Research Article

Genetics of fertility restoration of ‘Wild Abortive’ system based Cytoplasmic Male Sterility (CMS) in hybrid rice (Oryza sativa L.)

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Mahalingam A, R Saraswathi

Published on: 28 Mar 2016 | Pages: 1-9

Success in the development of rice hybrids largely depends on the availability of effective restorers and precise basic knowledge on the genetics of fertility restoration of CMS and restorer lines. In a study using twenty diverse restorers and five 'WA' type cytoplasmic genetic male sterile (CMS) line, revealed the fertility restoration to be governed by two major genes with epistatic interactions that differed from crosses to crosses. The inheritance of fertility restoration in CRMS 32A × AD 06084R and ten other cross combinations revealed an F2 segregation ratio of 12:3:1 (FF: SF: CS), indicating the involvement of two dominant genes which exhibit dominant epistasis. In COMS 24A x IET 20899R hybrid, pollen fertility of F2 segregation fell into the digenic ratio 9FF: 3SF: 4CS showed the involvement of digenic supplementary or an epistasis with recessive gene action. F2 segregation ratio of 9:6:1 with two dominant genes which exhibiting epistasis with incomplete dominance was observed in COMS 24A × IET 20898 R and fourteen other cross combinations suggesting the two dominant genes Rf3 and Rf4 seem to control the fertility restoration. The differential mode of action of restorer genes could presumably be due to the influence of the female parent genotype or to the variable expression of the weaker gene in different genetic backgrounds. The differential segregation behaviour could also be due to the existence of certain modifiers influencing the penetrance and expressivity of the fertility-restorer genes.

Morphological, Physiological and Biochemical characteristics of Xanthomonas campestris pv. campestris by black rot of cabbage

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M Deivamani, M Muthamilan

Published on: 28 Mar 2016 | Pages: 10-18

Black rot, the most serious disease of crucifers especially Brassica oleracea var. capitata (Cabbage) causes huge yield losses. Black rot is a systemic vascular disease. Typical disease symptoms are V-shaped yellow lesions starting from the leaf margins and blackening of veins. The cabbage leaves were tested for Xanthomonas campestris pv. campestris infection through morphological, physiological and biochemical analysis. The aim of the study was to identify and confirmation of X. campestris pv. campestris in cabbage. The assay of detected X. campestris pv. campestris infections in diseased plants and from bacterial colonies isolated on selective media, and was more sensitive and specific. Among the ten isolates, isolate I6 produced the maximum growth, lesion size and positive growth in different organic and inorganic sources, different biochemical and morphological analysis.

SSR marker diversity analysis for WA cytoplasm based fertility restorer genes of hybrid rice (Oryza sativa L.)

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Mahalingam A, R Saraswathi, J Ramalingam

Published on: 28 Mar 2016 | Pages: 19-27

An understanding of genetic diversity among the parental lines is useful in hybrid rice breeding through informed selection of the parental lines to maximize heterosis. Present investigation was carried out to estimate genetic divergence among the 51 restorer and five CMS lines by using 16 simple sequence repeats (SSR) markers co-segregating with fertility restorer genes (Rf3, Rf4 and Rf7) of hybrid rice. Among them, 10 SSRs were found to be polymorphic and the number of amplified fragments ranged from one to five. The highest PIC value (more than 0.60) was observed for eight primers viz., AB 443, RM 3, RM 29, RM 226, RM 228, RM 304, RM 1812 and RM 3873 with average PIC value of 0.444. Cluster analysis using NTSYS generated dendrogram divided all the 56 parental lines into thirteen different clusters 80 % coefficient of similarity. With greater polymorphism revealed by SSR markers, parental lines having the similar genetic background from pedigree information were grouped into different clusters. The combination of pedigree analysis and SSR markers could be a more reliable method to study the diversity and grouping of parental lines of hybrid rice.

Optimizing phosphorous dose for higher paddy yield under agro-ecological conditions of Sheikhupura

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Phosphorus fertilization for getting higher paddy yields is quite necessary owing to its vital role in crop plant development, so a field experiment was conducted to evaluate the appropriate level of phosphorous fertilizer for rice (Super basmati) at Adaptive Research Farm, Sheikhupura during Kharif 2012, 2013 and 2014. Different levels of phosphorous (34, 45, 68, 90, 102 and 136 kg ha-1) were used as treatments in randomized complete block design (RCBD) with 3 replications. The crop was sown using traditional transplanting method during 1st week of July every year. All other agronomic practices were kept uniform for the entire growth season every year. Data related to agronomic parameters including plant height, number of productive tillers, number of grains per spike, 1000-grain weight and paddy yield was recorded using standard procedures. Results revealed that 90 kg ha-1 phosphorous was the most appropriate dose for getting maximum paddy yield under agro-ecological conditions of Sheikhupura.