Tassel Branch Research Articles

Inbreeding in two maize subpopulations selected for tassel size

The present work was based on the evaluation of full sib and S1 progenies from the maize (Zea mays L.) population ESALQ-PB1 after six cycles of divergent selection for tassel size. The following traits were analyzed: plant height , ear height, tassel branch number, tassel length, and tassel weight. For all traits, the experimental units were means of three plants per plot. Progenies were evaluated in eleven experiments (completely randomized blocks) with three replications in Piracicaba -- SP, Brazil. Means of inbred (m1) and non-inbred (m0) progenies were used to estimate inbreeding depression (I = m1 -- m0) and the contribution of homozygotes (mu0 + a*) and heterozygotes (d*) to the population mean. Considering the five traits under study, inbreeding depression varied from 1.9 to 15.9% but significance for that effect was detected only for plant height. Plant traits exhibited higher depression than tassel traits; and tassel branch number seems to be more sensitive to inbreeding than the other two tassel traits. Except for plant height, it was apparent that inbreeding depression was higher in the subpopulation negatively selected for tassel size (T--). Estimates of A = mu0 + a* and d* indicate a smaller effect of dominance deviations for all traits, as compared to the contribution of homozygotes. Significant variability among progenies was detected in most instances.

Zea nicaraguensis (Poaceae), a New Teosinte from Pacific Coastal Nicaragua

Zea nicaraguensis (Poaceae), a New Teosinte from Pacific Coastal Nicaragua

Environmental effects on the early stages of tassel morphogenesis in maize (Zea mays L.)

ABSTRACTThe effects of various environmental conditions on the initiation of tassel branches (NTB) and spikelet‐pairs (NSP) were examined in the stress‐sensitive maize inbred F53. Chilling induced the most important effect, with a dramatic decrease in both NTB and NSP, provided it was applied at the end of the vegetative phase and start of the floral transition phase. The primary cause of chilling‐induced abortion of the tassel branches could be oxidative stress in the leaves, since lowering light irradiance during chilling greatly reduced the effect of cold. The comparison of inbreds F53 and F2 revealed that both genotypes exhibited a similar period of cold sensitivity at the floral transition phase, although F2 was considered from field observations as a stress‐insensitive genotype (at least for tassel development). However, our results also showed a chilling acclimation response in inbred F2 but not in inbred F53. The similarities with the work by Lejeune & Bernier (1996Plant, Cell and Environment 19, 217–224.) concerning the effect of chilling on ear initiation in the sensitive inbred, B22, are emphasized.

Initiation of the Vascular System and the Transition to Flowering in Early Tassels of Zea mays Land Race Chapalote (Poaceae).

Serial transections of young tassels of (Zea mays land race) chapalote revealed relationships between the vascular system in its procambial state and the lateral primordia along the axis. A lateral tassel primordium usually consists of an indefinite rim with a prolongation that will become a tassel branch or spikelet pair. A lateral tassel primordium usually develops via modifications of the vegetative leaf primordium in which the leaf apex is enhanced but the leaf base and the bud it produces are suppressed. The clearest sign of the transition from the vegetative state to the tassel is the scale leaf, which is intermediate in form between a vegetative leaf and a lateral tassel primordium. Procambial traces differentiate in isolation in the tassel axis in response to the lateral tassel primordia. Adjacent procambial traces then link axially into sympodia to initiate the three-dimensional vascular system of the tassel axis. Older sympodia occur near the center of the axis interior to more recently initiated procambial traces. Procambial continuity does not occur between the tassel axis and the lateral primordia until isolated traces in the lateral primordia link with the sympodia in the tassel axis. The transition from distichy to polystichy by the lateral tassel primordia occurs as the narrowing of the leaf base makes space available on the tassel axis for lateral primordia out of the vegetative distichous plane.

Genetic analysis of adaptation differences between highland and lowland tropical maize using molecular markers

Molecular-marker loci were used to investigate the adaptation differences between highland and lowland tropical maize. An F2 population from the cross of two inbred lines independently derived from highland and lowland maize germplasm was developed, and extracted F3:4 lines were phenotype in replicated field trials at four thermally diverse tropical testing sites, ranging from lowland to extreme highland (mean growing season temperature range 13.2–24.6°C). Traits closely related with adaptation, such as biomass and grain yield, yield components, days from sowing to male and female flowering, total leaf number, plant height and number of primary tassel branches (TBN), were analyzed. A large line × environment interaction was observed for most traits. The genetic basis of this interaction was reflected by significant, but systematic, changes from lowland to highland sites in the correlation between the trait value and genomic composition (designated by the proportion of marker alleles with the same origin). Joint analysis of quantitative trait loci (QTLs) over sites detected 5–8 QTLs for each trait (except disease scores, with data only from one site). With the exception of one QTL for TBN, none of these accounted for more than 15% of the total phenotypic variation. In total, detected QTLs accounted for 24–61% of the variation at each site on average. For yield, yield components and disease scores, alleles generally favored the site of origin. Highland-derived alleles had little effect at lowland sites, while lowland-derived alleles showed relatively broader adaptation. Gradual changes in the estimated QTL effects with increasing mean site temperature were observed, and paralleled the observed patterns of adaptation in highland and lowland germplasm. Several clusters of QTLs for different traits reflected the relative importance in the adaptation differences between the two germplasm types, and pleiotropy is suggested as the main cause for the clustering. Breeding for broad thermal adaptation should be possible by pooling genes showing adaptation to specific thermal regimes, though perhaps at the expense of reduced progress for adaptation to a specific site. Molecular marker-assisted selection would be an ideal tool for this task, since it could greatly reduce the linkage drag caused by the unintentional transfer of undesirable traits.

Quantitative Trait Loci for Tassel Traits in Maize

The inheritance of tassel traits in maize (Zea mays L.) is not well understood. This study was conducted to estimate the chromosomal location and magnitude of effect of major quantitative trait loci (QTL) affecting tassel branch angle (ANGLE), branches per tassel (BRANCH#), and tassel weight (TASSWT) in 200 S1 lines derived from a single F1 plant from a cross of Illinois High Oil (IHO) by Illinois Low Oil (Early Maturity) [ILO(EM)]. The restriction fragment length polymorphism (RFLP) genotypes of the 200 S1 lines were determined at 80 polymorphic loci. These lines were measured for ANGLE, BRANCH#, and TASSWT in replicated field trials during 1992 and 1993 at Urbana, IL. Composite interval mapping using selected markers as cofactors detected several QTL for each tassel trait. Six QTL located on chromosomes 2, 3, 5, 6, and 10 were significantly associated with ANGLE. They showed primarily dominant gene action and explained 43.1 and 50.7% of the phenotypic and genetic variance, respectively. Three QTL located on chromosomes 2, 4, and 7 were significantly associated with BRANCH#. They showed primarily additive gene action and explained 44.3 and 49.3% of the phenotypic and genetic variance, respectively. The QTL for BRANCH# on chromosome 7 explained 35.3% (R2) of the phenotypic variance. Seven QTL located on chromosomes 1, 2, 3, 4, and 7 were significantly associated with TASSWT. They showed primarily negative dominant gene action and explained 35.1 and 43.4% of the phenotypic and genetic variance, respectively. Most of the major QTL detected for these tassel traits were not associated with anthesis date (ANTH) in this population.

Selection Improves Drought Tolerance in Tropical Maize Populations: II. Direct and Correlated Responses among Secondary Traits

Recurrent selection for drought tolerance for three to eight cycles has increased grain yield (GY) under drought at flowering by 30 to 50% in three lowland tropical maize (Zea mays L.) populations. The relationships among secondary traits as a result of this selection have not been determined, however. The objectives of this study were to measure direct and correlated changes due to selection in secondary traits by evaluating cycles of selection and appropriate check entries at five water‐stressed (mean yield 2.35, range 1.01–4.48 Mg ha−1) and five well‐watered environments (mean yield 7.96, range 5.81–10.40 Mg ha−1). Under drought, changes per cycle with recurrent S1 selection (P < 0.05) were as follows: GY 12.6%, fertile ears per plant (EPP) 8.9%, grains per fertile ear (GPE) 6.3%, grain number per square meter 12.2%, 1000 grain weight no change, anthesis‐silking interval (ASI) −22.0%, days from sowing to 50% anthesis −0.7%, plant height −2.0%, primary tassel branch number −5.9%, and senesced leaf area 2.7%. Responses under well‐watered conditions were smaller but generally of the same sign. Grain yield was strongly associated with grain number per square meter in both water‐stressed and well‐watered environments Grain yield, EPP, and GPE were strongly correlated with ASI across entries under drought , though not when water was plentiful. The use of managed stress environments that consistently reveal genetic variation for these traits at specific times during crop development is endorsed for selection purposes.

The liguleless2 gene of maize functions during the transition from the vegetative to the reproductive shoot apex.

During a maize plant's (Zea mays) development, the shoot apical meristem (SAM) generates an apex that proceeds through different phases: juvenile vegetative, adult vegetative and reproductive. During each phase the structures produced are distinguishable from structures produced during the other phases. In this paper, we demonstrate that the LIGULELESS2 (LG2) function is required for an accurate vegetative to reproductive phase transition. The maize gene liguleless2 (lg2) has been shown to encode a basic-leucine zipper (bZIP) protein and to function in narrowing the region from which the ligule and auricle develop in a typical maize leaf. Here we show that lg2 mutant plants can have reduced long tassel branches, extra vegetative leaves and extra husk leaves when compared to wild-type siblings. This indicates a role for the lg2 gene in the vegetative to reproductive phase transition of the shoot apex. We also discuss a potential role for the lg2 gene in general phase transition processes.

Organ and Cell Fusions in the Adherent1 Mutant in Maize

The plant epidermis is only rarely involved in fusion events. These events often occur when the epidermis has been wounded or removed. The adherentl (adl) mutation in maize shows fusions between cells and organs in the presence of an intact epidermis. Fusions are not limited to a particular stage of organ development. The first fusion events occur very early in development and adherent leaves can be seen in ungerminated embryos. In the vegetative parts of the plant the coleoptile can fuse to the first leaf and juvenile leaves can fuse to each other. At the onset of reproduction, tassel branches can adhere to each other, the flag leaf can fuse to the tassel, and the glumes can fuse to the anthers. While fused regions appear to have an intact cuticle, cell surfaces are perturbed in the mutation. Time-lapse replicas reveal that trichome fusion on organ surfaces is postgenital. The extracellular matrix can exert control over organs and tissues in plants; the Adl gene may represent a product that determines the composition or function of this extracellular matrix.

Potential of twenty exotic germplasms to improve Brazilian maize architecture

Temperate and temperate x tropical germplasms were introduced into the maize breeding of the Department of Genetics (ESALQ-USP). Twenty populations designated as P-1 to P-20 and a check population were evaluated in a randomized complete block design with two replications at Piracicaba, SP, Brazil. Plots were 2.0 m long, spaced 1.0 m apart, with 10 plants per plot after thinning. The following traits were evaluated: PH, plant height; EH, ear height; TB, tassel branch number; KW, 100 kernels weight; EL, ear length; ED, ear diameter; KR, kernels per row, and RN, number of rows of kernels. The means of the exotic populations showed a variation in performance for all traits. The population means were greater than check means for KW, EL, and KR. Populations P-9, P-10, P-12, and P-13 showed low relative ear placement values (EH/PH index), indicating that these materials could contribute to lower ear placement in local populations. P-1 and P-9 showed a high potential to reduce TB. The phenotypic correlation coefficients among populations were positive for most combinations, except for RN with PH, EH, TB, and KW. Predictions of 19 composite means were obtained for all traits.

Organogenesis of Fascicled ear mutant inflorescences in maize (Poaceae)

The ontogeny of staminate tassels and pistillate ears in the maize mutant Fascicled ear was examined using scanning electron microscopy. The normal pattern of inflorescence development is perturbed by the Fascicled ear mutation at the transition stage. The Fascicled ear mutation promotes the development of an abnormal transition stage axis that is both shorter and broader than the wild type. The inflorescence apical meristem then undergoes a bifurcation, and two inflorescence axes arise in place of a single axis. Each derived inflorescence apical meristem may undergo a similar perturbation sequence. This expression of the Fascicled ear mutation may be repeated one to several times, which leads to the development of a fascicled pistillate inflorescence and a fascicled central spike in the staminate inflorescence. The apical meristems of some tassel branches are also bifurcated. Subsequent organogenesis during paired-spikelet and floral development in Fascicled ear plants follows the pattern of normal maize. However, triplet spikelets are occasionally observed. The organogenic disruption by the Fascicled ear mutation that we describe will aid genetic and molecular analysis on the regulation of inflorescence development in maize and other members of the genus Zea.

The importance of the anthesis-silking interval in breeding for drought tolerance in tropical maize

Selection for improved performance under drought based on grain yield alone has often been considered inefficient, but the use of secondary traits of adaptive value whose genetic variability increases under drought can increase selection efficiency. In the course of recurrent selection for drought tolerance in six tropical maize ( Zea mays L.) populations, a total of 3509 inbred progenies (S 1 to S 3 level) were evaluated in 50 separate yield trials under two or three water regimes during the dry winter seasons of 1986–1990 at Tlaltizapán, México. In over 90% of the trials, ears plant −1, kernels plant −1, weight kernel −1, anthesis-silking interval (ASI), tassel branch number and visual scores for leaf angle, leaf rolling and leaf senescence were determined. Low scores indicated erect, unrolled or green leaves. Canopy temperature, leaf chlorophyll concentration and stem-leaf extension rate were measured in 20–50% of the trials. Across all trials, linear phenotypic correlations ( P < 0.01) between grain yield under drought and these traits, in order listed, were 0.77, 0.90, 0.46, −0.53, −0.16, 0.06 NS, −0.18, −0.11, −0.27, 0.17 and 0.10. Genetic correlations were generally similar in size and sign. None of physiological or morphological traits indicative of improved water status correlated with grain yield under drought, although some had relatively high heritabilities. Genetic variances for grain yield, kernels ear −1, kernels plant −1 and weight kernel −1 decreased with increasing drought, but those for ASI and ears plant −1 increased. Broad-sense heritability for grain yield averaged around 0.6, but fell to values near 0.4 at very low grain yield levels. Genetic correlations between grain yield and ASI or ears plant −1 were weak under well-watered conditions, but approached −0.6 and 0.9, respectively, under severe moisture stress. These results show that secondary traits are not lacking genetic variability within elite maize populations. Their low correlation with grain yield may indicate that variation in grain yield under moisture stress is dominated by variation in ear-setting processes related to biomass partitioning at flowering, and much less by factors putatively linked to crop water status. Field-based selection programs for drought tolerance should consider these results.

Characterization of Interpopulation Genetic Variability in Three Hybrid Maize Populations

A cross-classification (North Carolina Design II) mating design was used to produce half-sib and full-sib families in three hybrid maize (Zea mays L.) populations: BSSSC0 × BSCB1C0, BSSS(R)C9 × BSCB1(R)C9, and BS13(S)C3 × BSCB1(R)C9. Families were evaluated in a replications-within-sets, randomized incomplete block design with two replications at five locations. Data were collected for grain yield, grain moisture, root and stalk lodging, dropped ears, plant and ear height, days from planting to anthesis and silking, and number of tassel branches. The objective was to estlmate genetic variance components, heritabilities, genetic correlations, and genetic gains for the three hybrid populations. The additive genetic variance component was the most important component of genetic variability for all traits. Except for grain yield, additive by environment interpopulation variance estimates were smaller than their corresponding additive variances. For grain yield, the additive variance components increased with selection; however, the original population cross showed greater additive by environment interaction variance than the improved population crosses. The estimates of additive genetic variance increased for plant and ear height and decreased for root and stalk lodging with reciprocal recurrent selection for grain yield. Except for grain yield, all traits exhibited a decrease in estimates of the dominance variance component after recurrent selection. The BSSS additive genetic contribution to the total interpopulation additive variance became more important with selection except for days to anthesis, days to silking, and number of tassel branches. Heritability estimates for grain yield increased with recurrent selection. Heritablity estimates of the original and selected cross populations were similar for the other traits. Grain yield had positive genotypic correlations with grain moisture, plant height, and ear height and negative correlations with stalk lodging. Correlations between traits were not affected by selection for yield. The results suggest that reciprocal recurrent selection was an effective method for improving the population cross for yield without decreasing genetic variability.

Suppressor of sessile spikelets1 (Sosl): a dominant mutant affecting inflorescence development in maize

Suppressor of sessile spikeletsl (Sos1) is a dominant mutant of maize that blocks branching of the spikelet‐pair primordium to form the sessile spikelet during ear development. As a result, Sos1 mutant ears and tassels possess single spikelets as opposed to the normal condition of paired spikelets, one sessile and the other pedicellate. Sos1 also causes a reduction in the number of tassel branches and the number of orthostichies (or cupule ranks) in the ear. The sos1 genetic locus maps to the short arm of maize chromosome 4. The Sos1 single spikelet phenotype appears similar to the single spikelet phenotype found in teosinte, the probable progenitor of maize. This similarity invites the hypothesis that sos1 had a role in the evolution of maize from teosinte. However, genetic mapping data and a comparison of the developmental basis of the single spikelet condition in the Sos1 mutant and teosinte demonstrate that their similar phenotypes result from distinct genetic‐developmental mechanisms. These results indicate that sos1 was not involved in the evolution of maize and caution against drawing conclusions of homology based solely on similar adult phenotypes.

Genetic Changes Associated with Different Methods of Recurrent Selection in Five Maize Populations: II. Indirectly Selected Traits

Recurrent selection in a population can result in changes in traits other than those used directly as selection criteria. Such changes usually are not easily predicted or understood because they do not occur in a consistent manner. This study was conducted to compare changes in indirectly sdected traits (plant height, ear height, tassel branch number, and days to anthesis and silking) in five maize (Zea mays L.) populations (CGSynA, CGSynB, CGG, CGN, and CGW) that were selected for performance indices based on grain yield, grain moisture, and standability. Four selection methods were compared: modified ear‐to‐row (ME) in CGSynA, CGSynB, CGG, and CGN; half‐sib family (HS) in all five populations; selfed progeny (S) in five populations; and reciprocal recurrent selection (RRS) in CGSynA and CGW. Generally, response to indirect selection depended on (i) the selection method used, (ii) the initial mean value of a trait the original population, and (ii) correlations between indirectly and directly selected traits. The combination of these factors seems to determine whether an indirectly selected trait will increase, decrease, or remain constant in advanced cycles of selection. No general trend for response to indirect selection was observed for ear height, plant height, or tassel branch number. Days to anthesis and silking were mainly reduced. This uniform response of days to tlowering was partly due to non‐documented selection against later flowering plants in initial cycles of selection. Genetic drift generally acted in the opposite direction from response to selection, and I‐IS resulted in the least genetic drift. Generally, it seems that the indirectly selected traits changed in the way that would most efficiently contribute to the desirable changes of the directly selected traits.

Use of Tassel‐Seed (Ts‐5) Maize for Assimilate Transport Studies Using Intact or Detached Tassel Branches

The anatomy of normal maize (Zea mays L.) ears precludes easy access to the kernel pedicel tissue for in vivo assimilate transport experiments. We investigated the possibility of using the Tassel‐seed (Ts‐5) mutant of maize as a model system for studies of assimilate movement into developing maize kernels. Hypodermic needles (26 gauge, 9.5 mm long) inserted under the pedicel epidermis of intact plants were used to introduce solutes into the pedicel free space. Additionally, excised tassel branches were incubated in buffered solutions containing 100 mM 14C.labeled sugars. The movement of apoplastic and symplastic fluorescent dyes as well as 14C‐iabeled assimilates and incubation solutions showed that Ts‐5 maize provides a useful experimental system for study of the mechanism of assimilate transport into developing kernels.

Heterochronic Effects of Teopod 2 on the Growth and Photosensitivity of the Maize Shoot.

Teopod 2 (Tp2) is a semidominant mutation of maize that prolongs the expression of juvenile vegetative traits, increases the total number of leaves produced by the shoot, and transforms reproductive structures into vegetative ones. Here, we show that Tp2 prolongs the duration of vegetative growth without prolonging the overall duration of shoot growth. Mutant shoots produce leaves at the same rate as wild-type plants and continue to produce leaves after wild-type plants have initiated a tassel. Although Tp2/+ plants initiate a tassel later than their wild-type siblings, this mutant tassel ceases differentiation at the same time as, or shortly before, the primary meristem of a wild-type tassel completes its development. To investigate the relationship between the vegetative and reproductive development of the shoot, Tp2/+ and wild-type plants were exposed to floral inductive short day (SD) treatments at various stages of shoot growth. Tassel initiation in wild-type plants (which normally produced 18 to 19 leaves) was maximally sensitive to SD between plastochrons 15 and 16, whereas tassel branching was maximally sensitive to SD between plastochrons 15 and 18. Tassel initiation and tassel morphology in Tp2/+ plants (which normally produced 21 to 26 leaves) were both maximally sensitive to SD between plastochrons 15 and 18. Thus, the constitutive expression of a juvenile vegetative program in Tp2/+ plants does not significantly delay the reproductive maturation of the shoot.

INFLORESCENCE DEVELOPMENT IN TWO ANNUAL TEOSINTES: ZEA MAYS SUBSP. MEXICANA AND Z. MAYS SUBSP. PARVIGLUMIS.

The ontogeny of tassels and ears in two annual Mexican teosintes, Zea mays subsp. mexicana and Z. mays subsp. parviglumis, was examined using scanning electron microscopy and light microscopy. Ear development in these annual teosintes follows a pattern previously described as leading to the bisexual mixed inflorescence in Z. diploperennis. Common bud primordia are initiated in the axils of distichously arranged bracts along the ear axis. These common primordia bifurcate to form paired sessile and pedicellate spikelet primordia. Development of pedicellate spikelets is arrested leaving the sessile spikelets, along with the adjoining rachis segment, to form solitary grains enclosed within cupulate fruitcases. Development of the central tassel spike is similar to that previously described in the Z. diploperennis tassel, except that the first formed axillary bud primordia form precocious tassel branches. The origin of these tassel branches suggests a possible mechanism for the transition from a distichous spike, characteristic of teosinte, to a polystichous spike, typical of maize.

Recurrent Selection for Reduced Tassel Branch Number and Reduced Leaf Area Density above the Ear in Tropical Maize Populations1

Tropical maize (Zea mays L) is characterized by large tassels, broad, long leaves above the ear, and by a low harvest index. This study was conducted to evaluate direct and correlated responses to selection for reduced tassel primary branch number and for reduced leaf area density above the ear (LADAE). Leaf area density above the ear was defined as (number of leaves above the ear ✕ mean area of leaves EL + 1, EL + 3)/(plant height — ear height) ✕ land area occupied per piano, where EL refers to the position of the ear leaf. Six cycles of full‐sib recurrent selection for each of these traits was conducted in each of two populations (‘Tuxpeño‐l’ and ‘Antigua‐República Dominicana’). In a third population, ‘ETO Blanco’, there was simultaneous selection for both traits. Evaluation of Cycles 0 and 6 of single trait selections and Cycle 0,2,4, and 6 of combined trait selection, plus checks, was at several plant densities at three locations in Mexico over 2 yr. Significant (P = 0.05) mean gains per cycle for tassel branch number, LADAE, grain yield, and harvest index were: (i) Tuxpeño‐l: selection for reduced tassel branch number:−7.4, not significant (NS), 2.2, and 2.4%; selection for reduced LADAE: −1.2, −3.8, NS, and 3.8%; (ii) Antigua‐República Dominicana: selection for reduced tassel branch number: −8.6, −1.6, 2.4, and 2.2%; selection for reduced LADAE: −5.7, −2.6, 2.0, and 2.2%; and (iii) ETO Bianco, selection for reduced tassel branch number and LADAE: −6.8, −1.8, 2.5, and 2.9%, respectively. The correlation between LADAE and mean maximum leaf width, after removing the population effect, was 0.95**, significant at the 0.01 probability level (13 df. In all populations, selections resulted in significant increases in the predicted optimum plant density for grain yield, significant decreases in the anthesis‐to‐silking interval, and a shorter interval from planting to 50% silking.

An evaluation for genetic variation within maize inbred lines maintained by sib-mating and self-pollination

Maintaining maize (Zea mays L.) inbred lines without genetic change is an important concern of maize breeders and seed producers. Long-time inbred lines, however, have been shown to be genetically unstable, and with selection pressure acting on the resulting genetic variation, these lines have evolved into different strains. The objective of this study was to compare maintenance of line integrity under reproduction by sib-mating and self-pollination in ear-to-row progenies. Ten lines, varying from 5 to 35 generations of previous ear-to-row selfing, were maintained for 11 successive generations under each method of reproduction. Alternate generations were compared by using a randomized complete-block design with each family of lines as a separate experiment. Data were collected for 10 plant and yield traits: pollen shed and silk emergence dates, plant and ear heights, tassel branch number, kernel row number, ear length and diameter, grain yield, and 300-kernel weight. Summarizing for F-tests over all traits and experiments, 30% were significant among sib-mated generations and 56% among selfed generations. Also, overall generation means of the two methods were different for 51% of the comparisons, and the selfed lines were less vigorous for 79% of the significant comparisons. It was concluded that sib-mating lessens the effect of genetic instability and that a reproduction system of sib-mating with intermittent generations of selfing may be more beneficial than continuous ear-to-row selfing for certain lines.