Optimization of controlled pollination in avocado (Persea americana Mill., Lauraceae)

Abstract

a b s t r a c tAvocado has a singular synchronous protogynous dichogamy breeding system that promotes outcrossing. In this work different steps have been optimized to improve controlled pollinations in avocado in order to perform basic studies of reproductive biology and directed crosses in breeding programs. The results show that, in order to achieve successful fruit set, male flowers should be collected when all the anthers have dehisced and the pollen transferred by direct contact of the anthers with the stigma during the female stage using preferentially determinate inflorescences and pollinating at least 11 flowers per inflorescence. To perform crosses between cultivars of complementary floral groups, the flowers should be stored under high relative humidity during the hand pollination process. When the crosses involved cultivars of the same floral group, the male flowers should be collected just before anther dehiscence and could be stored for several days at 4 • C. Pollen application should be performed preferentially on flowers within determinate inflorescences or within indeterminate inflorescences where vegetative growth has been removed. The results obtained are useful to optimize controlled pollinations in avocado and can help to increase fruit set in breeding programs and avoid the incorrect interpretation from pollination experiments in studies of reproductive biology.

Bumblebees (Bombus terrestris) Improve ‘Hass’ Avocado (Persea americana) Pollination

“…On 30 April, 100 ‘Hass’ flowers (20 flowers per tree × 5 trees) from each of the three distances (60, 120, and 180 m) from the BB hives were sampled randomly. The flowers were collected at the end of their female phase [ 7 ] and were fixed in FAA (70% ethanol:glacial acetic acid:formalin (18:1:1, v / v )) [ 31 , 32 ]. At the end of the flowering season, the flowers were washed three times with distilled water, 1 h per wash, and left overnight in 5% ( w / v ) sodium sulfite.…”

Fruit Set in Avocado: Pollen Limitation, Pollen Load Size, and Selective Fruit Abortion

“…One hundred 'Hass' (floral type A) flowers were hand-pollinated daily at the male and female stages using pollen from 'Fuerte' (floral type B) following the procedure described by Alcaraz and Hormaza [11]. Another set of 'Hass' flowers at the female stage was emasculated and bagged to avoid insect pollination.…”

“…Since avocado shows protogynous dichogamy, pollen storage is necessary to perform self-pollinations. Since short-term pollen storage at 4 • C has no effect on the pollen capacity to fertilize the avocado ovule [11], male-stage flowers of 'Hass' were collected when all the anthers were dehisced and stored at 4 • C, whereas male-stage flowers from 'Fuerte' (a type B cultivar of green skin fruits used as pollen donor for 'Hass' in different avocado growing regions) were collected at midday, just before performing hand pollinations. Ten flowers of 'Hass' were hand-pollinated daily in each inflorescence by direct contact of the stigma with the dehisced anthers; 5 of them were cross-pollinated with pollen from 'Fuerte' and 5 with pollen from 'Hass'.…”

“…Several reasons have been proposed to explain this low fruit set in avocado. Among them, the limiting environmental conditions at flowering, lack of sufficient pollinating insects, inefficient use of pollinizer varieties or low flower quality [9][10][11][12][13]. However, general observation in many plant species is that one of the most important factors determining reproductive success in plants is pollination.…”

Evaluation of efficiency of controlled pollination based parentage analysis in a Larix gmelinii var. principis-rupprechtii Mayr. seed orchard

“…Controlled pollination (CP) is essential to tree breeding programs to increase genetic gains and integrate targeted traits from individual genotypes [ 20 ]. Although only a few studies have confirmed the success of CP using SSR markers, including in loblolly pine ( Pinus taeda ) [ 21 ] and cacao [ 18 ], to the best of our knowledge, no reports have examined the efficiency of CP in Prince Rupprecht's larch seed orchards.…”