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.     

Genetic interaction and mapping studies on the leaflet development (lld) mutant in Pisum sativum

In Pisum sativum, the completely penetrant leaflet development (lld) mutation is known to sporadically abort pinnae suborgans in the unipinnate compound leaf. Here, the frequency and morphology of abortion was studied in each of the leaf suborgans in 36 genotypes and in presence of auxin and gibberellin, and their antagonists. Various lld genotypes were constructed by multifariously recombining lld with a coch homeotic stipule mutation and with af, ins, mare, mfp, tl and uni-tac leaf morphology mutations. It was observed that the suborgans at all levels of pinna subdivisions underwent lld-led abortion events at different stages of development. As in leafblades, lld aborted the pinnae in leaf-like compound coch stipules. The lld mutation interacted with mfp synergistically and with other leaf mutations additively. The rod-shaped and trumpet-shaped aborted pea leaf suborgans mimicked the phenotype of aborted leaves in HD-ZIP-III-deficient Arabidopsis thaliana mutants. Suborganwise aborted morphologies in lld gnotypes were in agreement with basipetal differentiation of leaflets and acropetal differentiation in tendrils. Altogether, the observations suggested that LLD was the master regulator of pinna development. On the basis of molecular markers found linked to lld, its locus was positioned on the linkage group III of the P. sativum genetic map.     

Scutellar Amylase Activity in Naturally Aged and Accelerated Aged Wheat Seeds

Scutellum extracts of dry unaged and differentially aged wheatseeds showed appreciable and ß amylase activities,these being higher in unaged and lower in aged seeds. This indicatesthat scutellar amylase may remain long-lived in seeds. Duringgermination of both unaged and aged seeds an increase in scutellaramylase (particularly ß) occurs. Initiation of thisgermination associated increase in amylase activity, however,was found to occur relatively late during imbibition. Further,while scutellar amylase increased considerably during imbibitionin unaged seeds, in differentially aged seeds the increase wassmall. This also contributes to the reduced scutellar amylaseactivities in aged seeds. Triticum aestivum L., wheat, naturally aged, accelerated aged, unaged, germination, scutellar and ß amylase     

Studies into Causes of Non-germination of Aged Wheat Seeds

Excised embryos of aged non-germinating wheat seeds, when placedon sucrose/glucose germinated well and grew into normal plantlets,while on agar alone they remained ungerminated as in the intactseed. From the results of amylase assays in seeds of differentages it appears that failure of amylolytic activity in agedseeds could be a cause of unavailability of utilizable subtrateto the embryonic axis of aged seeds. This would bring abouta limitation in the capacity of germination and growth of theembryonic axis even before the embryo becomes non-viable. Wheat (Triticum aestimon L. cv. Sonalilca), embryo, germination, sucrose, amylase     

Characterization of variation and quantitative trait loci related to terpenoid indole alkaloid yield in a recombinant inbred line mapping population of <Emphasis Type="Italic">Catharanthus roseus</Emphasis>

Improved Catharanthus roseus cultivars are required for high yields of vinblastine, vindoline and catharanthine and/or serpentine and ajmalicine, the pharmaceutical terpenoid indole alkaloids. An approach to derive them is to map QTL for terpenoid indole alkaloids yields, identify DNA markers tightly linked to the QTL and apply marker assisted selection. Towards the end, 197 recombinant inbred lines from a cross were grown over two seasons to characterize variability for seven biomass and 23 terpenoid indole alkaloids content-traits and yield-traits. The recombinant inbred lines were genotyped for 178 DNA markers which formed a framework genetic map of eight linkage groups (LG), spanning 1786.5 cM, with 10.0 cM average intermarker distance. Estimates of correlations between traits allowed selection of seven relatively more important traits for terpenoid indole alkaloids yields. QTL analysis was performed on them using single marker (regression) analysis, simple interval mapping and composite interval mapping procedures. A total of 20 QTL were detected on five of eight LG, 10 for five traits on LG1, five for four traits on LG2, three for one trait on LG3 and one each for different traits on LG three and four. QTL for the same or different traits were found clustered on three LG. Co-location of two QTL for biomass traits was in accord of correlation between them. The QTL were validated for use in marker assisted selection by the recombinant inbred line which transgressively expressed 16 traits contributory to the yield vinblastine, vindoline and catharanthine from leaves and roots that possessed favourable alleles of 13 relevant QTL.     

Germination of Rye Embryos Following Hydration-Dehydration Treatments: Enhancement of Protein and RNA Synthesis and Earlier Induction of DNA Replication

On germination of low viability embryos of rye, var. LovaszPatonai, the rate of protein synthesis increases during theearly hours of imbibition and high rates of DNA replicationcommence around the 9th hour. If embryos are imbibed for 3 or6 h then dehydrated back to their original weight, their rateof protein synthesis when next imbibed closely corresponds tothat of embryos germinated for a period equal to that of thehydration pre-treatment plus the duration of the second imbibition.Pre-treatment also enhances subsequent RNA synthesis and embryoshydrated for 9 h then dehydrated start major DNA synthesis atonce as water is again supplied. Many changes occurring duringthese periods of hydration pre-treatment must therefore be stableto subsequent dehydration. Damage occurs to areas that are firstactive in protein and RNA synthesis if pre-treatments extendbeyond 9 h and subsequent germination of the embryo is thenimpaired. The implications of these results are discussed inrelation to the effects of hydration pre-treatments upon enhancedgermination and the stability to dehydration of the productsof early RNA and protein synthesis.