Crossing Wheat Without a Breeding Station
Manpreet grows wheat on six acres near Sangrur. His own saved variety yields 5.2 tonnes per hectare, but in the last two seasons about a third of the crop was hit by yellow rust and needed two fungicide sprays. His neighbour's desi variety, grown without any spray, stays almost clean, but yields only 3.1 tonnes per hectare, and being tall it lodges after wind and heavy irrigation. Manpreet wants one variety that is both high-yielding and rust-resistant, and he wants the seed in three years. He has saved seed of both varieties. His plan is to sow them in alternate rows in one field, let wind and insects do the crossing, and then collect seed only from the tall, clean-looking plants, because he believes those must be the hybrids. He also intends to sell the leftover seed to other farmers in the village next season.
1. Why will Manpreet's alternate-row plan almost certainly not give him hybrid seed? Describe what he would actually have to do.
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Wheat is self-pollinated. The anthers and stigma sit in the same floret, and pollen is shed and lands on the stigma before the glumes open widely, so wind and insects contribute very little foreign pollen. Sowing two varieties side by side therefore mostly produces selfed seed. On top of that, his selection rule is self-defeating: a tall, clean plant in that field is far more likely to be the desi parent itself than a hybrid, so he is selecting the low-yielding parent.
A real cross needs hand work: choose the female parent, open the florets and remove the anthers before they shed pollen (emasculation), cover the ear with a butter-paper bag to stop stray pollen, collect pollen from the rust-resistant parent, dust it on the exposed stigmas, re-bag, and label with date and parents. Only seed from that treated ear is F1. Selling the bulk field seed as 'hybrid' next season would be selling ordinary selfed seed.
2. Suppose he somehow obtains F1 seed. Why will the next generation look mixed, and why can he not simply keep the best plants and stop?
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F1 plants are all heterozygous and therefore uniform. When they self-pollinate, the two alleles of each gene separate at gamete formation, so F2 shows a mixture. For a single gene the ratio is 3:1, but yield, height and lodging are polygenic, so F2 is a spread of heights and yields with only a few plants combining high yield with resistance. Resistance may also be recessive, in which case the F1 itself will rust, and the resistant type reappears only in F2.
He must therefore select individual plants, self each one, grow its progeny in a separate row, discard rows that rust, and repeat for five or six generations until the selected line breeds true. Each generation is a season, and testing against rust needs deliberate exposure, not just a lucky field. That is the reason plant breeding stations take years, and why a farmer's single field cannot compress the process.
3. Give two reasons the three-year target is unrealistic and suggest a practical alternative for Manpreet.
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First, six generations of selfing and selection cannot fit into three seasons, and each generation must be grown and screened. Second, rust resistance is often race-specific: a single resistance gene can be defeated by a new rust race within a few years, so even a success can collapse - the classic boom-and-bust cycle. A variety bred from one resistance source is a temporary fix, and durable resistance usually needs several genes together.
A practical alternative: grow a released rust-resistant variety from a recognised breeding station on most of the area, keep the desi variety as a small multiline or border planting, and treat his own crossing as a long-term experiment with a realistic six-to-eight-year horizon. He could also join a varietal trial or a farmers' participatory selection programme, where material is already segregating and being screened under institutional conditions. Selling seed from an unverified line to neighbours should be dropped entirely, because he cannot guarantee either purity or resistance.