Stalk Breaking Research Articles

Design and Parameter Optimization of Conveying and Baling Devices for Ramie Cutting and Baling Machine

Conveying and baling are two important links in the mechanized harvesting of ramie, in the face of ramie cutting and baling harvesting technology research gaps, low stalk conveying rate, high breaking rate and other problems. In this paper, according to the technical requirements of ramie harvesting, we designed a conveying and baling device, the hand-held ramie cutter. First, the key mechanism of the conveying and baling device of the equipment was designed. Then, we analyzed the location of stem clogging and the reasons for the breaking problem during the conveying and baling process. The field harvesting experiments were carried out according to the principles of Box–Behnken experimental design. Taking the machine travelling speed, conveying speed and ramie raking frequency as the test factors and using the Design-Expert V8.0.6.1 to process the data, we established a regression model for each experimental factor on the conveying rate and breaking rate. The order of influence of several factors on the breaking rate is: X2 > X1 > X3; and the effects of the three factors on the conveying rate were X3 > X2 > X1. Through response surface analysis (RSA), the effects of the factors on the indicators were explained, as was the impact of the factors on the indicators. Finally, the parameter optimization was carried out with the delivery rate as the core index. The best combination of motion parameters was obtained as follows: the travelling speed was 0.37 m/s, the chain conveying speed was 1.1 m/s, and the raking frequency was 144 times/min. With the combination of parameters under the field test verification, the results show that compared with the original work quality, the stalk delivery rate increased from 85.2% to 93% (an increase of 7.8%), the stalk breaking rate fell from 31.1% to 20.4% (a decrease of 10.7%). The performance of ramie harvesting and baling was greatly improved, and we achieved relatively satisfactory results.

STUDY OF PHENOTYPIC AND GENETIC VARIABILITY IN MAIZE CROSSINGS BETWEEN CYCLE I INBRED LINES AND ELITE LINES (CYCLE II)

Maize inbred lines derived from local populations (Cycle I lines) were tested using cycle II elite inbred lines. In the cross system, hybrids have a wide variability for yield (6601-10571 kg/ha), the highest differences between hybrids are due to the non-additive genetic effects; undesirable traits transmitted by cycle I inbred lines are weak resistance to stalk breaking and fallen plants; for the percentage of unbroken plants, the genetic variability is high, the percentage of unbroken plants for simple hybrids has a range value between 65.02% and 89.70%.There were calculated the correlations coefficients between ”per se” values for the correlation of inbred lines from crossbreeding system and additive genetic effects values calculated in the crossbreeding system ”m x n”. Positive correlations were identified between the values per se and the positive genetic effects for yield, ear weight, ear length, numbers of kernels per ear, TKW, kernel depth. These high positive correlation values indicate the possibility to use phenotypic markers in the process of inbred lines creation.

Effects of Corn Varieties and Moisture Content on Mechanical Properties of Corn

The purpose of this study is to explore how corn varieties and moisture content affect the mechanical properties of corn with high moisture content (26.0~36.4%). The mechanical properties of corn that affect corn threshing quality are determined by establishing the contact mechanical model of the threshing elements and corn kernels. These mechanical properties of corn include the size characteristics of corn (corn ear weight and corn kernel triaxial size) in addition to the mechanical characteristics of corn (corn elastic modulus, corn kernel breaking force, and corn stalk breaking force). The effects of corn varieties and moisture content on the mechanical properties of corn were tested. The results showed that the corn varieties and moisture content had significant effects on the mechanical properties of corn. Among them, the different levels of moisture content levels have significant differences in the mechanical properties of corn, while corn varieties have different significant differences in the mechanical properties of corn. The ear weight, corn kernel triaxial size, and the axial and radial breaking force of corn pedicels all increased significantly as the moisture content increased. Corn’s elastic modulus, kernel breaking force, and the normal breaking force of corn pedicels all decreased significantly as moisture content increased. The breaking force of corn kernels at different positions is in the order of ventral, lateral, and top surface, and the breaking force of corn pedicels in different directions is in the order of normal, axial, and radial. When the moisture content is between 26.0% and 36.4%, the maximum breaking force of a corn kernel is 401.62 N, and the minimum is 35.47 N. The maximum breaking force of corn pedicels is 32.72 N, and the minimum is 5.37 N. Understanding the influences of these relationships is very important for applications related to the threshing process, such as selecting the threshing mode, designing the threshing mechanism, and setting the threshing parameters.

Maize Lodging Resistance with Plastic Film Removal, Increased Planting Density, and Cultivars with Different Maturity Periods.

While plastic film mulching and proper high-density planting are important methods that can improve maize yield, years of accumulated residual film have created soil pollution and degraded soil, and thus has impeded sustainable agriculture development. Here, we compared the stalk and root lodging resistances of three maize cultivars grown at two planting densities both with (FM) and without (NM) plastic film mulch. Our aim was to provide a theoretical basis that may help assure a future of successful no-film planting with increased planting density. The results showed that, compared with FM, the average dry weight per unit length and bending strength of basal internode decreased for all cultivars at both planting densities in the NM treatment. At 9.0 × 104 plants ha−1, the stalk breaking force (SFC) of Xinyu77, KWS9384, and KWS2030 in the NM treatment decreased by 4%, 21%, and 22%, respectively. At 12.0 × 104 plants ha−1, SFC of Xinyu77 and KWS2030 increased by 14% and 1%, respectively, while KWS9384 decreased by 10%. Additionally, the root diameter, length, volume, width, depth, and the vertical root-pulling force of maize decreased. Although the lodging resistance of maize grown without film mulch was lower than that of maize grown with it, those adverse effects can be mitigated by selecting suitable cultivars and by using proper high-density planting and appropriate cultivation measures.

Relationship between yield and lodging traits of maize under different planting densities

AbstractMaize (Zea mays L.) is one of the main food crops in China but the problems with lodging have seriously affected the quality and production. In this study, lodging resistant and density tolerant varieties of maize were screened. The relationships between rind penetration strength (RPS), stalk breaking strength (SBS), and yield under two different planting densities were studied. Eight hybrid combinations were set up under the planting densities of 75,000 and 90,000 plants ha–2 and their effects on yield were determined with a regression equation method. The results showed that density had a greater effect on yield through its effect on lodging rate. Finally, high‐yielding maize varieties JKY143 and JKY182 with stronger planting density tolerance were selected to provide reference points and technical support for maize‐breeding programs focusing on plant density tolerance and lodging resistance.

Effects of Nitrogen Fertilizer Management on Stalk Lodging Resistance Traits in Summer Maize

Stalk lodging in Huang-Huai-Hai summer maize is a serious problem that reduces maize yields and precludes the use of mechanical grain harvesting equipment. In order to determine the effect of nitrogen management on the lodging resistance of maize stalk, three nitrogen application rates of 150, 250, and 350 kg ha−1 (denoted as N150, N250, and N350), and different nitrogen application periods (sowing, 6-leaf, 12-leaf, silking) were set. Plant morphology, stalk mechanical strength, total carbohydrate, nitrogen content, and yield were measured in the different treatments. The results showed that as the nitrogen application rate increased and nitrogen application was postponed, the stalk breaking force, plant height, ear height, center of gravity height, stalk basal internode diameter, rind penetration strength, content of carbohydrate, and total N of maize stalk also increased. The stalk lodging resistance was improved by the increased nitrogen application rate and postponed nitrogen application by increasing the stalk material accumulation and mechanical strength. The nitrogen application rates had no significant effect on grain yield. Under N250 and N350, the treatments with no base fertilizer significantly decreased the kernel number per ear, reflected in some in grain yield. In summary, under the conditions of integrated water and fertilizer drip irrigation and fractional nitrogen fertilizer applications, increased nitrogen fertilizer input can stimulate the growth of high-quality maize populations, significantly improve stalk lodging resistance in the early growth stage, delay stalk senescence, improve stalk strength and influence stalk composition in later growth stages. Based on the summer maize grain yield and stalk lodging resistance, under N250 treatment, a base fertilizer combined with topdressing at the 12-leaf and silking stages was beneficial to the growth of summer maize.

Evaluation of maize lodging resistance based on the critical wind speed of stalk breaking during the late growth stage

BackgroundThe accurate evaluation of the stalk-lodging resistance during the late stage of maize growth can provide a basis for the selection of cultivars, the evaluation of cultivation techniques, and timely mechanical grain harvesting. In this study, the critical wind speed of stalk breaking, plant morphology, stalk mechanical strength, and lodging rate were investigated in 10 maize cultivars to identify the parameters evaluate lodging resistance during the later growth stage of maize. Clarify the relationship with the stalk mechanical strength, critical wind speed of stalk breaking, and natural lodging rate in the field.ResultsThe results showed that, in the late growth stage, with increasing number of days after physiological maturity, (1) the stalk lodging rate gradually increased, (2) the stalk breaking force and rind penetration strength (RPS) of the third internode above the soil gradually decreased, and (3) the critical wind speed of stalk breaking increased first and then decreased, and was highest at about 16–24 days after physiological maturity. The position of stalk lodging mostly occurred between second and fifth internodes. The torque at the base of maize plant increased as wind speed increased, and the different of torque was excited among different maize cultivars under same wind speed. Furthermore, the stalk lodging rate was significantly negatively correlated with the critical wind speed of stalk breaking. Additionally, the critical wind speed of stalk breaking was significantly positively correlated with the stalk breaking force and the RPS.ConclusionThis indicates that the critical wind speed of stalk breaking is a superior way to determine the stalk lodging resistance. These results suggest that, in the late growth stage, the decrease in the stalk mechanical strength is an important reason for the decrease in the critical wind speed of stalk breaking and the increase in the lodging rate.

Device for determining critical wind speed of stalk breaking to evaluate maize lodging resistance

The accurate evaluation of the lodging resistance of maize plants can provide a basis for the breeding of lodging-resistant cultivars and the regulation of cultivation measures. However, the traditional methods for evaluating maize lodging resistance in terms of plant morphology and stalk mechanical strength have certain limitations. The objective of this research was to develop a device for determining the critical wind speed of maize stalk breaking. The device used a centrifugal fan to supply airflow and was powered by a frequency conversion motor. The frequency converter adjusted the motor speed and thus adjusted the wind speed. The wind speed decreased first and then increased with increasing height above the outlet of the device, and maximum wind speed can reach 40 m/s. This device was convenient for transportation in the field, has a low cost, and can quickly, accurately, and objectively determine the lodging resistance. Field tests showed that the device ran stably for a long time. The coefficient of variation of three repeated measurements was between 1.5% and 4.8% for four maize cultivars. The new device can measure the critical wind speed of maize lodging and identify the lodging resistance for different maize cultivars, cultivation practices, and plant health conditions, and can thus overcome barriers to measuring the maize lodging resistance under natural wind conditions. Keywords: maize, stalk lodging, critical wind speed, turbofan, measuring device, wind pressure DOI: 10.25165/j.ijabe.20201305.6033 Citation: Xue J, Ming B, Wang K R, Xie R Z, Hou P, Li S K. Device for determining critical wind speed of stalk breaking to evaluate maize lodging resistance. Int J Agric & Biol Eng, 2020; 13(5): 1–7.

Key indicators affecting maize stalk lodging resistance of different growth periods under different sowing dates

The accurate evaluation of maize stalk lodging resistance in different growth periods enables timely management of lodging risks and ensures stable and high maize yields. Here, we established five different sowing dates to create different conditions for maize growth. We evaluated the effects of the different growth conditions on lodging resistance by determining stalk morphology, moisture content, mechanical strength and dry matter, and the relationship between stalk breaking force and these indicators during the silking stage (R1), milk stage (R3), physiological maturity stage (R6), and 20 days after R6. Plant height at R1 positively affected stalk breaking force. At R3, the coefficient of ear height and the dry weight per unit length of basal internodes were key indicators of stalk lodging resistance. At R6, the key indicators were the coefficient of the center of gravity height and plant fresh weight. After R6, the key indicator was the coefficient of the center of gravity height. The crushing strength of the fourth internode correlated significantly and positively with the stalk breaking force from R1 to R6, which indicates that crushing strength is a reliable indicator of stalk mechanical strength. These results suggest that high stalk strength and low ear height benefit lodging resistance prior to R6. During and after R6, the coefficient of the center of gravity height and the mechanical strength of basal internodes can be used to evaluate plant lodging resistance and the appropriate time for harvesting in fields with a high lodging risk.

Nitrogen Split Application Can Improve the Stalk Lodging Resistance of Maize Planted at High Density

The decrease of maize stalk quality is an important reason for stalk lodging during the grain filling stage. In the present study, a maize cultivar was planted at densities of 7.5, 9.0, 10.5, 12.0, and 13.5 × 104 plants ha−1 and subjected to nitrogen application rates of 0, 270, 360, and 450 kg ha−1 (denoted as N0, N270, N360, and N450). The stalk breaking force, mechanical strength, carbohydrate content, and nitrogen content of basal internodes were determined to study the effects of nitrogen application rate on the stalk lodging resistance of maize under different planting densities with integrated watering and fertilization using drip irrigation. At densities of 7.5 to 10.5 × 104 plants ha−1, the stalk breaking force, rind penetration strength (RPS), and crushing strength (CS) of the basal internode decreased first and then increased with increasing nitrogen application rate, with the lowest values obtained for the N270 treatment. Meanwhile, at planting densities of 12.0 × 104 plants ha−1 and above, the stalk breaking force, RPS, and CS increased with increasing nitrogen application rate. The basal internode dry weight per unit length (DWUL) and total N content increased with increasing nitrogen application rate. The breaking force was significantly positively correlated with the DWUL and mechanical strength of the basal internode. The RPS showed a positive linear correlation with the contents of cellulose, lignin, and total N of the third internode. Under the split application of water and fertilizer, the maize stalk total dry matter and contents of cellulose, lignin, and total nitrogen increased with increasing nitrogen fertilization rate during the grain filling stage at high planting density, so the stalk lodging resistance improved.

Traits of plant morphology, stalk mechanical strength, and biomass accumulation in the selection of lodging-resistant maize cultivars

• There is no correlation in current maize cultivar’s resistance to stalk or root lodging. • Stalk breakage is primarily affected by dry weight per unit length during grain filling. • Vertical root pulling resistance is primarily affected by the ratio of root depth to width. • High ratios of shoot fresh weight to vertical root pulling resistance increase maize root lodging risk. Lodging resistance is a major desired trait in modern maize breeding. Identifying parameters to evaluate lodging resistance could help crop breeders develop maize cultivars with improved lodging resistance. Thirty-four summer maize cultivars currently planted in China were grown in 2017 and 2018 in order to identify relationships between stalk and root lodging resistance and to analyze the main reasons for differences in lodging resistance between maize cultivars. Twenty-five lodging resistance indicators, including aspects of morphology, dry matter, moisture content, and the mechanical strength of the stalk and root, were investigated at silking and 35 d after silking. The experiments showed that the ratio of shoot fresh weight to vertical root pulling resistance (VRPR) was a better indicator of root lodging potential than VRPR alone. Stalk breaking force was not associated with VRPR and was significantly positively correlated with shoot fresh weight/VRPR. Classification of the 34 cultivars revealed that resistance to stalk and root lodging were not correlated. Correlation and regression analyses revealed that approximately 63 % of the breaking force was explained by the average dry weight per unit length (DWUL) of the basal three internodes, ear height, and fresh weight of the basal three internodes at silking. At 35 d after silking, approximately 88 % of the difference in breaking force was explained by the plant height, ear ratio, crush strength (CS) of the fourth internode, average DWUL and fresh weight per unit volume (FWUV) of the basal three internodes. The main indicator affecting VRPR was the ratio of root depth to width at 35 d after silking. Therefore, an important strategy for increasing maize lodging resistance is to breed cultivars with high internode DWUL, low ear position, and deep roots.

Device for determining critical wind speed of stalk breaking to evaluate maize lodging resistance

The accurate evaluation of the lodging resistance of maize plants can provide a basis for the breeding of lodging-resistant cultivars and the regulation of cultivation measures. However, the traditional methods for evaluating maize lodging resistance in terms of plant morphology and stalk mechanical strength have certain limitations. The objective of this research was to develop a device for determining the critical wind speed of maize stalk breaking. The device used a centrifugal fan to supply airflow and was powered by a frequency conversion motor. The frequency converter adjusted the motor speed and thus adjusted the wind speed. The wind speed decreased first and then increased with increasing height above the outlet of the device, and maximum wind speed can reach 40 m/s. This device was convenient for transportation in the field, has a low cost, and can quickly, accurately, and objectively determine the lodging resistance. Field tests showed that the device ran stably for a long time. The coefficient of variation of three repeated measurements was between 1.5% and 4.8% for four maize cultivars. The new device can measure the critical wind speed of maize lodging and identify the lodging resistance for different maize cultivars, cultivation practices, and plant health conditions, and can thus overcome barriers to measuring the maize lodging resistance under natural wind conditions. Keywords: maize, stalk lodging, critical wind speed, turbofan, measuring device, wind pressure DOI: 10.25165/j.ijabe.20201305.6033 Citation: Xue J, Ming B, Wang K R, Xie R Z, Hou P, Li S K. Device for determining critical wind speed of stalk breaking to evaluate maize lodging resistance. Int J Agric & Biol Eng, 2020; 13(5): 1–7.

Corn stalk integrity is improved by fungicide combinations containing carboxamide

ABSTRACT Conservation of vegetative organs, as leaves and stalks, is essential to achieve high maize production. The objective of this work was to evaluate the effects of leaf area maintenance due to fungicides spraying on stalk integrity, its chemical composition and grain yield. The experiment was conducted in Uberlândia - MG, during the second season of 2016. The experiment design was a randomized complete block with six replications and six treatments, representing combinations of fungicides belonging to carboxamide, strobilurin, triazole, and dithiocarbamate chemical groups, and the check treatment (without fungicides). The assessed traits were leaf green area, wet and dry stalk density, stalk breaking strength and height, stalk lignin and cellulose percentage, stalk dry matter, stalk lignin and cellulose content per hectare and grain yield. Treatments containing fungicides, especially the ones containing carboxamide, resulted in higher leaf green area and stalk density. Application of fungicides also increased stalk breaking strength and height; however, no effect was observed on stalk lignin and cellulose percentage. Grain yield, stalk dry matter production, and stalk lignin and cellulose contents per hectare were enhanced by fungicide application, with higher improvements in plants treated with carboxamide. Application of fungicides, mainly when combined with carboxamides, promotes higher maintenance of leaf green area, which leads to improved stalk integrity, higher grain yield, and higher straw production.

Prolificacy Study of Maize ( Zea mays L.) Inbred Lines and Hybrids on ARDS-Turda

In 2014 year, an very favourable year for maize ( Zea mays L.) crops, were studied, in the Maize breeding laboratory from ARDS-Turda, eight maize inbred lines (four prolific and four non-prolific) and eight maize hybrids (four prolific and four non-prolific).Research aims were prolificacy study on three different culture densities and correlated traits. The study was carried out for three culture densities, first density- 40,000, second density- 60,000, and third density- 80,000 plants/ha; there were determined the number of ears per plant, stalk breaking strength and crop yield production. For this study, the maize inbred lines and hybrids came from ARDS-Turda, from their own certified germplasm. The average amplitude of hybrids production ranged between 11,005 kg/ha at 40,000 plants/ha density, and 12,531 kg/ha at 80,000 plants/ha. Highest grain yield value was registered in A 451-3 hybrid production, with 15,194 kg/ha on 80,000 plants/ ha density. For the inbred lines average amplitude ranged between 5,355 kg/ha at 40,000 plants/ha density and 7,742 kg/ha at 80,000 plants/ha density. The highest grain yield value to the inbred lines was registered at TA 470 inbred line, with 9,925 kg/ha on 80,000 plants/ha density. The highest number of plant-ears was realized on A 451-3 hybrid with 2.6 ears on first density, 2.1 ears on second density and 1.6 ears/plant on third density. Also, the highest value for same character on inbred lines, was registered on PI 187, with 2.5 ears on first density and 2.0 ears on second and third densities. This research project suggest that prolificacy of maize inbred lines and hybrids is important for higher grain yield.Also the improved crop stand uniformity under lower densities is essential for stable grain yield per unit area.

Comparison Between some Corn Synthetic Populations Obtained from Transylvanian

Synthetic varieties of corn are open-pollinated populations obtained by cross-pollination of a group of inbred lines. Besides the inbred lines, corn synthetics can be obtained from local populations or hybrids. In general, they are superior to local populations but not exceeding heterotic hybrids. The main advantage of corn synthetic varieties is that their heterosis does not diminish significantly in F 2 generation. Interest in this biological category increased after 1999, when CIMMYT's considered viable alternatives in areas where use of hybrid seed is too expensive (especially in developing countries). Obtaining corn synthetics from local populations aims at enriching their gene pool with a large number of valuable genes derived from local populations that are characteristic to some agricultural areas. SCDA Turda tried to exploit the large number of local populations still existing in Romania, and obtained a series of synthetics intended for areas that still practice subsistence agriculture. To assess their value, we tested six synthetics obtained from local populations in comparison with one traditional synthetic derived from inbred lines; two locations and two experimental years have been considered and the conclusions have been included in this paper. Synthetic populations derived from a combination of local populations cannot be used as such in production due to their lower yield performance and low resistance to stalk breaking and falling. Nevertheless, they can be valuable sources of genes for the following traits: vegetative period, earliness, resistance to low spring temperatures, resistance to Fusarium , precocity and the content of fat, protein, fiber and minerals.

Características fenológicas, produtivas e qualitativas de híbridos de girassol em diferentes épocas de semeadura para produção de silagem

Objetivou-se verificar o efeito de três épocas de semeadura - outubro (antecipada), novembro (normal) e dezembro (tardia) - sobre as características fenológicas, produtivas e qualitativas de quatro híbridos de girassol: Rumbosol-91 (forrageiro), M-734 (duplo propósito), C-11 (duplo propósito) e BRS-191 (granífero) destinados à produção de silagem. O delineamento experimental foi em blocos ao acaso, com arranjo fatorial 4 x 3 (quatro híbridos x três épocas de semeadura) e quatro repetições. A semeadura em outubro resultou em ciclo mais longo, altura de planta mais elevada e diâmetro e participação de capítulo menores, como conseqüência da temperatura, da insolação e do fotoperíodo, que foram mais baixos nessa época. Os híbridos Rumbosol-91 e BRS-191 semeados em novembro apresentaram taxas de acamamento mais quebramento maiores, de 49,6 e 65,7%, respectivamente. Os híbridos BRS-191 e M-734 semeados em dezembro apresentaram produtividades de fitomassa maiores, com 39,71 e 43,76 t ha-1 de matéria verde e 11,31 e 11,41 t ha-1 de matéria seca, respectivamente. Nos constituintes da planta, os teores de PB aumentaram e os de FDN, FDA e LDA diminuíram, respectivamente, para colmo, folhas e capítulo. Na planta inteira, os teores de MS oscilaram de 23,2%, para o híbrido Rumbosol-91 semeado em novembro, a 47,9%, para o híbrido C-11 semeado em dezembro, indicando que os híbridos possuem capacidade diferenciada de retenção de umidade em estádio de maturidade fisiológica semelhante da cultura (fase R-9). Os teores de PB variaram de 7,0 a 15,7%, demonstrando a riqueza protéica da cultura. Os teores de LDA da planta inteira oscilaram de 6,5 a 12,4%, sendo que os híbridos M-734 semeado em dezembro e C-11 semeado em outubro apresentaram os teores mais baixos. Visando à produção de silagem de elevada qualidade, o híbrido M-734 semeado em dezembro apresentou melhor relação entre fenologia, produtividade e composição bromatológica.

Comparison of local and exotic maize varieties for stalk lodging components in a desert climate

A 2-year study on the influence of certain plant morphological traits as well as the chemical composition of the stalk on lodging in exotic and local maize groups was done at Sultan Qaboos University. The exotic group consisted of six varieties, while five varieties were represented in the local group. The soil type was classified as saline, the EC being 3.9–4.2 dS/m. In both maize groups, lodging was negatively correlated with grain yield, rind thickness and stalk breaking strength. Weight of 5-cm stalk section was negatively correlated with lodging in the local group but the exotic group showed no such correlation. In the exotic group, lodging was positively correlated with ear height and negatively correlated with stalk lignin and total nonstructural carbohydrate (TNC) concentration but no such correlations were represented in the local group. In a stepwise regression analysis, a four-variable model consisting of shelling percentage, stalk breaking strength, rind thickness and TNC had a coefficient of determination ( R 2) of 0.66, suggesting that 66% of the variability in lodging was due to variability in these characters acting together. Based on this result it was suggested that, in breeding for lodging resistance in maize in a desert climate, it may be worthwhile to focus on these four parameters.

Localization of quantitative trait loci (QTL) for agronomic important characters by the use of a RFLP map in barley (Hordeum vulgare L.)

Two hundred and fifty doubled haploid lines were studied from a cross between two 2-row winter barley varieties. The lines were evaluated for several characters in a field experiment for 3 years on two locations with two replications. From a total of 431 RFLP probes 50 were found to be polymorphic and subsequently used to construct a linkage map. Quantitative trait loci (QTLs) were determined and localized for resistance against Rhynchosporium secalis and Erysiphe graminis, for lodging, stalk breaking and ear breaking tendency, for the physical state before harvest, plant height, heading date, several kernel parameters and kernel yield. The heritability of the traits ranged from 0.56 to 0.89. For each trait except for kernel thickness, QTLs have been localized that explain 5-52% of the genetic variance. Transgressive segregation occurred for all of the traits studied.

EVALUATION OF QUANTITATIVE METHODS FOR DETERMINING STALK QUALITY IN SHORT-SEASON CORN GENOTYPES

Several quantitative methods of stalk quality evaluation were assessed to determine which of them would be effective in predicting field stalk lodging performance in corn. Measurements that gave the highest negative correlation with field stalk lodging and were also effective in detecting differences in lodging resistance levels of the hybrids were stalk crushing strength, rind puncture, stalk breaking force, weight of 5.1-cm stalk sections and stalk sugar content. The rind puncture method came closest to meeting all the desired criteria for the best stalk lodging resistance indicator by being simple to determine, highly correlated with stalk lodging and consistent in effectively distinguishing between the lodging resistance levels of the hybrids under both high and low lodging conditions. Relationships of the various stalk lodging characteristics with grain yield suggested that stalk strength can be improved without affecting grain yield.