Читать книгу Ecology - Michael Begon - Страница 45

There have been many striking cases where the geographic range of a crop species has been extended into colder regions of the world by plant breeders. Traditional crop breeding practices have generally used crossing of closely related varieties to produce new crops with desired cold‐tolerance traits.

A key challenge for plant breeders is to introgress desirable traits from wild and even quite distantly related species into important domesticated crops but at the same time retain the favourable traits of the crop. Sugar cane (Saccharum spp.) is a major crop whose tropical heritage makes it cold sensitive and generally restricted to latitudes between 30°N and 35°S. Another member of the Poaceae family of tall grasses, Miscanthus spp., on the other hand, is a temperate‐adapted species with marked cold tolerance. Głowacka et al. (2016) have shown that the chilling tolerance of Miscanthus can be transferred to sugarcane (Figure 2.15) without significant loss of overall sugarcane productivity. The chilling‐tolerant hybrid of sugarcane and Miscanthus (Miscane US87‐1019) has immediate potential for increased stock food and biofuel production, and at the same time provides the basis for extending sugarcane’s range as a crop into higher latitudes and altitudes, once we better understand the genes that confer the cold‐tolerance advantage.

Figure 2.15 The chilling tolerance of Miscanthus can be transferred to Saccharum. Comparison of cold tolerance in a laboratory experiment involving plants of sugarcane (Saccharum sp. L79‐1002), Miscanthus (Mxg ‘Illinois’) and a hybrid of Saccharum and Miscanthus, referred to as ‘Miscane’ (US87‐1019). The light‐saturated leaf net CO₂ uptake rate (A_sat in μmol m^–2 s^–1) is shown for warm conditions before chilling treatment (25ºC day, 20ºC night: dashed line), after transfer of plants to chilling (day 0: 10ºC day, 5ºC night), on day 11 of chilling treatment and one day after transfer of plants back to warm conditions (day 12: recovery) expressed as a percentage of rates observed in warm conditions before chilling (control). A plus sign indicates a significantly lower value than the control. As expected, Miscanthus was the most cold tolerant, sugarcane the most cold sensitive, while the hybrid did not differ significantly from Miscanthus after recovery.

Source: From Głowacka et al. (2016).

potential of genomics, transcriptomics and proteomics in crop breeding

Future crop improvements to increase production and range in colder environments are certain to involve identification of the genes responsible for cold tolerance (both chilling and sub‐zero tolerance) and acclimatisation. Erath et al. (2017) have, for example, identified genomic regions involved in frost tolerance of winter rye (Secale cereale) by mapping of quantitative trait loci (QTLs). A QTL is a section of DNA that correlates with variation in the quantitative trait of the phenotype (cold tolerance in this case); the QTL can be expected to contain the genes that control the trait. In winter rye, a QTL on chromosome 5R harbours the Frost resistance locus 2 (Fr‐R2) and the ‘Puma’ allele at this locus was found to significantly increase frost tolerance. Discoveries of this kind can be expected to increase selection intensity for frost tolerance by preselecting plant breeding lines based on markers from the Fr‐R2 locus.