pi-2 -- a novel pistillate mutant
Rick, C.M.
Dept. of Veg. Crops, Univ. of California, Davis, CA 95616
Pistillate-2 (pi-2) originated from EMS treatment of cv. Castlemart.
Carrying a stock number of 3-802, it was given a provisional name of "green
pistillate", which some investigators who utilized it might recognize. The M1
and subsequently produced F1's had normal phenotype. The recessive
homozygotes have a unique phenotype. Plant size and vigor are reduced. A
tendency toward inflorescence abortion often delays flowering, and casual
examination might fail to detect the reduced, inconspicuous inflorescence.
Instead of normal flowers, small structures appear that have only calyx and
pistil. At anthesis the calyx appears juvenile, failing to elongate and
spread its segments but remaining tightly adpressed to the pistil. Thus, in
these morphological respects, pi-2 differs from pi, whose flowers have a
corolla, albeit highly modified, and open sufficiently to permit exposure of
the stigma. Application of viable pollen results in irregular fruit set and
subnormal seed production. Consequently pi-2 is not the answer to the
breeder's prayer for a functional male sterile mutant useful for hybrid seed
production.
The original M2 segregated 15 + : 2 pi-2. Additional F2's and BC's
were generated from F1's of pi-2/pi-2 x normal Castlemart. A series of 7 F2's
yielded a total of 82 + and 20 mutant phenotypes, a deficiency of the latter
being consistent in most families. For small BC families were obtained with
totals of 25 + and 12 pi-2/pi-2. The deficiency of mutant homozygotes,
characteristic of both generations, is not unusual for induced mutations,
especially those of weaker constitution. It therefore seems reasonable to
assume that a single recessive gene is responsible for this trait. Limited
seed supplies are available for distribution to interested parties.