Traditional Combining‐Ability and Gardner‐Eberhart Analyses of a Diallel for Cold Resistance in Winter Wheat
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The success of winter × spring wheat hybridization programmes depends upon the ability of the genotypes of these two physiologically distinct ecotypes to combine well with each other. Hence the present investigation was undertaken to study the combining ability and nature of gene action for various morpho-physiological and yield-contributing traits in crosses involving winter and spring wheat genotypes. Five elite and diverse genotypes each of winter and spring wheat ecotypes and their F 1 (spring × spring, winter × winter and winter × spring) hybrids, generated in a diallel mating design excluding reciprocals, were evaluated in a random block design with three replications. Considerable variability was observed among the spring and winter wheat genotypes for all the traits under study. Furthermore, these traits were highly influenced by the winter and spring wheat genetic backgrounds, resulting in significant differences between the spring × spring, winter × winter and winter × spring wheat hybrids for some of the traits. The winter × spring wheat hybrids were observed to be the best with respect to yieldcontributing traits. On the basis of GCA effects, the spring wheat parents HPW 42, HPW 89, HW 3024, PW 552 and UP 2418 and the winter wheat parents Saptdhara, VWFW 452, W 10 and WW 24 were found to be good combiners for the majority of traits. These spring and winter wheat parents could be effectively utilized in future hybridization programmes for wheat improvement. Superior hybrid combinations for one or more traits were identified, all of which involved at least one good general combiner for one or more traits in their parentage, and can thus be exploited in successive generations to develop potential recombinants through various breeding strategies. Genetic studies revealed the preponderance of additive gene action for days to flowering, days to maturity and harvest index, and non-additive gene action for the remaining six traits.

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Duration of hardening and cold hardiness in winter wheat

Canadian Journal of Botany ◽

10.1139/b79-188 ◽

1979 ◽

Vol 57 (14) ◽

pp. 1511-1517 ◽

Cited By ~ 15

Author(s):

D. W. A. Roberts

Keyword(s):

Winter Wheat ◽

Cold Hardiness ◽

Cold Resistance ◽

Maximum Level ◽

Late Winter ◽

Carbohydrate Reserves ◽

Stage Of Development ◽

Temperature Regimes ◽

Number Of Leaves ◽

Additional Reason

Experiments in which winter wheat plants were exposed to two different controlled hardening-temperature regimes (constant 3 °C, and 5.5 °C (day): 3.5 °C (night)) for long periods (up to 15 weeks) indicate that cold hardiness changes with time.The cold hardiness in plants grown from seed at 3 °C drops rapidly immediately after moistening and reaches a minimum 2–3 weeks later. Hardiness then begins to increase and reaches a maximum that lasts approximately from the 7th to the 11th week of growth after which it slowly declines.The patterns of change in cold hardiness during growth at 3 °C, and 5.5 °C:3.5 °C were almost synchronous if hardiness was plotted against duration of hardening, but were not synchronous if hardiness was plotted against stage of development as measured by the number of leaves produced. A somewhat similar result was obtained if plants grown for 3 weeks at 21 °C before hardening were compared with plants grown from dry seeds under the same hardening conditions. These experiments show that duration of hardening is more important in determining the level of cold resistance and the ability of wheat to retain its cold resistance than is stage of development, as measured by the number of leaves produced at the time cold resistance is measured.When plants seeded outdoors in mid-September were transferred at various dates (0–30 weeks after seeding) during the fall or winter to standardized hardening conditions in a growth cabinet for 0–15 weeks before freezing, their cold resistance changed in a way that suggests that plants in the field undergo the same pattern of changes in cold resistance as plants reared continuously in a growth chamber. This result suggests that the long exposure to hardening temperatures is one of the reasons why wheat in the field has less cold resistance in late winter than in autumn. Loss of carbohydrate reserves during winter may be an additional reason for this phenomenon.Under both growth cabinet and field conditions, increasing cold hardiness coincided with vernalization. Maximum cold hardiness was retained for several weeks after the completion of vernalization. These results suggest that the development of the maximum level of cold resistance may be related to the vernalization process.

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