Enhanced grain yield in rice hybrids through complementation of fertility restoration by Rf3 and Rf4 genes as revealed by multilocation evaluation of tropical japonica derived rice (Oryza sativa) hybrids

Thirty-one tropical japonica derived Rf gene carrying rice hybrids were classified into three classes as Rf3, Rf4 and Rf3 + Rf4 hybrids. These hybrids were tested under three different mega-environments. Between Rf3 class and both the classes of hybrids possessing Rf4 genes, significant variation for spikelet and pollen fertility and grain yield was found. The pollen fertility was five times higher among Rf4 hybrids than that of hybrids carrying Rf3 alone. Likewise, spikelet fertility among Rf4 hybrids was two times higher than that of Rf3 hybrids. Parallel grain yield increase in Rf4 hybrids was 2.4 times than in Rf3 hybrids. However, Rf3 gene was found complementing Rf4 to truncate the range of pollen and spikelet fertility. Hybrids possessing Rf3 alone exhibited partial pollen and spikelet sterility, and significant negative standard heterosis for grain yield. The high yielding hybrid, “HYB36” carrying both the Rf genes was found to be widely adapted. The present study established that Rf4 gene is essential either alone or in combination with Rf3 for fertility restoration to achieve enhanced grain yield in WA-CMS based hybrids.     

The host background of rice influences the resistance expression of a three genes pyramid (xa5 + xa13 + Xa21) to bacterial blight (Xanthomonas oryzae pv. oryzae) pathotypes of Indian mainland and Bay islands

Bacterial blight (BB) is a major disease of rice for which host resistance is the only effective solution. The three genes pyramid xa5 + xa13 + Xa21 is recently the most utilized combination for developing resistant varieties through marker‐assisted breeding. Our study was carried out to elicit the detailed response of twenty lines possessing these three genes in five genetic backgrounds to twelve diverse BB pathotypes in India. The lines developed from ADT 47 variety showed incomplete resistance to most of the pathotypes, whereas susceptibility varied from 8.3% to 16.6% in ADT 43 and IR24, respectively. However, in IMP ASD16/60 and Improved Samba Mahsuri, complete resistance against all pathotypes was observed. The overall results confirmed that genetic background plays crucial role for the effective expression of xa5 + xa13 + Xa21 combination. Molecular studies did not reveal correlation between origin of pathotypes and their virulence potential. It is suggested to deploy Improved Samba Mahsuri, IMP ASD 16/60 and AD1306 varieties in the bacterial blight prone areas or use them as donors for realizing wider and durable resistance.     

Postcolumn Fluorimetric HPLC Procedure for Determination of Niacin Content of Cereals

Analytical procedures for determining niacin or vitamin B3 content of foods are tedious, require large quantities of toxic chemicals, and are timeconsuming. In addition, food matrices are difficult as samples because of their complex nature. A selective, sensitive HPLC technique was developed with postcolumn derivatization as well as fluorescence and spectroscopic detection systems. Niacin was separated and retained for 6.5 min on a polymeric column with an aqueous mobile phase containing sodium acetate buffer. A postcolumn system consisting of a stainless-steel pump and reaction coil allowed detection and quantitation of niacin. An acid-enzyme sample-extraction method was most compatible with HPLC and postcolumn derivatization with 5% each of acidified p-aminophenol and cyanogen bromide. Lower detection limit and mean recovery were 3.6 ng and 99.43%, respectively. Fluorescence response for nicotinamide was half that of nicotinic acid. A lower response for nicotinamide was also noted with conventional spectroscopy. However, the new method yielded comparable values for six of eight ready-to-eat commercial cereal samples. No significant difference was observed between the AACC reference and HPLC fluorimetric methods. Chemical derivatization was done within a reaction coil with reagents at half strength, limiting exposure to hazards and minimizing waste-disposal problems.     

Molecular detection of WA‐CMS restorers from tropical japonica‐derived lines,their evaluation for fertility restoration and adaptation

Hybrid rice based on wild‐abortive cytoplasmic male sterility (WA‐CMS) is important in boosting rice production, which requires diverse parents to harness heterosis. For this, exploiting the diversity of japonica through tropical japonica (TRJ) lines is an excellent route. In this study, 310 TRJ‐based new plant type (NPT) lines were developed and evaluated for Rf3 and Rf4 genes. Gene‐based (DRRM‐Rf3‐5 and DRRM‐Rf3‐10) and functional marker (RMS‐SF21‐5) targeted Rf3 locus, while gene‐linked (RM6100) and functional marker (RMS‐PPR9‐1) targeted the Rf4 locus. The frequency of the restorer allele of Rf3 gene was lower when compared to that of Rf4. Combined phenotypic and molecular screening using gene‐based and functional markers identified 42 lines that carried Rf3 and/or Rf4 genes. All the selected lines produced fertile F₁s when crossed to a WA‐CMS line, “Pusa 6A”, but with varying levels of spikelet fertility. This is the first report of a marker‐cum‐phenotype‐based restorer selection using TRJ‐derived lines. Multilocation evaluation of these lines at three locations indicated better adaptation for grain yield in some of the lines.     

Quantitative trait loci for stay-greenness and agronomic traits provide new insights into chlorophyll homeostasis and nitrogen use in rice

Functional stay-green (FSG) is characterized by delayed senescence during the reproductive stage in rice. A recombinant inbred line (RIL) population derived from ‘Pusa 677’/‘PSG16’ was used to study the genetics of FSG in a rice mutant, ‘PSG16’. The RILs exhibited significant variation under two N regimes for agro-morphological traits, leaf chlorophyll content, flowering time, yield components and nitrogen (N) use. Using a genome wide linkage map spanning 1910.8 cM with 104 polymorphic markers, we have mapped six major quantitative trait loci (QTLs). One robust QTL on chromosome 1 was associated consistently across different N regimes with chlorophyll content and flowering time. The QTL on chromosome 7 was associated with grain number, whereas the QTL on chromosome 6 was found related to N harvest index and spikelet fertility. Although ‘PSG16’ showed a clear advantage in grain yield as well as having better N assimilation, we could not establish a direct genetic relationship SG trait and N use. Based on the QTL information, FSG trait of ‘PSG16’ could be useful in deciphering multiple stress responses in rice.     

The BamHI site in the Internal Transcribed Spacer Region of Mungbean ribosomal RNA gene is partially methylated

The 18s-5.8s-25s ribosomal gene (18s-25s rDNA) in higher plants is present in multiple copies, on different chromosomes, as tandemly repeated units. Among the multiple BamHI sites that occur in the repeat unit, only the site in the middle of the 25s rRNA coding region is methylated in most cereals and pulses. BamHI restriction enzyme analyses of the mungbean 18s-25s rDNA showed the presence of two populations. Nearly 50% of the 18s-25s rDNA population had BamHI site situated in the internal transcribed spacer region (ITS-BamHI) resistant to cleavage by BamHI. The amplified ITS fragment was completely digestible by BamHI showing that partial cleavage by BamHI is not due to variation in the recognition sequence but most probably due to methylation. The complete cleavage of the ITS-BamHI site by BstYI that recognizes BamHI site but is insensitive to methylation confirms that the ITS-BamHI site is methylated. Methylation is probably due to the presence of a guanosine residue adjacent to the 3′ cytosine in the recognition sequence. This revised version was published online in July 2006 with corrections to the Cover Date.     

Chlorophyll Content, Hill Reaction and PEPcase Activity in Relation to Hybrid Vigour in Pearl Millet during Early Seedling Growth

Three hybrids of Pennisetum americanum L. Leeke were analyzed for growth and photosynthetic components during early growth and compared with their respective parents. Growth in terms of shoot length, fresh weight and dry weight along with the chlorophylls, and Hill activity revealed better parental and/or mid parental heterosis in all the hybrids over their respective parents. However, PEPcase activity displayed heterosis only in BJ-104. In other two hybrids no heterosis over the parents could be observed indicating thereby that the activity of this enzyme may not be rate limiting in parental lines.
Nevertheless, it appears that in pearl millet hybrids improved photosynthetic apparatus as observed in chlorophyll contents and Hill reaction may be one of the early expressions of hybrid vigour.     

Functional Properties of Ethyl Acetate-methanol Extract of Commonly Edible Molluscs

ABSTRACT

Marine molluscs are consumed as culinary delicacies and represent a relatively untapped source of natural functional food ingredients. The bioactive potential of ethyl acetate-methanol (C₂H₅OAc/CH₃OH) extract of molluscs Uroteuthis duvaucelii, Amphioctopus marginatus, Crassostrea madrasensis, and Sepiella inermis were demonstrated using different in vitro systems. The C₂H₅OAc/CH₃OH extract of A. marginatus displayed greater 2, 2-diphenyl-1-picryl-hydrazil (IC₉₀ 1.76 mg mL^?1) radical quenching capacity along with potential hydroxymethylglutaryl coenzyme-A reductase (HMGCR)-inhibiting activity (IC₉₀ 1.21 mg mL^?1) and angiotensin converting enzyme-I inhibitory property (ACE-I) (IC₉₀ 0.87 mg mL^?1) compared to those displayed by other molluscs. The organic extract of S. inermis set forth significantly higher pro-inflammatory 5-lipoxygenase inhibitory property (IC₉₀ 1.96 mg mL^?1) along with potential antidiabetic activity as determined by dipeptidyl peptidase-4 (DPP-4) antagonistic activities (IC₉₀ 2.62 mg mL^?1, P < .05). Significant correlations were observed between bioactive properties and electronegative groups of organic extracts of a mollusc. The free radical quenching property of the extracts exhibited a positive correlation towards other bioactivities, implicating the role of antioxidant property of the compounds in the extract to inhibit lifestyle ailments. The present study indicated that S. inermis and A. marginatus could be utilized as functional food ingredients to combat hypertension, hyperlipidemia, and inflammation-related risks.