Posts Tagged ‘Zea mays’

Detection of genetic integrity of conserved maize (Zea mays L.) germplasm in genebanks using SNP markers

Posted by on , in Journal Articles

Published in Genetic Resources and Crop Evolution 58(2): 189-207 (2011)

Detection of genetic integrity of conserved maize (Zea mays L.) germplasm in genebanks using SNP markers

Weiwei Wen, Suketoshi Taba, Trushar Shah, Victor H. Chavez Tovar and Jianbing Yan

Twenty maize landrace accessions regenerated and conserved in five maize genebanks were investigated for genetic integrity using 1,150 Single Nucleotide Polymorphisms (SNPs) and 235 SNP haplotypes. The genetic diversity of three accessions changed significantly in terms of the average number of alleles per locus. Ten out of twenty accessions had significantly different SNP allelic frequencies, either after regeneration or in the same accession held in different genebanks. The proportion of loci with significant changes in SNP allelic frequency was very low (37/1,150). Changes in the major allelic frequency (MAF) for the majority of SNP loci (60.2–75.2%) were less than 0.05. For SNP haplotypes, the genetic diversity of four accessions changed significantly in terms of average number of haplotype alleles and polymorphic information content (PIC) per locus. The proportion of SNP haplotype alleles lost in the later generations ranged between 0 and 22.6%, and at the same time 0–19.9% of the SNP haplotype alleles appeared in later generations, however, these were absent in the earlier generations. Dynamic changes in genetic integrity, in terms of presence and absence of genes (alleles), by both SNP and SNP haplotype analysis were detected during regeneration. A suboptimum number of ears harvested in one generation can be combined with those from another, repeated regeneration to capture the diversity of the previous generation. Use of molecular markers during regeneration of accessions can help in understanding the extent of genetic integrity of the maize accessions in ex situ genebanks and in recommending the best practice for maintaining the original genetic diversity of the genebank accessions.

Morpho-physiological traits associated with cold stress tolerance in tropical maize (Zea mays L.)

Posted by on , in Journal Articles

Published in Maydica 55(3-4): 201-208

Morpho-physiological traits associated with cold stress tolerance in tropical maize (Zea mays L.)

P.H. Zaidi, M. Yadav, P. Maniselvan, R. Khan, T.V. Shadakshari, R.P. Singh, D. Pal

Winter season maize (Zea mays L.) has emerged a new crop in many parts of South and Southeast Asia, where the crop has to face low temperature regimes (<5°C) for few weeks during vegetative growth stage. The objective of this study was to identify the morphological and physiological traits associated with cold stress tolerance during vegetative growth period, when maximum dry matter is accumulated and floral primodia are formed. A total of 80 cultivars, including hybrids and open pollinated varieties (OPVs) from International Maize and Wheat Improvement Center (CIMMYT) and Indian maize program were evaluated in replicated trials at Indian Agricultural Research Institute (IARI), New Delhi and at Regional Research Station, Haryana Agriculture University, Karnal, India during the winter season, where critical period of vegetative growth and floral primodia developmental stage was exposed to <10°C temperature. Data on various growth and developmental traits and key physiological traits were recorded during the low temperature regime. Except ears per plant and physiological maturity, the cold stress significantly affected all the growth and developmental traits and also physiological traits studied. However, significant genotypic variability was observed for most of the traits studied. Genotypes with relatively high leaf appearance and extension rate, less cold injury symptoms and cell membrane damage showed good level of cold tolerance in terms of reproductive behavior and eventually grain yield under cold stress. These secondary traits could be used in selection index along with days to anthesis, anthesis-silking interval (ASI) and grain yield for selection and improvement of tropical maize for low temperature adaptation.

How yield relates to ash content, Delta 13C and Delta 18O in maize grown under different water regimes

Posted by on , in Journal Articles

Published in Annals of Botany 104(6): 1207-1216

How yield relates to ash content, Delta 13C and Delta18O in maize grown under different water regimes

Llorenç Cabrera-Bosquet, Ciro Sánchez and José Luis Araus

Background and Aims: Stable isotopes have proved a valuable phenotyping tool when breeding for yield potential and drought adaptation; however, the cost and technical skills involved in isotope analysis limit its large-scale application in breeding programmes. This is particularly so for Delta 18O despite the potential relevance of this trait in C4 crops. The accumulation of minerals (measured as ash content) has been proposed as an inexpensive way to evaluate drought adaptation and yield in C3 cereals, but little is known of the usefulness of this measure in C4 cereals such as maize (Zea mays). The present study investigates how yield relates to ash content, Delta 13C and Delta 18O, and evaluates the use of ash content as an alternative or complementary criterion to stable isotopes in assessing yield potential and drought resistance in maize.

Methods: A set of tropical maize hybrids developed by CIMMYT were subjected to different water availabilities, in order to induce water stress during the reproductive stages under field conditions. Ash content and Delta 13C were determined in leaves and kernels. In addition, Delta 18O was measured in kernels.

Key Results: Water regime significantly affected yield, ash content and stable isotopes. The results revealed a close relationship between ash content in leaves and the traits informing about plant water status. Ash content in kernels appeared to reflect differences in sink–source balance. Genotypic variation in grain yield was mainly explained by the combination of ash content and Delta 18O, whilst Delta 13C did not explain a significant percentage of such variation.

Conclusions: Ash content in leaves and kernels proved a useful alternative or complementary criterion to Delta 18O in kernels for assessing yield performance in maize grown under drought conditions.