Crop Effects on Broad‐Sense Heritabilities and Genetic Variances of Sugarcane Yield Components

Abstract

Estimates of genetic variances and derived statistics of pertinent traits are essential for efficient plant breeding programs. For clonal sugarcane (Saccharum spp.) populations in Louisiana, such estimates (and unconfoanded estimates of genotype by environment [GE] and genotype by crop [GC] variances) were lacking. The objectives of this study were to estimate broad‐sense genetic and GE variance components for a clonal sugarcane population representative of initial stages of replicated testing and to determine the relative importance of years, locations, and crops. Thirty‐seven genotypes were planted in 1983 and replanted in 1984 in replicated tests at five locations. Data from two 3‐yr. crop cycles were used. Genetic advance (GA) indicated considerable improvement potential in sucrose yield, cane yield, and stalk number and weight. Genotypic variance was generally secondary to error variance in determining phenotypic variance; GE variances were tertiary to genotypic and error variances. Within a crop, genotype by location (GL) variances tended to be larger than genotype by year (GY). Estimates of potential of plant cane sucrose yields over years and locations implied testing across locations could substitute for years, effectively reducing the time to identify elite clones. Analysis across crops showed GC, GL and GYL interaction variances were usually larger than GY. Estimates of GA showed no difference in potential gain from replicating across years vs. crops. For several traits, the most potential for improvement is in older crop performance, and selection is best practiced with regard to crop.

Heritability and Correlation among Sugarcane (<i>Saccharum</i> spp.) Yield and Some Agronomic and Sugar Quality Traits in Ethiopia

“…Genetic coefficients of variation provide a unit less measure of a trait's genetic variance relative to its mean and permit comparisons among traits with different units and scales and give perspective to available variability to be potentially exploited for genetic gain [8]. The phenotypic coefficient of variation (%) was calculated as PCV = 100σ p /phenotypic mean of a trait, and genotypic coefficient of variation as GCV = 100σ g /phenotypic mean of a trait.…”

“…Expected genetic advance (GA) for each trait was calculated as a proportion of the general mean to allow comparison among traits for potential improvement through selection [8] where i = selection intensity, σ p = phenotypic standard deviation of trait, h 2 = heritability. Genetic (r g ) and phenotypic (r p ) correlation coefficients and their standard errors were obtained among all the traits by estimating genetic, genotype by environment and error covariances combined across locations using version 9 of SAS Proc Mixed and the REML analysis method based on the variance and covariance components according to [23] as:…”

“…This knowledge can be used when devising appropriate selection strategies for particular traits in a sugarcane breeding program [7]. Number of millable stalks, stalk height and stalk diameter were reported to be positively associated with cane yield [8] [9]. Reference [10] studied phenotypic associations between yield and its components in sugarcane and concluded that selecting for stalk number, diameter and length should be emphasized in sugarcane variety development programs where high cane yield was the primary goal.…”

The Effect of Two Different Agro Climatic Conditions on Growth and Yield Performance of Sugarcane Genotypes

“…Changes in ranking make it difficult for the plant breeder to decide which genotype should be selected (Nguyen et al, 1980). The importance of G x E interactions in sugarcane selection is widely recognized (Milligan et al, 1990). Environmental effects on sugarcane yields may be due to differing nutrient deficiencies (Anderson et al, 1995), disease pressures or climatic differences among locations (Magarey and Mewing, 1994).…”

QTL Analysis in a Complex Autopolyploid: Genetic Control of Sugar Content in Sugarcane

“…Pure inbred lines do not exist due to the difficulty of self-pollination and the random pairing of multiple homologous chromosomes. The segregating populations used in genetic studies are the progenies (first generation) derived from crosses between two cultivated varieties (Kang et al 1983;Milligan et al 1990) or cultivated varieties and wild species (Guimarães et al 1997;Ming et al 1998). Chromosome transmission is normal for most crosses, yielding n‫ן+ן‬n progeny (Burner 1997), but 2n‫ן+ן‬n transmission predominates in S. officinarum (2n = 80) ‫ן‬ S. spontaneum F 1 and BC 1 crosses, a phenomenon known as "female restitution" (Bremer 1923;Price 1957).…”