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Stamp P.,ETH Zurich | Renlai W.,Maize Research Institute Zemun Polje | Le-Huy H.,Agricultural Genetics Institute | Jompuk C.,Kasetsart University | Jampatong S.,National Corn and Sorghum Research Center
Maydica | Year: 2014

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 eating 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. © 2014 Consiglio per la Ricercame la sperimentazione in Agrcoltura. All rights reserved. Source

Bunkoed W.,Kasetsart University | Bunkoed W.,National Corn and Sorghum Research Center | Kasam S.,Kasetsart University | Chaijuckam P.,Kasetsart University | And 2 more authors.
Kasetsart Journal - Natural Science | Year: 2014

Setosphaeria turcica, a teleomorph of Exserohilum turcicum, is the casual agent of northern corn leaf blight, a major disease of corn in Thailand. It is a heterothallic fungus, with two mating types: mating type A and mating type a. This study was the first to investigate the sexual reproduction of S. turcica in Thailand. Pseudothecia (sexual state) were found on heavily infected corn leaves from natural fields, even though until this time, the sexual state has not yet been discovered in the natural world. S. turcica isolates collected from nine corn fields were capable of sexual reproduction in culture when opposite mating types were paired, regardless of the origin of the isolates. Pseudothecia, asci and ascospores could be induced on potato dextrose agar and on Sach's agar at 23°C and 25-30°C. This study designed mating type-specific primers for both mating types and identified mating type of 225 S. turcica isolates. The result revealed near mating type equilibrium in that 104 and 121 isolates were mating type A and mating type a, respectively. Both mating types were present in every field population. The data suggested that sexual reproduction of S. turcica may be common in corn fields in Thailand and has caused genetic variation in the fungal pathogen, supported by previous analysis with inter-simple sequence repeat markers. Furthermore, the virulence may be enhanced or new physiological races may be generated through sexual hybridization. Source

Rupitak Q.,ETH Zurich | Rupitak Q.,Burapha University | Stamp P.,ETH Zurich | Jampatong S.,National Corn and Sorghum Research Center | And 2 more authors.
Maydica | Year: 2011

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. Source

Jampatong S.,National Corn and Sorghum Research Center | Wongpila W.,National Corn and Sorghum Research Center | Stamp P.,ETH Zurich | Messmer R.,ETH Zurich
Maydica | Year: 2012

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. Source

Rupitak Q.,ETH Zurich | Stamp P.,ETH Zurich | Jampatong S.,National Corn and Sorghum Research Center | Chowchong S.,National Corn and Sorghum Research Center | Messmer R.,ETH Zurich
Crop Science | Year: 2010

The initiation of kernels along the maize ear depends on the temporal dynamics of silk emergence and pollen shedding. We conducted a nondestructive examination of the dynamics of silk emergence of tropical sweet maize (Zea mays L.); flint-type grains were the visual markers. The silks were pollinated on consecutive days with pollen of sweet maize (recessive allele) on 6 d and with pollen of flint-type maize (dominant allele) on 1 d (one pollination treatment for each of the seven possible days). The resulting hard kernels could be distinguished from the shriveled sweet kernels. The time of pollination had a strong effect on kernel set. The highest percentage of daily kernel set was observed on the first day of silking (Day 1). It accounted for 31 (2007) and 42% (2008) of the total kernels per ear. The distribution of these kernels followed a bell-shaped curve with a peak at around the position of the tenth kernel from the bottom of the ear. On the following days, kernel set followed a double bell-shaped curve with the peak shifting to the tip of the ear followed by a steady decrease. The minor peak, at the bottom of the ears, almost disappeared by Day 4 of silking. More than 90% of the final number of kernels was set within five (2007) or three (2008) days. The visual marker system successfully traced the dynamics of silk emergence and its impact on kernel set as well as its dependence on environmental conditions during flowering. © Crop Science Society of America. Source

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