Fw Ellison

Enzymes from rain-damaged and laboratory-germinated wheat I. Effects on product quality

A range of products was made from flours derived from five Australian wheats subjected to a laboratory wetting treatment in a rain-simulator and compared with others affected by field weathering. Severe product defects were observed in Cantonese and Korean noodles, while lesser but still deleterious effects were observed with Arabic flat-breads. However, the quality of pan breads made from rain-damaged grain was better than that from corresponding untreated wheats, although loaves made from the most damaged cultivar, Hartog, could not be sliced mechanically. Comparison of increased levels of enzyme activity for six enzymes (a-amylase, protease, catalase, peroxidase, lipoxygenase and phenol oxidase) from these varieties in grain and flour revealed that changes in flour properties and product defects were related to levels of flour protease and a-amylase. The significance of the levels of individual enzymes is considered in relation to aspects of individual product quality. Information on the tolerance and sensitivity to rain damage of a range of products is derived from the results.

Inheritance of physiological characters associated with yield variation in bread wheat

SummaryPost anthesis physiological characters were examined in four genotypes and a diallel set of their progenies. Variation in total carbon uptake by photosynthetic tissue above the flag leaf node was primarily related to leaf area and ear size differences during the early grain filling period. Flag leaf apparent photosynthetic rates during the late grain filling period were closely correlated with flag leaf chorophyl levels. During the period of rapid growth, genotypes differed in the proportion and total quantity of current assimilate translocated to the grain. Total rather than proportional translocation was correlated with grain number and grain yield. Differences in total grain protein were primarily related to total plant nitrogen at anthesis and secondarily to the proportion of this nitrogen translocated to the grain. The level of post anthesis nitrate reductase activity decreased with increasing flag leaf age, but genotypic differences were not closely related to differences in total grain protein contents.Significant general combining ability effects were found for flag leaf chlorophyll levels, flag leaf photosynthetic rates at higher illuminances during the late grain filling period, total plant carbon uptake, total ear carbon uptake, and proportional carbon translocation to the grain. A preponderance of significant general combining ability variances suggests that additive gene action is of particular importance in the inheritance of these physiological characters.

Inheritance of root regrowth as an indicator of apparent aluminum tolerance in triticale

Aluminum (Al) toxicity is a predominant growth-limiting factor in acid soils. Better understanding of the genetic mechanisms by which plants tolerate toxic Al expedites the development of tolerant plant genotypes. The genetic behavior of apparent Al tolerance in two triticale crosses as measured by root regrowth of seedlings at a level of 10 μg · g−1 Al stress in nutrient solutions was analyzed by following a bi-parental (BIP) mating design. The validity of the additive-dominance genetic model was tested with relevant gene effects estimated. The continuous variation of regrown root length showed that apparent Al tolerance was a metrical character in nature. Both the additive and dominance effects were responsible while the additive effects played a major role in the expression of Al tolerance. Non-allelic interaction (or epistasis) was indicated from the inadequacy of the model and different types of epistatic gene effects were detected in the two crosses. These results suggest that Al tolerance was of polygenic system rather than simply inherited. One to three pairs of genes were involved in apparent Al tolerance for the parental difference. The moderately high value of estimates of heritability together with the estimates of genetic advance (GA) could be used in planning a selective breeding program aimed at greater Al tolerance.

Optimal regimes of selection for grain yield and harvest index in spring wheat

SummaryAlternative strategies of multi-site testing of advanced lines in the northern wheat belt of New South Wales have been evaluated, using genetic parameters for large plot grain yield and hill plot harvest index estimated from dryland and irrigated trials at regional sites during 1975–1981. The average pairwise genetic correlation of large plot grain yields recorded at different sites within years was 0.45±.03, with a mean repeatability within trials of 0.56±.05. Harvest index measured in 20-grain hill plots in 1978 showe genetic correlations of 0.98±.08 with plot yield at the same site, and 0.39±0.06 with plot yield assessed at other sites in the same year.The genetic correlation between harvest index in hill plots and total biological yield in large plots at the same site was 0.84±.13, the relationship showing no evidence of curvilinearity. Selection for harvest index in hill plots is therefore expected to lead to an increase in biological yield as well as grain yield in the breeding populations studied. Quantitative genetic theory suggests that the response to selection for grain yield can be increased by approximately 40% with an initial screening using hill plot harvest index at three sites instead of one, and reallocation of resources in the first stage of large plot yield assessment to include 6–8 sites, rather than dryland and irrigated trials at a single location.

Combining ability for aluminium tolerance in triticale

Root re-growth, following aluminium (Al) stress, has been used as an indicator of Al stress tolerance. Genetic variation in root re-growth characteristics among eight triticale genotypes was investigated by a diallel analysis. Highly significant variation due to both general combining ability (GCA) effects and specific combining ability (SCA) effects indicated that both additive effects and non-additive effects were important in explaining the genetic variation for Al tolerance. The high estimates of heritability and the predictability ratio for root re-growth revealed the preponderance of additive genetic variance in the inheritance of Al tolerance. Differences in patterns of GCA effects and SCA effects among the parents provided strong evidence that the genetic control of variation for Al tolerance as assessed by root re-growth was a complex polygenic system. Three Al-tolerant genotypes, Tahara, Abacus, and 19th ITSN 70-4, were found to be the best general combiners for larger root re-growth, and they could be used in hybridization programmes to improve Al stress tolerance by following a simple pedigree method of selective breeding.

The potential use of gametophytic factors in the production of F1 hybrid varieties

SummaryAttention is drawn to the potential of gametophytic (Ga) factors which act only in pollen, or preferably in both pollen and egg cells, in the production of F1 hybrids in a wide range of crop plants when used in conjunction with linked chromosomal male sterility genes. The genetic stocks required to develop practical hybrid production systems are outlined along with the potential advantages and disadvantages of the use of gametophytic factors in hybrid breeding systems.

Differential response and genetic analysis of acidic stress tolerance, with particular reference to aluminium stress tolerance in triticale

Differential aluminium (Al) resistance responses can be established through measurement of root re-growth characters in hydroponics with a modified Al pulse method. A screening concentration of 10 mg·L−1 Al (pH 4.5) imposed for 24 hr duration provides efficient discrimination between resistant and sensitive cultivars. The extent of root re-growth provides useful indices of Al resistance.