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Al Lien and James R. Baggett

Pod detachment characteristics were studied in `EZ Pick', an unusually easy-picking cultivar, and `OREGON 91G', a normal cultivar. When `EZ Pick' pods were harvested by hand or by machine, they tended to separate at the pedicel-stem juncture or at the pedicel-calyx juncture, while `OREGON 91G' pods tended to break at the neck. When machine-harvested,'EZ Pick' had fewer broken pods, a higher recovery rate, and more trash than did `OREGON 91G'.

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James R. Baggett and Deborah Kean

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James R. Baggett and Deborah Kean

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James R. Baggett and Janice Tibbs

Incidence of head smut [Sphacelotheca reiliana (Kuhn) Clinton] in F corn (Zea mays L.) families derived from homozygous starchy (Su) F ears was less than that observed in starchy or sugary (su) families derived from segregating ears or sugary families derived from homozygous sugary ears. This difference was observed at high levels of disease incidence resulting from clipping seedlings and at a lower disease incidence in unclipped plants. Differences in seedling vigor and earliness of starchy and sugary families and differences related to homozygous and heterozygous sources suggest that seedling vigor may be involved in the observed differences in head smut susceptibility.

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James R. Baggett and Deborah Kean

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James R. Baggett and Deborah Kean

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Akhtar Ali and James R. Baggett

The inheritance in corn (Zea mays L.) of resistance to head smut disease incited by Sphacelotheca reiliana (Kuhn) Clinton was studied in the field on crosses of resistant dent corn line N6 with two susceptible sweet corn (su1) inbred lines. Disease incidence in the resistant parent (Pr) was 0% to 4%, and 83% to 96% in the susceptible parent (Ps). Predisposition of seedlings by clipping just above ground level increased percent infected in progeny populations by as much as 4-fold, but did not affect disease incidence in the, parents. At the lower disease incidence of unclipped plots, the F1, F2, and BCr means were close to the mean of Pr, suggesting dominance of resistance. At the high disease incidence of clipped plots, the relationship of parent and progeny means “suggested additive inheritance. Epistasis was also generally present with a higher level indicated for unclipped plots. Inheritance was concluded to be quantitative. Reciprocal differences were observed only in backcrosses. In the F2 and BCs populations, plants grown from dent (Su1) seed were lower in disease incidence than plants grown from su1 seed.

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James R. Baggett and R.O. Hampton

The inheritance of tolerance to infection by bean leaf roll luteovirus (BLRV) in Pisum sativum L. was studied in the cross of cv. Parlay (sensitive to BLRV infection) × cv. Oregon Sugarpod II (BLRV tolerant). The parents, reciprocal F1, back-crosses, F2, and 234 random F3 families were screened in 1986 and 1987 in the field at Twin Falls, Idaho, under natural BLRV inoculation by aphids. Overall disease index scores for the F1, F2, and F3 were about intermediate between indices of the parents, with the F1 usually slightly higher than midparent values. Backcross disease indices were intermediate between the F1 and the respective parent involved. Distribution of individual F3 family indices was continuous and semi-normal. BLRV-sensitivity ranges within parents and selected cultivars, as well as segregating populations showed continuous variation and differed between the 2 years, suggesting that expression of a major gene was significantly influenced by natural variation in BLRV inoculation pressure and timing. An apparent “additive gene action” was probably an artifact of nonuniform timing and levels of infection within plant populations. Chi-square analyses of segregating populations indicated that a major recessive gene, called lrv, conferred BLR disease tolerance.

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Rebecca J. McGee and James R. Baggett

There was no difference in percentage in vitro germination of pollen from stringless pea (Pisum sativum L.) cv. Sugar Daddy and stringy `Oregon Sugarpod II' (OSP) and `OSU 705' (705). However, pollen tubes of `Sugar Daddy' grew more slowly in vitro than those of OSP or 705. Differences in pollen tube growth rate were demonstrated in vivo following time-course pollinations involving reciprocal crosses of `Sugar Daddy' with OSP and 705, along with the selfed parents. After 8 hours, pollen tubes from stringless peas (“stringless” pollen) had entered 13% of the ovules compared with 51% for those from stringy peas (“stringy” pollen). Stringless pollen tubes entered 29% and stringy pollen tubes 66% of the ovules after 10 hours. The slower growth of stringless compared with stringy pollen tubes is a plausible explanation for previously observed deficiencies of stringless plants in segregating populations.

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James R. Baggett, Deborah Kean and Kathryn Kasimor

Broccoli (Brassica oleracea L. Italica Group) lines with heads borne above the foliage (exserted) favorably for mechanical harvest were crossed with inbred lines with nonexserted heads. Length of the heads, defined as the portion of the plant above the highest major leaf, was ≈50% of the total plant height in short and tall parents and all plants of the F1, F2, and backcross generations. The principal characteristic identified with good head exsertion was long internodes. Internode length was inherited mostly in an additive manner, with some effect of hybrid vigor apparent in the F1, F2, and backcross to the tall parent. Plant height was also inherited in an additive manner. Head weight in the high-exsertion parent was much lower than in the low-exsertion parent. Within each parent and the F1, head weight was greater in plants with longer internodes and greater plant height. In the segregating generations (F2 and backcross), head weight increased with decreasing internode length, indicating that selection for high head exsertion would result in smaller heads and reduced yield.