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Aims: Root angles are widely recognized to play an important role in determining rooting depth and drought tolerance in crop plants. But there has been no report revealing any association between root angle and yield performance under drought conditions in maize. There is also no simple method available to screen root angles. The objectives of this study were to evaluate genetic variation in seminal and nodal root angles in maize in greenhouse condition and their association with drought tolerance in field condition. Methods: Eighteen hybrids, of which nine were higher-yielding and nine were lower-yielding under water-stressed condition in field, were evaluated for root angle variation. Root angle was estimated as the distance between the horizontal soil surface line and slope of the root at 2 cm position from root base using a protractor. Results: Significant phenotypic variation was observed among hybrids for seminal and nodal root angles and primary root diameter. These root traits showed strong positive correlations with grain yield under drought condition. All the higher-yielding hybrids had steeper root growth angle than the lower-yielding hybrids. A strong correlation between seminal and nodal root angles was observed. A strong correlation was also observed between 5th and 4th node nodal root angles. Conclusion: Either seminal or nodal root angle could be used for selection for the improvement drought tolerance. The current screening system for root angle is simple and inexpensive, and could be used for screening a large number of genotypes. [ABSTRACT FROM AUTHOR]

Chromosome segment substitution line (CSSL) population is potential in precisely detecting and pyramiding genes/QTL/segments due to the genetic background noise removed. To exploit and utilize the favorable wild alleles, a CSSL population with 151 lines ( SojaCSSLP1) was generated using a wild soybean ( Glycine soja Sieb. et Zucc.) N24852 as donor parent and the elite cultivar NN1138- 2 as its genetic background. An improved CSSL construction strategy was used, i.e. continuous backcross after initial crossing followed with alternation of backcross and selfing combined with marker-assisted selection based on pedigree DNA pools and phenotypic differences among pedigrees. The SojaCSSLP1 with an average recovery ratio of 95.7 % of the NN1138- 2 genome could cover the entire genome of wild soybean. Four wild alleles/segments for each of the two wild characteristics, longer plant height (PH) and more number of nodes on main stem (NN), in a total of six segments, were detected with additive effects all positive. Among them, Satt243 on Chr.10 and Sat_286 on Chr.19 associated with both PH and NN while Satt338 and SOYGPATR on Chr.4 and Satt314 neighboring with Satt192 on Chr.12 had the former and latter on each chromosome associated with PH and NN, respectively. That could explain the high positive correlation between the two traits ( r = 0.88). Compared with those in the literature, three QTL/segments for PH and one for NN were detected also among cultivated soybeans, indicating allele differentiation happened not only between wild and cultivated but also among cultivated soybeans. Therefore these QTL/segments might be the key ones to explain the domestication and evolution of soybean. In addition, SojaCSSLP1 should be also potential in studies for multiple wild traits due to its broad variation. [ABSTRACT FROM AUTHOR]

An efficient and reproducible plant regeneration procedure is essential for introducing genes of interest in important crops through genetic transformation. However, some crops, such as soybean [Glycine max (L.) Merrill], are difficult to manipulate in vitro, often depending on their genotype, and the reproduction of the established protocols is not always possible. The purpose of this paper is the optimization of a regeneration protocol for soybean shoots of the Cuban variety Incasoy-36 to enable its reproduction. Cotyledonary nodes of mature seeds were the explants of choice to promote regeneration under specific culture conditions. The effect of several concentrations of benzylaminopurine on shoot induction was evaluated and it was demonstrated that the age of explants is essential for regeneration. Shoot formation was increased with 1.5 mg/L of benzylaminopurine, producing a regeneration frequency of 96.8 % and 4.3 shoots in explants with a 6 day germination period. The elongation of shoots, as well as rooting occurred in an MSB5 medium without hormones. Regenerated plantlets were obtained 7-8 weeks after the start of the culture and they were morphologically similar to plants of this variety. [ABSTRACT FROM AUTHOR]

An efficient and reproducible plant regeneration procedure is essential for introducing genes of interest in important crops through genetic transformation. However, some crops, such as soybean [Glycine max (L.) Merrill], are difficult to manipulate in vitro, often depending on their genotype, and the reproduction of the established protocols is not always possible. The purpose of this paper is the optimization of a regeneration protocol for soybean shoots of the Cuban variety Incasoy-36 to enable its reproduction. Cotyledonary nodes of mature seeds were the explants of choice to promote regeneration under specific culture conditions. The effect of several concentrations of benzylaminopurine on shoot induction was evaluated and it was demonstrated that the age of explants is essential for regeneration. Shoot formation was increased with 1.5 mg/L of benzylaminopurine, producing a regeneration frequency of 96.8 % and 4.3 shoots in explants with a 6 day germination period. The elongation of shoots, as well as rooting occurred in an MSB5 medium without hormones. Regenerated plantlets were obtained 7-8 weeks after the start of the culture and they were morphologically similar to plants of this variety. [ABSTRACT FROM AUTHOR]

Chromosome segment substitution line (CSSL) population is potential in precisely detecting and pyramiding genes/QTL/segments due to the genetic background noise removed. To exploit and utilize the favorable wild alleles, a CSSL population with 151 lines ( SojaCSSLP1) was generated using a wild soybean ( Glycine soja Sieb. et Zucc.) N24852 as donor parent and the elite cultivar NN1138- 2 as its genetic background. An improved CSSL construction strategy was used, i.e. continuous backcross after initial crossing followed with alternation of backcross and selfing combined with marker-assisted selection based on pedigree DNA pools and phenotypic differences among pedigrees. The SojaCSSLP1 with an average recovery ratio of 95.7 % of the NN1138- 2 genome could cover the entire genome of wild soybean. Four wild alleles/segments for each of the two wild characteristics, longer plant height (PH) and more number of nodes on main stem (NN), in a total of six segments, were detected with additive effects all positive. Among them, Satt243 on Chr.10 and Sat_286 on Chr.19 associated with both PH and NN while Satt338 and SOYGPATR on Chr.4 and Satt314 neighboring with Satt192 on Chr.12 had the former and latter on each chromosome associated with PH and NN, respectively. That could explain the high positive correlation between the two traits ( r = 0.88). Compared with those in the literature, three QTL/segments for PH and one for NN were detected also among cultivated soybeans, indicating allele differentiation happened not only between wild and cultivated but also among cultivated soybeans. Therefore these QTL/segments might be the key ones to explain the domestication and evolution of soybean. In addition, SojaCSSLP1 should be also potential in studies for multiple wild traits due to its broad variation. [ABSTRACT FROM AUTHOR]