Genetics of flowering time in bread wheat <Emphasis Type="Italic">Triticum aestivum</Emphasis>: complementary interaction between vernalization-insensitive and photoperiod-insensitive mutations imparts very early flowering habit to spring wheat

Time to flowering in the winter growth habit bread wheat is dependent on vernalization (exposure to cold conditions) and exposure to long days (photoperiod). Dominant Vrn-1 (Vrn-A1, Vrn-B1 and Vrn-D1) alleles are associated with vernalization independent spring growth habit. The semidominant Ppd-D1a mutation confers photoperiod-insensitivity or rapid flowering in wheat under short day and long day conditions. The objective of this study was to reveal the nature of interaction between Vrn-1 and Ppd-D1a mutations (active alleles of the respective genes vrn-1 and Ppd-D1b). Twelve Indian spring wheat cultivars and the spring wheat landrace Chinese Spring were characterized for their flowering times by seeding them every month for five years under natural field conditions in New Delhi. Near isogenic Vrn-1 Ppd-D1 and Vrn-1 Ppd-D1a lines constructed in two genetic backgrounds were also phenotyped for flowering time by seeding in two different seasons. The wheat lines of Vrn-A1a Vrn-B1 Vrn-D1 Ppd-D1a, Vrn-A1a Vrn-B1 Ppd-D1a and Vrn-A1a Vrn-D1 Ppd-D1a (or Vrn-1 Ppd-D1a) genotypes flowered several weeks earlier than that of Vrn-A1a Vrn-B1 Vrn-D1 Ppd-D1b, Vrn-A1b Ppd-D1b and Vrn-D1 Ppd-D1b (or Vrn-1 Ppd-D1b) genotypes. The flowering time phenotypes of the isogenic vernalization-insensitive lines confirmed that Ppd-D1a hastened flowering by several weeks. It was concluded that complementary interaction between Vrn-1 and Ppd-D1a active alleles imparted super/very-early flowering habit to spring wheats. The early and late flowering wheat varieties showed differences in flowering time between short day and long day conditions. The flowering time in Vrn-1 Ppd-D1a genotypes was hastened by higher temperatures under long day conditions. The ambient air temperature and photoperiod parameters for flowering in spring wheat were estimated at 25°C and 12 h, respectively.     

Phylogenetic Analysis of Dipterocarps Using Random Amplified Polymorphic DNA Markers

The phylogenetic relationships among 12 species belonging tothree different genera (Shorea, HopeaandAnisoptera) of Dipterocarpaceaewere studied using random amplified polymorphic DNA (RAPD) markers.A modified CTAB DNA extraction protocol was used to obtain tannin-and polysaccharide-free genomic DNA from mature leaves. Clusteranalysis of data from six random primers placed the 12 speciesin three groups corresponding to their respective genera. Fourdistinct nodes ofShoreaspp. and two ofHopeaspp. could be identified.Anisopteramegistocarpaserved as an outgroup, and was unique when comparedto the other genera examined. RAPD profiles of five individualsofH. odoratawith six random primers were identical, suggestingthat there is little intraspecific variation in this species.The RAPD technique can thus be successfully applied for thestudy of phylogenetic relationships of this important groupof tropical timber trees.Copyright 1998 Annals of Botany Company Dipterocarpaceae,Anisopteraspp.,Hopeaspp.,Shoreaspp., RAPD markers, tropical timber trees.