incompletely dominant allele conferring the trait, whereas two other spontaneous mutants, P24743 and P25582, and two induced mutants, P26021 and P21238, each carried a single recessive allele conferring the trait. The RB alleles present in P26021 and P21238 seem to be the same, and to be at the same locus as (or tightly linked to) the allele controlling the RB trait in P21227. Similarly, the genes present in P21227 and the induced mutant P25735 appear to be the same when these lines are crossed. However, they do not behave the same in crosses with P26021: thus we propose that there are at least three alleles at the same locus (or at tightly linked loci) that confer RB. Normal-branching plants that are heterozygous at an RB locus generally have fewer leaves on the uppermost branch than homozygous-normal plants. Similarly, RB plants that are heterozygous generally have fewer branchless nodes on the main stem than homozygous-RB plants. The RB trait is associated with a small but significant reduction in the number of leaves on the main stem. However, this relationship is weak and will not prevent plant breeders from selecting both early- and late-flowering RB genotypes. This revised version was published online in July 2006 with corrections to the Cover Date.     

Bio-extraction of Potassium from Glauconite Nano-particle in an Alfisols of Southern India

ABSTRACT

Glauconite is a potassium (K) bearing mineral, which generally contains 6–10% K₂O and mostly available in various natural deposits in India. Glauconite mineral was converted to nano-particle form by grinding in a high-energy ball mill. The release of K from glauconite nano-particle in soil was studied in a pot culture experiment. Five different treatments viz., 0 mg K₂O kg^?1, 100 mg K₂O kg^?1, 150 mg K₂O kg^?1, 200 mg K₂O kg^?1 used glauconite nano-particle (GNP) as a K source and 100 mg K₂O kg^?1 from muriate of potash (MOP), were applied in soil to grow maize (Zea mays L.) plant. The highest K⁺ concentration was observed in shoot at the application of 200 mg K₂O kg^?1 through GNP and recorded 2 times more K⁺ concentration in shoots as compared to 0 mg K₂O kg^?1 treatment whereas 1.1 times more than the MOP treated soil at 5^th harvesting stage. Selected plant physiological parameters namely electrical conductivity of plant cell, height, leaf area and nitrate reductase activity were also recorded maximum at 200 mg K₂O kg^?1 GNP treated soil. Overall, glauconite nano-particle could supply K throughout the growth period and enhanced biomass yield of maize plant without showing any K deficiency symptom.     

Natural outcrossing in common buckwheat

Common buckwheat is an obligate cross pollinating crop because of its sporophytic self-incompatibility system. Therefore a study to assess the extent of natural outcrossing was undertaken for two years at Morden and Portage la Prairie, Manitoba using the semi-dwarf character, which is due to a homozygous genotype with regard to a single recessive gene, as a marker. The semi-dwarf genotype was grown in 100 m rows running in four directions at 90 ° from a central 36 m² plot of a normal, tall variety. At maturity, seed samples were taken from the semi-dwarf population at designated intervals. At least 200 F₁ seeds from each sample were grown in the greenhouse to the 3-4 leaf stage and the proportion of tall plants was used to determine the percentage of outcrossing. Approximately 50% outcrossing occurred where the semi-dwarf plants were immediately next to the normal plants and then the proportion decreased with increasing distance. Although outcrossing occurred throughout the distance tested, there were no significant differences from 12 m onward from the pollen source. Lack of directional influence in outcrossing and a sharp reduction in the proportion of tall plants within a 3 m distance from the pollen source suggested that wind was not a major factor in dispersing the buckwheat pollen over long distances. Although a substantial cross pollination was limited to a few metres from the pollen source, nearly 1% outcrossing occurred even at 100 m. Since the distance in this experiment was limited to 100 m from the pollen source, the present results do not allow us to recommend the minimum isolation distance required to meet certain standards for buckwheat seed production. This revised version was published online in July 2006 with corrections to the Cover Date.     

Inheritance of wheat stem rust resistance in triticale

Genetic studies were conducted on nine triticale cultivars and lines lo determine the presence and identity of stem rust resistance genes. The lines were intercrossed and their F₂ and F₃ generations were tested with selected pathotypes of Puccinia graminis tritici. Segregation in seedling tesis showed the presence of two new genes SrLal and SrLa2 in ‘Lasko’, SrBj anil SrJ in ‘Bejon’. SrVen in ‘Currency’, SrBj in ‘Abacus’ and ‘RM4’ and SrNin in ‘Tahara’, ‘Maidan’ and ‘Madonna’ SrBj, SrNin, SrLal and SrLa2 were genetically independent and each conferred resistance to the currently important Australian P. graminis tritici pt 34-2.12.13, whereas SrJ and SrVen conferred moderately susceptible reactions to the same pathotype. SrVen segregated independently of SrBj, but the relationship of SrVen with the other genes was noi determined. The typical low infection types conferred by SrBj and SrJ were best expressed at temperatures above 21 C, Prolamine separations nsinj; sodium dodecyl sulphate-polyacrylamide gel elcclrophoresis confirmed that SiNin and SrBj were located in chromosome 2R. The gene SrLal behaved as a third allele at or near the Sr27, SrSatu locus in chromosome 3R, The present work demonstrated that chromosomes 2R and 3R are important bearers of genes Tor stem rust resistance in hexaploid iriticale.     

Real-time PCR Quantification and Mycotoxin Production of Fusarium graminearum in Wheat Inoculated with Isolates Collected from Potato, Sugar Beet, and Wheat

ABSTRACT Fusarium graminearum causes Fusarium head blight (FHB) in small grains worldwide. Although primarily a pathogen of cereals, it also can infect noncereal crops such as potato and sugar beet in the United States. We used a real-time polymerase chain reaction (PCR) method based on intergenic sequences specific to the trichodiene synthase gene (Tri5) from F. graminearum. TaqMan probe and primers were designed and used to estimate DNA content of the pathogen (FgDNA) in the susceptible wheat cv. Grandin after inoculation with the 21 isolates of F. graminearum collected from potato, sugar beet, and wheat. The presence of nine mycotoxins was analyzed in the inoculated wheat heads by gas chromatography and mass spectrometry. All isolates contained the Tri5 gene and were virulent to cv. Grandin. Isolates of F. graminearum differed significantly in virulence (expressed as disease severity), FgDNA content, and mycotoxin accumulation. Potato isolates showed greater variability in producing different mycotoxins than sugar beet and wheat isolates. Correlation analysis showed a significant (P < 0.001) positive relationship between FgDNA content and FHB severity or deoxynivalenol (DON) production. Moreover, a significant (P < 0.001) positive correlation between FHB severity and DON content was observed. Our findings revealed that F. graminearum causing potato dry rot and sugar beet decay could be potential sources of inoculum for FHB epidemics in wheat. Real-time PCR assay provides sensitive and accurate quantification of F. graminearum in wheat and can be useful for monitoring the colonization of wheat grains by F. graminearum in controlled environments, and evaluating wheat germplasms for resistance to FHB.     

A Distributed Lag Analysis of the Relationship Between Gibberella zeae Inoculum Density on Wheat Spikes and Weather Variables

ABSTRACT In an effort to characterize the association between weather variables and inoculum of Gibberella zeae in wheat canopies, spikes were sampled and assayed for pathogen propagules from plots established in Indiana, North Dakota, Ohio, Pennsylvania, South Dakota, and Manitoba between 1999 and 2005. Inoculum abundance was quantified as the daily number of colony forming units per spike (CFU/spike). A total of 49 individual weather variables for 24-h periods were generated from measurements of ambient weather data. Polynomial distributed lag regression analysis, followed by linear mixed model analysis, was used to (i) identify weather variables significantly related to log-transformed CFU/spike (the response variable; Y), (ii) determine the time window (i.e., lag length) over which each weather variable affected Y, (iii) determine the form of the relationship between each weather variable and Y (defined in terms of the polynomial degree for the relationship between the parameter weights for the weather variables and the time lag involved), and (iv) account for location-specific effects and random effects of years within locations on the response variable. Both location and year within location affected the magnitude of Y, but there was no consistent trend in Y over time. Y on each day was significantly and simultaneously related to weather variables on the day of sampling and on the 8 days prior to sampling (giving a 9-day time window). The structural relationship corresponded to polynomial degrees of 0, 1, or 2, generally showing a smooth change in the parameter weights and time lag. Moisture- (e.g., relative humidity-) related variables had the strongest relationship with Y, but air temperature- and rainfall-related variables also significantly affected Y. The overall marginal effect of each weather variable on Y was positive. Thus, local weather conditions can be utilized to improve estimates of spore density on wheat spikes around the time of flowering.     

Bacterial blight of rice and its control in Nepal

Research on Xanthomonas oryzae pv. oryzae, the bacterial blight of rice pathogen, was initiated at the Institute of Agriculture and Animal Science (IAAS) with the main objective of assessing the population structure of X. o. pv. oryzae through the use of both conventional and molecular markers in combination with virulence typing. A high DNA polymorphism was detected in the pathogen populations using different DNA probes and rep-PCR primers. Most strains were avirulent to cultivars containing the bacterial blight resistance gene Xa-21, which suggested the strategy that targets gene deployment is feasible in Nepal.     

Susceptibility in oats to stem rust induced by co-infection with leaf rust

Induction of susceptibility in oats to a normally avirulent pathotype of Puccinia graminis f.sp. avenae was studied in the presence of different pathotypes of P. coronata f.sp. avenae . Induction occurred on seedlings only in the presence of a virulent culture of P. coronata avenae and was not dependent on time or order of inoculation of either pathogen. This phenomenon was restricted to seedlings of lines possessing the Pg-a source of oat stem rust resistance. The specificity of induced susceptibility can be used as a valuable bioassay for screening and identifying Pg-a . Induced susceptibility occurred only at the seedling stage, and apparently provides no obstacle to the use of Pg-a as a source of stem rust resistance in oats.