Summer stratification and germination: A viable option for recovery of hybrid seedlings in low chill peach and nectarines

Abstract

In-vitro embryo rescue; and summer stratification and germination under controlled conditions was tested for recovering hybrid seedlings in crosses involving low chilling peach and nectarines. The embryos from all the cross combinations showed very high in vitro embryo germination (>85%) on basal MS medium, which can be effectively performed at hard mature or full ripe stage. The stratification period of the hybrid seed varied from 36.3 days in Shan-i-Punjab × Florda Prince to 44.7 days in Tropic Beauty × Florda Grand. At the end of four weeks of transfering the cultures to culture room, maximum plant height (33.7 mm) was recorded in Shan-i- Punjab × Tropic Beauty, which did not differ significantly from the cross Florda Crest × Tropic Beauty. The fruit development period of the seed parent varied from 78.3 days in Shan-i-Punjab × Tropic Beauty and Shan-i-Punjab × Florda Prince to 104.7 days in Tropic Beauty × Florda Grand. Stratification media of cocopeat + vermiculite + perlite (2:1:1) resulted in the highest seed germination but, the actual germination percentage varied with cross combinations. Highest germination (81.5%) was recorded in the cross FlordaGlo × Tropic Sweet, which did not differ significantly from Tropic Beauty × Florda Grand. It was followed by seed germination (68.0%) in Florda Grand × Tropic Beauty. Under high density nursery system, the hybrid seedlings of FlordaGlo × Tropic Sweet showed highest growth (160 cm) and branches (13). The germination of hybrid seeds was positively correlated (0.86) with fruit development period of the seed parent (FDP) and negatively correlated (-0.85) with chilling requirement of seed parent. The proportion of rosseted seedlings was negatively correlated with FDP (-0.61) and positively correlated (0.39) with chilling requirement of the seed parent. The cross combinations with higher FDP of seed parent resulted in higher seed germination of hybrid seed. Hence, controlled climate stratification and germination after harvest can be a viable option for recovery of hybrid seedlings and reducing the breeding cycle in crosses involving seed parents with higher FDP.