Sources of earliness and winter habit in durum wheat

C.O. QUALSET and Y.P. PURI¹⁾

Department of Agronomy and Range Science, University of California, Davis, California 95616, U.S.A.

We have made a systematic survey of the U.S. Department of Agriculture World Collection of Wheat (durum section) for many characters to provide new sources of variability for use in an applied breeding program. Of major interest for the California breeding program was new sources of photoperiod- and thermal-insensitive genotypes. Many of the improved durum wheats with spring habit from the International Maize and Wheat Improvement Center in Mexico are photo-insensitive, but many apparently have a vernalization requirement (thermal-sensitivity) as evidenced by failure to head when planted in July at Davis, California (minimum temperatures 50^oF). Thus, sources not having a cold requirement for heading were desired in the breeding program.

The durum collection (about 3,500 entries) was grown at Davis (38^o32'N; 16 m elevation) with July planting in 1969 and Tulelake, California (41^o58^'N; 1240 m elevation) with April planting. The methods used and the variation in heading time observed at the two locations were discussed in more detail elsewhere (QUALSET and PURI, 1973). By examining the heading responses jointly for the two locations it was possible to identify very early heading types that are very likely both photo- and thermal-insensitive. There were about 350 entries that fell in this category, of which 130 are listed in Table 1. About 1,000 of the entries failed to head at Davis with summer planting. Of this group, only 85 failed to head at Tulekake and these are believed to have strong vernalization requirements and would be useful in breeding durum varieties with winter habit (Table 2).

The group that failed to head at Davis in the summer, but did head at Tulelake and thus having spring growth habit, probably have weak photoperiod sensitivity and/or vernalization requirement. This group (not listed here) should be examined under conditions of better control of temperature and light intensity to determine the vernalization and photoperiod requirements in these spring wheats.

Requests for seed stocks of these entries should be made to Dr. Joseph C. CRADDOCK, Germplasm Resources Laboratory, Building No. 046, Beltsville, Agricultural Research Center, Beltsville, Maryland 20705, U.S.A.

Literature cited

QUALSET, C.O. and Y.P. PUPI. 1973. Heading time in a world collection of durum wheat : Latitudinal response and geographic origins relating to photo- and thermal-sensitivity. Proc. Eucarpia Symp. Genetics and Breeding of Durum Wheat. Univ. Bari. Italy. (In press).

(Received November 13, 1973)