High relative humidity reduces anther dehiscence in apricot, peach, and almond

The regulation of anther dehiscence by relative humidity (RW) was assessed for detached anthers and detached whole flowers from a limited selection of apricot (Prunus armeniaca L.),peach [P.persica (L.) Batsch], and almond [P . dulcis (Mill.) D,A, Webb, syn. P, anygdalus Batsch; P, communis (L.) Arca ngeli, non Huds.] genotypes, as well as an almond X peach F-2 progeny. Dehi scence was evaluated, at 33, 64, 87, 93 and 97% RH for detached anthers, an d at 33, 64 and 97% RW for whole detached flowers, Anther dehiscence was su ppressed with increasing RH for all genotypes. Apricot anthers showed the g reatest dehiscence at low RE and measurable dehiscence at high RE even when detached. Anther dehiscence In almond appeared more suppressed than in apr icot at all RH levels tested, being completely suppressed by high RE in det ached anthers, Peach genotypes exhibited the full range of variability betw een apricot and almond patterns. Evidence for transgressive segregation of RH-controlled anther dehiscence was observed in the occurrence of cleistoga my in an almond x peach F-2 progeny. Rates of anther dehiscence were approx imately linear with change in RH in detached anthers but exhibited a more b uffered, step-wise response when detached whole flowers were tested. Result s are consistent with field observations, and highlight the low but measura ble risk of cleistogamy in these species, as well as opportunities to modif y the breeding systems and crossing environments to facilitate controlled h ybridization, and to reduce pollination vulnerability to adverse environmen ts.