Is it possible to diagnose at harvest a problem of pollen sterility in wheat?

We tested if various plant parameters, easy to measure at maturity in a wheat crop, could discriminate between situations with and without limitations in grain set caused by pollen sterility. In a pot experiment, plants were subjected to two treatments: shading during stem elongation, reducing growth; and climatic stress (low radiation and chilling) at meiosis, inducing pollen sterility. The percentage of grain setting among the two oldest florets within each spikelet (LF) and the ratios of grain number to (i) biomass of the chaff and (ii) biomass of the straw plus chaff were markedly reduced by the stress at meiosis and either little or not affected by shading during stem elongation.

Two indices were tested in the field: LF and the ratio, RK, of the grain number per ear to an estimate, based on chaff biomass, of the potential number in the absence of sterility. These indices were measured in a network of five field experiments with six cultivars. The fluctuations in the indices were compared to those of a reference criterion that identified sterility: the rate of grain setting among the two oldest florets of each spikelet, measured in bagged ears to prevent cross-pollination. Both indices were reduced when the reference criterion diagnosed a major sterility but they did not always decrease in case of minor sterility. Classification of the cultivars based on the reference criterion was similar to that based on LF, but not on RK. LF diagnosis of sterility was in agreement with the occurrence of climatic conditions likely to induce sterility.