Identification and introgression of QTLs implicated in resistance to sorghum downy mildew (Peronosclerospora sorghi (Weston and Uppal) C. G. Shaw) in maize through marker-assisted selection

Sorghum downy mildew caused by Peronosclerospora sorghi is a major disease of maize and resistance is under the control of polygenes which necessitated identification of quantitative-trait loci (QTLs) for initiating marker-assisted introgression of resistant QTLs in elite susceptible inbred lines. In the present study, QTLs for sorghum downy mildew (SDM) resistance in maize were identified based on cosegregation with linked simple sequence repeats in 185 F₂ progeny from a cross between susceptible (CM500-19) and resistant (MAI105) parents. F₃ families were screened in the National Sorghum Downy Mildew Screening Nursery during 2010 and 2011. High heritability was observed for the disease reaction. The final map generated using 87 SSR markers had 10 linkage groups, spanning a length of 1210.3 cM. Although, we used only 87 SSR markers for mapping, the per cent of genome within 20 cM to the nearest marker was 88.5. Three putative QTLs for SDM resistance were located on chromosomes 3 (bin 3.01), 6 (bin 6.01) and 2 (bin 2.02) using composite interval mapping. The locus on chromosome 3 had a major effect and explained up to 12.6% of the phenotypic variation. The other two QTLs on chromosomes 6 and 2 had minor effects with phenotypic variation of 7.1 and 2%. The three QTLs appeared to have additive effects on resistance. The QTLs on chromosomes 3 and 6 were successfully used in the marker-assisted selection programme for introgression of resistance to SDM in eight susceptible maize lines.     

Role of root hydrophobic barriers in salt exclusion of a mangrove plant Avicennia officinalis

Salt exclusion at the roots and salt secretion in the leaves were examined in a mangrove, Avicennia officinalis. The non‐secretor mangrove Bruguiera cylindrica was used for comparative study of hydrophobic barrier formation in the roots. Bypass flow was reduced when seedlings were previously treated with high salt concentration. A biseriate exodermis was detected in the salt‐treated roots, along with an enhanced deposition of hydrophobic barriers in the endodermis. These barriers reduced Na⁺ loading into the xylem, accounting for a 90–95% salt exclusion in A. officinalis. Prominent barriers were found in the roots of B. cylindrica even in the absence of salt treatment. A cytochrome P450 gene that may regulate suberin biosynthesis was up‐regulated within hours of salt treatment in A. officinalis roots and leaves, corresponding with increased suberin deposition. X‐ray microanalysis showed preferential deposition of Na⁺ and Cl^? in the root cortex compared with the stele, suggesting that the endodermis is the primary site of salt exclusion. Enhanced salt secretion and increased suberin deposition surrounding the salt glands were seen in the leaves with salt treatment. Overall, these data show that the deposition of apoplastic barriers increases resistance to bypass flow leading to efficient salt exclusion at the roots in mangroves.     

Morphology of some polystichoid ferns

The morphology of the spores and prothalli of Arachniodes aristata, A. assamica, Cyrtomium caryotideum, C. falcatum and 10 species of Polystichum is described. The spores are bilateral with a smooth exine and the perine smooth in Cyrtomium and granulose to spinulose in the others. Spore germination is of the Vittaria type and prothallial development is of the Aspidium type. The adult prothallus of Arachniodes and Polystichum is cordate, with profuse papillate hairs. Sex organs are of the common leptosporangiate type. The antheridium dehisces by a pore-like opening in the cap cell in Polystichum , whereas the cap cell collapses at dehiscence in Arachniodes. Both species of Cyrtomium are apogamous; the thallus becomes irregular in shape in C. caryotideum but is cordate in C. falcatum.     

Some aspects of the morphology and distribution of Microsoriurn linguaeforrne (Polypodiaceae)

Microsorium linguaeforme is reported for the first time from India. Its rhizome is slender, much elongated with a highly dissected stele and leaf gaps in a single median dorsal row. The characteristic branching pattern is a modification of the common pattern in Polypodiaceae, resulting from the displacement of leaf-associated branches and the precocious development of the most basal secondary branch of each primary branch. The first two or three leaves of juvenile plants have no associated branches; thereafter, abaxially-originating traces t o solitary branches are progressively displaced so that the branch trace is close to the preceding leaf trace. Stomata of adult leaves are Copolomesoperigenous and of juvenile leaves Eupolomesoperigenous. The spores are monolete and with a smooth exine. Spore germination is of the Vitiariatype and prothallial development of the Kauliniatype. It is concluded that M. linguaeforme is closely allied to Leptochilus and is probably parental to it.     

Palynology of South Indian Zingiberaceae

MANGALY, J. K. & NAYAR, J. 1990. Palynology of South Indian Zingiberaceae. Light microscope studies on pollen morphology of 21 Old World, tropical taxa of Zingiberaceae reveal that an exine is absent only in Kaempferia . A discontinuous exine layer consisting of circular plates joined together at margins occurs in Alpinia galanga and Amomum hypoleucum while all other taxa possess an uninterrupted exine layer which is commonly 0.7 μm to less than 2.0 μrn thick (3.2 μm in Zingiber zerumbet , 2.5 μm in Amomum hypoleucum ). Exine is spinose in Alpinia (smooth in Alpinia sanderae ), Amomum and Boesenbergia , verrucose in Eleltaria , tuberculate to areolate or striate in Zingiber , papillose in Globba and smooth or nearly so in Curcuma, Costus and Hedychiurn . Pollen grains are spheroidal, 50–90 μm in size (35 μm in Globba ophioglossa ), and inaparturate (foraminate in Costus ), except in Curcuma and Zingiber where they are ovoid to ellipsoidal, 70–135 times 60–80 μm in size and sulcate. A lamellated intine, much thicker than the exine, occurs in all, and it is thinner at the apertural region in Curcuma, Costus and Zingiber; in Elettaria and Hedychiurn it is thinner in one or few large scattered circular areas, and in Boesenbergia and Alpinia zerumbet on one side of the grains. Palynologirally Alpinia, Amomum, Boesenbergia, Kaempferia and Zingiber constitute one group while Elettaria, Hedychiurn and Costus constitute another.     

Vascular Organization and some Aspects of the Morphology of the Rhizome of Gymnogrammitis dareiformis

Gymnogrammitis dareiformis, the taxonomically controversialdavalliaceous fern has a parenchymatous rhizome, in the groundtissue of which groups of 1–16 thick-walled cells (withpeg-like protrusions on inner walls) are irregularly scattered.Paleae clothing the rhizome are basally attached, gland-tippedand bearing unicellular marginal hairs. The vascular cylinderis a radially-symmetric dictyostele dissected by spirally-arrangedleaf gaps into slender reticulated meristeles. Some of the dorso-laterallyplaced leaves alone are fully developed; most other leaves aresuppressed and some are highly reduced (the larger reduced leavesappear as protrusions on the rhizome and have a well-formedleaf base). The leaf trace of developed as well as the largerreduced leaves is a channel-shaped loose reticulum of four vascularstrands; the trace of the reduced leaves is smaller and endsblindly at the leaf base. The leaf trace of the smaller reducedleaves is vestigial and represented often by only a pair ofvascular strands fusing into one and ending blindly in the cortexof the rhizome. The leaf trace of suppressed leaves fuses backwith the stelar cylinder, forming a convex reticulum bridgingthe sides of the leaf gap. It is suggested that the characteristic stelar organizationof the Davalliaceae is derived by suppression of leaves froma radiallysymmetric dictyostele with spirally-arranged leafgaps as found in Nephrolepis and that Gymnogrammitis with itsreduced and suppressed leaves indicates the process of transition.The creeping solenostelic rhizome with two-ranked leaf arrangementcould be derived from an erectgrowing dictyostelic one by supppressionof leaves.