Accelerated generation of elite inbreds in maize using doubled haploid technology

The creation of homozygous parental lines for hybrid development is one of the key components of commercial maize breeding programs. It usually takes up to 6 to 7 generations of selfing to obtain homozygous inbreds from the initial cross using the conventional pedigree method. Using doubled haploid (DH) method, concurrent fixation of all the genes covering entire chromosomes is possible within a single generation. For generation of DH lines, haploids are generated first by several means such as in-vitro method using tissue culture technique and in-vivo method using the haploid inducer (HI) lines. Of which, tissue culture-based methods have shown little promise for large-scale DH production as it needs good infrastructures and technical requirements. In contrast, inducer-based method provides more optimistic solutions for large-scale DH lines production. Due to its rapidity, DH technology is now being adopted in many countries including India for reducing the breeding cycle

Validation of molecular markers linked to low glucosinolate QTLs for marker assisted selection in Indian mustard (Brassica juncea L. Czern & Coss)

Not AvailableSix earlier reported markers closely linked to low glucosinolate QTLs of Brassica juncea, spread across ‘A’ genome (A2, A3 and A9) were validated in a recombinant inbred line (RIL) population of a cross between Pusa Mustard-21 (low erucic acid) and EC-597325 (double low) genotypes, to utilize them in marker-assisted selection (MAS). Of them, four markers viz., GER 1 amplified alleles of 650 bp and of 950 bp, GER 5 amplified 310 bp and 350 bp, At5gAJ67 amplified 500 bp and 450 bp and Myb28 amplified alleles of size 900 bp and 920 bp in EC597325 and Pusa Mustard-21, respectively and therefore differentiated low and high glucosinolate parents. These four polymorphic markers were then used to genotype the phenotyped RIL population consisting 608 plants. Marker-trait association was tested for goodness of fit using c2 test. Of the four markers, GER1 and GER5 showed higher phenotypic variance (R2 value) compared to the others, indicating their significance in determination of glucosinolates and prospects for use in MAS for development of Indian mustard genotypes with low glucosinolates content.Not Availabl

Characterization of maize genotypes using microsatellite markers associated with QTLs for kernel iron and zinc

224-234Crop genetic resources rich in Fe and Zn provide sustainable and cost-effective solution to alleviate micronutrient malnutrition. Maize being the leading staple crop assumes great significance as a target crop for biofortification. We report here wide genetic variation for kernel Fe and Zn among 20 diverse maize inbreds lines, majority of which were bred for quality protein maize (QPM) and provitamin-A. Kernel Fe ranged from 30.0 - 46.13 mg/kg, while kernel Zn ranged from 8.68-39.56 mg/kg. Moderate but positive correlation was observed between the micronutrients. Characterization using 25 Single sequence repeats (SSRs) linked to QTLs for kernel Fe produced 58 alleles. Similarly, 86 alleles were identified from 35 SSRs linked to QTLs for kernel Zn. One unique allele for kernel Fe and three unique alleles for kernel Zn were identified. The mean polymorphic information content (PIC) was 0.40 for both kernel Fe and  Zn. Jaccard’s dissimilarity coefficients varied from 0.25 - 0.91 with a mean of 0.58 for kernel-Fe while 0.27- 0.88 with a mean of 0.57 for kernel Zn. Principal coordinate analysis depicted diversity of inbreds. Cluster analysis grouped the inbreds into three major clusters for both kernel Fe and Zn. Potential cross combinations have been proposed to develop micronutrient rich hybrids and novel inbreds with higher Fe and Zn. The information generated here would help the maize biofortification programme to develop nutritionally enriched hybrids

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Not AvailableTraditional maize (Zea mays L.) is deficient in iron (Fe) and zinc (Zn). Metal transporter proteins play pivotal role in uptake, translocation and accumulation of minerals. Here, a set of 70 intergenic SSRs, 20 intragenic SSRs and 20 intragenic InDel markers encompassing 62 metal transporter genes were used for characterization of 24 diverse inbreds varying for Fe (13.95–37.34 µg/g) and Zn (11.83–37.90 µg/g). A total of 356 alleles, with 26 unique (7.03%) and 36 rare (10.11%) alleles were observed. Cluster analysis categorized the inbreds into two main clusters. Five candidate gene-based intragenic SSRs were significantly associated with Fe (r = 0.46–0.52). Two intragenic InDel markers and 11 SSRs were significantly correlated with Zn (r = 0.44–0.76). HUZM-185 and HKI-323 possessed favourable allele of five genes that showed significantly high correlation with Fe. At least six significantly associated genes for Zn were found in BQPML-5207-4-2, CML152, CML169 and HKI193-1. Based on genetic distance, presence of genes and high micronutrients, potential cross combinations were identified for the exploitation of heterosis. This study is the first report on characterizing maize inbreds using markers for metal transporter genes.Not Availabl

Allelic variations for lycopene-ε-cyclase and β-carotene hydroxylase genes in maize inbreds and their utilization in β-carotene enrichment programme

Vitamin A deficiency is a global health problem and can be effectively alleviated through crop biofortification. Quantification of carotenoids using high-performance liquid chromatography is expensive and time-consuming, thereby posing a challenge in the selection of genotypes with high provitamin A. Favourable alleles possessing rare genetic variation in lycopene-ε-cyclase (lcyE) and β-carotene hydroxylase (crtRB1) genes are associated with higher accumulation of provitamin A, especially β-carotene; and selection of these alleles holds immense promise in reducing large-scale phenotypic assays. Screening of a diverse set of 385 maize inbred lines of indigenous and exotic origin detected the presence of two alleles (amplicon size: 250 and 650 bp) of lcyE and three alleles (amplicon size: 296, 543 and 875 bp) of crtRB1 in the inbred panel. Favourable alleles of both the genes were rare among the traditional maize germplasm; 3.38% of the inbreds possessed the favourable allele (650 bp) of lcyE, while 3.90% inbreds had the favourable allele (543 bp) of crtRB1. Five inbreds (1.3%) with favourable alleles of both the genes were found. Inbreds with favourable alleles of crtRB1 and lcyE serve as rich genetic resources for effective utilization in the maize biofortification programme

Urinary tract infection due to Chryseobacterium gleum, an uncommon pathogen

Chryseobacterium species are gaining importance as an emerging opportunistic nosocomial pathogen. Limited availability of clinical data necessitates reporting of such isolates. We report a case of nosocomial urinary tract infection by metallo-β-lactamase-producing Chryseobacterium gleum in an elderly diabetic male with chronic renal disease. Identification and antibiotic sensitivity test performed by conventional methods were confirmed by Matrix-assisted Laser Desorption Ionization Time-of-Flight and VITEK-2 systems, respectively. The patient responded well to intravenous ciprofloxacin therapy

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Not AvailableSweet corn has gained worldwide popularity. Traditional sweet corn possesses low concentration of essential nutrients such as lysine (0.15–0.25%), tryptophan (0.03–0.04%) and provitamin-A (proA 3–4 ppm), and deficiency leads to serious health problems in humans. Here, stacking of shrunken2 (sh2), opaque2 (o2), lycopene epsilon cyclase (lcyE) and β‐carotene hydroxylase (crtRB1) genes were undertaken in the parents of four hybrids viz., APQH1, APHQ4, APHQ5 and APHQ7 using marker-assisted backcross breeding (MABB). Gene-linked markers (umc2276 and umc1320) for sh2, while gene-based markers for o2 (umc1066 and phi057), lcyE (5′TE-InDel) and crtRB1 (3′TE-InDel), were used for genotyping in BC1F1, BC2F1 and BC2F2. Selected backcross progenies showed high recovery of recurrent parent genome (92.4–97.7%). The reconstituted sweet corn hybrids possessed significantly high lysine (0.390%), tryptophan (0.082%) and proA (21.14 ppm), coupled with high kernel sweetness (brix 18.96%). The improved sweet corn hybrids had high cob yield (12.22–15.33 t/ha) across three environments. These newly developed biofortified sweet corn hybrids possess great significance in providing balanced nutrition. This is the first report of combining sh2, o2, lcyE and crtRB1 genes for enrichment of sweet corn hybrids with multiple essential nutrients.Not Availabl

Development of β-carotene rich maize hybrids through marker-assisted introgression of β-carotene hydroxylase allele.

Development of vitamin A-rich cereals can help in alleviating the widespread problem of vitamin A deficiency. We report here significant enhancement of kernel β-carotene in elite maize genotypes through accelerated marker-assisted backcross breeding. A favourable allele (543 bp) of the β-carotene hydroxylase (crtRB1) gene was introgressed in the seven elite inbred parents, which were low (1.4 µg/g) in kernel β-carotene, by using a crtRB1-specific DNA marker for foreground selection. About 90% of the recurrent parent genome was recovered in the selected progenies within two backcross generations. Concentration of β-carotene among the crtRB1-introgressed inbreds varied from 8.6 to 17.5 µg/g - a maximum increase up to 12.6-fold over recurrent parent. The reconstituted hybrids developed from improved parental inbreds also showed enhanced kernel β-carotene as high as 21.7 µg/g, compared to 2.6 µg/g in the original hybrid. The reconstituted hybrids evaluated at two locations possessed similar grain yield to that of original hybrids. These β-carotene enriched high yielding hybrids can be effectively utilized in the maize biofortification programs across the globe

Opaque16, a high lysine and tryptophan mutant, does not influence the key physico-biochemical characteristics in maize kernel.

The enhancement of lysine and tryptophan in maize is so far basedon opaque2(o2) mutant, that along with the endosperm-modifiersled to development of Quality Protein Maize[QPM]. Though many mutants improving the endospermic protein quality were discovered, they could not be successfully deployed. Recently discovered opaque16 (o16)mutant enhances the lysine and tryptophan content in maize endosperm. In the present study, the influence of o16 on the endosperm modification was analyzed in four F2 populations, two each segregating for o16 allele alone and in combination with o2. The recessive o16o16 seed endosperm was found to be vitreousphenotypically similar to wild-O16O16. The mutant did not influence the degree of kernel opaqueness in o2o2 genetic background as opaqueness in o2o2/O16O16 and o2o2/o16o16 was similar. Grain hardness of o16o16 was comparable with the normal and QPM maize. The pattern of microscopic organization of proteinaceous matrix and starch granules, and zein profiling of the storage protein in o16o16 were found to be similar with normal maize endosperm, but distinct from the o2o2-soft genotype. The pattern in o2o2/o16o16 was unique and different from o2o2 and o16o16 as well. Here we demonstrated the effects of o16 on physico-biochemical characteristics of endosperm and report of o16 possessing negligible influence on kernel modification and hardness, which holds a great significance in maize quality breeding programme