Determination of Effective Pollination Period (EPP) in the Late-Bloom Almond (Prunus dulcis Mill.) Cultivar "Shahrood 12"

Limited ovule longevity is a major obstacle to fruit set and productivity in most fruit trees including almond. Therefore, a study of Effective Pollination Period (EPP) in fruit trees is of special importance. The present research was carried out to determine EPP in the almond cv. 'Shahrood 12' during 2005 growing season. Flowers of "Shahrood 12" (?) as a mother plant were pollinated with the pollen of "Supernova" (?) and "15-5" (?) cultivars 1, 2, 3, 4, 5, 6 and 7 days after anthesis. Pollinated flowers were sampled for microscopic examinations of the pollen tube growth in the style after 24, 48, 72, 96 and 120 hours past from pollination. The samples were fixed in FAA solution, stained with aniline blue and prepared for being observed for pollen tube growth under florescence microscope equipped with UV light. In addition, fruit number set was recorded on the 75th Days After Full Bloom (DAFB). Results indicated 34 and 37% fruit set when "Shahrood 12" (?) pollinated with "Supernova" (?) cultivar on days 2 and 4 after anthesis respectively. Also, fruit sets of 37 and 42% were observed when "Shahrood 12" (?) was pollinated with "15-5" (?) cultivar on 2 and 4 days after anthesis, respectively. In addition, results as based on the microscopic examinations of the pollen tube growth in the style showed the low fruit set from those flowers pollinated 7 days after anthesis which was due to the less longevity of ovules and stigma. In conclusion, results as based on the field and microscopic examinations showed the better results for fruit set when flowers of "Shahrood 12" (?) pollinated with pollen of "Supernova" (?) and "15-5" (?) cultivars on the 2nd and 4th days after anthesis. Any later pollination of the mother plant is not suggested because of low fruit set leading to reduction of yield. Pollination at 2-4 days after anthesis is suggested to maximize fruit set and to further crop production throught lengthening the overlap duration of the flowering periods of compatible pollinizers with "Shahrood 12" under Karaj environmental conditions.