Search

Yield and profitability of sugarcane (a complex hybrid of Saccharum spp.) grown on sand soils are much lower than on organic soils in Florida owing to biotic and abiotic stresses. A greenhouse study was conducted using a sand soil to identify effects of water deficit stress (WS) during sugarcane early growth on leaf photosynthetic components, plant growth, and dry matter accumulation. Treatments included two sugarcane genotypes (C p 01-2390 and Cp 80-1743) and two water regimes (well watered (WW) and WS). All plants were well watered before initiating WS. Water was withheld from the WS pots when plants reached seven to eight leaves on the primary stem. During the WS treatment, plant growth and leaf photosynthetic components were measured. Final green leaf area (GLA) and shoot biomass were determined at the end of the experiment. Water stress depressed leaf relative chlorophyll level (SpAD), stomatal conductance (g s ), leaf net photosynthetic rate ( pn), transpiration rate (Tr), transpiration use efficiency (TUE) of photosynthesis, and GLA, resulting in reduced shoot biomass. C p 01-2390 was superior to C p 80-1743 in most measured physiological and growth traits under the WW and WS conditions, suggesting that selection of genotypes with tolerance to WS while improving irrigation management will improve sugarcane yields on sand soils. physiological and growth traits, such as SpAD, g s , pn, Tr, TUE, GLA, tillering, and stalk length, may be useful for early detection of WS and for evaluation of sugarcane genotypes in the stress tolerance.

Leaf refl ectance has been used to estimate crop leaf chemical and physiological characteristics. Sugarcane (Saccharum spp.) leaf N, C, and chlorophyll levels are important traits for high yields and perhaps useful for genotype evaluation. The objectives of this study were to identify sugarcane genotypic variation in leaf hyperspectral refl ectance, leaf chemical (chlorophyll, N, and C), and yield (juice sucrose content, commercial recoverable sucrose [CRS], cane yield in tonnes of cane per hectare [TCH], and sucrose yield in tonnes of sucrose per hectare [TSH]) traits and to determine relationships between leaf refl ectance and these chemical and yield traits. In Stage II of the Canal Point, FL, sugarcane cultivar development program, we measured spectral refl ectance and chemical traits on three leaves of the top visible dewlap from each of 87 genotypes in December 2008 and 208 and 124 genotypes in May, July, September, and October 2009 and 2010, respectively. Yield traits were determined on mature plants. Genotypic variation of leaf refl ectance mainly occurred in 540 to 1200 nm. Leaf relative chlorophyll, N, C, and C to N ratio varied among genotypes and during the growing season. Highly signifi cant calibrations were developed for leaf chemical traits using leaf refl ectance (P < 0.0001). Correlations of juice sucrose, CRS, TCH, and TSH with leaf refl ectance were poor. Measurement of leaf refl ectance is a promising tool for estimating leaf chemical traits but not for predicting yield traits across a large number of diverse genotypes in early selection stages of a sugarcane breeding program.

Thirteen chromosome substitution lines (CS-B) lines with individual 3-79 Gossypium barbadense L. chromosome or arms substituted into TM-1, G. hirsutum L., were crossed with fi ve Upland cultivars and additive and dominance effects for fi ber micronaire, elongation, length, and strength were measured over four environments. Additive genetic effects were considerably larger than dominance or environmental interaction effects. Fiber strength of 3-79 and FM966 were 282 and 240 kN m kg −1 , respectively. FM966 had greater additive effects for fi ber length (1.13 mm) and strength (12.90 kN m kg −1 ) than any CS-B line; however, CS-B25 had the greatest additive effects (8.97 kN m kg −1 ) for strength among CS-B lines. The greatest negative additive effect for fi ber length was −1.29 mm (CS-B22sh). Although several CS-B lines had negative additive effects on strength, none was more negative than TM-1 (−5.31 kN m kg −1 ). CS-B02 and CS-B25 had additive effects on strength of 2.36 and 8.97 kN m kg −1 . SG747 had the greatest negative additive effect (−12.13 kN m kg −1 ) for strength among cultivars and CS-B lines. CSB07 and CS-B18 had negative additive effects for fi ber strength but had signifi cant and positive dominance effects with FM966. When individual CS-B lines were crossed with elite cultivars benefi cial alleles for fi ber properties were uncovered on specifi c chromosomes or chromosome arms that should aid introgression of alleles from 3-79 into Upland.

Upland cotton (Gossypium hirsutum L.) is cultivated in warmer climates throughout the world. The genetic base of modern upland cultivars is narrow. As yield and fiber quality traits are improved, the genetic base should be extended by the incorporation of new germplasm into cultivars. In this study, 114 day-neutral derived primitive accessions were crossed to two cultivars, Stoneville 474 and SureGrow 747 (female parents). In a 2-yr study, parents and F2 hybrids were evaluated in field plots where agronomic and fiber traits were measured. An extended additive-dominance genetic model was used, and the data were analyzed on the basis of the mixed model approach. Dominance effects were the primary genetic effects controlling agronomic and fiber traits, while additive effects were small for most of these traits. Consequently, strong heterosis in some F1 and F2 hybrids for most traits would be expected. The genetic resources from the primitive accessions, determined on the basis of cluster analyses, did not show any consistent pattern for collection location or taxonomic classification. Even though dominance effects were the most common for traits measured, results indicate that these day-neutral derived primitive accessions provide genes with significant additive effects for fiber quality traits, while the additive effects for yield improvement was not significantly decreased. Thus, these derived germplasm accessions can provide favorable gene resources for developing high yielding cultivars or hybrids with improved fiber quality.

Gossypium barbadense L. line 3–79 is lower in yield, has smaller bolls and longer, finer, and stronger fibers than upland cotton G. hirsutum L. Thirteen chromosome substitution (CS-B) lines with individual 3–79 chromosomes or arms substituted into TM-1, G. hirsutum, were top crossed with five elite cultivars and additive and dominance effects for the yield components, lint percentage, boll weight, seed cotton yield, and lint yield, were measured over four environments. Additiveeffectsweregreaterthandominanceeffectsforalltraits.CS-B lines had smaller additive and homozygous dominance effects than the cultivars for most traits. Many CS-B lines had negative additive effects; however,chromosomesubstitutedarms22shand22Loshowedadditive effects for lint yield that were significantly greater than homologous chromosome arms in TM-1. Hybrids of DP90 3 CS-B15sh, ST 474 3 CS-B17, and FM 966 3 CS-B02 had positive dominance effects for lint yield significantly greater than the homologous chromosomes in TM-1. Severalchromosomesorarmswereassociatedwithsignificantnegative additive or dominance effects. These data provide a valuable baseline on yield components for the utility of these CS-B lines in commercial breeding programs. When individual chromosomes or chromosome arms, via CS-B lines, are used in crosses with cultivars, alleles for yield components on specific G. barbadense chromosomes were uncovered that showed positive interactions with alleles in elite germplasm.

In addition to additive (A) and dominant (D) genetic effects, the A x A interaction (or A x A epistatic) effects that control many quantitative traits are important for genetic and breeding studies. To estimate these genetic variance components, including genotype x environment (G x E) interaction, one usually expects to have data from at least two generations (i.e., F 1 and F 2 ) and parents with the same entries in all environments. Practical difficulties may arise in implementing such a design. In this study, we performed Monte Carlo simulations to compare the estimated variance components between four partial and two complete genetic designs (GDs) using the mixed linear model approach. Our definition for GD is different from the traditional definitions of genetic mating designs. Simulation results showed that the estimated genetic variance components for A, A x E, A x A epistatic, and A X A x E effects were unbiased for the six designs. Among four partial designs, two provided the comparable results for D and D × E effects compared with the complete GDs, but with slightly larger mean square errors (MSEs), indicating that some partial GDs can be used when the genetic resources are limited.

Genetic transformation of sugarcane (Saccharum spp.) holds promise for increasing yields and disease resistance. However, the tissue culture and transformation process may produce undesirable field characteristics in transgenic sugarcane. The primary objective of this study was to evaluate variability in agronomic characteristics and field disease resistance of sugarcane transformed for resistance to Sugarcane mosaic virus (SCMV) strain E. One hundred plants derived from cultivars CP 84-1198 (n = 82) and CP 80-1827 (n = 18), consisting of independent virus resistant lines VR 1 (n = 14), VR 4 (n = 24), VR 14 (n = 4), and VR 18 (n = 58) were evaluated in Exp. 1. Transgenics derived from CP 84-1198 had significantly greater tonnes of sucrose per hectare (TSH) and significantly lower SCMV disease incidence than those from CP 80-1827 in the plant-cane (PC), first-ratoon (1R), and second-ratoon (2R) crops. Plants from the VR 18 line had significantly greater economic indices and lower SCMV disease incidence than the VR 4 line in all three crops. Phenotypic variation was high in Exp. 1, with tonnes of cane per hectare (TCH) ranging from 26 to 211 and TSH from 3.2 to 28.9 in the PC crop. Agronomic trait variation decreased with increased selection pressure in Exp. 2, evaluating 30 VR 18 lines, with TCH ranging from 70 to 149 and TSH from 8.5 to 19.0 in PC. The large variability in yield characteristics and disease resistance encountered in this study demonstrates the necessity of thorough field evaluation of transgenic sugarcane while selecting genetically stable and agronomically acceptable material for commercial use.

Primitive accession derived germplasm of cotton, Gossypium hirsutum L., may provide useful traits for cultivar improvement. The ability to predict advanced generation performance when crossed with commercial cultivars would enhance their utility and encourage their use in breeding programs. Our objective for this study was to predict genetic effects for day-neutral derived lines derived from primitive accessions and crossed to cultivars using a mixed linear model approach. Parents and F 2 populations were grown at two field locations in 1998 and 1999 and parents and F 3 s were grown at two locations in 2000. Lint yield, yield components, and fiber quality traits were evaluated. An additive-dominance additive × additive (ADAA) model was used for genetic analysis. A mixed linear model, minimum norm quadratic unbiased estimation (MINQUE) was used to predict genetic effects and genotype values. Generally, the female cultivar parents had higher additive effects for lint yield and lint percentage; however, these females generally had lower additive effects for fiber strength. Significant AA effects widely existed among parents and F 2 populations for lint percentage, boll weight, and fiber strength. The correlation coefficients between observed values and predicted values were mainly high among traits and environments. These data suggest that it is appropriate to use the ADAA genetic model to predict genetic effects and hybrid genotypic values for advanced generations. Our study showed that fiber strength may be significantly improved over that of the female parents, while the lint yield was slightly but not significantly predicted to be less than their female parents. This study suggested that day-neutral primitive germplasm accessions provided a valuable gene resource for selecting high yielding lines with significantly improved fiber strength.

Cotton, Gossypium hirsutum L., is grown primarily for its spinnable fibers. To meet textile mill requirements and producer demands, both fiber quality and yield must be improved. This study was conducted to compare yield and fiber quality when exotic derived lines were crossed to cultivars. Fourteen germplasm lines with high fiber strength derived from selected primitive accessions were crossed as male parents to each of five cultivars. The F 2 populations and parents were grown at two different field locations in 1998 and 1999. Parents and F 3 s were grown at two locations in 2000. Parents, F 2 , and F 3 populations were evaluated for yield, yield components, and fiber quality traits. Combination of location and year was considered an environment for data analyses. An additive-dominance, additive × additive (ADAA), and genotype × environment interaction genetic model was used for data analysis. A mixed linear model approach, minimum norm quadratic unbiased estimation (MINQUE) was used to estimate genetic variance components on the basis of the ADAA model. Cultivars had higher yields and lint percentages than germplasm lines. Fiber strength for germplasm lines exceeded cultivars. Lint percentage, boll weight, micronaire reading, elongation, and fiber length were similar between F 2 and F 3 populations and near mid-parent values. Both additive and additive × additive (AA) epistatic effects significantly controlled all agronomic and most fiber traits. Significant dominance effects were detected for all traits except fiber elongation. Additive x environment and dominance × environment interaction effects were detected for most traits. Significant AA × environment interaction effects were detected for agronomic traits but not fiber traits. The additive × environment effect was significant; however, it made a small contribution to the total variance. This study suggest that crosses between day-neutral derived lines from photoperiodic primitive accessions and commercial cultivars may allow both the utilization of heterosis and the use of genetic variation for pure line development.

Knowledge of genetic diversity and relationships among breeding materials has a significant impact on crop improvement. Association between parental divergence and progeny performance has not been well documented in cotton (Gossypium hirsutum L.). The objectives of this study were to estimate genetic diversity among selected cotton genotypes on the basis of simple sequence repeat (SSR) markers, and to investigate the relationship between genetic diversity and Frbulk population performance. Five U.S. and four Australian cultivars, and two day-neutral converted lines of G. hirsutum were genotyped by means of 90 SSR primer pairs providing 69 polymorphic marker loci. Genetic distance (GD) between genotypes ranged from 0.06 to 0.34 for the 11 parental genotypes. The highest GD (0.34) was observed between ST474 and the day-neutral converted line B1388. The lowest GD (0.06) was detected between cultivars FM832 and FM975. The GD between day-neutral converted lines and cultivars ranged from 0.26 to 0.34. Among the Australian cultivars, GD ranged from 0.06 to 0.19 while GD among U.S. cultivars varied from 0.10 to 0.22, indicating a narrow genetic base. Significant correlations between agronomic and fiber traits of F 2 -bulk populations and GD ranged from negative to positive depending on the traits, genetic background, and environment. On the basis of SSR markers, GD revealed a lack of genetic diversity among all genotypes and it was a poor predictor of overall F 2 performance. However, when genotypes with maximum range of GD were present, it was a better predictor for some traits.

Effective use of converted day-neutral Gossypium hirsutum L. race stocks in cotton genetic improvement programs depends on the extent of genetic variation for desirable alleles and the accurate characterization of the variability within and among germplasm accessions in the collection. This study was conducted to survey the molecular variation in the converted race stock collection by using simple sequence repeat (SSR) DNA markers and to determine the genetic distance of each race stock from a typical G. hirsutum cultigen. The molecular marker data will also provide a measure of the degree to which the recurrent photoperiodic parent has been recovered during backcross conversion to day-neutral stocks. Fifty-six flourescently labeled SSR primer pairs arranged in multiplex bins were used to genotype 97 day-neutral BC 4 F 4 race stock accessions. The majority of the accessions had genetic distances 0.25. In some families, the primitive photoperiodic parent was recovered, and in others there was extensive linkage drag from the day-neutral donor parent. The recovery of the primitive recurrent parent could be improved by marker-assisted backcrossing with SSR markers reported in this experiment. Careful genotyping with SSR markers prior to introgression into breeding programs is suggested to ensure maximum genetic diversity and integrity of the exotic race-stock donor germplasm.

Many of the primitive accessions of cotton, Gossypium hirsutum L., are photoperiodic and not readily useable by plant breeders. Five generations of day-neutral progenies (F 5 , BC 1 F 5 , BC 2 F 5 , BC 3 F 5 , and BC 4 F 5 ) derived from 16 accessions crossed to 'Deltapine 16' were evaluated for agronomic and fiber traits for 3 yr. Genetic variance components for each trait and correlation among these traits were studied. Variation of accession generation was highly significant for all traits studied. Main effects for accessions and generations were significant; however, the magnitude was relatively small compared with the interaction variation. The breeding merit of day-neutral progenies should be evaluated according to specific accessions. Lint yield had significant but small positive phenotypic correlation with lint percentage, boll size, and 2.5% span length, but not with the other traits studied. Highly significant positive correlations were found for effects of accession, generation, and accession x generation between lint yield and lint percentage. With the use of multiple backcrosses to introgress day-neutral genes in primitive cotton accessions large interaction can be expected between accession and backcross generation; therefore, specific generations should be evaluated for the trait of interest.

Primitive accessions of cotton, Gossypium hirsutum L., may provide useful traits for cultivar development. Genetic effects for yield, yield components, and fiber traits were analyzed for five generations of day-neutral progenies. The genetic material was derived from introgressing day-neutral genes from 'Deltapine 16' into 16 primitive accessions with single and multiple backcrosses creating 80 populations representing one to four doses of the unadapted accession. Yield and fiber traits were determined from field plot studies conducted for 3 yr. Significant accession effects were detected for all the traits studied. Significant generation main effects were found for three yield traits and one fiber trait. As expected, yield was predicted to decrease with more cycles of backcrossing to the accession. Accessions × generation interactions were detected for some traits which indicated that not all generations were having equal effects. This genetic analysis provides useful information when utilizing these accessions.

The southern root-knot nematode (RKN), Meloidogyne incognita (Kofoid and White) Chitwood, is a major pest of cotton (Gossypium hirsutum L.). A high level of resistance has been identified in eight germplasm lines; however, these lines are not as productive in yield as current cultivars. This study was conducted to determine the possibility of using F 2 populations from crosses of these RKN resistant germplasm lines with five current cultivars as a means of combining RKN resistance with high yield potential. Two F 2 populations were evaluated for their level of nematode resistance. Resistance in these F 2 populations was greater than the cultivar parents but less than the RKN resistant germplasm parents. The resistance level of the F 2 population, however, was nearer the germplasm parent than the cultivar parent, indicating that the F 2 hybrids possess a useful level of resistance. Yield and fiber properties among the F 2 hybrids indicated that by careful selection of parents, F 2 populations that were equal in yield and fiber quality to the best of the cultivar parents could be produced. Results of this study indicate that F 2 populations may provide a rapid way to combine high levels of RKN resistance with the higher yield and superior fiber properties of current cultivars.

Seventeen germplasm lines (Reg. no. GP-836 through GP-852, PI 636346 to PI 636362) were each developed by hypoaneuploid-based backcross substitution of a different Gossypium barbadense chromosome or chromosome segment into a Gossypium hirsutum genetic background by the Texas Agricultural Experiment Station, the USDA-ARS and the Mississippi Agricultural and Forestry Experiment Station, and released in 2004. The substitution lines are genetically similar to TM-1, an Upland cotton (G. hirsutum) genetic standard, and to each other, except that each line differs by the replacement of a specific homologous pair of chromosomes or chromosome segments from the donor line 3-79, a G. barbadense genetic standard. TM-1 is an inbred line extracted from the commercial cultivar Deltapine 14 and has been maintained over 40 generations by self-pollination. Line 3-79 originated as a doubled-haploid from G. barbadense. The high fibre quality and genetic uniformity of 3-79 and the availability of hypoaneuploid stocks in TM-1 background influenced the choice of parental lines. The 17 germplasm lines were released because attempts to incorporate genes from G. barbadense for exceptional fibre length, strength and fineness into Upland cotton have generally not achieved stable introgression.

The recent conversion of primitive cotton (Gossypium hirsutum L.) stocks to the day-neutral flowering habit has effectively made these accessions readily available for direct use in plant breeding programs. Genetic analysis of these accessions would be useful in ascertaining parental material for improvement of specific traits. The objective of this study was to estimate genetic variances for 13 yield, fiber, and other agronomic traits in 79 accessions and 11 cultivars. A minimum norm quadratic unbiased estimation (MINQUE) method was used for estimating genetic variance components and an adjusted unbiased prediction method for predicting genetic effects. Additive x environment interaction variances were significant for lint yield and node of first fruiting branch. The additive variance components made relatively high contributions to the phenotypic variances for lint percentage and boll size. Additive variances were relatively low for other traits. Narrow-sense heritabilities ranged from 8 to 50% for the traits studied. The proportion of accessions displaying significant, positive effects ranged from 12.7% for 50% span length to 30.4% for lint percentage and 2.5 span length. Positive additive effects for yield, lint percentage, and fiber traits except micronaire and negative effects for N1FB, NOMS, and plant height could be considered favorable effects. Although 16 of the primitive accessions showed significant positive additive effects for lint yield, only MDN-74 and MDN-101could be predicted to produce stronger fiber, as well as higher lint yield and lint percentage. Results indicate that many primitive accessions may be used in crosses with commercial cultivars without serious loss of agronomic potential in the progeny.

Although pest-resistant cotton (Gossypuim hirsutum L.) germplasm is available, it is generally not equal to adapted cultivars and other elite germplasm in yield. Cotton F 2 hybrids could provide a means to combine beneficial traits of high-yielding adapted cultivar (elite) germplasm with those of pest-resistant germplasms. In the F 2 heterosis and combining ability were studied for lint yield and the primary yield component boll number as well as for the secondary yield components of lint percentage and boll weight (.)

Estimates of combining ability and heterosis for fiber properties among pest-resistant cotton (Gossypium hirsutum L.) gene pools and cultivars are necessary for efficient F 2 hybrid development. Four cultivars were crossed as female with 16 pest-resistant germplasm lines in a North Carolina Design II to evaluate combining ability and potential heterosis of F 2 hybrids for six fiber characteristics. The 20 parents and 64 F 2 hybrids were evaluated in four environments at Mississippi State, MS (.)

Cotton plants, Gossypium hirsutum L., initiate more fruiting buds than are matured. This research quantified the boll set percentage and boll size by fruiting site in a population of cotton plants. The fruiting sites of harvestable bolls were recorded for 2 yr in eight cultivars : Stoneville 213 (ST 213), Stoneville 506 (ST506), Stoneville 825 (ST 825), Tamcot CAMD-E (CAMD-E), Deltapine 50 (DPL 50), McNair 235 (MC 235), DES 119, and Deltapine 20 (DPL 20) (...)