When foreign pollen comes in handy

HYBRID CUSTARD Hand pollination in the Arka Sahan variety is a maiden instance of growers practising it to exploit the dramatic influence of foreign pollen on the fruit, explains Shrikant Jallikop

In several plant species, pollination followed by fertilisation is essential for fruit development. Fruit development will take place when pollination occurs either from the pollen of the same plant as in self-pollination or from another related plant as in cross-pollination.

Generally the fruit attributes are not altered irrespective of pollen source. But poor pollination results in misshapen and undersized fruits which not only reduce the yield, but affect the marketability of the fruits.

At times, pollen do have a bearing on the seed and fruit traits, and this is called xenia.

In certain crops like maize, cotton, pistachio, almond and vine cacti, the pollen source is known to alter colour, number and weight of seeds, fruit and embryo size, and oil content. But commercial application of this phenomenon is limited, as either the effect produced by the pollen is insignificant or its exploitation not feasible.


An interesting instance of foreign pollen influencing several fruit traits of commercial value was encountered in custard apple breeding programme of Indian Institute of Horticultural Research, Bangalore. From 1983 onwards, for over a decade, thousands of custard apple hybrids were produced using several related species as parents and each progeny was tested for fruit yield and quality.

Though hybrid progenies were highly heterogenous, not a single hybrid was superior to their parents. However, fruits of one inter-species hybrid were exceptionally good with extremely sweet pulp, few small seeds and good shelf life. But this hybrid plant produced just a few, small, misshapen fruits.

The rare hybrid was identified for further improvement. It was backcrossed with common custard apple in order to derive better recombinant. However, the resultant progeny were extremely weak; some of them failed to flower and fruit, and were much inferior to the hybrid parent. Similar results were observed in the next generation or F2 of the hybrid.

Both these breeding generations practically involve high degree of inbreeding. The innate genetic heterozygosity (having two different alleles for a single trait) of custard apple species coupled with inter-species nature of this hybrid resulted in production of weaklings in both these generations.

Custard apple belongs to annonaceae, a primitive plant family whose members generally pose serious problem of pollination. In the two important fruits of this family, atemoya and cherimoya, manual or hand pollination with own pollen is done as they do not yield a good crop on their own.

The flowers of the hybrid were manually pollinated with its own pollen to see if this could promote fruit yield. Unfortunately this had a marginal influence on fruit size and fruit number in the plant. Use of other related species pollen also did not give encouraging results.

Efforts that paid off

However when hybrid flowers were pollinated with the common custard apple (annonasquamosa) pollen, it produced amazing results.

The fruits thus produced were three-four times bigger than the naturally set fruits, weighing on an average 600 gram with symmetrical shape. Good pollen compatibility and high proportion of fertile pollen grains in the pollen samples of this species resulted in more than 90 per cent of the pollinated flowers developing into harvestable fruits.

The most desirable traits of the hybrid, like sweetness, seed per cent and shelf life of the fruit was unchanged. However, when this pollen source was tested on other custard apple relatives including flowers of atemoya, neither fruit size nor shape changed, thereby indicating the specificity of this pollen. In the hybrid, the pollen source was highly efficient in boosting the fruit yield per tree by substantially increasing the fruit number and size, the two key yield components.

This hybrid is now popular under the name Arka Sahan. Fruits of this variety are by far superior to those of sitaphal (sharifa or custard apple). The large attractive fruits have very sweet pulp, small few seeds and good keeping quality.


Growers are procuring planting material of Arka Sahan from Indian Institute of Horticultural Research and are adopting hand pollination with the pollen of common custard apple. Hand pollination is done in some crops either for improving yield or for hybrid seed production.

It is commonly practised in fruit crops like apple, pear, blueberry, cherimoya, atemoya and date palm mainly for enhancing fruit set.

But hand pollination in Arka Sahan is a maiden instance of growers practising it to exploit the dramatic influence of foreign pollen on the fruit.

The unique benefits lie in realising 300 to 400 per cent fruit size increase and uniform fruit shape without altering fruit quality. Further, hand pollination in Arka Sahan is much easier than in many other fruit crops because of larger flowers besides excellent fruit set percent.