Late Maturity Α-amylase Research Articles

Approaches to improve wheat grain quality: Breeding for the falling number

The falling number (FN) reflects the level of alpha amylase activity in grain/flour and serves as an international standard of grain quality. The lower the FN the lower the quality of grain and its price. The main factor responsible for high α amylase levels and low FN values is visible or hidden preharvest sprouting (PHS) under adverse weather conditions. The decisive role in obtaining consistently high FNs belongs to breeding for preharvest sprouting resistance (PHSR) and directly for the FN. In recent decades, significant progress has been made in understanding biochemical and molecular processes accompanying PHS and the genetic control (PHSR) and the FN, as well as in the development of methods of breeding for PHSR and the FN. However, breeding for these traits and the corresponding theoretical studies have not yet been properly developed or reflected in the Russian literature. This review illustrates the genetic complexity and context dependence of the PHSR and FN traits. A specific feature of breeding for high PHSR and the FN is that it involves eliminating late maturity α-amylase (LMA) genotypes from early hybrid generations and choosing parents for crossing; the choice of genetically distinct donors of target traits; methods of evaluating varieties and lines for PHSR and the FN under different environmental conditions; determining F2 population sizes with regard to the combination of PHSR, FN, high performance, grain quality, and other commercial traits. New methods and approaches in breeding have opened new prospects. They include the doubled haploid (DH) method, allowing homozygotes to be obtained from early hybrid generations, and DNA technologies, which permit a genetically reasonable selection of the PHSR and FN donors, pyramiding of desirable alleles, and efficient selection of desired offspring using closely linked molecular markers.

Approaches to improve wheat grain quality: breeding for falling number

Falling number (FN) reflects the level of alpha amylase activity in grain. The main factor responsible for high α amylase levels and low FN values is visible or hidden preharvest sprouting (PHS) under adverse weather conditions. In recent decades, great progress has been made in the understanding of biochemical and molecular processes accompanying PHS and the genetic control of preharvest sprouting resistance (PHSR) and FN, as well as in the development of methods of breeding for PHSR and FN. However, breeding for these traits and the corresponding theoretical studies have not yet been properly developed or reflected in the Russian literature. The purpose of the review is to fill this gap. It illustrates the genetic complexity and context dependence of the PHSR and FN traits and of major factors impairing FN. A specific feature of breeding for high PHSR and FN is that it involves elimination of late maturity α-amylase (LMA) genotypes in choosing parents for crossing and from early hybrid generations; choice of donors of target traits with regard to their genetic diversity; methods of evaluation of varieties and lines for PHSR and FN under different environmental conditions; determination of F2 population size with regard to combination of PHSR, FN, high performance, grain quality, and other commercial traits. New methods and approaches in breeding open new prospects. They include the doubled haploid (DH) method, allowing homozygotes to be obtained from early hybrid generations; and DNA technologies, which permit genetically reasonable selection of PHSR and FN donors, pyramiding of desirable alleles, and efficient selection of desired offspring using closely linked molecular markers.

Additive-dominance genetic model analyses for late-maturity alpha-amylase activity in a bread wheat factorial crossing population

Elevated level of late maturity α-amylase activity (LMAA) can result in low falling number scores, reduced grain quality, and downgrade of wheat (Triticum aestivum L.) class. A mating population was developed by crossing parents with different levels of LMAA. The F2 and F3 hybrids and their parents were evaluated for LMAA, and data were analyzed using the R software package 'qgtools' integrated with an additive-dominance genetic model and a mixed linear model approach. Simulated results showed high testing powers for additive and additive × environment variances, and comparatively low powers for dominance and dominance × environment variances. All variance components and their proportions to the phenotypic variance for the parents and hybrids were significant except for the dominance × environment variance. The estimated narrow-sense heritability and broad-sense heritability for LMAA were 14 and 54%, respectively. High significant negative additive effects for parents suggest that spring wheat cultivars 'Lancer' and 'Chester' can serve as good general combiners, and that 'Kinsman' and 'Seri-82' had negative specific combining ability in some hybrids despite of their own significant positive additive effects, suggesting they can be used as parents to reduce LMAA levels. Seri-82 showed very good general combining ability effect when used as a male parent, indicating the importance of reciprocal effects. High significant negative dominance effects and high-parent heterosis for hybrids demonstrated that the specific hybrid combinations; Chester × Kinsman, 'Lerma52' × Lancer, Lerma52 × 'LoSprout' and 'Janz' × Seri-82 could be generated to produce cultivars with significantly reduced LMAA level.

A rapid, automated method for measuring α-amylase in pre-harvest sprouted (sprout damaged) wheat

The quality of wheat for baking is critically dependent on the level of α-amylase (1,4-α-D-glucan glucanohydrolase, EC 3.2.1.1), which can be present as “late maturity α-amylase” (LMA), or due to pre-harvest sprouting due to high rainfall and humidity at the time of harvesting. The most commonly used method to measure α-amylase in wheat grain is the Hagberg Falling Number method, but values are also influenced by rheological properties of starch in the grain. In this study we describe a simple, rapid, automated method (Amylase SD) for measurement of α-amylase in pre-harvest sprouted (sprout damaged) wheat grain. The method (Amylase SD) measures the release of p-nitrophenol from 4,6-O-ethylidene-α-4-nitrophenyl-maltoheptaoside by α-amylase in the presence of α-glucosidase. The absorbance of p-nitrophenolate measured at 405 nm in a ChemWell®-T auto-analyser is directly related to the level of α-amylase activity present in the milled wheat grain extract. The Amylase SD method generated <6%CV and correlation to the Falling Number method was represented by an inflection point at ∼160 s. The precision, sensitivity and speed of this method provides an ideal alternative to the Falling Number method for measurement of α-amylase (sprout damage) in wheat grain in wheat breeding programmes or at grain receival points.

Wheat grain preharvest sprouting and late maturity alpha-amylase.

Preharvest sprouting (PHS) and late maturity α-amylase (LMA) are the two major causes of unacceptably high levels of α-amylase in ripe wheat grain. High α-amylase activity in harvested grain results in substantially lower prices for wheat growers and at least in the case of PHS, is associated with adverse effects on the quality of a range of end-products and loss of viability during storage. The high levels of α-amylase are reflected in low falling number, the internationally accepted measure for grain receival and trade. Given the significant losses that can occur, elimination of these defects remains a major focus for wheat breeding programs in many parts of the world. In addition, the genetic, biochemical and molecular mechanisms involved in the control of PHS and LMA as well as the interactions with environmental factors have attracted a sustained research interest. PHS and LMA are independent, genetically controlled traits that are strongly influenced by the environment, where the effects of particular environmental factors vary substantially depending on the stage of grain development and ripening. This review is a summary and an assessment of results of recent research on these important grain quality defects.

Analysis of high pI α-Amy-1 gene family members expressed in late maturity α-amylase in wheat (Triticum aestivum L.)

Late maturity α-amylase (LMA) is a genetic defect involving the synthesis of high pI isozymes of α-amylase encoded by α-Amy-1 genes during the later stages of grain development. The aims of this investigation were to determine both the number of expressed α-Amy-1 genes and their relative transcript abundance. Sub-cloning and sequencing of expressed high pI α-amylase genes in developing wheat seeds revealed three insertion/deletion patterns in the 3′ untranslated region and numerous single nucleotide polymorphisms at the 3′ end of α-Amy-1. The genetic variations defined 36 α-Amy-1 gene sequences that were expressed on the onset of LMA in doubled haploid progenies (SpM25, SpM52 and SpM127) derived from the cross Spica (LMA)/Maringa (non-LMA). Five isoelectric point groups were predicted based on the translated partial coding sequences. The potential application of quantitative real-time RT-PCR in screening wheat genotypes for LMA is discussed.Electronic supplementary materialThe online version of this article (doi:10.1007/s11032-013-9968-z) contains supplementary material, which is available to authorized users.

Genetic, Hormonal, and Physiological Analysis of Late Maturity α-Amylase in Wheat

Late maturity α-amylase (LMA) is a genetic defect that is commonly found in bread wheat (Triticum aestivum) cultivars and can result in commercially unacceptably high levels of α-amylase in harvest-ripe grain in the absence of rain or preharvest sprouting. This defect represents a serious problem for wheat farmers, and apart from the circumstantial evidence that gibberellins are somehow involved in the expression of LMA, the mechanisms or genes underlying LMA are unknown. In this work, we use a doubled haploid population segregating for constitutive LMA to physiologically analyze the appearance of LMA during grain development and to profile the transcriptomic and hormonal changes associated with this phenomenon. Our results show that LMA is a consequence of a very narrow and transitory peak of expression of genes encoding high-isoelectric point α-amylase during grain development and that the LMA phenotype seems to be a partial or incomplete gibberellin response emerging from a strongly altered hormonal environment.

Determination of the influence of climate on falling number of winter wheat in the dryland production areas of the Free State Province of South Africa

Preharvest sprouting (PHS) has been recognised as the primary cause of low falling numbers (FNs) in wheat. From recent research it is clear that there are a number of additional causes of low FNs, including late maturity α-amylase. FNs of certain cultivars have varied considerably from year to year and across environments in the wheat producing areas of the Free State Province. In this study we aimed to determine whether climatic conditions could contribute to unexpectedly low FNs. Eleven cultivars were planted over a 5 year period in five different locations in the Free State Province. Total rainfall, minimum and maximum temperatures and growing degree days were determined during six environmental periods. Results from this study indicated that rainfall during the later stages of grain filling and grain maturity had a negative effect on the FNs of 7 of the 11 cultivars, while maximum temperatures during these growing periods were positively correlated with FN in 8 of the 11 cultivars. Minimum temperatures just prior to harvest could also determine the FNs of certain cultivars. Principal component analysis identified three groupings of cultivars varying in the frequency of low FNs experienced over the 5 years of the study. It is clear from this study that rainfall just prior to harvest, and therefore PHS, was not the major factor responsible for the low FNs obtained during this study.

Association mapping of late maturity α-amylase (LMA) activity in a collection of synthetic hexaploid wheat

Late maturity α-amylase (LMA) is a genetic defect of wheat which results in the production of α-amylase, shown as substandard falling numbers, in the absence of preharvest rain and under cool temperatures during ripening. The present study is an attempt to use a whole-genome scan with DArT markers to identify chromosomal regions influencing LMA in synthetic hexaploid wheat (SHW). A high heritability estimate of 86.6% was calculated for LMA phenotype measured as optical density in a collection of 91 SHWs. Linkage disequilibrium extended up to 10 cM, and with controls for false positives, significant markers were detected at the chromosome 7B region previously linked to LMA in bread wheat, but not at the chromosome 3B region. Of potentially great interest is a region on chromosome 6B, which was identified as having a significant association with LMA phenotypes in the SHW accessions. Previous investigations suggested existence of an LMA gene on the long arm of 6B, but this is the first time it has been mapped to lie within the centromeric region of chromosome 6B, a region that harbours the Amy-1 genes and whose expression governs activity of the high pI α-amylase isoenzymes.

Genetics of late maturity α-amylase in a doubled haploid wheat population

Late maturity α-amylase (LMA) in wheat is a defect where high-isoelectric point (pI) α-amylase accumulates in the ripening grain. Wheat genotypes vary in expression from zero to high levels of α-amylase, the latter with detrimental consequences on their use for value-added end products. Expression in each genotype is characterised by varying numbers of grains affected and different levels in each grain. Analysis of a doubled haploid (DH) population (188 lines) from WW1842 × Whistler has identified significant QTL on chromosomes 2DL, 3A, 3B, 3D, 4B, 4D, 5DS and 5BL. The 4B LMA allele (P &lt; 0.0001) from Whistler is closely linked to the QTL for the ‘tall’ allele (P &lt; 0.0001) of the Rht-B1 gene. The 4D LMA QTL (P &lt; 0.0001) in WW1842 co-locates with the QTL for the ‘tall’ allele (P &lt; 0.0001) of the Rht-D1 gene. This study has shown for the first time that a DH cross between two semi-dwarf cultivars with low or no LMA produces ~25% of progeny lines of the ‘tall’ genotypes with a high frequency of LMA. This is attributed to the large additive positive effects from the combination of one recessive ‘tall’ Rht-B1 gene and one recessive ‘tall’ Rht-D1 gene. High-yielding semi-dwarf genotypes with different combinations of Rht-B1 and Rht-D1 alleles which have very low or non-existent LMA expression (e.g. WW1842 and Whistler) may meet industry criteria for registration as commercial wheat varieties. However, when they are used as breeding lines, the cross produces some progeny genotypes with severe levels of LMA. These LMA genotypes comprise the gibberellic acid-sensitive ‘tall’ progenies and a very small proportion of semi-dwarfs. Thus, it is of paramount importance to screen the defect in wheat breeding programs. The suite of QTL identified for LMA will enable the use of marker assisted selection in the pyramiding of the beneficial QTL to maximise yield and minimise (or eliminate) LMA in semi-dwarf genotypes.

Late maturity α-amylase in synthetic hexaploid wheat

Late maturity α-amylase (LMA) is a genetic defect that is fairly widely spread in bread wheat (Triticum aestivum L.) germplasm, and recently detected in durum cultivars, which can result in unacceptably high α-amylase activity (low falling number) in ripe grain. LMA has also been observed at unexpectedly high frequency and severity in synthetic hexaploid wheats derived from the interspecific hybridisation of Triticum durum (AABB) and Aegilops tauschii (DD). Since synthetic hexaploids represent an important new source of resistances/tolerances to a range of biotic and abiotic stresses for wheat breeders, there is a pressing need to understand the mechanisms involved in LMA in synthetics and develop strategies for avoiding its adverse effects on grain quality. The objectives of this study were to firstly, compare the LMA phenotype of synthetics that varied for plant height, secondly, to characterise the LMA phenotype in groups of synthetics derived from the same durum parents and finally to determine whether LMA in primary synthetics is associated with the QTL previously reported in conventional bread wheat. More than 250 synthetic hexaploids, a range of durum cultivars and a doubled haploid population derived from Worrakatta (non-LMA) × AUS29663 (high LMA synthetic) were phenotyped and genotyped with markers reported to be linked to LMA in conventional bread wheat and markers diagnostic for the semi-dwarfing gene, Rht1. More than 85% of synthetics were prone to LMA, approximately 60% ranked as very high. Genetic control of LMA in synthetic hexaploids appeared to involve QTL located on 7B, and to a lesser extent 3B, similar to bread wheats. However, the LMA phenotype of many synthetic hexaploids appeared to be more extreme than could be explained by comparisons with bread wheat even taking into account the apparent absence of Rht1 in most genotypes. Other mechanisms, possibly triggered by the interaction between the AABB and DD genomes cannot be excluded. The presence of wild type rht1 in most synthetic hexaploids and their extreme height is difficult to reconcile with the semi-dwarf, Rht1, stature of many of the durums used in the interspecific hybridisation process. Mechanisms that could explain this observation remain unclear.

Improving the accuracy of selection for late maturity α-amylase in wheat using multi-phase designs

The assessment of grain defect traits is assuming greater importance in wheat germplasm selection. Late maturity α-amylase is one such characteristic that renders wheat unsuitable for high value end products, even though the grain may appear sound. Phenotyping defect traits typically involves a multi-phase process, where genetic material for assay has been affected by non-genetic sources of variation in one or more previous linked stages of experimentation or preparation. The adoption of appropriate statistical design and analysis methods in these situations is, however, not widespread. Substantial sources of non-genetic variation were identified in the analysis of a designed experiment to measure late maturity α-amylase expression, indicating the potential for improved selection decisions. A simulation study based on these results suggests that significant gains over current methods in the accuracy of phenotyping this grain defect can be achieved with sound multi-phase statistical design and analysis techniques. Although restricted in scope, the simulation also indicates that a considerable increase in estimated heritability could be expected from the proposed methodology.

Genetic variation for quality traits in synthetic wheat germplasm

Synthetic hexaploid wheats offer breeders ready access to potentially novel genetic variation associated with the D genome of Aegilops tauschii. In order to assess the application of this germplasm to wheat quality improvement, collections of primary and derived synthetic hexaploid wheat lines were surveyed for traits that determine colour and colour stability in Asian noodles and the frequency of a genetic defect know as late maturity α-amylase (LMA). The range of variation was then compared with bread wheat and durum wheat cultivar collections. Primary synthetics contained substantial genetic variation for quality traits associated with colour and colour stability of Asian noodles including near-zero extremes for polyphenol oxidase and lipoxygenase. These extremes represent a significant advantage compared with current bread wheat cultivars and are similar to the best durum wheats. While alternative strategies for reducing polyphenol oxidase and lipoxygenase are available, the synthetics nevertheless provide a useful resource for wheat breeders attempting to develop improved wheat cultivars for the Asian noodle market. Unfortunately, however, most primary synthetics were prone to late maturity α-amylase and mature grain contained unacceptably high levels of α-amylase. Elimination of this genetic defect, or selection within breeding populations for low or non-LMA, is both time consuming and labour intensive and presents a significant obstacle to exploitation of variation for other traits. As proof of concept, near-zero polyphenol oxidase (PPO) lines, free from LMA, were recovered from backcross populations involving a high LMA primary synthetic.

α-Amylase and programmed cell death in aleurone of ripening wheat grains

Late maturity alpha-amylase (LMA) in wheat is a genetic defect that may result in the accumulation of unacceptable levels of high pI alpha-amylase in grain in the absence of germination or weather damage. During germination, gibberellin produced in the embryo triggers expression of alpha-Amy genes, the synthesis of alpha-amylase and, subsequently, cell death in the aleurone. LMA also involves the aleurone and whilst LMA appears to be independent of the embryo there is nevertheless some evidence that gibberellin is involved. The aim of this investigation was to determine whether the increase in alpha-amylase activity in LMA-prone genotypes, like alpha-amylase synthesis by aleurone cells in germinating or GA-challenged grains, is followed by aleurone cell death. Programmed cell death was seen in aleurone layers from developing, ripe and germinated grains using confocal microscopy and fluorescent probes specific for dead or living cells. Small pockets of dying cells were observed distributed at random throughout the aleurone of ripening LMA-affected grains and by harvest-ripeness these cells were clearly dead. The first appearance of dying cells, 35 d post-anthesis, coincided with the later part of the 'window of sensitivity' in grain development in LMA-prone wheat cultivars. No dead or dying cells were present in ripening or fully ripe grains of control cultivars. In germinating grains, dying cells were observed in the aleurone adjacent to the scutellum and, as germination progressed, the number of dead cells increased and the affected area extended further towards the distal end of the grain. Aside from the obvious differences in spatial distribution, dying cells in 20-24 h germinated grains were similar to dying cells in developing LMA-affected grains, consistent with previous measurements of alpha-amylase activity. The increase in high pI alpha-amylase activity in developing grains of LMA-prone cultivars, like alpha-amylase synthesis in germinating grains, is associated with cell death, providing further evidence for the involvement of gibberellin in the LMA response.

WHEAT SEED QUALITY IN RESPONSE TO MOLYBDENUM AND PHOSPHORUS

ABSTRACT Similarity of the molybdate and phosphate anions suggests that these nutrients are likely to interact in plant metabolism. This relationship has not been explained with respect to seed quality. The objective of this study was to examine wheat (Triticum aestivum L.) seed quality in response to varying nutrient solution concentrations of molybdenum (Mo) and phosphorus (P). Seeds of wheat, cultivar Tugela DN, were produced in pots under controlled environmental conditions. Plants were watered twice a week with a modified Hoagland's nutrient solution containing no Mo and 10 mg L−1 P, supplied from a separate source, as a control. Separate Mo (1.8, 3.6, and 5.4 mg L−1) and P (10, 20, and 30 mg L−1) treatments were also applied simultaneously as the Hoagland's solution to plants from one week after pre-germination in a growth chamber to seed maturity. Seed yield, germination, α-amylase activity and total protein concentration were determined in seeds harvested at a moisture content of about 12%. Results showed that P did not affect Mo suppression of α-amylase activity, but there was a negative interaction between Mo and P with respect to seed germination. Both Mo and P increased seed protein content, seed yield and seedling vigor. These data suggest that while P fertilization contradicts the induction of seed dormancy by Mo, this interaction does not negate the reduction of late maturity α-amylase activity by Mo. Since late maturity α-amylase reduction is the major goal of pre-harvest sprouting alleviation, these data could be useful in providing an agronomic tool to alleviate pre-harvest sprouting while simultaneously enhancing wheat seed vigor.

Screening methods and identification of QTLs associated with late maturity α-amylase in wheat

The synthesis of high levels of germination-type (high pI isozymes) α-amylase was induced in wheat genotypes prone to late maturityα-amylase (LMA) following the exposure of detached tillers to cool temperature during grain development. The detached tiller method was successfully applied to a range of genotypes and to a doubled haploid (DH) population derived from the cross Cranbrook (LMA genotype) × Halberd (low amylase). The number of grains in ripe, treated tillers that contained high pI α-amylase isozymes was measured using an ELISA antibody kit highly specific for high pI isozymes. Quantitative trait loci (QTL) controlling the expression of LMA in wheat were detected in DH population Cranbrook × Halberd. The DH population and parents were sown in 2 replicated sowings at the same location with sowing times differing by 2 weeks. QTL analyses were conducted separately for each sowing, but results from both sowings were consistent and indicated a highly significant (it p > 0.01) QTL on the long arm of chromosome7B, with Cranbrook contributing the higher value allele. A second QTL with less significant effect was found on the long arm of chromosome 3B, on the basis of data from the first sowing.

Germplasm improvement for preharvest sprouting resistance in Chinese white-grained wheat: An overview of the current strategy

Most modern white-grained wheat (Triticum aestivum L.) cultivars in China lack sprouting resistance. Some white grain varieties showed lower preharvest sprouting percentage in different years. Tolerance to sprouting in most cultivars comes from the varieties, Wanxian White, Fulingxuxu White, Suiningtuotuo, and Yongchuan White. The α-amylase inhibitor gene under a wheat genetic background inhibited α-amylase activity and delayed sprouting. The falling number of six suspected sources, out of 835Chinese leading varieties since 1950', was independent of late maturityα-amylase.

Quantitative trait locus analysis of late maturity a-amylase in wheat using the doubled haploid population Cranbrook Halberd

Mapping of the late maturity α-amylase (LMA) gene using quantitative trait locus (QTL) analysis represents an important step in identification of potential molecular markers that would greatly improve efficiency and accuracy of screening for LMA. QTL controlling the expression of LMA in wheat were detected in a doubled haploid (DH) cross/population derived from wheat (Triticum aestivum L. em. Thell) cultivars Cranbrook (LMA source) and Halberd (non-LMA). The DH population and parents were sown in replicated trials at Narrabri with sowing times differing by 2 weeks. Cool temperature treatment of detached tillers was used to induce expression of LMA in lines carrying the defect. The number of grains in ripe, treated tillers that contained high pI (malt, germination type) α-amylase isozymes was measured using an ELISA antibody kit highly specific for high pI isozymes. QTL analyses were conducted separately for each sowing, but results from both sowings were consistent and indicated that there was a highly significant (P &lt; 0.001) QTL on the long arm of chromosome 7B (accounting for 31% of the variation in the first experiment), with Cranbrook contributing the higher value allele. A second QTL that accounted for 13% of the variation was found close to the centromere on chromosome 3B. Although it was less important than the QTL on 7B it was nevertheless still significant (P &lt; 0.05).

Induction of late maturity a-amylase in wheat by cool temperature

Wheat genotypes prone to late maturity α-amylase (LMA) produced high levels of germination-type (high pI isozymes) α-amylase following exposure to cool temperature during grain development. Plants grown in the glasshouse, plants grown in the field and transplanted to the glasshouse after flowering, and tillers taken from field or glasshouse grown plants all responded in a similar manner. Plants or detached tillers can therefore be used in screening tests to identify germplasm with the LMA genotype. The cool temperature treatment was effective when applied continuously from shortly after flowering until near-ripeness, or when limited to the phase of grain development (26–35 days after anthesis) in LMA-prone genotypes that appears to be most sensitive to cool temperature. Based on these observations, guidelines for screening wheat germplasm are proposed and the advantages of using detached tillers discussed. The detached tiller method was successfully applied to a range of genotypes, some of which were known to be prone to LMA, and to a doubled haploid population derived from the cross Janz (low amylase) BD159 (LMA genotype). The preliminary data from this population were consistent with control by a single gene and similar therefore to the model proposed previously for cv. Spica.

Regulation of high pI α-amylase synthesis in wheat aleurone by a gene(s) located on chromosome 6B

Synthesis of high and low pI α-amylase in germinating wheat grains and GA3-treated de-embryonated grains of Chinese Spring (CS) and its ditelosomic derivative (CS dit 6BS) were compared and related to high pI α-amylase production in grains affected by late maturity α-amylase (LMA). In de-embryonated grains of CS dit 6BS (lacking the long arm of chromosome 6B) treated with GA3, synthesis of high pI α-amylase isozymes controlled by Amy-1 genes on chromosomes 6A and 6D was dramatically reduced compared to Chinese Spring. The results suggest the presence of a gene(s) on the long arm of chromosome 6B, which is (are) required for GA-induced α-amylase synthesis in the aleurone. Similarly, in wheat grains affected by LMA, high pI α- Amy genes on the group 6 chromosomes are activated apparently by a single gene, tentatively located on chromosome 6B. Both genes may be part of the GA-induced amylase synthesis pathway in the aleurone. By contrast, synthesis of the high pI α-amylase isozymes in the early stages of germination of CS dit 6BS grains was very similar to CS. This contrast between GA3-treated de-embryonated grains and germinating grains could be explained by control of α-amylase synthesis in scutellum in the early stages of germination being different to that in GA3-treated aleurone.