Morphological,cytological and reproductive characterization of tri-species hybrids (GOS) between <Emphasis Type="Italic">Pennisetum glaucum</Emphasis>, <Emphasis Type="Italic">P. orientale</Emphasis> and <Emphasis Type="Italic">P. squamulatum</Emphasis>

New tri-species hybrids (GOS) in the genus Pennisetum involving the cultivated species pearl millet (P. glaucum L.) and two wild species, viz. P. squamulatum Fresen and P. orientale L. C. Rich, are reported. Six hybrid plants were recovered after crossing a backcross hybrid (2n = 3x = 23, GGO) between P. glaucum (2n = 2x = 14, GG) and P. orientale (2n = 2x = 18, OO) with F₁s (2n = 6x = 42, GGSSSS) between P. glaucum (2n = 4x = 28, GGGG) and P. squamulatum (2n = 8x = 56, SSSSSSSS). The hybrids were perennial, morphologically intermediate to their parents, and represented characters from the three contributing species. The hybrids contained 2n = 44 chromosomes (GGGSSO) representing 21, 14 and nine chromosomes from P. glaucum, P. squamulatum and P. orientale, respectively. Meiotic and flow-cytometric analysis suggested origin of these hybrids from unreduced female and reduced male gametes. Average chromosome configuration (8.42_I + 14.32_II + 1.62_III + 0.52_IV) at Meiosis showed limited inter-genomic pairing indicating absence of significant homology between the three genomes. The hybrids were male sterile (except one) and highly aposporous. P. orientale was identified to induce apospory in hybrid background with P. glaucum at diploid and above levels, though it was quantitatively affected by genomic doses from sexual parent. A case of inducible and recurrent apospory is presented whereby a transition from Polygonum-type sexual embryo-sacs to Panicum-type aposporous embryo-sacs was observed in diploid interspecific hybrids. Results supported independent origin and partitioning of the three apomixis-components (apomeiosis, parthenogenesis, and functional endosperm development), reported for the first time in Pennisetum. Potential utilization of GOS hybrids in understanding genome interactions involved in complex traits, such as perenniality and apomixis, is discussed.     

Reproductive pathways of seed development in apomictic guinea grass (<Emphasis Type="Italic">Panicum maximum</Emphasis> Jacq.) reveal uncoupling of apomixis components

One hundred and sixty accessions representing global germplasm of guinea grass (Panicum maximum Jacq.), an important apomictic (aposporous) fodder crop, were subjected to study on reproductive diversity in apomictic seed development utilizing ovule clearing and flow cytometric seed screen (FCSS). Single seed FCSS of selected 14 tetraploid and five hexaploid lines demonstrated uncoupling between the three apomixis components, viz. apomeiosis, parthenogenesis and functional endosperm development, in natural as well as experimental populations, though it differed across ploidy levels and genotypes. Reconstruction of reproductive pathways yielded a total of eight different pathways of seed development, arising by uncoupling/recombination between apomixis components. Amongst these, two pathways involving modifications in embryo-sac (ES) (presence of two polar nuclei in aposporous ES that fuse prior to fertilization) and fertilization process (fusion of only one polar nucleus in a sexual ES) have been reported for the first time. Some of the combinations, such as M_I (haploids arising from parthenogenetic development of reduced egg cell), were found viable only in hexaploid background. Germplasm lines with higher expression of individual components were also identified. These components (including autonomous endosperm development) were also experimentally partitioned in hexaploid progenies (derived from a tetraploid parent viz. accession IG 04-164) that showed segregation in their reproductive capacities, and are reported for the first time. Occurrence of several apomixis recombinants (phenotypic) in guinea grass lines suggested their hybrid origin, favors a multigene model for apomixis, with their penetrance affected by modifiers and epigenetic mechanisms, in contrast to earlier reports of single locus control. Implications of partitioning components on apomixis research are discussed.     

Sources of resistance to Indian pathotypes of Puccinia graminis tritici and P. triticina in durum wheat

Stem rust and leaf rust are important diseases affecting durum wheat production in India. Inheritance and extent of diversity in resistance were studied in five durum genotypes, viz. ?B 662', ?ED 2398‐A', ?HG 110', ?IWP 5019' and ?Line 1172? using Pgt pathotypes 40A and 117‐6, and Pt pathotypes 12‐2 and 104‐2. F₂ and F₃ analyses showed that resistance was conferred by one or two genes in each line. In all, four genes for resistance to 40A, and eight each for pathotypes 117‐6 and 12‐2 were identified among the five genotypes, and three for resistance to 104‐2 among B 662, ED 2398‐A and IWP 5019 were indicated by tests of allelism. Although the gene identities are not known, at least some of them should be different from Sr2, Sr7b, Sr8a, Sr8b, Sr9e, Sr9g, Sr11, Sr12, Sr13, Sr14, Sr17, Sr23 and Sr28; and from Lr3, Lr14a, Lr23 and Lr27 + Lr31. These genotypes enrich the diversity of resistance to stem rust and leaf rust for durum wheat improvement.     

Alleviation of drought stress in maize (Zea mays L.) by using endogenous endophyte Bacillus subtilis in North West Himalayas

ABSTRACT

In the present study, we reported the isolation and molecular characterisation of 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase-producing endophyte and its effect on alleviating drought stress in maize. Ten morphologically distinct indigenous plant growth-promoting rhizobacteria (PGPR) from maize roots and rhizosphere were screened for multiple plant growth-promoting (PGP) traits, and of ten, two strains (DHK and B1N1) possessing maximum PGP traits were evaluated at three water stress regimes in maize: (i) 80% field capacity (FC), (ii) 60% FC, and (iii) 40% FC for 45 days, starting 15 days after sowing to the maturity. Inoculation of DHK strain with maize at 80% FC induced a significant increase in plant biomass (root biomass, 86.67%; shoot biomass, 111.63%) together with decreased reactive oxygen species and increased activity of antioxidant enzymes (superoxide dismutase, 14.11?U/g fresh weight; peroxidase, 1.14?U/g fresh weight and catalase; 14.91?U/g fresh weight) compared to uninoculated control at same water regime (80% FC). The derivative strain also significantly accrued nutrients in maize and enhanced total chlorophyll and amino acid content in comparison with non-inoculated plants. 16S rDNA analysis of DHK strain revealed its lineage to Bacillus subtilis. Present investigations demonstrated the potential of the bacterial partner in alleviating drought stress in maize.     

Effect of placement of urea and coated urea fertilizers on yield and quality of soybean (Glycine max (L.) Merr.) seeds

The objective of the present study was to record the seed yield and to examine visually the quality of soybean seeds cultivated under different types and placements of urea fertilizers. In addition to the conventional fertilizer application (including ammonium sulfate 16 kg N ha^-1 broadcasting (100 kg N ha^-1 of urea (0B) and X00-d type coated urea CU-100 (CUB), and deep placement (100 kg N ha^-1) of urea (UD) and 100-d type coated urea CU-100 (CUD) was conducted in separate plots in a paddy field converted to an upland field located at Shindori Experimental Station of Niigata University. Soybean plant growth was periodically analyzed and the quality of harvested seeds was also visually examined (hereafter referred to as “visual quality”). It was found that the deep placement treatments were more conducive 1o nitrogen (N₂)fixation, based on the relative mreide N concentration in the xylem sap, which is a good indicator of N~fixation by soybean. Also the total seed yield was the highest in CUD (82 g plant^-1) and 0D (81 g plant^-1), compared to the control (62 g plant^-1), UB (68 g plant^-1), and CUB (68 g plant^-1). The visual quality of harvested seeds showed that CUD enhanced the quality of seeds compared to the other treatments, in which the percentage of good quality seeds, hereafter referred to as "good seeds," based on the dry weight was 51 (control), 65 (K3B), 61 (CUB), 61 (0D), and 6696 (CUD). In terms of diseased seeds, the percentage of turtle wrinkle and broken seed coats was found to decrease by N application compared to the control. Thus, it is suggested that N fertilization management is important for maximum yield of soybean as well as for the enhancement of seed quality.     

Effect of conjoint application of indigenous PGPR and chemical fertilizers on productivity of maize (Zea mays L.) under mid hills of Himachal Pradesh

The present study was conducted to work out the conjoint application of indigenous PGPR (plant growth promoting rhizobacteria) and chemical fertilizers levels on the productivity of maize (Zea mays L.). Three best PGPR isolates (B1N1, MAT1 and DHK) having maximum PGP (plant growth promoting) traits were screened at different recommended doses (80%, 60% and 40%) of NP (Nitrogen and Phosphorous) under net house conditions, and finally two isolates (B1N1 and MAT1) along with optimum dose i.e. 80% of NP were selected for field experimentation, which was performed for two years consecutively i.e. 2013–2015 under random block design (RBD). Conjoint application of 80% recommended doses of NP with PGPR (B1N1) significantly increased maize yield (11.7%), plant height (12.9%) and biomass (17.9%), over control (100% recommend dose of fertilizer (RDF) of chemical fertilizer). Therefore, the results revealed the potential of indigenous PGPR isolates to supplement about 20% NP fertilizers without hampering the productivity of maize.     

Ploidy manipulation in guinea grass (Panicum maximum Jacq., Poaceae) utilizing a Hybridization-supplemented Apomixis-components Partitioning Approach (HAPA)

Ploidy manipulations are achieved by utilizing unreduced gametes, somatic chromosome doubling or haploidization. Apomixis, the asexual mode of reproduction through seeds, involves two of these phenomena viz., apomeiosis (unreduced embryo-sac formation) and parthenogenesis (fertilization-independent embryogenesis). The two components when partitioned may yield high frequencies of triploids and haploids, and thus, serve as a tool to manipulate ploidy levels when appropriately supplemented with hybridization schemes. Utilizing this H ybridization-supplemented A pomixis-components P artitioning A pproach (HAPA), the largest ploidy series in a crop plant was generated in guinea grass ( Panicum maximum Jacq.). Eighty-nine diverse guinea grass accessions were characterized for their reproductive capacities to identify tetraploid (2 n  = 4 x  = 32) accession(s) with high apospory but reduced parthenogenetic capacity, thereby producing a high frequency of hexaploid seeds. Seeds from accession IG 04-164 were utilized to produce a ploidy series by appropriately combining partitioned apomixis components and hybridizations in two seasonal cycles. We successfully obtained plants representing ploidies 3 x, 4 x , 5 x , 6 x , 8 x and 9 x , all derived from a single 4 x progenitor. Production methodology, reproducibility and utilization of HAPA in cytogenetic and molecular studies are discussed.