Temperature as a component of the expression of developmental responses in wheat

Abstract

Studies were made of days to ear emergence under the constant temperatures of 9, 14, 19 and 25'C and 16 h photoperiod in three sets of wheat lines each possessing genotypes differing for developmental responses .Days to ear emergence in three near-isogenic lines of the wheat cultivar Triple Dirk, which differed for vernalization response, increased as the strength of the response increased . At the four temperatures Triple Dirk D (Vrn 1 vrn 2) was not significantly different from normal Triple Dirk (Vrn I Vrn 2) but Triple Dirk B (vrn 1 Vrn 2) was significantly (P = 0 .01) later than normal Triple Dirk at each temperature . This indicates that the vrn 1 allele confers stronger vernalization response than vrn 2 over the range of temperatures (9-24°C) . However, Triple Dirk C (vrn 1 vrn 2) failed to head after 120 days at each temperature indicating strong interaction between vrn 1 and vrn 2 with each other (and possibly the Triple Dirk background) to give a much stronger vernalization response than predictions from additivity of their individual effects.The second set comprised the four Chinese Spring/Thatcher chromosome substitution lines CS/T 3B, 6B, 7B and 5D, plus Chinese Spring and Thatcher, and were grown in the unvernalized condition . CS/T 5D was similar in days to ear emergence as Chinese Spring at all four temperatures but the other three lines were earlier to ear emergence, particularly as the temperature increased . Days to ear emergence was fastest at 14°C in all lines, except CS/T 3B, in which it decreased progressively from 9 to 24°C .The third set of Chinese Spring and Thatcher and the homoeologous group 2 chromosomes of Thatcher substituted in Chinese Spring, the group which is considered to be involved in the control of photoperiod sensitivity . The three substitution lines responded differently to temperature compared with Chinese Spring and with each other, with chromosome 2D being the least, and chromosome 2B the most, responsive to temperature.

Basic Development Rate in Spring Wheat1

“…Although there were substantial differences in the length of the vegetative phase between these two cultivars, the duration of the post initiation phase was less variable, although generally longer, in Pinnacle. There was a consistent duration of the phase from terminal spikelet to ear emergence in 13 gibberellininsensitive wheats, embracing a wide range of vernalization responses (Flood, 1983). Similarly, Pirasteh and Welsh (1980) showed that days to heading and degree hours for spring and winter wheats (artificially vernalized) were similar, although there were differences between cultivars within each group, indicating that after floral induction in spring and winter wheat cultivars "sequential plant development is driven by the same sets of energy and photoperiod requirements in both growth habits."…”

“…Moench) had alleles which exhibited different responses to temperature. If differences in basic development rate in wheat were due to variation for temperature-sensitive genes, this process may exhibit close interaction with photoperiod response (Flood and Halloran, 1984).…”

Developmental Rates of Wild Oats (Avena fatua) and Wheat (Triticum aestivum)

“…In addition, specific growth stages may be more effective than days after emergence for scheduling other pest management, research, and cultural management procedures (1). Differences in temperature and growing conditions among different planting dates and years cause developmental rates to change relative to chronological time (3,4,9). Therefore, it would be useful to relate development to morphological stages rather than chronological time (1,5).…”

Physical Mapping and Chromosomal Location of the Photoperiod Response Gene Ppd2 in Common Wheat

“…Chromosomal location of Ppd3 on chromosome 2A was contradictory. Halloran and Boydell (1967), Zveinek (1983), Flood and Halloran (1984) and Whitechurch and Slafer (2001) did not find a significant effect of chromosome 2A of 'Chinese Spring' substitution lines on photoperiod sensitivity, whereas Law et al (1978) reported positive effects. Breeding for photoperiod sensitivity will be facilitated by using only 2 dominant Ppd genes, namely Ppd1 and Ppd2, and, possibly, a number of minor genes controlling photoperiod response identified on several other chromosomes (Halloran and Boydall 1967, Islam-Faridi et al 1996.…”