ALBERT

Description: SUMMARYThirty-eight spring wheat genotypes of north temperate or low latitude origin, all reasonably well adapted to the English environment, were grown in controlled environments providing the four combinations of 10 and 14 h photoperiods and temperatures of 8 and 16 °C for 6 weeks. They were then transferred to a glasshouse to assess their responses to these treatments. In separate experiments the responses of the genotypes to vernalization for 2 and 4 weeks at 2 and 8 °C were compared with unvernalized controls. The genotypes were also compared in field experiments from early, intermediate or late sowing over 3 years.Both high temperatures and long days hastened ear emergence. At the higher temperature more leaves and spikelets were produced on the main stem while in long days the plants had fewer leaves and spikelets.Most genotypes of north temperate and low latitude origin were responsive to photoperiod but not to the vernalization treatments. As a group, the low latitude ones were as responsive as the north temperate group. Five genotypes of north temperate origin were responsive to vernalization but not to photoperiod and were designated as ‘winter’ ones. Pitic 62 and Hork, from low latitudes, were responsive to vernalization and Hork was unique in also being responsive to photoperiod. The main difference between the north temperate and low latitude genotypes was in time to ear emergence and it is suggested that these differences were due to the effects of earliness genes as distinct from those determining photoperiodic response.Taking all genotypes individually there were no correlations between yield or its sensitivity to sowing date and any of the attributes measured in controlled environments. However, considering class means, the winter genotypes were the latest to reach ear emergence in the field, and their yields, while greatest from the earliest sowings, were proportionally more depressed by late sowing than the others of the north temperate origin. Thus, it may be unwise for plant breeders to incorporate a vernalization response in spring wheat varieties unless genes for ‘earliness’ are also included. The low latitude class gave only slightly lower yields than the north temperate class.It is concluded that genes other than those controlling responses to photoperiod, temperature and vernalization were more important determinants of the differences in yield among this set of genotypes.

Description: SummaryField experiments comparing 13 winter wheat varieties representing very old, old, intermediate and modern groups were carried out over three seasons. The experimental sites were on soils of high fertility and weeds, diseases and pests were controlled by applications of proprietary agrochemicals. Lodging was prevented by supporting the plants with coarse-mesh netting.The average yield of all varieties over the three harvest years 1984, 1985 and 1986 was 7·7 t/ha (at 15% moisture content). Compared with the very old varieties which were grown by farmers during the 19th century, the modern varieties gave 59% more grain, had 14% more ears/m2 and 30% more grains per ear, but a similar mean grain mass. The modern varieties yielded slightly more biomass (total above-ground dry matter at harvest), were much shorter and reached anthesis about 6 days earlier than the older ones. In 1984, when the yields were greater than in 1985 and 1986, the yield advantage of the modern varieties was more in percentage and absolute terms than in the other years. Also, in 1984, the differences between the very old and the modern varieties in biomass was the greatest.The genetic gain in yield measured in these experiments is compared with those estimated for other countries and reasons for the variation are discussed.

Description: SummaryIn experiments harvested in 1985 and 1986 the grain yields of 61 F1 hybrids among winter wheat varieties and advanced breeding lines were 5·9% greater than the yields of the best parents. In a trial with 430 hybrids in 1986, the hybrids yielded 3·6% more grain than the best parents. Among these 430 hybrids heterosis for yield was greatest for those from the lowest yielding parents. This result is taken to indicate that among these genotypes most genes for high yield have been fixed in the highest yielding parents.The hybrids had slightly fewer ears/m2, but more grains per ear and heavier grains than the highest yielding parents. They yielded more straw as well as more grain.The results are compared with those from other studies and it is concluded that yield advantage of F1 hybrids so far tested is not generally sufficient to justify their introduction into U.K. agriculture.

Description: SUMMARYSelections for high (H) and low (L) number of ears were made from crosses between three pairs of winter wheat varieties. By the F5 generation there were consistent, heritable differences between H and L selections in each cross. In an irrigated trial the H lines outyielded the L lines even in one experiment where compensatory increases occurred in the weight of grain per ear of the L lines. Drought for the 5 weeks before an thesis reduced the final number of ears of the H lines by 14% but did not affect the final number of ears of the L lines. This reduction in the final number of ears of H lines resulted in them being outyielded by L lines by 8%. Drought from anthesis to maturity did not significantly reduce grain yields of either H or L lines below their values under full irrigation.When fully irrigated, the evapotranspiration of H and L lines from 1 April until maturity was approximately 360 mm. The drought before anthesis reduced water use to about 320 mm, there being no difference between selections in total water use by the crops during this period. However, the L lines extracted significantly more water from the soil below a depth of 0.9 m during this drought than the H lines, and this appeared to make the L lines less susceptible to drought at this stage. Water use by the crop during the late drought could not be reliably estimated because by this time water was being extracted from below the level of the neutron probe access tubes.It is concluded that in an environment where a pre-anthesis drought is unlikely to occur, varieties with high ear-bearing capacity may give the best yields. Selection for types showing a limited tillering capacity may prove to be an effective compromise in regions with erratic rainfall where pre-anthesis droughts can occur.

Description: SUMMARYFive experiments, involving 37 varieties, were carried out over three seasons to estimate the increase in yield potential in spring barley achieved by plant breeding during the last 100 years. Most of the important spring barley varieties grown in Britain between 1880 and 1980 were represented. In three experiments disease was controlled by a fungicide while in the other two experiments fungicide application was a main treatment. To prevent yield loss due to lodging, plants were supported as a main treatment in two trials.In all experiments most of the modern varieties yielded more than the older ones. The genetic gain in yield was 0·39% per year during the 100-year period and 0·84% per year between 1953 and 1980.Modern varieties had higher grain yields, shorter straw, and higher harvest index denned as the proportion of grain dry weight to total above-ground dry weight; more of the tillers they produced survived to give ears. There was a weak association between biological yield (total above-ground dry weight) and grain yield.It is suggested that although much of the improvement in yield described here could be attributed to increased harvest index, the scope for further improvement in this character may be limited. Further yield improvements might be achieved by combining high biological yield with high harvest index.