K. G. Briggs

The association of culm anatomy with lodging susceptibility in modern spring wheat genotypes

Selection for lodging resistant cultivars in cereal breeding programs is difficult due to the challenge of screening for this trait under natural field conditions. The identification of easily measurable culm traits related to lodging resistance would simplify the selection process. The present study was conducted to determine if differences in culm anatomy exist among modern wheat genotypes differing in lodging susceptibility, and to determine the association between culm characters and lodging. From a 2-year field study conducted in Edmonton, Alberta, 13 spring wheat cultivars were chosen based on predetermined susceptibility to artificially induced lodging. Morphological and anatomical culm measurements were made visually and with an environmental scanning electron microscope. Genotypes differed (P < 0.05) for plant height, number of internodes per culm, basal internode length and diameter, culm wall thickness and the number of vascular bundles, but not for adventitious root frequency, lumen diameter or sclerenchyma ring thickness. Mean genotype field scores for artificially induced lodging were correlated (P < 0.05) with plant height (r= 0.51) and the length of the fourth basal internode (r= 0.51). Short, wide basal internodes and thick culm walls were characteristic of three lodging tolerant genotypes: Kohika, Sapphire and Olso. Nevertheless, despite such apparent genotype specific association between culm anatomy and field lodging, general applicable associations were not observed for most traits. The most practical and easily selectable trait for lodging resistance within a wheat breeding program remains plant height.

Early generation selection for yield and breadmaking quality of hard red spring wheat (Triticum aestivum L.em thell.)

SummaryEvaluation of the effect of selection in 3 different F3 populations of hard red spring wheat was achieved for yield and breadmaking quality parameters by examining the subsequent performance of F3 selections as populations of F5 lines. For baking absorption the mean performance of the F5 populations was positively related to the performance of the F3 selections in each of the 3 population-years. A significant relationship between the performance in F3 and in F5 was not obtained in any of the 3 years for bushel weight, flour ash, remix loaf volume, farinograph mixing tolerance index or for flour color grade. A high positive relationship between performance in F3 and F5 was found in two out of three years for protein content, flour protein content and 1,000-kernel weight. Predictive ability for sedimentation value, flour yield, farinograph development time and blend loaf volume was inconsistent for different population-years.A positive relationship between the yield of F3 plots and the mean yield of F5 populations was found in only 1 year. In the other 2 years the relationship between F3 and F5 yields ranged from nonsignificant to low, negative and significant. The latter results were possibly related to the relatively narrow high yielding range of the total F3 variability for yield which was sampled in each of those years. In all 3 population-years the highest yielding F5 populations were derived from F3 lines which were high yielding on a plot basis and also very high yielding relative to the yield of their adjacent control in the F3 nursery.Broad sense heritabilities calculated for the F5 generation support the thesis that selection between F3-derived populations would be a worthwhile plant breeding procedure for many of the breadmaking quality parameters.

Genetic and physiological analysis of doubled-haploid, aluminium-resistant lines of wheat provide evidence for the involvement of a 23 kD, root exudate polypeptide in mediating resistance

We have made use of a genetic approach to develop homozygous, near-isogenic germplasm for investigating aluminium (Al) resistance in Triticum aestivum L. A conventional backcross program was used to transfer Al resistance from the Al-resistant cultivar, Maringa, to a locally-adapted, Al-sensitive cultivar, Katepwa. At the third backcross stage, a single, resistant isoline (Alikat = Katepwa*3/Maringa) was chosen on the basis of superior root growth after 14 days of exposure to a broad range of Al concentrations (0 to 600 µM). Genetic analysis of doubled-haploid lines (DH) developed from this isoline suggested that resistance is controlled by a single dominant gene. Crosses between DH Alikat and DH Katepwa yielded an Al-resistant F1 population. Backcrossing this F1 population to DH Katepwa produced a population which segregated 1:1 for Al resistance, while selfing produced a population segregating 3 : 1 for Al resistance. Under conditions of Al stress, Al-resistant F2 plants released a suite of novel low molecular weight polypeptides into the rhizosphere. One of these polypeptides (23 kD) shows substantive Al-binding capacity and segregates with the resistant phenotype. While the precise mechanisms that mediate Al resistance are still unknown, this research has provided support for a possible role of the 23 kD exudate polypeptide in mediating resistance to Al. To more fully understand the role that this polypeptide plays in Al-resistance, we are attempting to clone this gene from microsequence data obtained from purified protein.

Effects of pre-anthesis moisture stress on floret sterility in some semi-dwarf and conventional height spring wheat cultivars

This study was conducted to investigate the response of some semi-dwarf Canada Prairie Spring wheat (Triticum aestivum) and conventional height (tall) cultivars of Canada Western Red Spring wheat to moisture stress at the booting stage. The effect on the frequency of sterile florets was determined in the two height groups. Drought tolerance was investigated using the electrolyte leakage test. The association of floret sterility with pollen viability under moisture stress conditions was also investigated. When fully watered, several of the semidwarf cultivars had a lower frequency of sterile florets compared with the tall cultivars. Moisture stress increased the frequency of sterile florets in both semi-dwarf and tall wheat cultivars. As moisture stress increased, the resulting sterility was significantly higher in semidwarf cultivars, relative to the tall cultivars (P ≤ 0.01). Comparisons between floret sterility and desiccation injury (estimated by electrolyte leakage tests) suggest that a high degree of...

Floret sterility and outcrossing in two spring wheat cultivars

A tendency for higher outcrossing potential in Canadian semidwarf wheat (Triticum aestivum L.) cultivars compared with tall Canadian cultivars has been postulated by breeders and seed growers. In the present study, the outcrossing potential of a semidwarf Canada Prairie Spring wheat (Triticum aestivum L.) cv. Cutler and a conventional height Canada Western Red Spring wheat, cv. Roblin was determined under controlled greenhouse conditions. Outcrossing of each cultivar was induced by applying moisture stress followed by exposure to pollen from a phenotypic marker stock, cv. P8901. In the controlled absence of external pollen, moisture stress significantly reduced seed set in both cultivars. Application of external pollen following moisture stress increased seed set significantly in Cutler and nonsignificantly in Roblin, and was associated with a higher level of floret opening in Cutler. Outcrossing frequency was also assessed by analysing progeny seed (selfed or outcrossed) using acidic polyacrylamide gel e...

Pedigree analysis of the origin of manganese tolerance in Canadian spring wheat (Triticum aestivum L.) cultivars

SummaryBreeding wheat (Triticum aestivum L.) for tolerance to manganese (Mn) might be in some cases more feasible and economical than use of soil amendments. As part of research on the heritability of Mn tolerance, a study on the level of Mn tolerance in Canadian wheat cultivars and its probable origin was accomplished by analysis of cultivar pedigrees and drawing phylogenetic maps to discern filial relationships. Cultivar tolerance to Mn was determined by relative root weight (RRW) in solution culture in the presence of 500 μM Mn. A total of 91 cultivars were screened, 76 of which were Canadian. These data, together with data from another 28 cultivars reported in the literature, were used to draw two pedigree maps, a map for Canadian cultivars only, and a map for the Mn-tolerant Canadian cultivars Norquay and Laura. Results indicated a range of tolerance to Mn among Canadian cultivars. Manganese tolerance, found in either Canadian or foreign germplasm, and of either recent or older selection or origin, seems to have originated from land races from Rio Grande do Sul, the southernmost state of Brazil. Tolerance may have been introduced into Canadian germplasm directly by the use of Brazilian cultivars as parents, or indirectly by the introduction of Mexican germplasm with Brazilian parentages. This information will help the plant breeder to develop plant breeding systems, and may also help in the study of the mechanisms for Mn tolerance in wheat.

PRODUCTION OF CALCIUM OXALATE CRYSTALS BY TWO SPECIES OF CYATHUS IN CULTURE AND INFESTED PLANT DEBRIS

Abstract Hyphae of Cyathus striatus and C. olla in culture and on infested plant debris were heavily encrusted with crystals. Scanning electron microscopy revealed that raphide-and styloid shaped crystals were associated with the hyphae of C. olla in canola stubble and in culture. Bipyramidal crystals were also present in culture. Distinct raphide druses developed on C. striatus hyphae colonizing wood chips, but in culture most crystals were bipyramidal or other shapes. Energy-dispersive X-ray microanalyses, FT/IR spectroscopy, and 13C NMR spectros copy determined that these crystals were calcium oxalate. This is the first report of calcium oxalate crystal production by these fungi. This characteristic has implications towards decomposition of organic matter, biomineralization, nutrient cycling, and soil genesis.

Aluminum tolerance in Canadian spring wheats

Abstract Canadian spring wheat cultivars (Triticum aestivum L.) and imported reference cultivars were grown in nutrient solution at varying aluminum concentrations and treatment durations. Relative root lengths, with and without aluminum, and hematoxylin ratings were the criteria used in evaluating aluminum tolerance. Relative root length results indicated a wide range in aluminum tolerance, but three tolerance classes (tolerant, intermediate and sensitive) were constructed based on reference cultivar performance. Most of the tolerant cultivars (HY 320, Romany, Kenya Kongoni, Maringa, PF 7748, and Cinquentenario) were all derived from Brazilian or Mexican cultivars. Vernon ranked as tolerant in contrast to its recurrent parent, Opal, which was intermediate in reaction to aluminum. Some of the older Canadian cultivars (Kitchener, Chinook, Renown, Marquis and Prelude) exhibited tolerance but the lineage of aluminum tolerance could not be determined. It appears that plant selection for characters other than ...

Genetic variation for aluminum tolerance in Kenyan wheat cultivars

Abstract A study was conducted to examine the genetic variability for tolerance to aluminum toxicity in several Kenyan cultivars. The F2 seedlings from eleven crosses between tolerant and intolerant cultivars exhibited a wide range of segregation ratios and indicated that aluminum tolerance in this group of parents was conditioned by two or more genes in each cross. Four of the individual crosses fitted a two‐gene model, and none fitted a single gene model. Expression of the tolerance genes in the F2 progeny was dependent on the genetic background. In three out of four crosses between tolerant parents, a high frequency of susceptible segregates was obtained. The segregation ratio tests performed on the F2 seedling populations suggested that the tolerant parents Romany, PF7748, K. Kongoni and K. Tembo had different tolerance genes. The results from crosses involving K. Fahari, K. Swara and Siete Cerros (all susceptible) indicated that aluminum susceptibility was controlled by recessive genes. The F2 progen...

Effectiveness of selection for plant characters of barley in simulated segregating rows

SummarySingle plants of 12 barley (Hordeum vulgare L. and H. distichum L.) cultivars were randomized to form simulated segregating (mixed) rows. There were 16 mixed rows 15 cm apart, each row containing 24 plants 5 cm apart. In addition, every third row was a control row of one of the cultivars, Bonanza. Each plant was harvested separately.The cultivars differed significantly for all seven characters measured. These seven characters fell into 3 performance groups. Group I characters, seeds/head, 1000 kernel weight, days to ripe and height, showed a higher variance in the mixed rows than in the control rows, had high average heritabilities, and were consistent in performance from one row to another when measured by correlation amongst the cultivars. In Group II, yield/plant and seeds/plant, variance, heritabilities and performance consistency were all low or non-significant. Group III, heads/plant, fell between Groups I and II. These results suggested that single plants with the desired genotype could be successfully selected for characters in Group I only.The frequency with which the most desirable genotype would actually have been chosen with 12.5% selection intensity generally confirmed the above conclusions but indicated that the degree of differences among genotypes was also important in selecting the most desirable genotypes.