Pseudo-xenic Effect of Allied Annona spp. Pollen in Hand Pollination of cv. ‘Arka Sahan’ [(A. cherimola × A. squamosa) × A. squamosa]

Abstract

<jats:p>Annonaceous fruits are characterized by a serious problem of fruit set, and hand pollination is commonly practiced for improving the set. Because we observed that allied <jats:italic>Annona</jats:italic> spp. are freely crossable and often produce attractive F<jats:sub>o</jats:sub> fruits, the possibility of using their pollen in hand pollination was investigated. A total of 1080 flowers of cv. Arka Sahan in 2003 and 3420 in 2004 were pollinated with <jats:italic>A. atemoya</jats:italic> Hort., <jats:italic>A. cherimola</jats:italic> Mill., <jats:italic>A. reticulata</jats:italic> L., <jats:italic>A. squamosa</jats:italic> L., and self-pollen. Pollen source had significant effects in both or either year on all 14 fruit traits studied except days to ripening. <jats:italic>A. squamosa</jats:italic> pollen gave the highest fruit set (greater than 91%) and the heaviest fruits (greater than 600 g). Good to moderate fruit set was recorded with <jats:italic>A. reticulata</jats:italic> and self-pollen (31% to 86%); and with <jats:italic>A. atemoya</jats:italic> and <jats:italic>A. cherimola</jats:italic> pollen, the set was poor (4% to 13%), whereas natural set was as low as 2%. ‘Arka Sahan’ fruits resulting from <jats:italic>A. squamosa</jats:italic> pollen showed quicker fruit maturity (128 days) and least weight loss on ripening (13%). Evaluation of fruit pulp quality revealed that pollen source and year had significant effects on the total soluble solids and acidity but not their ratio. Mean number of seeds per 100 g fruit was found to vary (6 to 11) with pollen source used. <jats:italic>A. squamosa</jats:italic> and <jats:italic>A. reticulata</jats:italic> pollen had higher seed count with good to moderate fruit size and symmetrical shape, but those from the rest of the pollen sources neither possessed good size nor shape. Results clearly showed that ‘Arka Sahan’ could be successfully hand pollinated with <jats:italic>A. squamosa</jats:italic> pollen. The differential ability of pollen sources to fertilize number of ovules and set seeds per fruit rather than the pollen genotype had a significant effect on many fruit traits like size, symmetry, skin thickness, and total soluble solids, which we describe as ”pseudo-xenia.” Useful pseudo-xenic effect is worth exploiting in fruit culture.</jats:p>

Tree and fruit traits of progenies from the cross between (Annona cherimola Mill. × A. squamosa L.) × A. reticulata L. and approaches for the introgression of valuable genes from A. reticulata L.

“…The parents of the cross produce fruits weighing as much as 500-600 g, but the mean fruit weight of the fruit produced by the progenies was very low. This result can be explained by the earlier findings of Jalikop and Kumar (2007), who noted that pollen of interspecific Annona hybrids have a higher proportion of tetrads and a low proportion of fertile grains; when this pollen was used in hand pollination, low-weight fruits were produced. Fruits of A. reticulata have a stout stalk (13.4 mm), which is in contrast to atemoya (4.6 mm), but none of the offspring had fruit stalks measuring more than 7.1 mm in diameter which was, by far, less than the mid-parental value.…”

“…that is shed from the anthers is incompletely formed (dyad and tetrad stages) (Peña 2003). Among the edible annonas, A. squamosa pollen has the highest concentration of viable normal grains (Sahoo et al 2000;Jalikop and Kumar 2007); hence, supplementary pollination is not practiced in this species. Subjecting F 1 progeny of (A. cherimola 9 A. squamosa) 9 A. reticulata to a backcross with A. squamosa, a highly fertile species, is expected to yield productive introgressants in which the proportion of the A. squamosa genome will be extended from 25 to 62.5% in the F 1 BC 1 progeny.…”

“…In our Annona breeding programme, an outstanding recombinant isolated from atemoya 9 A. squamosa family gained commercial significance under the name 'Arka Sahan' (Jalikop and Kumar 2007). Atemoya 9 A. reticulata was another cross combination that has attracted interest as A. reticulata carries genes for uniform heart-shaped fruits with a stout stalk and smooth and attractive skin colour as well as having a robust root system and compact tree habit (Council of Scientific and Industrial Research 1985).…”

Inheritance of foliage characteristics in (Annona cherimola Mill. × A. squamosa L.) × A. reticulata L. hybrids

“…Atemoya 9 A. reticulata hybrids are relatively easy to obtain despite some field causality that possibly does not seriously distort the segregation in this interspecific cross. However poor fruit set observed in this cross combination (*20%) could be attributed to higher frequency of dyads and tetrads in the pollen of A. reticulata (Jalikop and Kumar 2007), besides involvement of three species in the cross. Selfpollination in annonas is hindered by the presence of marked protogyny (Kahn et al 1994) leading to cross pollination and as a consequence Annona spp.…”

“…), sugar apple (A. squamosa L.) and the hybrid between the two, atemoya, are popular (Peña et al 2002;Jalikop and Kumar 2007). Another allied species, A. reticulata L. (bullock's heart) is grown on a limited scale.…”