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A BPH-resistant locus designated as Bph34 identified in Oryza nivara acc. IRGC104646 on long arm of chromosome 4 using high-resolution mapping with 50 K SNP chip. BPH resistance contributed by locus showed dominant inheritance in F and F. The Bph34 locus is 91 kb in size and contains 11 candidate genes. In addition to SNP markers, SSR markers, RM16994 and RM17007 co-segregated with the BPH resistance. These two SSR markers can facilitate marker-assisted transfer of the Bph34 locus into elite rice cultivars in all labs. Brown planthopper (BPH, Nilaparvata lugen Stål) is one of the most destructive insects of rice (Oryza sativa L.) causing significant yield losses annually. Exploiting host plant resistance to BPH and incorporating resistant genes in susceptible commercial cultivars is economical and environmentally friendly approach to manage this pest. Here, we report high-resolution mapping of a novel genetic locus for resistance to BPH, designated as Bph34 on long arm of rice chromosome 4. The locus was mapped using an interspecific F population derived from a cross between susceptible indica cultivar PR122 and BPH-resistant wild species, O. nivara acc. IRGC104646. Inheritance studies performed using F and F populations revealed the presence of single dominant gene. Construction of high-density linkage map using 50 K SNP chip (OsSNPnks) followed by QTL mapping identified single major locus at 28.8 LOD score between SNP markers, AX-95952039 and AX-95921548. The major locus contributing resistance to BPH designated as Bph34 and explained 68.3% of total phenotypic variance. The Bph34 locus is 91 Kb in size on Nipponbare reference genome-IRGSP-1.0 and contains 11 candidate genes. In addition to associated SNP markers, two SSR markers, RM16994 and RM17007, also co-segregated with the Bph34 which can be used efficiently for markers assisted transfer into elite rice cultivars across the labs.

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sue culture medium manipulations (Comeau et al., 1992;Suenaga, 1994;Kammholz et al., 1996). The genotypic A number of maize (Zea mays L.) genotypes were tested for their specificity became evident gradually, more as a result influence on induction and regeneration of haploid wheat (Triticum aestivum L.) embryos to improve further the efficiency of the wheat ϫ of a consensus emerging from several studies with varied maize system of haploid production. Fifteen maize genotypes were objectives than from a direct investigation of this phecrossed to five diverse wheat F 1 hybrids in a line ϫ tester fashion in nomenon. As a consequence of this situation, very few three replications. Two efficiency parameters, caryopses formation studies address this problem systematically, e.g., the gefrequency (CFF-number of caryopses/100 pollinated florets) and notypic specificity of only the maize or only the wheat embryo formation frequency (EFF-number of embryo-carrying carygenotypes was studied, the data was either based on a opses/100 pollinated florets), were estimated. Analysis of variance single replication (Suenaga and Nakajima, 1989; Laurie revealed that lines (wheat genotypes), testers (maize genotypes), and and Reymondie, 1991; Ushiyama et al., 1991; Amrani their interaction showed significant effects on both efficiency parameet al. Sarrafi et al., 1994;Suenaga, 1994; ters, but the effect of maize genotypes was greater than that of wheat al., 1995), or the study was based on only a few parents

Modern rice varieties that ushered in the green revolution brought about dramatic increase in rice production worldwide but at the cost of genetic diversity at the farmers' Welds. The wild species germplasm can be used for broadening the genetic base and improving productivity. Mining of alleles at productivity QTL from related wild species under simultaneous backcrossing and evaluation, accompanied by molecular marker analysis has emerged as an eVective plant breeding strategy for utilization of wild species germplasm. In the present study, a limited backcross strategy was used to introgress QTL associated with yield and yield components from Oryza ruWpogon (acc. IRGC 105491) to cultivated rice, O. sativa cv IR64. A set of 12 BC 2 F 6 progenies, selected from among more than 100 BC 2 F 5 progenies were evaluated for yield and yield components. For plant height, days to 50% Xowering and tillers/plant, the introgression lines did not show any signiWcant change compared to the recurrent parent IR64. For yield, 9 of the 12 introgression lines showed signiWcantly higher yield (19-38%) than the recurrent parent IR64. Four of these lines originating from a common lineage showed higher yield due to increase in grain weight and another three also from a common lineage showed yield increase due to increase in grain number per panicle. For analyzing the introgression at molecular level all the 12 lines were analyzed for 259 polymorphic SSR markers. Of the total 259 SSR markers analyzed, only 18 (7.0%) showed introgression from O. ruWpogon for chromosomes 1, 2, 3, 5, 6 and 11. Graphical genotypes have been prepared for each line and association between the introgression regions and the traits that increased yield is reported. Based on marker trait association it appears that some of the QTL are stable across the environments and genetic backgrounds and can be exploited universally.

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embryos. Here, we report a simple but effective method for the Embryo rescue is an important step in the wheat x maize system of identification of embryo-carrying seeds prior to dissection in induced haploidy in wheat. On average, only one-third ofthe seeds carry the sterile chamber. embryos, but they all have to be dissected because no morphologicalThe immature seeds from wheat x maize crosses have a tenddistinction is available to distinguish between seeds with and without ency to turn translucent 15-18 days after pollination, which is embryos. We here report a simple technique in which immature seeds ^lso the stage for rescue of haploid embryos. Placing the seeds from wheat X maize crosses are placed on a transparent surface and c y.^^ ^ surface ltt from below does not allow any distinction of lllummated from above. The free-fioatmg embryo, settled at the bottom ,of the seed, can be seen from below or in an image refiected on a plane embryo-carrymg seeds. The free-floating haploid embryo tends mirror. Using this technique 97.8% of the embryo-containing seeds ^^ ^^"^^ ^^ the bottom of the seed and so is not visible through could be detected prior to dissection. The technique will be useful in the watery endosperm when viewed from above. However, placreducing the time and labour involved in embryo culture, thereby ing a light source (60 W bulb) above the seeds makes the scaling up haploid production. embryos within them visible when viewed from below ( Fig. la).For ease of sorting a plane mirror can be used, as shown in Fig. Key words: Triticum aestivum -Zea mays -embryo culture -i b, which allows more convenient viewing, haploidy -wheat x maize crosses Using the 'inverted light technique' we were able to identify haploid embryos from a wheat F, ('PBW 343' x 'HD 2329') Wheat X maize systems ofhaploid production represents wheat-crossed to a maize population ('MZ 1'). Field-grown wheat breeding tool aimed at speeding up the breeding cycle. After P^^"'^^ ^^^^ emasculated 3-5 days prior to anthesis by opening the initial demonstration of wheat x maize system for the pro-^P ^he lemma and palea and removing the anthers, unlike the duction of wheat haploids by Laurie and Bennett (1988), it has conventional practice of cutting them to expose the androecium. been the subject of several studies aimed at evaluating and ^^^ ^^^s pollinated with maize were injected with a 2,4-D soluenhancing its plant breeding utility. Studies have been aimed at ^ion (100 p.p.m.) into the uppermost internode daily each eveenhancing the embryo formation frequency by choice of proper "ing for 4 days, beginning 1 day after pollination. Embryos were crossing procedures and pollinators. Improvement in embryo rescued 18 days after pollination and cultured on a medium development has been sought by use of post-pollination hor-containing Murashige and Skoog basal salts supplemented with monal treatments. Culture media manipulations have been kinetin (0.5 mg/1), indole acetic acid (0.5 mg/1), L-glutamine attempted for increasing the regeneration fre...

Basmati rice, owing to its characteristic aroma and long, slender grains, is a specialized group of rice (Oryza sativa L.) and is high in demand. Traditional basmati cultivars are tall, low yielding, and susceptible to diseases, especially bacterial blight. Conventional plant breeding approaches could bring only marginal improvement in basmati yield. This study reports improvement of traditional basmati cultivars for bacterial blight resistance and plant height. Using marker‐assisted backcrossing we transferred two bacterial blight resistance genes, xa13 and Xa21, and semidwarfing gene, sd‐1, into two traditional basmati cultivars, Basmati 370 and Basmati 386. Markers were also used for selecting aroma and amylose content of basmati cultivars. Along with marker‐assisted selection (MAS), we practiced stringent phenotypic selection in the target environment in all the generations for faster recovery of the recurrent parent genotype. A set of BC2F6 progenies selected for semidwarf stature, bacterial blight resistance, aroma and nonsticky grains and having more than 90% of the recurrent‐parent genome were evaluated for yield and yield components. Lines that significantly outyielded the recurrent parent and the check cultivars in station trials are being evaluated in multiple locations in national‐level nurseries for identifying the lines that could be released as varieties. These lines, in addition to being released as cultivars, can also be used as immediate donors for further basmati improvement.