Genetic and environmental factors affecting grain texture in common wheat
Introduction
In common wheat (Triticum aestivum L.) the Pina-D1 and Pinb-D1 loci on the short arm of chromosome 5D encode for puroindolines a (Pin-A) and b (Pin-B), respectively (Giroux and Morris, 1997). Cultivars with soft grain possess wild-type a alleles at those loci (Gazza et al., 2005; Morris, 2002), and accumulate Pin-A and Pin-B on the surface of starch granules in the developing endosperm (Blochet et al., 1993; Gautier et al., 1994; Greenwell and Schofield, 1989; Morris et al., 1994). On the other hand, medium-hard and hard wheat cultivars contain mutant alleles at Pinb-D1 (Corona et al., 2001a, Corona et al., 2001b; Giroux and Morris, 1997, Giroux and Morris, 1998; Lillemo and Morris, 2000), and deposit reduced or null amounts of Pin-B on starch granules (Corona et al., 2001a, Corona et al., 2001b), whereas most wheats with extra-hard grain texture lack Pin-A due to the presence of a null allele at Pina-D1 (Gazza et al., 2005; Morris, 2002). Interestingly, the presence of a null Pin-A allele was found to drastically reduce the amount of wild-type Pin-B bound to starch granules as well (Corona et al., 2001a; Pogna et al., 2002), suggesting that deposition of Pin-B on starch granules in developing kernels requires the presence of Pin-A (Corona et al., 2001a; Giroux and Morris, 1998). More recently, the synergic effects of wild-type Pin-A and Pin-B on kernel hardness have been demonstrated in wheat lines transformed with both Pina-D1a and Pinb-D1a sequences, the softening effects of these alleles being correlated with accumulation of puroindolines on starch granules (Hogg et al., 2004).
The lipid-binding properties of puroindolines are likely involved in their interaction with the amyloplast membranes, and are also assumed to account for the permeabilizing properties of puroindolines on bacterial and fungal membranes (Blochet et al., 1993; Jing et al., 2003; Krishnamurthy et al., 2001). In addition, the affinity of puroindolines for polar lipid is claimed to be responsible for their effects on crumb structure of bread and rheological properties of wheat dough (Dubreil et al., 1997, Dubreil et al., 1998; Gautier et al., 1994; Igrejas et al., 2001).
Genes other than Pina-D1 and Pinb-D1 were shown to contribute to variation in kernel texture, their effects being very small relative to the puroindoline genes. In particular, quantitative trait loci (QTL) with single-factor effects on kernel texture occur on chromosomes 1A, 1B, 1D, 2A, 2B, 2D, 3A, 3B, 3D, 4B, 5AL, 5B, 5DL, 6B and 6D (Breseghello et al., 2005; Campbell et al., 1999; Galande et al., 2001; Igrejas et al., 2002; Perretant et al., 2000; Sourdille et al., 1996; Turner et al., 2004), whereas three other QTLs with interaction effects are located on chromosomes 5A, 6D and 7A (Sourdille et al., 1996). Additional factors correlated with hardness are protein content (Bushuk, 1998; Giroux et al., 2000; Igrejas et al., 2002; Martin et al., 2001; Slaughter et al., 1992), hectolitre weight (Pomeranz and Williams, 1990) and kernel weight (Giroux et al., 2000; Martin et al., 2001; Pomeranz and Williams, 1990).
Kernel hardness is a main determinant in end product quality because of its strong effects on milling conditions, granularity of flour and starch granule integrity. Here this important characteristic of wheat grain is analysed in 13 common wheat cultivars grown at seven locations in a field trial with three replications. Analysis of variance (ANOVA) was used to assess the effects that Pina-D1 and Pinb-D1 loci, puroindoline deposition on starch granules, protein content and kernel weight have on kernel texture, as determined by the Single Kernel Characterization System (SKCS).
Section snippets
Plant material, field trials and quality analyses
A group of 13 common wheat cultivars not related genetically to each other and showing contrasting hardness characteristics, were included in the present study. All genotypes were grown at six locations in North Italy in 2004–05, using a randomised block design with three replications. Each 10 m2 plot was sown with 450 kernels in 8 rows, 17 cm apart. Quality analyses were performed on mature kernels from the three replications combined. Protein content of kernels ground on a Cyclotec 1093 mill
Grain characteristics and allele compositions at Pina-D1 and Pinb-D1
Significant genetic variation was observed for kernel hardness, as measured in terms of SKCS units (Table 1). Seven cultivars (mean SKCS value=33.6, range=26.5–43.1) produced significant softer kernels compared to six cultivars with medium-hard texture (mean SKCS value=64.7, range=61.1–71.4). The soft texture class (STC) could not be differentiated statistically from the hard texture class (HTC) for kernel weight and protein content. However, 1000-kernel weight in the hard textured Pinb-D1b
Discussion
The wheat cultivars analysed here have been released in Italy or France in the period 1987–2003, and currently occupy approximately 41% of the Italian land cultivated with common wheat. Variation in kernel hardness amongst these cultivars was largely assignable to allele composition at the Pinb-D1 locus. In particular, allele composition Pina-D1a+Pinb-D1a in STC cultivars was found to be associated with low SKCS values (mean value=33.6) and deposition of high amounts of both Pin-A and Pin-B
References (41)
- et al.
Relation of several quality characteristics to hardness in two spring wheat crosses
Canadian Journal of Plant Science
(1975) - et al.
Expression of wild-type PinB sequence in transgenic wheat complements a hard phenotype
Theoretical and Applied Genetics
(2002) - et al.
Complete amino acid sequence of puroindoline, a new basic and cystine-rich protein with a unique tryptophan-rich domain, isolated from wheat endosperm by Triton X-114 phase partitioning
Federation of European Biochemical Societies Letters
(1993) - et al.
Genetic loci related to kernel quality differences between a softy and a hard wheat cultivar
Crop Science
(2005) Wheat breeding for end-product use
Euphytica
(1998)- et al.
Quantitative trait loci associated with kernel traits in a hard x soft wheat cross
Crop Science
(1999) - et al.
Puroindoline A-gene expression is involved in association of puroindolines to starch
Theoretical of Applied Genetics
(2003) - et al.
Variation in friabilin composition as determined by A-PAGE fractionation and PCR amplification, and its relationship to grain hardness in bread wheat
Journal of Cereal Science
(2001) - et al.
A tryptophan-to-arginine change in the triptophan-rich domain of puroindoline b in five French bread wheat cultivars
Journal of Genetics & Breeding
(2001) - et al.
A plant DNA minipreparation: Version II
Plant Molecular Biology Report
(1983)
Interaction of puroindoline with wheat flour polar lipids determines their foaming properties
Journal of Agricultural and Food Chemistry
Effect of puroindolines on the breadmaking properties of wheat flour
Cereal Chemistry
Genetic analysis of kernel hardness in bread wheat using PCR-based markers
Theoretical and Applied Genetics
Triticum aestivum puroindolines, two basic cysteine-rich seed proteins: cDNA sequence analysis and developmental gene expression
Plant Molecular Biology
Genetic and biochemical analysis of common wheat cultivars lacking puroindoline a
Theoretical and Applied Genetics
Molecular characterization of puroindolines and their encoding genes in Aegilops ventricosa
Molecular Breeding
A glycine to serine change in puroindoline b is associated with grain hardness and low levels of starch-surface friabilin
Theoretical and Applied Genetics
Wheat grain hardness results from highly conserved mutations in the friabilin components puroindoline a and b
Proceedings of the National Academy of Science USA
Association of puroindoline sequence type and grain hardness in hard red spring wheat
Crop Science
The chemical basis of grain hardness and softness
Cited by (29)
Visualized analysis of amino acids and organic acids in wheat caryopsis in response to multigenerational effects of elevated atmospheric CO<inf>2</inf> concentration
2023, Environmental and Experimental BotanyAn evaluation of selected engineering properties of polish durum wheat grain
2022, Journal of Cereal ScienceCitation Excerpt :The presence of correlations between kernel weight and protein content was also observed by El-Khayat et al. (2006) and Başlar et al. (2012). In some studies, protein content influenced grain hardness (Gazza et al., 2008). However, according to Mikulíková (2007), the compressive strength of kernels is not determined by their protein content, but by the composition and distribution of protein in kernels.
A wheat grain quantitative evaluation of vitreousness by light transmission analysis
2018, Journal of Cereal ScienceCitation Excerpt :This observation possibly suggests that light transmission, and thus vitreousness, is affected by the different genetic background of these wheat samples. Indeed, the soft line containing the wild-type puroindolines would have a lower starch-protein adhesion due to the higher puroindoline content at the starch granule surface in the endosperm (Igrejas et al., 2001; Gazza et al., 2008). The weak starch-protein adhesion could act as a network of internal microcracks.
Milling, processing and end-use quality traits of CIMMYT spring bread wheat germplasm under drought and heat stress
2018, Field Crops ResearchCitation Excerpt :Compared to the full irrigation optimum environments, harder and softer grains were found in the drought and heat stress environments, respectively. Based on the literature, grains are probably harder in drought stress due to higher protein content (Peterson et al., 1992) than to smaller grain size (Gazza et al., 2008). But this does not provide a completely clear explanation as to why softer grains under heat stress were found, where protein content was higher and the grain was smaller compared to drought stress.
Changes in the starch-protein interface depending on common wheat grain hardness revealed using atomic force microscopy
2015, Plant ScienceCitation Excerpt :Our AFM observation unambiguously revealed possible mechanical differences at the starch granule surface mediated by lipids in the soft endosperm. As shown previously, a Glycine to Serine mutation at position 46 in PINB, next to the tryptophan rich domain, reduces its lipid-binding capacity [52], leading to a lower amount of the deposited PINs at the starch granule surface and to a hardness increase in comparison with wheat grains containing the wild-type allele [4,53–55]. A higher association and stabilization of polar lipids around the starch granule with wild-type PINs was previously demonstrated [31] which could explain the unique AFM abrasion profile found in soft NIL grains.
Development of an aegilops longissima substitution line with improved bread-making quality
2014, Journal of Cereal ScienceCitation Excerpt :DAL1Sl showed very high protein content and significantly lower kernel weight compared with CS; the two traits were largely determined by environmental factors. Taking into account that the single kernel characterization system index correlates positively with protein content and negatively with kernel weight (Gazza et al., 2008), the increased grain hardness of CS-DAL1Sl might have been due to its high protein content and low kernel weight. It is also suspected that the additional 1Sl carried a minor hardness locus and contributed to the increased grain hardness in DAL1Sl.