Accelerated development of quality protein maize hybrid through marker‐assisted introgression of opaque‐2 allele

Vivek Maize Hybrid 9‐ a popular single‐cross hybrid developed by crossing CM 212 and CM 145 was released for commercial cultivation in India. The parental lines, being deficient in lysine and tryptophan, were selected for introgression of opaque‐2 allele using CML 180 and CML 170 as donor lines through marker‐assisted backcross breeding. The opaque‐2 homozygous recessive genotypes with >90% recovery of the recurrent parent genome were selected in BC₂F_2, and the seeds with <25% opaqueness in BC₂F₃ were forwarded for seed multiplication. Vivek Quality Protein Maize (QPM) 9, the improved QPM hybrid, showed 41% increase in tryptophan and 30% increase in lysine over the original hybrid. The grain yield of the improved hybrid was on par with the original hybrid. The newly improved QPM maize hybrid released in 2008 will help in reducing the protein malnutrition because its biological value is superior over the normal maize hybrids. This short duration QPM maize hybrid has been adopted in several hill states of North Western and North Eastern Himalayan regions.     

Marker‐assisted introgression of rare allele of β‐carotene hydroxylase (crtRB1) gene into elite quality protein maize inbred for combining high lysine,tryptophan and provitamin A in maize

Vitamin A deficiency in humans is a widespread health problem. Quality protein maize (QPM) is a popular food rich in lysine and tryptophan, but poor in provitamin A (proA). Here, we report the improvement of an elite QPM inbred, HKI1128Q for proA using marker‐assisted introgression of crtRB1‐favourable allele. HKI1128 was one of the parental lines of three popular hybrids in India and was converted to QPM in our earlier programme. Severe segregation distortion for crtRB1 was observed in BC₁F₁, BC₂F₁ and BC₂F₂. Background selection by 100 SSRs revealed mean recovery of 91.07% recurrent parent genome varying from 88.78% to 93.88%. Across years, introgressed progenies possessed higher mean β‐carotene (BC: 9.22 µg/g), β‐cryptoxanthin (BCX: 3.05 µg/g) and provitamin A (proA: 10.75 µg/g) compared to HKI1128Q (BC: 2.26 µg/g, BCX: 2.26 µg/g and proA: 3.38 µg/g). High concentration of essential amino acids, viz. lysine (mean: 0.303%) and tryptophan (0.080%) in endosperm, was also retained. Multi‐year evaluation showed that introgressed progenies possessed similar grain yield (1,759–1,879 kg/ha) with HKI1128Q (1,778 kg/ha). Introgressed progenies with higher lysine, tryptophan and proA hold immense potential as donors and parents in developing biofortified hybrids.     

Genetic control of kernel modification found in South African quality protein maize inbred lines

Summary The genetic control of endosperm modification in 12 opaque-2 maize (Zea mays L.) inbred lines was investigated by means of a diallel cross experiment conducted across two environments. Kernel vitreousness and kernel hardness were determined by partially dominant genes. Additive gene action was largely responsible for kernel modification. A favourable general combining ability for kernel vitreousness and kernel hardness was positively correlated with an accumulation of dominant kernel modifying genes. South African sources of endosperm modifiers have been found to be similar to those used in other quality protein maize breeding programmes. Certain inbred lines displayed sufficient genetic potential for use in a quality protein maize hybrid breeding programme.     

Molecular mapping of quantitative trait loci for grain moisture at harvest in maize

In maize, high grain moisture (GM) at harvest causes problems in harvesting, threshing, artificial drying, storage, transportation and processing. Understanding the genetic basis of GM will be useful for breeding low‐GM varieties. A quantitative genetics approach was used to identify quantitative trait loci (QTL) related to GM at harvest in field‐grown maize. The GM of a double haploid population consisting of 240 lines derived from Xianyu335 was evaluated in three planting seasons and a high‐density genetic linkage map covering 1546.4 cM was constructed. The broad‐sense heritability of GM at harvest was 71.0%. Using composite interval mapping, six QTL for GM at harvest were identified on five chromosomes (Chr). Two QTL located on Chr1, qgm1‐1 and qgm1‐2, explained 5.0% and 10.8% of the phenotypic variation in GM at harvest, respectively. The QTL qgm2, qgm3, qgm4 and qgm5 accounted for 3.3%, 8.3%, 5.4% and 11.0% of the mean phenotypic variation, respectively. Because of their consistent detection over multiple planting seasons, the detected QTL appear to be robust and reliable for the breeding of low‐GM varieties.     

Genetic effects of embryo and endosperm for four malting quality traits of barley

Seed of seven cultivars of two-rowed barley (Hordeum Vulgare L.) and F2 seed from a half-diallel set of crosses among the cultivars were malted in two years to obtain data on diastatic power (DP), alpha-amylase activity (αAA), beta- amylase activity (βAA) and malt nitrogen (N) content. Embryo and endosperm genetic effects on the traits were studied by using a genetic model including genotype × environment interaction for malting quality characters. Variation of the four malting quality traits was affected by gentic effects and environmental interaction. Performance of DP and βAA was mainly controlled not only by endosperm dominance effects but also by embryo genotype × environment interaction and endosperm dominance × environment interaction. Variation of αAA and malt N content was controlled by both embryo and endosperm genetic effects, but the embryo dominance and endosperm additive effects contributed a major part to the total genetic effects. Significant interaction variances (embryo additive × environment and dominance × environment and endosperm dominance × environment) were also observed for αAA and malt N content. Diastatic power was related positively to βAA. Malt N content was associated positively with DP, largely because of the relationship between malt N and βAA. No obvious phenotype association between DP and αAA was found. General narrow-sense heritabilities of αAA and malt N content were 26.1% and 27.8%, respectively. This revised version was published online in July 2006 with corrections to the Cover Date.     

Molecular cytogenetic characterization of two partial wheat Elytrigia elongata amphiploids resistant to powdery mildew

Two new partial amphiploids SN20 and SN122, derived from crosses between Elytrigia elongata and common wheat Yannong15 and Shannongfu63, were found resistant to powdery mildew, a serious fungal wheat disease. Cytogenetic observations showed that each SN20 and SN122 plant had 56 chromosomes. The chromosomes in most pollen mother cells formed approximately 28 bivalents, thereby showing a high degree of cytogenetic stability. Genomic in situ hybridization using St‐genomic DNA from Pseudoroegneria strigosa as a probe and ABD‐genomic DNA from Chinese Spring wheat as a blocker demonstrated that the genomic formulas for the alien chromosomes in SN20 and SN122 were 2 St + 10 J^S + 2 J and 2 St + 8 J^S + 4 J, respectively. These wheat E. elongata partial amphiploids represent a potential novel source of resistance to powdery mildew for wheat breeding.     

Inheritance and characterization of the new and rare gene Rph25 conferring seedling resistance in Hordeum vulgare against Puccinia hordei

In this study, we characterized and mapped a new and rare resistance gene (RphFT) in the Chinese barley variety ‘Fong Tien’. RphFT, a dominant gene, was mapped to chromosome 5HL at a genetic position of 142.1 cM using DArT‐seq markers. The gene was also confirmed to be present in Australian cultivar ‘Yagan’ based on allelic tests, and likely ‘Lockyer’ based on multipathotype tests. The genetic studies also confirmed the presence of Rph12 in Australian cultivar ‘Baudin’. Rph12 is also located on chromosome 5HL close to RphFT, and the two loci were confirmed to be independent. Gene RphFT is of limited breeding value because it is effective to only one pathotype of P. hordei, 220P+ +Rph13 in Australia; nevertheless, it may play a role in controlling leaf rust if used in combination with other Rph genes. The locus symbol Rph25 is recommended for RphFT in accordance with the rules and numbering system of barley gene nomenclature.     

Identification and characterization of sources for photo‐ and thermo‐insensitivity in Vigna species

Cultivation of the same varieties of mungbean and blackgram across different seasons and locations is constrained by their photo‐ and thermo‐sensitive behaviour. Developing insensitive genotypes, which can fit well across all seasons, requires robust donors which would provide genes imparting this trait. This study was undertaken to identify such donors in the Vigna species. Forty‐eight accessions belonging to 13 Vigna species and eight released cultivars were evaluated under natural field conditions. Among these, two accessions, viz. V. umbellata (IC251442) and V. glabrescens (IC251372) were found photo‐ and thermo‐insensitive as these were able to flower and set pods at temperatures as high as 43.9°C and as low as 2.7°C. Pollen viability studies indicated viable pollen (>75% at 2.7°C and >85% at 41.9°C) and normal pollen tube growth at both the extremes of temperature. The identified V. glabrescens accession has long, constricted pods and dark green, mottled seeds while V. umbellata has smooth, curved pods and shining, oval, large seeds. Both these accessions can be utilized in developing photo–thermo insensitive genotypes in cultivated Vigna species.     

Genetic effects of the soft starch (h) and background loci on volume of starch granules in five inbreds of maize

Larger particle volume is beneficial for many aspects of maize starch processing, and may improve the performance of some starch attributes. This study focused on the soft starch (h) locus to identify its potentially influential role in starch particle volume distribution. The objectives were to study the genetic expression of starch particle volume of the h locus in different genetic backgrounds and the gene action conditioning starch particle volume of other loci in both normal‐starch and h‐starch backgrounds. Forty‐five populations (five intra‐inbred F_1s, 10 hybrid F_1s 10 F_2s, 10 BC₁F_1s to h/h parent, and 10 BC₁ to h:h conversion of normal parent) were planted in 1993 at two locations and in 1995 at one location. Selfed heterozygotes (±/h) in all generations provided intra‐ear comparisons of normal and h starch, and F₃ and BC₁F₂ generations provided inter‐ear comparisons. Significant differences were found between normal and h:h genotypes in all intra‐ear and inter‐ear comparisons. In all cases, general combining ability effects were highly significant, suggesting the presence of additive gene effects. Generation mean analysis of normal and h:h starch materials yielded similar results, indicating the predominance of additive and some dominance effects for other loci on starch particle volume. These results indicate the usefulness of the soft starch gene and additional genetic variation among inbreds in the improvement of starch particle volume for increased starch recovery in wet milling.     

叶面施用氨基酸对菜心产量和品质的影响

通过盆栽试验研究了叶面喷施氨基酸对菜心产量和品质的影响。结果表明喷施200 mg/kg甘氨酸和丙氨酸均能提高菜心产量;喷施氨基酸能够显著提高可溶性糖含量,以200 mg/kg甘氨酸效果最佳;施用氨基酸对菜心叶片叶绿素无明显影响,维生素C含量有所降低;喷施甘氨酸能显著降低菜心硝酸盐和草酸含量,最高降低幅度分别为85.03%和70.19%,而喷施丙氨酸硝酸盐含量降低幅度较小,草酸含量显著增加;同时,喷施氨基酸均能够显著提高硝酸还原酶(NR)和谷氨酸脱氢酶(GDH)活性,而且甘氨酸处理效果优于丙氨酸。说明喷施氨基酸,尤其是喷施甘氨酸有利于提高菜心产量,改善品质。     

Development of chloroplast‐specific microsatellite markers for molecular characterization of alloplasmic lines and phylogenetic analysis in wheat

Wheat (Triticum aestivum L.) is strictly a self‐pollinated crop, where hybrid breeding requires well‐characterized cytoplasmic male sterile (CMS) lines. The CMS has mostly been developed by substituting nuclear genome of wheat into the cytoplasm from wild relatives. Molecular characterization of 90 genotypes including 82 CMS lines originating from five different species, namely Aegilops speltoides, Ae. kotschyi, Ae. variabilis, Triticum araraticum and T. timopheevii, and eight popular varieties was carried out. Consequently, a set of 25 microsatellite markers specific to chloroplast (cpSSRs) were designed and successfully validated for specificity of amplification. A total of 15 cpSSRs (60%) were found polymorphic, of which three cpSSRs (TaCM7, TaCM8 and TaCM11) in genic region and twelve cpSSRs were located in intergenic region. Phylogenetic analysis of genotypes using cpSSRs revealed two major groups well in accordance with respective origin. A set of cpSSRs and phylogeny of CMS belonging to different origins developed, which will be helpful for the improvement in CMS system in wheat. The genic cpSSRs can be used for the allele mining and evolutionary studies.     

Development and study of a maize cultivar rich in anthocyanins: coloured polenta,a new functional food

Among the phytonutrients, anthocyanins have been extensively studied because of their antioxidant power, the characteristic supposedly responsible for their capacity for chronic disease prevention. Anthocyanins can also be synthesized in maize even though in Europe the colourless varieties have always been preferred. The aim of this study was to develop and characterize a new polenta variety of maize rich in anthocyanins, bred by a recurrent selection scheme, to increase the antioxidant power of this food. The recurrent selection was based on the anthocyanin content and other specific traits of the kernel. The coloured polenta obtained was analysed by TLC (Thin Layer Chromatography) analysis and DPPH (2,2‐diphenyl‐1‐picrylhydrazyl) radical scavenging ability, before and after cooking. The results obtained showed that even though cooking reduced the anthocyanin content by about 22%, the remaining anthocyanins exhibited twofolds higher antioxidant capacity, expressed as ARP (antiradical power) using acetone/water extraction buffer in DPPH assay, compared to the colourless control. Furthermore, our data showed that the anthocyanin content did not alter the taste of the coloured polenta.     

Germplasm enhancement of maize: a look into haploid induction and chromosomal doubling of haploids from temperate‐adapted tropical sources

The allelic diversity (AD) project of the Germplasm Enhancement of Maize (GEM) programme utilized the double haploid (DH) breeding method to expedite development and release of lines derived from 300 exotic maize races. Using 18 races in this study, differential effects on haploid induction rates (HIRs) and doubling rates (DRs) by the recurrent parents PHB47 and PHZ51, the elevation that the race is traditionally grown at, and by the race itself were addressed in this study. Races from the AD project were grouped by elevation of their origin, high, middle or low altitude. Six races per elevation were randomly selected and backcrossed using both recurrent parents to generate 36 populations. Ten replications were randomized in a complete randomized design for two growing seasons. The recurrent parent effect was significant, with PHB47 having a higher HIR than PHZ51. Effect of elevation was significant with higher HIR associated with low‐elevation origin, and race also proved to be significant. Effects of elevation, recurrent parent and race were not significant for DR.     

Identification and fine mapping of a candidate gene for oil yellow leaf 2 conferring yellow leaf phenotype in maize

Leaf colour is an important agronomic trait for studying molecular mechanisms in chlorophyll biosynthesis and chloroplast development. Here, a novel mutant oil yellow leaf 2 (Oy2) with a typical yellow leaf phenotype at the seedling stage was identified from the mutant population derived from the maize inbred line RP125. Compared with wild type, Oy2 mutant displays decreased chlorophyll content, reduced photosynthetic capacity and impaired chloroplast structure, which is likely controlled by a single recessive gene. The Oy2 locus was then delimited into a 117 kb region on chromosome 5 harbouring four genes, amongst which the gene Zm00001d013013, encoding a magnesium chelatase subunit D, was identified as the only candidate gene associated with Oy2 mutant phenotype. Moreover, the expression levels of candidate gene Oy2 and genes associated with chlorophyll biosynthesis and photosynthesis were tested by RNA‐seq and qRT‐PCR, implying that the causal gene Oy2 playing a critical role in chlorophyll synthesis. Taken together, we propose that the causal gene Oy2 highly associated with the yellow leaf phenotype may be helpful in elucidating photosynthetic pigments biosynthesis and chloroplast development in maize.     

Introgression of useful genes from Thinopyrum intermedium to wheat for improvement of bread‐making quality

To study the influence of genes from Thinopyrum intermedium on traits affecting the bread‐making quality of wheat, two derivatives from a putative disomic addition line in cultivar ‘Vilmorin 27’ were used in cytological, biochemical and molecular characterization. Cytological analysis suggested that one of the derivatives (Line‐1) had a terminal deletion involving the long arm of chromosome 1D (2n = 42, Del‐1DL”), and the other (Line‐2) was a conventional addition line, but also carried the same deletion on chromosome 1D (2n = 44, Thi”+Del‐1DL”). Amplification and sequencing of high‐molecular‐weight glutenin subunit (HMW‐GS) genes coded by the Th. intermedium chromosome in Line‐2 indicated the presence of one x‐type with an extra cysteine and four (rather than one) unique y‐type genes. Rheological studies of Line‐1 showed significantly lower dough strength compared to ‘Vilmorin 27’, confirming the recognized role of Glu‐1D coded HMW‐GSs. Line‐2 showed significantly higher dough strength compared to the background cultivar, indicating a significant potential of Th. intermedium for improvement of bread‐making quality in wheat.     

Prediction of deoxynivalenol and zearalenone concentrations in Fusarium graminearum inoculated backcross populations of maize by symptom rating and near‐infrared spectroscopy

Gibberella ear rot (GER) caused by Fusarium graminearum is a destructive disease in maize of temperate regions resulting in yield reduction and contamination by the mycotoxins deoxynivalenol (DON) and zearalenone (ZON). We wanted to analyse whether prediction of DON and ZON concentrations is feasible either by GER severity ratings or by near‐infrared spectroscopy (NIRS). We analysed 80 and 102 lines developed by backcrossing doubled‐haploid lines from segregating populations to the resistant and susceptible parent, respectively, by artificial infection at three locations in Germany and France. Both backcross (BC) populations differed substantially in their means for all traits with significant (P < 0.01) genotypic variances. DON and ZON concentrations measured by immunotests were significantly (P < 0.01) correlated with each other and with GER severity within each BC population (0.6 ≤ r ≤ 0.9, P < 0.01). DON concentration measured by immunotest and NIRS significantly correlated (r ≈ 0.9, P < 0.01). In conclusion, DON and ZON concentrations could be reliably predicted by GER severity. Additional NIRS analysis of DON concentration might be useful for the positively selected fraction.