CX8011, a pear-shaped line from Campbell's processing tomato breeding program, was initially considered for inclusion as a pear-shaped parent along with 'Roma' and 'Yellow Pear' in our report on genetics of pear-shaped fruit in tomato (Warnock, 1990). However, a mutant type which had round fruit was encountered in the CX8011 parental material while work was in progress. It has been established (see following report this volume) that the round variant carried the constricting corolla (cc) characteristic but differed from CX8011 at the oval (o) locus. This provided an opportunity to evaluate a round-fruited type with constricting corolla in a cross with a pear type in which segregation would occur at the o locus in the presence of homozygous cc.
Since the initial investigation was concerned with segregation for cc in a homozygous o background, reporting of the present work was delayed. However, the evaluation of the mutant type, the line from which it was selected, and investigation of segregation in a monogenic cross (CX8011 round x CX8011 pear), were conducted in conjunction with the previous work (Warnock, 1990).
The CX8011 pear-shaped line was crossed with 'Yellow Pear' and a total of 113 F1 plants were examined. All plants produced pear-shaped fruit, indicating that there was no genetic difference for pear shape in CX8011 pear and 'Yellow Pear'. The variant round-fruited selection was also crossed with the CX8011 pear-shaped type. The fruits of F1 plants of this cross were round with some few fruits having slightly sloping shoulders. Segregation in the F2 was 3 round to 1 pear. Of the 145 F2 plants examined 37 were classed as pear-shaped and the remaining 108 round. On progeny testing one selection classed as a pear type segregated for shape resulting in a final frequency of 109 round fruited plants to 36 pear shaped. These values were tested against and found to fit a 3:1 ratio (X2=.007, P=0.90-0.95). In this cross (homozygous cc) segregates for round and pear-shaped fruit were easy to distinguish in contrast to segregates for oval and pear-shaped fruit in oval by pear-shaped crosses (homozygous o). The ease of distinguishing the pear-shaped types in the homozygous cc cross was due to the fact that all elongated fruit types were pear-shaped. Only one errant classification was encountered on progeny testing of the pear selections. This contrasted to 30, 25, 20, and 14 plants errantly classed in the F2 of crosses in which cc segregated in a homozygous o background (Warnock 1990).
LITERATURE CITED
Warnock, S. J. 1990. Inheritance of pear-shaped fruit in tomato. Rept TGC 40:38-40.