Browsing by Author "Ball, Dale Warren"

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    Combining ability, protein, heterosis, and prediction of F₁ performance with RFLPs in a diallel of maize
    Ball, Dale Warren (Virginia Tech, 1994-07-06)
    Improving protein quality and identifying superior inbreds and hybrids are significant challenges in commercial maize breeding programs. These two problems were addressed in separate studies on inbreds and hybrids from a complete diallel cross of 12 elite proprietary inbred lines of maize evaluated in field trials in two locations for two years. One of the inbreds (WI) was a novel source of high quality protein obtained from Wilson Seeds, Inc. in Harlan, Iowa. In the first study, diallel analyses were used to study combining ability and types of gene action important in the inheritance of protein content, grain yield, grain moisture at harvest, time to silk, kernel hardness, and density. General combining ability (GCA) and specific combining ability (SCA) effects were highly significant for all traits indicating presence of both additive and non-additive effects, respectively. Reciprocal effects (REe), often assumed to be absent in maize diallel studies, were significant for grain yield and protein concentration, suggesting that choice of female parent may be important for these traits. Ratios expressing the relative importance of GCA and SCA indicated that protein concentration is controlled primarily by additive gene action. In the second study, restriction fragment length polymorphism (RFLP) data were obtained for the 12 inbreds using 42 genomic clones each with four restriction enzymes. Modified Roger's distances were calculated and used in cluster analyses for heterotic grouping of the inbreds. Two measures of level of heterozygosity and hybrid value were evaluated as means of predicting Fl performance of hybrids in the complete diallel set of hybrids and in groups of hybrids representing crosses between and within heterotic groups. Results from this study confirm those of previous investigations with respect to prediction of hybrid performance when comparable groupings of crosses between related and unrelated lines were evaluated. This study further indicates that RFLPs may also be useful for prediction of hybrid performance in situations typical of early generations of many maize breeding programs where recombinant inbreds are testcrossed to a common tester inbred.
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    Productivity and quality of tall fescue and switchgrass under two harvest managements and different harvest intensities
    Ball, Dale Warren (Virginia Tech, 1990-07-10)
    Tall fescue (Festuca arundinacea Schreb.) often becomes dormant in the hot summer months. Switchgrass (Panicum virgatum L.) has potential to supplement the limited carrying capacity of tall fescue in mid-summer. The objective of this study was to determine the seasonal dry matter distribution and quality of tall fescue and switchgrass as influenced by different harvest managements. Switchgrass and tall fescue were studied on a fine-loamy, mixed, mesic Ultic Hapludalf of the Duffield soil series at Blacksburg, VA during 1987 and 1988. Normal harvest management included harvests taken from the first growth in spring until mid to late August. Delayed management included harvests taken from regrowth after a hay crop in mid-May for tall fescue and early June for switchgrass until mid to late August. Three and four harvest intensities were imposed on tall fescue and switchgrass, respectively. Plots were harvested in 1989 to determine the accumulative influence of treatments. Yield, crude protein, neutral detergent fiber, and invitro dry matter digestibility were measured for each harvest of both species. Digestible yield and protein were calculated for each harvest. Clipping either switchgrass or tall fescue at any harvest intensity reduced potential yield compared to forage not clipped. Accumulated forage resulted in high yields but unsatisfactory quality. Delayed harvest management resulted in higher total yield than normal harvest management because of high hay yields. This study indicated that considerable overlap of forage production of tall fescue and switch grass occurred in late spring but abundant high quality switchgrass was available in midsummer when available tall fescue was low. Switchgrass warrants consideration in southwest Virginia as a solution to the problem of limited cool-season forage in midsummer.