Selection for resistance to pythium ultimum trow within four cultivars of cotton (Gossypium hirsutum L.)

Four commercial cotton (Gossypium hirsutum L.) cultivars were chosen for an experiment involving selection for resistance to Pythium ultimum Trow. Two cultivars, Auburn M and Delcot 277J, previously had been found to be slightly more susceptible than Coker 310 and Dixie King 3. The potential for inheritance of resistance was based on the large variation that occurred among plants within the cultivars. The relative susceptibility or resistance found previously was confirmed in a field test with the four cultivars. Pathogens were isolated with frequencies similar to that recorded in the literature. Parent seeds of the four cultivars were planted in sterilized sand and grown at 27 C for eight days before being inoculated with P. ultimum. Inoculated seedlings were incubated at 18 C and rated for dis-ease severity after seven days. Surviving seedlings of different ratings were transplanted to sterilized soil and grown to maturity. Plants were self-pollinated and progeny seeds obtained were planted in sterilized sand. Seedlings obtained were inoculated as before and rated for dis-ease severity after seven days. Heritability of each cultivar was calculated by three methods. Values obtained by the regression method were not different from zero at the 5% level of probability. Heritability values for Delcot 277J and Coker 310 were significantly different from zero at the 107. level. The partition of variance method was thought to contain too much error due to environmental effect and was included for comparison only. The realized heritability method was used to determine the response to one generation of selection. From values obtained by this method. Auburn M could have the most potential of the four cultivars in a future breeding program. Values for realized heritability can be employed to predict future response to selection. Coker 310 met the criteria necessary for accurate predictions

Stripping Burley Tobacco into Grades

Stripping burley tobacco into different grades has been a controversial topic for many years. The one-price years in the mid to late 80’s provided no incentive to the producer to strip into the appropriate grades. However, with the advent of contracting in the year 2000, many companies are suggesting four grades but still get a high percentage of three-grade tobacco. Tobacco companies can utilize a small percentage of mixed stripped tobacco, but the handling characteristics of the four stalk positions differ substantially during processing. As the companies make their blends, they look for specific characteristics that differ from grade to grade. A look at the 2001 variety test plots provides some insight into this topic. Although the variety test plot protocol for 2001 called for four grades, some cooperators stripped trials into three grades. A comparison of the percentages stripped into each grade reveals the different distribution of leaves between three-grade and four-grade tobacco

Interference and postemergence control of annual grasses in burley and dark fire-cured tobaccos

Interference studies with annual grasses were conducted in 1982 and 1983 in burley and dark fire-cured tobaccos (Nicotiana tabacum L.) at Greeneville and Springfield, Tennessee, respectively. Treatments consisted of annual grass-free periods of 2, 4, 6, 8, and 10 weeks from transplanting and 2, 4, 6, 8, and 10 weeks of interference followed by removal of all weeds and maintenance of weed-free conditions. A season long annual grass-free treatment and a season long annual grass-infested treatment served as controls. Annual grass-free periods were established and maintained by hand-hoeing. In 1982, the critical annual grass-free period and critical duration of interference of annual grasses for Federal grade and yield of burley tobacco and total cured plant and leaf yields of dark fire-cured tobacco were between 4 and 5 weeks after transplanting. Due to dry growing conditions and low annual grass populations yield responses in 1983 failed to indicate critical periods. Separate studies were conducted in 1982 and 1983 at the same locations to evaluate and compare the performance of sethoxydim {2-[1- (ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen- 1-one} alone and with a crop oil concentrate and fluazifop-butyl {(±)-butyl 2-[4-[(5-(triflouromethyl)-2-pyridinyl)oxy]phenoxy]propanoate} plus a crop oil concentrate for control of annual grasses and tobacco response. They were compared to conventional cultivation and a widely used preplant incorporated treatment of pendimethalin [N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine]. The above treatments were applied alone and in combination with acephate. In 1982, the postemergence herbicides controlled annual grasses as well or better than cultivation or pendimethalin. Tobacco treated with the postemergence herbicides produced yields equal to or less than tobacco treated with pendimethalin. Dark fire-cured tobacco treated with the postemergence herbicides yielded less than did tobacco in the cultivated checks. In 1983, all treatments produced good tobacco yields. Plants from plots treated with sethoxydim applied without a crop oil concentrate produced the lowest dark fire-cured tobacco yields. Acephate in combination with annual grass control treatments did not appear to enhance tobacco growth or yield. Some crystallization of acephate occurred when tank-mixed with sethoxydim and fluazifop-butyl

Nitrogen Source Effects on the Growth and Development of Burley Tobacco Transplants in the Float System

During the spring of 1996, many tobacco producers used a water soluble 20-10-20 fertilizer in their float beds, only to have to throw out the stunted sickly plants that resulted, and start over. The fertilizer that caused the problems turned out to have 100% of the nitrogen (N) as urea-N. It was hypothesized that the poor growth was related to with the conversion of the urea-N to other forms of N. There have been numerous other cases where producers using fertilizers high in urea-N or ammonium-N (NH4-N) have had problems with stunted plant growth. Further study of nitrogen transformations is warranted to determine what caused the poor growth, and to improve nitrogen management in tobacco float systems

Should Burley Tobacco Farmers be Concerned About High Rates of Nitrogen Fertilizers?

The use of nitrogen (N) fertilizer for tobacco production is necessary because (1) tobacco takes up sizable amounts of N, and (2) most soils cannot provide adequate amounts of N. Rates of fertilizer N recommended by the University of Kentucky for burley tobacco production vary based on past cropping history, and under certain conditions can be as high as 350 lbs. N/A However, since tobacco is a high value crop, and profit margins are high, farmers often apply more N than is recommended as insurance against crop losses. The perception of widespread over-application of fertilizer N has resulted in increased concern among tobacco buyers, and environmental groups. Burley tobacco farmers need to be aware of these concerns

Limitations and Benefits to Cultivating Tobacco

Historically, between-row cultivation for weed control has been an integral part of tobacco production. In one season, a grower might perform five or more cultivations and several hand weeding operations for adequate weed control. Early herbicide chemistries would control some weeds, but not all, forcing the producer to cultivate and hand weed. The development of better herbicides improved the range of weeds controlled, sometimes to the point that cultivation for weed control was not warranted. Many producers are so accustomed to cultivating they have forgotten why cultivation was necessary. The decision to cultivate should largely be based on the presence of weeds, but there are exceptions

Influence of Topping and Harvest Management on the Evaluation of Data From Burley Tobacco Variety Trials

Tobacco producers are always interested in new tobacco varieties, and are continually searching for the best variety. Producers receive information about varieties from a number of sources including; research and extension publications, county extension agents, neighbors, farm supply workers, and seed producers. To help producers evaluate varieties, county agents in cooperation with tobacco specialists conduct many burley tobacco variety trials at the county level

Factors Affecting Color of Cured Burley Leaf

Much interest has been shown by tobacco growers during recent months in fertilization and or other management practices that can be used to produce darker and redder cured leaf of burley tobacco. The purpose of this newsletter is to summarize what we know about some of the factors which affect color of cured leaf