No abstract

Plant breeders generally conduct the selection phase of their program at few locations, mainly on the basis of geography and resource limitations. We conducted this study to identify test locations that optimize genotype selection on the basis of discriminating ability and representativeness. GGE Biplot Pattern Explorer was used to rank six test locations in Louisiana for cotton (Gossypium hirsutum L.) lint yield and fiber length using data from the 1993 to 2003 Louisiana Official Variety Trials (early and medium maturity). Biplots were generated and distances between the “ideal” and actual test locations were measured. Locations with shorter distances were closer to the ideal location and were considered more desirable test locations for the traits of interest. Each test location's distance was standardized by the mean distance of all locations for each biplot. For lint yield, on the basis of its close proximity to the ideal test location and the low standard deviation, the most desirable selection location was St. Joseph loam (Commerce silt loam; fine‐silty, mixed, nonacid, thermic, Aeric, Fluvaquent). Winnsboro nonirrigated and Bossier City were not good selection locations for lint yield. For fiber length, Winnsboro irrigated was ranked first and St. Joseph loam was ranked third. Winnsboro nonirrigated was ranked sixth. A composite distance, reflecting the distance between the actual and “ideal” location for lint yield weighted at 60% and fiber length weighted at 40%, was used to determine the desirability of test locations on the basis of simultaneous selection for lint yield and fiber length. St. Joseph loam ranked first, Winnsboro irrigated ranked second, and Winnsboro nonirrigated ranked sixth. St. Joseph loam or Winnsboro irrigated should be used for selecting cultivars for lint yield and fiber length. Winnsboro nonirrigated should not be used for selecting cultivars because of its low level of discrimination and unique behavior.

The study of genotype × environment interaction is critical for accurate cultivar evaluation in large multi‐environment trials. Cultivars that exhibit high levels of mean performance and stability across a wide range of environmental conditions are desirable for rice production. Pure‐line varietal and hybrid rice cultivars are commercially produced in the U.S.; however, little research has been conducted comparing their stability for grain yield and milling quality. In this study, 15 hybrid and varietal cultivars were grown in 10 environments from 2005 to 2007 to determine the performance and stability of rough rice yield, whole milled rice percentages, and whole‐grain rice yield. Stability was analyzed using the coefficient of variation, Shukla's Stability Variance statistic with environment means as a covariate, and the Cultivar Superiority Measure. The hybrid rice cultivars XP723 and CLXL730 were ideal for high and stable rough rice and whole‐grain rice yields on the basis of the cultivar superiority measure; however, for whole milled rice percentage alone, they were among the least desirable cultivars. Among the varietal cultivars, Catahoula and Jupiter were ideal cultivar selections for high and stable whole‐grain rice yields. The results of this study indicate that the stability and performance of hybrid and varietal cultivars differ according to the trait of interest.

Improving essential amino acids or protein content, along with other phytonutrients in the food crops, will affect a great portion of the world population, especially in developing countries where rice grain is the main source of protein. Malnutrition, including deficiencies in protein/energy, iron/zinc, vitamin A, and iodine, causes a total 24,000 deaths per day worldwide. The problem is severe where rice is the major staple food. Protein deficiency involves both the quantity (amount) and quality (the content in essential amino acids) of the dietary protein. Various interventions, such as distribution, fortification, dietary diversification, and measures against infectious diseases, have been applied to reduce deficiency disorders. The problem, however, remains unsolved. Developing genetically novel lines with elevated content of essential amino acids together with other health benefit components becomes more feasible for the enhancement of breeding techniques, genomics, molecular manipulations, and genetic engineering. Advancement in basic genetic and genetic engineering has resulted in successful enrichment of some essential amino acids, such as lysine (Lys), tryptophan (Trp), and methionine (Met). Successful genetic enhancement has been largely restricted to the maize crop through enrichment of grain Lys and to some extends Trp. Since rice is the main source of calories and protein intake for billions of people, enhancing essential amino acids in rice represents a tremendous challenge. This paper will discuss and review the current status in basic genetics, molecular genetics, and genetic engineering associated with the enhancement of amino acids and other health benefit components in major grain crop improvement. Patents and future efforts associated with enhancing nutritional quality of the grain will also be reviewed as a concerted effort to solve the malnutrition problem and improve the quality of life worldwide.

Research was conducted for 2 yr on a Crowley silt loam soil (fi ne, smectitic, thermic Typic Albaqualfs) near Crowley, LA to evaluate the main eff ects of tillage, seeding and N rate and potential interactions on rice (Oryza sativa L.) density, yield, and yield components. Two tillage systems (conventional and fall-stale seedbed), four seeding rates (162, 323, 484, and 646 seed m -2 ) and four N rates (101, 134, 168, and 202 kg ha -1 ) were evaluated. 'Jupiter' and 'Cheniere' a medium and long grain cultivar, respectively, were evaluated in separate experiments. Conventional tillage reduced rice plant density as compared with fall-stale seedbed tillage due to crusting following fl ush irrigation during seedling emergence. A tillage by N rate interaction was not observed, suggesting optimal N rates are similar for rice grown using a conventional or fall-stale seedbed. Rough rice grain yield was optimized at 202 and 168 kg N ha -1 for Jupiter and Cheniere, respectively. Grain yields were optimized for Jupiter at 323 seed m -2 , while Cheniere required a seeding rate of more than 323 seed m -2 . Panicle density was found to be the single most infl uential yield component on rice yield and was able to explain 49 and 51% of the variation in yield for Jupiter and Cheniere, respectively. Filled grain panicle -1 was inversely related to panicle density highlighting the ability of rice to tiller as a yield compensatory measure when less than optimum rice densities exist. However, total yield compensation may not be feasible at low seeding rates.