62 PNL Volume 16 1984
Myers, J. R. and E. T. Gritton
Department of Agronomy
University of Wisconsin, Madison, WI USA
Because the pea has a cletstogaraous flower, the frequency of out-
crossing is low in most northern environments (1, 3). Thus, methods of
enhancing hybridization may be of interest to the breeder. We obtained
several pea lines segregating for male sterility and have characterized
them genetically and cytologically (2). Working in the field with F2
segregates of marker line-male sterile crosses, we observed pod set on
ms plants (Table 1). The percentage of ms plants with at least one pod
varied considerably among ms genes. Crosses between different marker
lines to the same male sterile exhibited similar pod set behavior.
However, plant height affected the amount of pod set with short plants
(le le) showing a lower percentage pod set than tall plants (Le/-).
Short plants of ms-2 and ms-6 exhibited lower percentage pod set, while
ms-7 had the highest percentage of both tall and dwarf plants. Seed
from the open pollinated pods were grown to determine floral phenotype.
It was expected that fertile progeny were the result of outcrossing
while most ms progeny were due to selfing. However, as much as
one-third of the progeny could be male sterile due to outcrossing in a
closed, randomly mating F_ population. Because these ms lines were
grown in the nursery among many other pea lines, the percentage of ms
progeny due to outcrossing would be somewhat less than one-third. As
shown in Table 2, ms-2, ms-5, and ms-6 exhibited 25.2% or fewer male
sterile progeny, suggesting that these genes confer a high degree of
male sterility. All other male steriles showed 43.2% or greater ms
progeny which indicates varying amounts of fertility restoration.
Bumblebees appeared to be the primary insect vector and were ob-
served gathering both pollen and nectar from older flowers. In
particular ms-2, ms-5, and ms-6 may have some value In facilitating
recombination where large amounts of crossed seed are required.
Loennig, W.-E. 1983. PNL 15:40.
Myers, J. R., and E. T. Gritton. 1984. PNL 16:60-61.
White, 0. 1917. Proc. Am. Phil. Soc. 56:487-588.
PNL Volume 16 1984