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Finger millet (Eleusine coracana(L.) Gaertn. subsp.coracana) is the most importantmillet in eastern Africa and perhaps the oldest domesticated cereal grain in Africa.One of the major factors limiting finger millet production is blast disease caused bythe fungusMagnaporthe grisea. Crop wild relatives and landraces present a poten-tial source of novel genes. This study investigated the response of cultivated and wildrelatives of finger millet to an isolate of blast disease from western Kenya. Previousgermplasm collections were purified through two generations of single-seed descentbefore screening alongside improved and farmer-preferred varieties (FPVs) under ascreen house across three seasons. Farmer-preferred varieties were identified throughparticipatory varietal selection (PVS). The plants were inoculated twice during eachgrowth period using hand-spraying method and data on disease incidence recorded atgrain-filling stage. Genotypic data was generated using diversity arrays technology(DArT) sequencing and data analysis done using Genstat 18.2 and TASSEL 5.2.58.We observed high heritability (81%), indicating that the variation observed was pre-dominantly genetic. Wild accessions were generally more resistant to the disease incomparison to the cultivated accessions. Preliminary genome-wide association study(GWAS) using general linear model with principal component analysis led to theidentification of 19 markers associated with blast disease that will be be developedinto assays for genotype quality control and trait introgression. Wild accessions andlandraces of finger millet present a good reservoir for novel genes that can be incor-porated into crop improvement programs.

Maize (Zea mays L.) germplasm exhibits large genetic variations in tolerance to high tempera- ture (HT) stress under fi eld conditions, but the mechanisms underling this variation are largely unknown. Based on many years of fi eld observa- tion, maize inbred line B76 consistently displays better tolerance to HT than B106. Heat waves during growing season cause leaf fi ring in devel- oping leaves and tassel blasting in B106 but not in B76. The difference in HT tolerance between the two inbred lines was confi rmed in growth chambers under controlled conditions. The two inbred lines showed similar level in the induction of heat shock proteins and a maize chloroplast protein synthesis elongation factor (EF-Tu), two mechanisms known to involve in HT tolerance in maize. A drastic decrease in photosynthetic system II (PSII) quantum effi ciency occurred at 34 to 35°C in B106; in B76, it occurred at a much higher temperature (>38°C). Cell membranes of B76 appeared to be more stable under HT than those of B106 based on electrolyte leak- age analysis. Lipid profi les of young develop- ing leaves by lipidomics showed that, among all lipids detected, only phosphatidic acid (PA) exhibited signifi cant higher level in B76 than in B106 under both normal and HT stressed condi- tions (p < 0.02). Moreover, PA was the only lipid that was signifi cantly increased by HT treatment (p < 0.05). Our results suggest that membrane thermostability is essential to HT tolerance and that PA may play an important role in imparting membrane thermostability, and, hence, HT tol- erance in maize.

Since 1 930, maize (Zea mays L.) yields in the United States have increased more than four-fold. Previous studies examining maize cultivars grown during that period have documented changes in yield, leaf angle, tassel size, drought tolerance, and insect resistance, but none have examined changes in vegetative phase change or resistance to common rust (Puccinia sorghi Schwein.). Vegetative phase change has been shown to affect both disease and insect resistance, and common rust can reduce yields in maize especially east of the Mississippi River. Thirty-six widely used northern Corn Belt cultivars spanning the years of pre-1930 to 2006 were evaluated for phase change traits and rust resistance. Cultivars were divided into early and late maturity groups from different eras and planted at two locations with two planting dates per location for 2 yr. Timing of vegetative phase change has not changed linearly over the eras examined. There was, however, a significant linear increase in rust resistance over that time. In the early maturity group, percentage of leaf area infected by rust was found to decrease at a rate of 0.1% yr -1 . Whole-plant rust resistance in the late maturity group was found to increase at a rate of 0.05% yr -1 .

Stress during tassel formation can reduce tassel size and cause insufficient pollen production in seed production. When stresses affect plant development, component compensation for grain yield is known to occur in some crops. Tassel component compensation for pollen production has not been previously reported. Chilling was imposed on two dent maize (Zea mays L.) inbreds (103 and 113 relative maturity [RM]) at the initiation of tassel formation, a critical period for maximizing pollen production. The 103 RM inbred showed limited response to chilling stress. The 113 RM inbred produced 60% fewer branches resulting in 45% fewer spikelets and 43% fewer pollen grains per tassel when chilling was applied during branch meristem initiation. For the same inbred, 42% fewer spikelets and 29% fewer pollen grains per tassel were produced when chilling was applied during spikelet meristem initiation. Chilling stress during meiosis of microsporogenesis did not decrease pollen production per anther. A decrease in the percentage of starch-filled pollen grains was found only in the lower florets on the lowest branch. The effect of decreased branch or spikelet production on total pollen production was not compensated by subsequent production of spikelets, florets, anthers, or pollen grains per anther. Susceptibility of pollen production to chilling stress during tassel formation varies among modern dent inbreds, although plasticity in the tassel for pollen yield was not observed.

Worldwide, tropical maize (Zea mays L.) is commonly exposed to low N conditions. Identification of low N tolerance-related traits would help to develop indirect selection for yield and marker assisted selection under stress. Tolerance to high plant population density has been proposed as an alternative breeding strategy to improve stress tolerance in maize. A better understanding of mechanisms underlying tolerance to high plant population density and low N is, however, needed. For this purpose, elite CIMMYT open-pollinated varieties (OPVs), inbred lines, and hybrids were grown under optimal, high plant population density and low N conditions. Yield, yield components, and a set of morpho-physiological traits (secondary traits) were assessed in the different treatments and germplasm types. Emphasis was placed on anthesis-silking interval and traits related to senescence, dry matter partitioning, and ovule and grain number. Association was observed under low N conditions between grain yield and anthesis-silking interval, delayed senescence as expressed by either chlorophyll concentration or the number of green leaves above the ear, and ear/ tassel weight ratio. Under optimal, high-plant population density and low N conditions, final grain number depended more on abortion rate than on the total number of ovules at anthesis. Under low N stress, grain yield was significantly negatively correlated with abortion rate. Under high plant population density, a positive association was noted between ovule number and abortion rate, suggesting a source limitation for C products. The effect of stress on yield components and the strength of association between secondary traits and yield varied greatly according to germplasm type.

Genetically modified maize (Zea mays L.) produced for regulated products such as pharmaceutical or industrial proteins will require methods to confine transgenic pollen. In one production system, nontransgenic maize would be used to pollinate detasseled transgenic inbred plants. Resulting hybrid kernels would be used for protein extraction or seed increase. The effect of different female inbred detasseling efficiency levels on gene flow was tested at three locations in southeastern Missouri in 2000 and 2001. Pollen sources were yellow inbred isolines representing transgenic females planted in alternating rows with white inbred maize representing nontransgenic males. During detasseling, female plants were intentionally missed at rates of 0, 730, 1460, and 7300 tassels ha -1 . Each detasseling treatment was matched with a maize isoline and traceable marker. White hybrid trap plots were planted on three dates at 200 and 300 m from pollen sources. Dates that maximized silking synchronization with yellow isoline tasseling were selected for sampling. Gene flow was detected by counting yellow kernels in white maize plots. When no tassels were removed from an isoline, the highest recorded gene flow was 0.03% at the 200 m and 0.02% at the 300 m isolation distances. At greater detasseling levels, gene flow decreased. Gene flow was 0.0013% or less when 730 tassels ha -1 remained. When complete detasseling was intended, one positive kernel with a tracer gene was detected at 200 m, and none was detected at 300 m. For effective control of regulated transgenes in pollen by detasseling, complete and timely tassel removal will be necessary.

Pollen production generally is not considered a limiting factor in modern maize (Zea mays L.) production. In some modern hybrids, however, smaller tassel size, use of male sterile blends, and top cross production may limit pollen availability. This study was conducted to establish the lower limits for pollen production needed to ensure maximum kernel set, and to devise a method for predicting pollen production from simple measures of tassel development. Isolated blocks of male fertile plants were established in a field of male sterile plants. The level of male fertility was varied from 0 to 100% by detasselling (Pioneer 3978) or by using mixtures of male fertile and male sterile isolines (Pioneer 3925 and 3925S). Pollen shed was measured daily with passive pollen traps. A Population Index, derived from the percentage of plants shedding pollen and the average pollen production per plant, accurately predicted the seasonal pattern and total pollen shed for each male fertility treatment. Hybrids used in this study shed pollen for 10 to 12 d, with a peak intensity 2 to 3 d after anthesis (50% plants shedding pollen). Individual tassels produced 4.5 × 10 6 pollen grains on average, and shed pollen for 5 or 6 d. Variation in grain yield across male fertility treatments was closely correlated to kernels per plant (r 2 = 0.998). Seasonal pollen production limited kernels per plant at pollen densities less than 3000 pollen grains silk -1 . This lower limit for effective kernel set occurred at male fertility levels less than 50% for both hybrids. Grain yield, however, was maintained at male fertility levels as low as 20% because of compensation in grain size. These results demonstrate that a minimum pollen shed density per exposed silk is required to achieve maximum kernel set and grain yield. They also show that the seasonal pattern of pollen shed can be predicted from simple measures of staminate flower development. Together, these results provide a rational basis for achieving high kernel set under field conditions in which pollen production might be limiting.

Light penetration into the canopy of maize (Zea mays L.) production fields is an important determinant of grain yield. Factors affecting light penetration include agricultural practices such as planting density and plant morphological factors such as leaf angle, leaf size, and tassel size. The objectives of this experiment were to identify genomic regions controlling the inheritance of leaf angle and tassel morphology in a B73 × Mo17 recombinant inbred population. Three quantitative trait loci (QTL) for tassel branch angle were detected which explained 35.6% of the phenotypic variation. Six QTL were detected for tassel branch number with three of these QTL on chromosome 2. Nine QTL were detected for leaf angle in one or more environments. Significant phenotypic correlations were detected between tassel branch angle and tassel branch number and between tassel branch number and leaf angle. Overlapping support intervals were identified between QTL detected for leaf angle and for tassel branch number on chromosome 2 near marker umc53a. Additionally, a QTL near marker bnl6.10 on chromosome 5 identified for tassel branch angle was in the same region as a QTL identified for leaf angle. The results of this study indicate that common genetic relationships exist between tassel traits and leaf angle.

Knowledge of the physiological stress mechanisms triggered by corn rootworm larval feeding damage may suggest new ways of maintaining maize (Zea mays L.) productivity in plants damaged by this important insect pest. Western corn rootworm [Diabrotica virgifera virgifera (LeConte)] larval feeding damage to maize root systems causes complex changes in leaf CO 2 assimilation. The objective of our study was to further explore the relationships between plant morphology and CO 2 assimilation in rootworm-damaged maize. The effects of moderate or severe root damage caused by larval feeding or by mechanical damage on root system morphology, shoot dry weight, leaf area, stomatal conductance, and CO 2 assimilation were investigated in greenhouse experiments. Rootworm larval feeding, which removed about 75% of the total root system volume, or mechanical cutting treatments imposed at the V12 leaf stage, which removed about 30% of the total root system volume, had no effect upon leaf CO 2 assimilation but significantly reduced stomatal conductance when measured at the tassel development stage. During the time when larvae were damaging root systems or when specific root node axes were mechanically cut, however, leaf CO 2 assimilation was less in root-damaged plants than in undamaged plants. Larval-damaged root systems had accelerated adventitious root axis growth and development in the nodes located immediately above the damaged nodes. This compensatory root growth was more pronounced under the moderate root feeding damage treatments than in the severe root damage treatments. Total leaf area and shoot CO 2 assimilation were less in plants with severe larval feeding damage than in plants with moderate damage or in control plants. Thus, the severity of root damage plus the level of root compensatory growth play important roles in mediating shoot growth and CO 2 assimilation responses to stress imposed by rootworm larval feeding.

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 S 1 lines derived from a single F 1 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 S 1 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% (R 2 ) 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.

The Latin American Maize Project (LAMP) evaluated nearly 12 000 maize (Zea mays L.) accessions in 12 countries to select germplasm that can be used in breeding programs to improve commercial materials. In Argentina, Chile, Uruguay, and the USA, 1692 and 988 native accessions were evaluated in the first and second period, respectively. Sixty-nine selected accessions were evaluated in all countries in the third stage. Accessions per se showed silk delay, indicating a lack of adaptation. The 69 selected accessions topcrossed with B73 × B14A, Oh43 × Mo17, and SR76 were evaluated in the four countries to (i) identify temperate accessions from Latin America and the USA that could enhance yield, tassel and silk synchronization, lodging resistance, and maturity; and (ii) identify the U.S. heterotic group to which the accessions belong. The topcross results identified germplasm equal or superior to the performance of the checks in all countries, indicating that selected germplasm could be used to increase yield. Even though topcrosses showed significant improvement for silk delay and stalk lodging across the accessions, additional improvement is needed to facilitate wider use of the material. The Argentinean accessions had the best mean per se and topcross performance. Some accessions performed well in most countries and should be included in cooperative enhancement efforts.

Grain yield improvement of maize (Zea mays L.) hybrids in Ontario has been associated with increased stress tolerance. Effects of shortterm water-deficit stress on canopy gas exchange of an old and a new maize hybrid were studied. Plants of Pride 5 (old) and Pioneer 3902 (new) were grown under controlled-environtrtent conditions until tassel emergence and, subsequently, plants were transferred to enclosures, each containing the aboveground parts of four plants. Canopy photosynthesis, respiration, transpiration, and stem water potential were measured continuously for 7 d. Plants were either well watered or exposed to a water-deficit stress by withholding water supply until net canopy photosynthesis declined to zero and, subsequently, plants were rehydrated. Under well-watered conditions, the two hybrids did not differ significantly in terms of canopy photosynthesis, transpiration, and stem water potential. In contrast, hybrids responded differently to a water-deficit stress. Cumulative canopy photosynthesis and transpiration during the drying cycle were reduced by 21 and 31%, respectively, in Pioneer 3902 and by 34 and 31%, respectively, in Pride 5. The threshold stem water potential related stomatal closure, and thus, photosynthesis and transpiration, was lower for Pioneer 3902 than for Pride 5. During the recovery day, canopy photosynthesis was 53% higher and canopy transpiration was 31% higher in Pioneer 3902 than in Ride 5. Respiration per unit CO 2 fixed was lower in Pioneer 3902 than in Pride 5 in all conditions.

Different lateral bud structures are generated along the main shoot axis in maize (Zea mays L.). This study was conducted to show how the structural diversity of the lateral buds is generated. The growth and development of lateral buds of three hybrids were investigated under field conditions at Tokyo, Japan, on a silt loam (Andosols). Six plants per hybrid were harvested as each leaf emerged and the morphological features and the length of each lateral bud were determined. We observed in mature plants that the lateral buds consisted of two discrete populations acropetally along the main stem (i) lower lateral buds that remained in a vegetative state, and (ii) upper lateral buds, including grain-bearing shoots, that terminated in reproductive organs. Lower lateral buds elongated sequentially up the stem and grew for a specific time interval. The phase transition of the apical meristem to tassel initiation evoked a change in the bud growth pattern. At tassel initiation, the upper lateral buds were still in an incipient state without establishing a complete bud structure. During the reproductive phase that followed, elongation of the upper lateral buds occurred simultaneously. These results suggest that lateral bud growth during the vegetative phase was regulated independently from the reproductive phase during plant development. Lateral buds that are at a certain development state could be responsive to the change in physiological signals during the transition between vegetative and reproductive phase.

Detasseling is used in hybrid corn (Zea mays L.) seed production to ensure harvested seeds have the desired genetic complement. Both mechanical and hand detasseling result in loss of some leaf tissue and plant N. The objective of this study was to determine if seed yield and quality and N content of grain and stover were affected by leaf removal during detasseling. The treatments evaluated were removal of tassel only, tassel plus one leaf, tassel plus two leaves, tassel plus three leaves, tassel plus four leaves, and no tissue removed (control). The leaf area index (LAI) declined linearly, about 0.16 LAI units per leaf removed. Grain and stover yield also declined linearly with number of leaves removed with the tassel (r 2 = 0.97 and 0.92, respectively). Each leaf removed reduced grain yield about 0.36 Mg ha −1 . Yield reduction was caused by decreased kernel size. Grain and stover N concentration and amount of N in stover did not vary among detasseled treatments. However, total N in the grain declined linearly as number of leaves removed increased (r 2 = 0.97). Warm and cold germination and warm germination after accelerated aging were not affected by leaf removal during detasseling. Results reported here suggest that when leaves are removed from the plant at detasseling, the loss of photosynthetic capacity, the ability to intercept light, and plant N all contribute to grain yield reduction

A shortened anthesis-to-silking interval (ASI) in maize (Zea mays L.) is associated with tolerance of stresses which occur around flowering. It is not known of this reflects differences in tassel and ear initiation dates, or in rates of development and growth. We examined these characteristics in selection cycles 0, 2, 4, 6, and 8 (designated C x , where the subscript indicates the cycle number) of the lowland tropical maize population 'Tuxpeno Sequia', which was selected recurrently for drought tolerance and whose selection cycles differ for ASI [...]

Photoperiod and temperature influence the time from sowing to tassel initiation (TI) in maize (Zea mays L.), with appreciable genetic differences in relative sensitivity to these factors. Three experiments were run to examine these photothermal responses and genetic differences within 12 diverse cultivars chosen to represent germplasm adapted to temperate, tropical highland, tropical lowland, and subtropical environments. Photoperiod influenced the rate of progress toward TI in all cultivars (P < 0.05), with a threefold differences in sensitivity among them. In three of the more photoperiod-sensitive cultivars (all adapted to the tropics or sub tropics), the value of the critical photoperiod, above which progress to TI is delayed by increase in photoperiod, was close to 13 h d⁻¹. Temperature also influenced rate of progress toward TI. For many cultivars the optimum temperature (Tₒ) for rate of progress towards TI was appreciably cooler than the range from 30 to 34 °C that is generally assumed to apply throughout development from sowing to anthesis in maize; estimated values of Tₒ in a 12-h photoperiod (Exp. 3) varied from 19 to 22 °C in the tropical highland cultivar H-32 to 31 °C in the tropical lowland cultivar Tuxpeno Crema I Cycle 18. In the five cultivars examined, inherent earliness (i.e., time taken to TI in optimum environments) was almost identical, despite considerable differences in Tₒ, while relations between rate of progress to TI and suboptimal temperatures were curvilinear, with similar base values (mean 9.4 °C). Curvilinear relations were also detected at supraoptimal temperatures in three of the five cultivars. Curvilinearity in each of these relations (in contrast with the linear relations reported in many other crops) may be compatible with symptoms of damage to maize plants exposed continuously to extreme temperatures (e.g., 12 and 37 °C).

Photoperiod has substantial effects on phenology in many cultivars of maize (Zea mays L.). This study investigated if photoperiod sensitivity ends at tassel initiation (TI) by considering whether photoperiod influences the duration from TI to tassel emergence (TE). In the first experiment, five diverse cultivars were grown in 12 different controlled environments until TI, and were then transferred to either short (11 h d -1 ) or long (16-18 h d -1 ) days(.)

(...)Plants were damaged at the V9 stage of leaf development by prior infestation with 50 or 150 larvae per plant or by cutting 25 or 75% of the root system from the plant. There were no differences in relative water content, leaf water potential or stomatal conductance between infested plants or controls at V9; at tassel, however, LWP was significantly higher and SC was significantly less in infested plants. Mechanical cutting of roots caused significant differences in RWC and SC at both sampling dates(...)

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 14 C-labeled sugars (.)

Four heat-tolerant and 3 susceptible inbreds were crossed in a diallel fashion. Tassels from field-grown F1 plants were excised at the start of anthesis and transferred to growth chambers with light/dark temperature regimes of 29/24 and 38/32°C. In vitro pollen germination, anther emergence and tassel colour were determined after 24 h in the growth chamber. Percentage nongerminated pollen (PNP) increased significantly at the higher temperature, the extent of the increase varying among genotypes. Mo17 had the most desirable general combining ability (GCA) effect for PNP at the higher temperature. Specific combining ability effects were significant for PNP, accounting for 51% of the genotype and genotype X temperature sum of squares. Anther emergence of the central tassel spike decreased differentially among hybrids at the higher temperature. Mo17 had the most desirable GCA effect for anther emergence. Anther emergence and pollen viability did not always respond in the same way to high temperature.

The heat unit concept, e.g. Growing Degree Days, is used extensively to account for temperature effects on maize (Zea mays L.) development in models which attmept to predict crop development and yield. Environmental effects on rate and duration of leaf initiation, which determine final leaf number, have received much less attention in such models, although leaf number and the period from planting to silking are highly correlated for maize. Photoperiod and temperature are two environmental variables known to affect leaf number. The objective of this study was to delineate the sensitive period during which leaf number of the short-season maize hybrid, Guelph GX 122, is influenced by photoperiod and temperature. Periods during which leaf number was influenced by temperature and photoperiod were determined by transferring plants to different photoperiod/temperature regimes at various stages of vegetative development. Leaf number was determined at tassel emergence and, in two of three experiments, leaf stage at which tassel initiation occurred was estimated by dissection of plants at regular intervals. AH experiments were conducted in the environmentally controlled growth cabinets of the University of Guelph. Results of these experiments indicate that initiated leaf number of Guelph GX 122 was influenced by temperature between the five- and the seven-leaf stage and by photoperiod betweenthe four- and the seven-leaf stage. The transition from vegetative to reproductive development (i.e., tassel initiation) occurred a leaf stage which was numerically equal to 50% of final leaf number. Photoperiod and temperature effects on leaf number were additive for Guelph GX 122 grown under the conditions of these experiments.

Inbreeding effects on five characteristics of two Zea mays varieties were estimated. Seven inbred subpopulations, ranging from F = O to 9/16, of each variety were obtained by using double-double (8-line) pedigrees. Environmental error and genotype-by-environment interaction components of variance were not significantly affected by the level of inbreeding. The regression of performance on expected inbreeding was linear for yield, number of days to tassel, ear height, and plant height. If epistatic effects are contributing to the variability in these two populations they must be of the type which lead to a linear relationship between average performance and inbreeding. Inbred progenies derived from sets of inbred lines were analyzed separately. Variability in response to inbreeding among such sets of genetic material was detected

Use of the vestigial glume gene (Vg) is a means of increasing kernel cut-off percent in processing sweet corn (Zea mays L,) if pollen production problems can be mastered. In this experiment, effect of the vestigial glume gene on amount of pollen shed and on length of tassel glume in a range of adapted Wisconsin inbreds was studied. Pollen production by Vg vg plants ranged from 0.65 to 15.95 ml/tassel for different inbreds, and tassel glume length from 0.65 to 5.20 ml. There was a highly significant relationship between pollen volume and length of tassel glume. Tassels of Vg Vg plants were very small and did not produce pollen. These results indicate that it should be possible to develop vestigial glume (Vg vg) hybrids with adequate pollen for commercial production.

Tassel culture of maize (L.) to obtain normal development has significant potential for both basic and applied research studies. However, potential use of this technique for genetic manipulations has been limited by genotype specificity. This study was conducted to screen 15 commercially used inbreds for tassel culture response and to determine conditions satisfactory for successful tassel culture of each genotype. Immature tassel meristems were cultured on different media. Different concentrations of sucrose (0.2– 0.3 M) were required for different genotypes. However, Murashige and Skoog medium with 0.1 μM kinetin and casein hydrolysate (30 mg L) was suitable for most of the genotypes. Tassels of Oh43 derivatives were responsive to culture, while B73 and Mo17 were more recalcitrant. The cultured tassels of the inbreds A619, A632, H99, LH38, Pa91 and U94 produced mature, trinucleate pollen. Thus, the tassel culture technique can be used across a broad range of elite maize germplasm.

In three of five cases, tassel removal from corn (Zea mays L.) at or near tassel emergence increased grain yields. The increase was larger and more consistent at higher populations. When leaf tissue was removed with the tassel, yields were decreased, although this effect was smaller at higher populations. A large portion of the yield response from detasseling resulted from the elimination of tassel light interception. Simulated small tassel size (produced by tassel side branch removal) resulted in increased grain yields.