Monoploid Peaches, Prunus persica Batch: Description and Meiotic Analysis1

Abstract

Two monoploid peaches are described. Analysis of one showed that the chromosomes were distributed at random in the first meiotic division, and that some irregularities occurred because chromosomes are occasionally excluded from the spindle, divide precociously, or show other irregular behavior. Only one bivalent was observed in 236 division figures. The second division was normal. Due to varying orientation of the second division spindles a significant percentage of diad sporads formed, which yielded normal, haploid isogenic gametes. Some pollen germinated and fruit was set following pollination of diploid plants with pollen from the monoploid.

Evaluating Combining Ability in Peach and Nectarine1

“…Information on the relative ability of cultivars or advanced selections to transmit their commercially desirable characteristics is useful to select prepotent parents for additional crosses, to estimate progeny size necessary to obtain desired recombinants with reasonable probabilities and to increase breeding efficiency. Estimates of combining ability may be obtained from the percentage of seedlings with desirable characteristics among open-pollinated or selfed progenies; combined progenies involving the same parent in several crosses; or topcrosses with inbred tester lines, ideally doubled haploids (3,5). The use of combined progenies involving the same parent in several crosses has the advantage that it does not require additional plantings or supplemental studies for estimating prepotency.…”

“…Therefore, ripening dates are differentiated only into months rather than weekly or half-weekly intervals, which would be needed to differentiate extreme segregates. The earliest-maturing seed parent, P. 0-766 3 , ripens 2H weeks before 53624 or 53625 and 10 days before 'McNeely', but fails to give more early-ripening segregates than any of them. 'McNeely' actually gives almost twice as many early-ripening segregates as does P. 3 A selection from the breeding program at Frosser, Washington; all other selections are from the Beltsville, Maryland, program.…”