Heritability (H) on a progeny mean basis is frequently estimated in recurrent selection experiments for the purpose of estimating the expected progress from family selection; however, appropriate measures of precision have been developed for only a few heritability estimators. The objective of this research was to develop a measure of precision for H for certain balanced linear models. Exact confidence intervals for H were derived and are not restricted to a specific experimental design. The confidence intervals were applied to sorghum [Sorghum bicolor (L.) Moench] half-sib family data.

An exact confidence interval for heritability on a progeny mean basis

The maize plant (Zea mays), characterized by an erect green stalk, is one of the 3 great grain crops of the world. Its kernels, like other seeds, are storage organs that contain essential components for plant growth and reproduction. Many of these kernel constituents, including starch, protein, and some micronutrients, are also required for human health. For this reason, and others, maize has become highly integrated into global agriculture, human diet, and cultural traditions. The nutritional quality and integrity of maize kernels are influenced by many factors including genetic background, environment, and kernel processing. Cooking procedures, including nixtamalization and fermentation, can increase accessibility of micronutrients such as niacin. However, man cannot live on maize alone. For one-third of the world's population, namely in sub-Saharan Africa, Southeast Asia, and Latin America, humans subsist on maize as a staple food but malnutrition pervades. Strategies to further improve kernel macronutrient and micronutrient quality and quantities are under intense investigation. The 2 most common routes to enhance grain nutritional value are exogenous and endogenous fortification. Although exogenous fortification, such as addition of multivitamin premixes to maize flour, has been successful, endogenous fortification, also known as “biofortification,” may provide a more sustainable and practical solution for chronically undernourished communities. Recent accomplishments, such as low-phytate, high-lysine, and multivitamin maize varieties, have been created using novel genetic and agronomic approaches. Investigational studies related to biofortified maize are currently underway to determine nutrient absorption and efficacy related to human health improvement.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1541-4337.2010.00117.x

Maize: A Paramount Staple Crop in the Context of Global Nutrition

Improving the protein content and composition of cereal grain

Clinical and consumer market interest is increasingly directed toward the use of plant-based proteins as dietary components aimed at preserving or increasing skeletal muscle mass. However, recent evidence suggests that the ingestion of the plant-based proteins in soy and wheat results in a lower muscle protein synthetic response when compared with several animal-based proteins. The possible lower anabolic properties of plant-based protein sources may be attributed to the lower digestibility of plant-based sources, in addition to greater splanchnic extraction and subsequent urea synthesis of plant protein-derived amino acids compared with animal-based proteins. The latter may be related to the relative lack of specific essential amino acids in plant- as opposed to animal-based proteins. Furthermore, most plant proteins have a relatively low leucine content, which may further reduce their anabolic properties when compared with animal proteins. However, few studies have actually assessed the postprandial muscle protein synthetic response to the ingestion of plant proteins, with soy and wheat protein being the primary sources studied. Despite the proposed lower anabolic properties of plant vs. animal proteins, various strategies may be applied to augment the anabolic properties of plant proteins. These may include the following: 1) fortification of plant-based protein sources with the amino acids methionine, lysine, and/or leucine; 2) selective breeding of plant sources to improve amino acid profiles; 3) consumption of greater amounts of plant-based protein sources; or 4) ingesting multiple protein sources to provide a more balanced amino acid profile. However, the efficacy of such dietary strategies on postprandial muscle protein synthesis remains to be studied. Future research comparing the anabolic properties of a variety of plant-based proteins should define the preferred protein sources to be used in nutritional interventions to support skeletal muscle mass gain or maintenance in both healthy and clinical populations.

/pdf/the-skeletal-muscle-anabolic-response-to-plant-versus-animal-i8etupgza8.pdf

The Skeletal Muscle Anabolic Response to Plant- versus Animal-Based Protein Consumption

Unintended effects and their detection in genetically modified crops

Maize (Zea mays L.) plays a very important role in human and animal nutrition in a number of developed and developing countries, worldwide. Breeding for improved protein quality in maize began in the mid-1960s with the discovery of mutants, such as opaque-2, that produce enhanced levels of lysine and tryptophan, the two amino acids deficient in maize endosperm proteins. However, adverse pleiotropic effects imposed severe constraints on successful exploitation of these mutants. Interdisciplinary and concerted research efforts led to amelioration of the negative features of the opaque phenotype, and the rebirth of Quality Protein Maize' (QPM). QPM holds superior nutritional and biological value and is essentially interchangeable with normal maize in cultivation and kernel phenotype. This paper deals with the salient sequence of events associated with the development of QPM, the present understanding of genetic, biochemical and molecular bases of QPM, and the recent technological developments that could potentially enhance the efficiency of QPM breeding and the reach of QPM cultivars.

Quality protein maize

Knowledge of interrelationships between grain yield and its contributing components will improve the efficiency of breeding programs through the use of appropriate selection indices. Previous path analyses studies in maize (Zea mays L.) treated yield components as first-order variables. The present study, based on evaluation of 90 experimental maize hybrids (comprising one diallel and one line x tester set) at two locations in India, utilizes a sequential path model for analysis of genetic associations among grain yield and its related traits by ordering the various variables in first-, second-, and third-order paths on the basis of their maximum direct effects and minimal collinearity. The sequential path model showed distinct advantages over the conventional path model in discerning the actual effects of different predictor variables. Two first-order variables, namely 100-grain weight and total number of kernels per ear, revealed highest direct effects on total grain weight (p = 0.74 and p = 0.78, respectively), while ear length, ear diameter, number of kernel rows, and number of kernels per row were found to fit as second-order variables. All direct effects were found to be significant, as indicated by bootstrap analysis. Test for the goodness-of-fit revealed that the sequential path model provided better fit to various datasets analyzed in the study. Correlations between the predicted values of various response variables in the second season dataset based on the path coefficients of the first season were high, except for ear length and number of kernels per row. The applicability of the model has been confirmed through analysis of two additional datasets during 2000. The results indicated the utility of the sequential path model for determining the interrelationships among grain yield and related traits in maize.

Sequential path model for determining interrelationships among grain yield and related characters in maize

Tolerance to excess moisture in maize (Zea mays L.): susceptible crop stages and identification of tolerant genotypes

The low nutritive value of maize endosperm protein is genetically corrected in quality protein maize (QPM), which contains the opaque2 gene along with numerous modifiers for kernel hardness. We report here a two generation marker-based backcross breeding program for incorporation of the opaque2 gene along with phenotypic selection for kernel modification in the background of an early maturing normal maize inbred line, V25. Using the flanking marker distances from opaque2 gene in the cross V25×CML176, optimum population size for the BC2 generation was computed in such a way that at least one double recombinant could be obtained. Whole genome background selection in the BC2 generation identified three plants with 93 to 96% recurrent parent genome content. The three BC2F2 families derived from marker identified BC2 individuals were subjected to foreground selection and phenotypic selection for kernel modification. The tryptophan concentration in endosperm protein was significantly enhanced in all the three classes of kernel modification viz., less than 25%, 25–50% and more than 50% opaqueness. BC2F3 lines developed from the hard endosperm kernels were evaluated for desirable agronomic and biochemical traits in replicated trials and the best line was chosen to represent the QPM version of V25, with tryptophan concentration of 0.85% in protein. The integrated breeding strategy reported here can be applied to reduce genetic drag as well as the time involved in a conventional line conversion program, and would prove valuable in rapid development of specialty corn germplasm.

Two-generation marker-aided backcrossing for rapid conversion of normal maize lines to quality protein maize (QPM)

We have mapped the quantitative trait loci (QTLs) conferring resistance to sorghum downy mildew (Peronosclerospora sorghi; SDM) and Rajasthan downy mildew (P. heteropogoni; RDM), two species of DM prevalent throughout India. QTL mapping was carried out on a backcross population of 151 individuals derived from a cross between CM139 (susceptible parent) and NAI116 (highly resistant to both SDM and RDM). Heritability estimates were 0.74 for SDM and 0.67 for RDM. Composite interval mapping combined with a linkage map constructed with 80 simple sequence repeat (SSR) markers resulted in the identification of three QTLs (one each on chromosomes 2, 3 and 6) for SDM resistance and two QTLs (one each on chromosomes 3 and 6) for RDM resistance, all of which were contributed by NAI116. The significance of the major QTL on chromosome 6 (bin 6.05) that confers resistance to diverse DMs in tropical Asia, including SDM and RDM in India, was also verified. The results confirmed that some common QTLs contribute to both SDM and RDM resistance, while additional loci might specifically govern resistance to SDM. The QTL information generated in this study provide information that will aid in undertaking an integrated breeding strategy for the transfer of resistance to SDM and RDM in maize lines using marker-assisted selection.

Identification and validation of QTLs conferring resistance to sorghum downy mildew ( Peronosclerospora sorghi ) and Rajasthan downy mildew ( P. heteropogoni ) in maize

N.N. Singh

Papers

Quality protein maize

Sequential path model for determining interrelationships among grain yield and related characters in maize

Tolerance to excess moisture in maize (Zea mays L.): susceptible crop stages and identification of tolerant genotypes

Two-generation marker-aided backcrossing for rapid conversion of normal maize lines to quality protein maize (QPM)

Identification and validation of QTLs conferring resistance to sorghum downy mildew ( Peronosclerospora sorghi ) and Rajasthan downy mildew ( P. heteropogoni ) in maize