Effect of processing conditions of hot pressurized solvent extraction in batch reactor on anthocyanins of purple field corn

Total anthocyanin content of the dried kernel and dried cob of purple field corn was investigated under hot pressurized solvent extraction conditions. The highest total anthocyanin content of 492.51 µg cyanidin-3-glucoside/g dry weight of sample was obtained from dried kernel extraction using water-ethanol ratio 1:3 as solvent at sample-solvent ratio 1:8 and extraction temperature of 80 oC. For the dried cob extraction, the highest total anthocyanin content obtained was 1890.49 µg cyanidin-3-glucoside/g dry weight of sample using water-ethanol ratio 1:1 as solvent at sample-solvent ratio 1:8, and extraction temperature of 100 oC. The extraction was carried out at pressure of 0.20 MPa and 15 min with N2 purging. Additionally, the antioxidant activities assessed by DPPH, ABTS and FRAP assays showed that the dried cob extract exhibited the greatest antioxidant activity in DPPH assay (IC50=3.83 mg/ml), ABTS assay (IC50=3.84 mg/ml) and FRAP assay (421.76 mmol FeSO4/100 g dry weight of sample)

Yield of tropical Asian maize (Zea mays L) at alternating row irrigation and at severe drought

Drought is a major reason for inconsistent grain yield of maize in lowland tropical and subtropical areas. In bimodal rainy seasons with unequal amounts of rainfall, the shorter season requires germplasm with sufficient residual yields at various situations of low water availability. Thus farmers will avoid the risk of cultivation failure. The respective adaptation of eight Thai hybrids was tested in two dry seasons from late November 2003 to April 2005. Furrow irrigation of 40 mm was applied at seven days intervals from planting to physiological maturity (control, W1); 50% less water supply than W1 from the sixth week onwards by alternating irrigation of one of two rows (W2); withholding water from 5 weeks after planting to the beginning of anthesis (W3). At W3, three hybrids excelled with yields above 350 g m-2, i.e. residual yields of more than two of them performed very well at W2 too, with more than 650 g m-2, a residual yield of about 80%. This genetic range is encouraging to breed for earlier hybrids that can be cultivated in the minor rainy season with a reduced risk of failure

Quality protein introduced into waxy maize landraces of ethnic minorities

Ethnic minorities in South East Asia use waxy maize as a staple food, lacking in essential amino acids. Recently, we combined the recessive waxy and opaque2 alleles to double quality grains (w/o, pure amylopectin, high quality protein), which still must be introgressed into germplasm acceptable to ethnic minorities. Two w/o lines of Chinese and Thai background, respectively, were crossed once with two Vietnamese waxy landraces of good taste, WVN 3 and WVN 10. At the preferred harvest time for eating, dough stage, homozygous w/o F2 offspring with WVN 3 were equal in dehusked ear yield with commercial waxy hybrids and 40% superior in yield compared with WVN 10 F2 offsprings. In WVN 3 F2 crosses and F2 backcrosses with WVN 3, all w/o dehusked ears were equal in eat¬ing quality, grain protein content and a good leaf health; but the yield of dehusked ears and the grain tryptophan content was highest in the topcross. High quality germplasm is available now as a source of high quality protein for ethnic minorities. The two original w/o lines led to equal results in crosses with landraces, but their test hybrid was extremely high-yielding, indicating a good potential to breed for commercial high protein quality snacks in South East Asia

Temporal dynamics of kernel set of tropical sweet maize (Zea mays L.) as influenced by genotype and mild drought

Maize grain yield is often affected by drought stress at flowering. Fast and synchronous emergence of silks probably is the key to high kernel set but non-destructive methods to follow the temporal grain set were missing. We solved this problem by marking flint kernels on the ears of sweet maize to reflect daily kernel set, as modern sweet maize is quite similar in vigor to field maize in Thailand. The effects of mild pre-anthesis drought stress and of the genotype were examined in two experiments (over two years both). The highest number of kernels resulted from pollination on the first or second day of silking. More than 90% of the kernels per ear were usually set by day four or five. Mild drought stress reduced the number of kernel-bearing positions along the ear as well as the number of kernels per position on each day of pollination in 2007 but there was no significant deviation in the principal grain set curve. As a consequence of mild drought stress, the differences in daily kernel set between the two water regimes were rather small compared to the differences among genotypes, for which genotype-specific deviations from the general pattern of daily kernel set were observed. Most important, a new tool exists now to reliably study variable stress situations, using normal grains on sweet maize ears or yellow grains on white grain ears as visual marker systems

Mapping of QTL affecting resistance against sorghum downy mildew (Peronosclerospora sorghi) in maize (Zea mays L)

Sorghum downy mildew (SDM) is one of the most destructive diseases of maize (Zea mays L) in South-East Asia. Understanding the genetic basis of downy mildew resistance (DMR) could increase the efficiency of breeding for disease resistant germplasm. The objectives of this study were to determine the number, genomic positions and genetic effects of quantitative trait loci (QTL) conferring resistance to SDM. The study included 251 F2:3 families derived from a cross between the two inbreds, Nei9008 (Thailand) and CML289 (CIMMYT), resistant and susceptible, respectively. Individuals in the population were genotyped for simple sequence repeat (SSR) and phenotypic resistance data were evaluated as percentage disease incidence in replicated field trials at three environments by Triple Lattice design. Heritability across environments was 94.3%. Traits were analyzed within and across environment using composite interval mapping. Nine QTLs were identified for resistance to SDM, one QTL each on chromosome 2, 3, 4, and 6, three QTLs on chromosome 5, and two QTLs on chromosome 9. Just one QTL on chromosome bin 5.07 came from the susceptible parent, all others from the resistant parent, Nei9008. The QTLs in chromosome bins 2.09 at umc1736, 5.03 at bnlg1902, and 6.01 at bnlg1867 had major effects and were consistent over all environments. A common map shows intriguing collocations of SDM QTLs with those for other disease and insect resistance QTLs from literature. As several consistent QTLs for downy mildew resistance are available now, an avenue is open for pyramiding multiple genes by marker assisted selection (MAS) that may control different mechanisms for resistance

Southeast Asian waxy maize (Zea mays L.), a resource for amylopectin starch quality types?

Amylose-free (waxy) maize has been a vegetable (cooked ears) and staple food in Southeast Asia for centuries, resulting in hundreds of landraces (LRs) across the region. The recessive waxy allele induces soft grains with preferred cooking and flavour properties. We hypothesized that eating preferences resulted in the additional selection for different starch properties, reflected in altered starch granule morphology or amylopectin structure. A total of 41 LRs were available as starting material that had been used by different ethnic groups in Vietnam and Thailand. Unluckily, some LR were not pure waxy, but we successfully regained the original pure waxy status for most. Twenty LR were chosen for analysis of starch traits according to their purity. Four different waxy mutations were identified, including two unknown alleles. This is a strong proof for parallel independent selection of waxy maize in the region. Starch granule morphology and size were similar among all LRs. Gelatinization properties differed only between waxy and wild-type LR, and all waxy LR were comparable to a commercial waxy hybrid. The fine structure of waxy amylopectin had fewer short chains compared with that in wild-type. So far, the differences observed in starch properties are likely associated exclusively with the waxy trait. Despite the strong selection for amylose-free starch, there was no evidence for additional region wide selection for other special starch properties in our collection. In conclusion, all analyses did not encourage further targeted research on allelic variation of other starch metabolism genes for future use in the food and feed industry.ISSN:1479-2621ISSN:1479-263