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.
Segregation for annual vs. biennial flowering habit was observed in F2 progenies from crosses of early and late-maturing broccoli (Brassica oleracea L. Italica Group) inbred lines with cabbage (B. oleracea L. Capitata Group), kohlrabi (B. oleracea L. Gongyloides Group), collards (B. oleracea L. Acephala Group), kale (B. oleracea L. Acephala Group), and brussels sprouts (B. oleracea L. Gemmifera Group). F, progenies were usually completely annual. F2 progenies from crosses involving late broccoli contained two to five times as many biennials as F2 progenies from early broccoli crosses. Maturity factors carried by the biennial parents also appeared to affect expression of flowering habit. Annual habit is dominant over biennial and is controlled by several major genes with a strong effect of modifiers from both the annual and biennial parent. Time of heading of annual plants in F2 progenies appeared to be controlled by quantitative, mainly additive, factors. Distribution of heading dates for the F1 and annual broccoli parents showed a large environmental or cultural effect. It appears that the biennial parents, especially brussels sprouts and collards, contributed strong factors for late maturity.
Height reduction of sweet corn (Zea mays L.) plants by head smut [Sphacelotheca reiliana (Kuhn) Clinton] was measured in four field studies using seed furrow inoculation. Infected plants were consistently stunted whether sori occurred on the ears only or on ears and tassels. There was a significant relationship between plant height and infection of individual plants. Difference in mean height between plants later determined to be infected or non-infected was measurable 5 weeks after planting and increased steadily until growth ceased. This suggested the possibility of elimination of weaker plants in segregating populations before maturity. Mean height reduction of individual hybrids and inbred lines ranged from 7% to 65% of the height of non-infected plants, with an average of ≍30% reduction for all cultivars. Correlations between mean percent height reduction and disease incidence of cultivars were variable and generally low, ranging from r = −0.34 to 0.17. This suggested that degree of height reduction would be a poor indicator of the susceptibility of a cultivar to infection.
Seven breeding lines of peas (Pisum sativum L.), OSU 547-29, OSU 559-6, OSU 564-3, OSU 584-16, OSU 589- 12, OSU 615-15, and OSU 620-1, resistant to pea seedborne mosaic virus (PSbMV) and pea enation mosaic virus (PEMV) have been released by the Oregon Agricultural Experiment Station. The lines resulted from three cycles of breeding to transfer pea seedborne mosaic virus resistance from PI lines to commercially usable peas. They have horticultural type approaching that of commercial cultivars, and all have good field resistance to pea enation mosaic virus. The development of cultivars resistant to PSbMV should relieve the pea seed industry of the restrictions and expenses involved in avoidance of PSbMV contamination of seed supplies.
‘Oregon 523’, a pea (Pisum sativum L.) cultivar of commercial freezing type, was bred for resistance to pea enation mosaic virus (PEMV) in the Willamette Valley of western Oregon. In this area, a normally heavy natural disease incidence permits annual selection for field resistance to PEMV. and also resistance to red clover vein mosaic virus (RCVMV), a prevalent virus that can cause severe damage in PEMV resistant peas. Because ‘Oregon 523’ has good field resistance to PEMV and RCVMV, it is expected to be more reliable in production than many cultivars when these diseases are present. It has shown acceptable quality and adequate yield for use by the western Oregon pea processing industry.
The winter survival of 10 pea cultivars of differing cold hardiness was studied under ground-level culture and on raised beds in moist semi-maritime conditions (CorvaUis, Oregon) and in more severe continental conditions (Weston, Oregon). There was survival in 7 cultivars at CorvaUis and 6 at Weston. Planting on raised beds at Corvallis significantly increased survival. This effect was consistent for all cultivars having appreciable survival rates. At Weston, the mean survival was higher on ground level plantings, but cultivars, responded differently to cultural systems. Of the 6 surviving cultivars, only the 2 least hardy had significantly higher survival on ground level plantings.
Pea seedborne mosaic virus (PSbMV) is of concern to breeders and seedsmen, especially in the Pacific Northwest where most of the pea (Pisum sativum L.) seed used in the U.S. is produced (4). Resistance to PSbMV is the best means to remove the threat of seed stock contamination and reduce the need for costly and restrictive assay programs and quarantines.
Broccoli cultivars differed greatly in their tendency for premature heading and total loss from this factor and from culls. Per cent premature heads was increased by the use of large transplant sizes in the 9 cultivars studied; total loss was generally, but less, affected in the same way. Significant interactions were found between varieties and plant size in both premature heading and total loss. Transplanting date affected premature heading and total loss in one of the 2 years it was considered. Nitrogen levels, included in one experiment, did not cause significant effects.
Methods of field inoculation of sweet corn (Zea mays L.) with Sphacelotheca reiliana (Kühn) Clinton for head smut resistance tests were evaluated. Application of a mixture of teliospores and slightly dampened vermiculite with the seed by means of a V-belt planter was the best method tested and resulted in a 95% disease incidence in the most susceptible cultivar. Application of this mixture by hand in individual planting holes resulted in greater disease incidence but required much more labor and inoculum.
When inbred lines of cabbage [Brassica oleracea L. (Capitata group)] and green sprouting broccoli [B. oleracea L. (Italica group)] were crossed, F1 plants were annual in flowering, tall, and generally resembled broccoli. Of 2,724 F2 plants, 43% developed visible flower buds during the field-growing season, which appeared to be too short for full expression of annual habit. Annual versus biennial habit and time of flower bud appearance in annual plants seemed to be under quantitative genetic control. Height varied from that of typical cabbage to that of broccoli and greater, and was not related to apparent annual habit or general appearance of the plants. Though some plants resembled cabbage in leaf type and form of the terminal rosette, no typical heading cabbages were recovered.