Shashi Banga

The importance of the type and time of inoculation and assessment in the determination of resistance in Brassia napus and B. juncea to Sclerotinia sclerotiorum

Sclerotinia stem rot (SSR) is a significant agricultural problem worldwide. Finding sources of resistance is crucial to the ongoing search for better management of this disease. Brassica germplasm from Australia, China and India was screened for resistance to SSR under Western Australian field conditions following stem inoculation, application of a spray of mycelial suspension, or as a consequence of myceliogenic germination originating from sclerotia resident in soil. Significant differences in response were observed among 53 genotypes using each of the three screening methods. There was a variable impact of the time of inoculation on the disease level depending upon time of assessment post-stem inoculation. However, this impact could be reduced to an insignificant level provided the assessment after stem inoculation was delayed until 3 weeks post-inoculation. The results of these studies indicate that the use of appropriate inoculation and assessment methods could significantly reduce variability in the responses commonly observed in screening for resistance in crop plants against Sclerotinia sclerotiorum.

Alloplasmic male-sterile Brassica juncea with Enarthrocarpus lyratus cytoplasm and the introgression of gene(s) for fertility restoration from cytoplasm donor species.

Abstract. A new cytoplasmic male sterility (CMS) source in Brassica juncea (2n = 36; AABB) was developed by substituting its nucleus into the cytoplasm of Enarthrocarpus lyratus (2n = 20; EℓEℓ). Male sterility was complete, stable and manifested in either petaloid- or rudimentary-anthers which were devoid of fertile pollen grains. Male sterile plants resembled the euplasmic B. juncea except for slight leaf yellowing and delayed maturity. Leaf yellowing was due mainly to higher level of carotenoids rather than a reduction in chlorophyll pigments. Female fertility in male-sterile plants varied; it was normal in lines having rudimentary anthers but poor in those with petaloid anthers. Each of the 62 evaluated germplasm lines of B. juncea was a functional maintainer of male sterility. The gene(s) for male-fertility restoration (Rf) were introgressed from the cytoplasm donor species through homoeologous pairing between A and Eℓ chromosomes in monosomic addition plants (2n = 18II+1Eℓ). The percent pollen fertility of restored F1 (lyr CMS × putative restorer) plants ranged from 60 to 80%. This, however, was sufficient to ensure complete seed set upon by bag selfing. The CMS (lyr) B. juncea compared favourably with the existing CMS systems for various productivity related characteristics. However, the reduced transmission frequency of the Rf gene(s) through pollen grains, which was evident from the sporadic occurrence of male-sterile plants in restored F1 hybrids, remains a limitation.

Expression and relationships of resistance to white rust (Albugo candida) at cotyledonary, seedling, and flowering stages in Brassica juncea germplasm from Australia, China, and India

White rust (Albugo candida) is a highly destructive disease of oilseed Brassicas such as Brassica juncea and B. rapa. Most commercial B. juncea or B. rapa varieties are highly susceptible and yield losses from combined infection of leaves and inflorescences can be up to 20% or 60% in Australia and India, respectively. In Australia, canola-quality B. juncea has been developed to extend oilseed Brassica production into lower rainfall areas, with the first commercial B. juncea canola-quality variety planned for release in 2006. It is essential to identify useful sources of host resistance in B. juncea as breeding and/or selection of material for resistance is the most cost-effective method of delivering control for farmers. Three experiments were undertaken under controlled-environmental conditions to identify the best methods of characterising host resistance and to identify sources of resistance in B. juncea germplasm from Australia, China, and India. Forty-four B. juncea genotypes, viz. 22 from India, 12 from Australia, and 10 from China, were tested. Four Chinese genotypes (CBJ-001, CBJ-002, CBJ-003, CBJ-004) and one Australian genotype (JR049) consistently showed high resistance to A. candida across the different plant growth stages against a pathotype prevailing in Australia. Similarly, the most susceptible genotypes (viz. Indian genotypes RH781, RL1359, RH819) were extremely susceptible irrespective of the plant growth stage. Overall, although disease severity on cotyledons and leaves at the different growth stages was significantly and positively correlated, there was, however, no significant correlation between the number of stagheads and any of the other disease parameters measured. Our study demonstrates that controlled-environmental conditions are suitable for rapid identification of resistant genotypes and that genotypes with high levels of resistance can be reliably identified at the cotyledonary, seedling, or flowering stages.

Hybrid cultivar development.

Heterosis: An Introduction / Male Sterility: Classfication and Concept / Male Sterility: Molecular Characterisation / Self-Incompatibility / Monoecious and Dioecious Floral Morphologies / Chemical Hybridizing Agents / Biotechnology and Hybrid Breeding/ Molecular Genetic Markers / Rice / Wheat / Maize / Barley / Pearl Millet / Sorghum / Cotton / Sunflower / Rapeseed and Mustard / Castor/ Pigeonpea / Tomato / Onion / Cole Crops / Capsicum / Muskmelon/ Watermelon.

Male sterility in Indian mustard (Brassica juncea (L.) Coss.) — a biochemical characterization

SummaryBiochemical studies were conducted on some male sterile and their fertile F1 analogues in Indian mustard. The variation in pH activity during microsporogenesis was normal, except in MS-3. Male sterile anthers had deficient sugar metabolism. Cytochemical analysis of sporogenous and tapetal tissue suggested an effect of sterility elements on the anabolic and catabolic fate of DNA and protein during microsporogenesis. Leaves of male sterile lines had a higher chl a/b ratio. Leaf peroxidase activity was low and different isozymes appeared when separated by starch electrophoresis.

Heterosis as Investigated in Terms of Polyploidy and Genetic Diversity Using Designed Brassica juncea Amphiploid and Its Progenitor Diploid Species

Fixed heterosis resulting from favorable interactions between the genes on their homoeologous genomes in an allopolyploid is considered analogous to classical heterosis accruing from interactions between homologous chromosomes in heterozygous plants of a diploid species. It has been hypothesized that fixed heterosis may be one of the causes of low classical heterosis in allopolyploids. We used Indian mustard (Brassica juncea, 2n = 36; AABB) as a model system to analyze this hypothesis due to ease of its resynthesis from its diploid progenitors, B. rapa (2n = 20; AA) and B. nigra (2n = 16; BB). Both forms of heterosis were investigated in terms of ploidy level, gene action and genetic diversity. To facilitate this, eleven B. juncea genotypes were resynthesized by hybridizing ten near inbred lines of B. rapa and nine of B. nigra. Three half diallel combinations involving resynthesized B. juncea (11×11) and the corresponding progenitor genotypes of B. rapa (10×10) and B. nigra (9×9) were evaluated. Genetic diversity was estimated based on DNA polymorphism generated by SSR primers. Heterosis and genetic diversity in parental diploid species appeared not to predict heterosis and genetic diversity at alloploid level. There was also no association between combining ability, genetic diversity and heterosis across ploidy. Though a large proportion (0.47) of combinations showed positive values, the average fixed heterosis was low for seed yield but high for biomass yield. The genetic diversity was a significant contributor to fixed heterosis for biomass yield, due possibly to adaptive advantage it may confer on de novo alloploids during evolution. Good general/specific combiners at diploid level did not necessarily produce good general/specific combiners at amphiploid level. It was also concluded that polyploidy impacts classical heterosis indirectly due to the negative association between fixed heterosis and classical heterosis.

A microsatellite (SSR) based linkage map of Brassica rapa.

In the present study we describe the construction of a genetic linkage map for the Brassica rapa (AA) genome that will act as a key resource in undertaking future structural and functional genomic studies in B. rapa. A F(2) mapping population consisting of 48 F(2) individual plants developed following hybridization of 2 inbred lines Bathari mandi and IC 331817 was used to construct the map. The map comprises 53 SSR markers derived from 3 different public domain resources. Nine linkage groups along with a small subgroup were identified and designated as R(1)-R(9) through alignment and orientation using SSR markers in common with existing B. rapa reference linkage maps. The total length of the genetic linkage map was 354.6 cm with an average interval of 6.6 cm between adjacent loci. The length of linkage groups ranged from 28.0 cm to 44.2 cm for R(6) and R(1A), respectively. The number variability of markers in the 9 linkage groups ranged from 3 for R(6) to 10 for R(1). Of the 53 SSR markers assigned to the linkage groups, only 5 (9.4%) showed deviation from the expected segregation ratio. The development of this map is vital to the genome integration and genetic information and will enable the international research community to share resources and data for the improvement of B. rapa and other cultivated Brassica species.

Molecular Characterization and Assessment of Genetic Diversity in Sesame (Sesamum indicum L.) Germplasm Collection Using ISSR Markers

Sesame (Sesamum indicum L.) is an important oilseed crop. Breeding programs in this crop are mostly based on selection hybridizations, and mutations. The present studies were conducted to establish genetic diversity in a morphologically and geographically diverse sesame germplasm (94 accessions). This was achieved through DNA polymorphism generated by a set of 34 confirmed polymorphic inter-simple sequence repeat (ISSR) markers. Allelic data were subjected to neighbor-joining-based clustering analysis using Paleontological Statistics (PAST) software version 2.11. The resultant dendrogram assigned the 94 genotypes to five clusters, all of mixed heritage. The dendrogram did not suggest any correspondence among pedigree, breeding center, or geographical origin of the accessions. Natural out-crossing in germplasm collection has possibly resulted in overlapping diversity patterns. It is suggested that sesame maintenance breeding should be carried out in areas either with minimal natural out-crossing or with selfing in areas where forced self-seed set is possible.

Moricandia arvensis cytoplasm based system of cytoplasmic male sterility in Brassica juncea: Reappraisal of fertility restoration and agronomic potential

Cytoplasmic male sterility (CMS) system based on the cytoplasm from Moricandia arvensis (mori) was investigated for fertility restoration and agronomic potential. Fertility restorer gene for mori CMS was introgressed from cytoplasm donor species as all the evaluated Brassica juncea genotypes (155) acted as sterility maintainers. The allosyndetic pairing between Ma and the A/B genome chromosomes in the monosomic addition plants (2n= 18II + 1Ma) facilitated the gene introgression. Partial fertility restoration (43–52% pollen grain stainability) in F1 hybrids and absence of segregation for male sterility in F2 progenies suggested gametophytic control of fertility restoration. The pollen fertility in the F1 hybrids was, however, sufficient to ensure complete seed set upon bag selfing. Introgression from M. arvensis also helped in correction of chlorosis associated with mori cytoplasm in CMS and fertile alloplasmic B. juncea plants. Yield evaluation of thirty F1 hybrids having the same nuclear genotype but varied male sterilizing cytoplasms (mori, oxy, lyr, refined ogu), in comparison to respective euplasmic hand bred control hybrids, allowed an estimate of yield penalty associated with different CMS systems. It ranged from 1.8% to 61.6%. Hybrids based on cytoplasmically refined ogu were most productive followed by those based on cytoplasmically refined mori CMS. The male sterility systems emanating from somatic hybridization were found superior than those developed from sexual hybridization.

Variability for Leaf and Seed Glucosinolate Contents and Profiles in a Germplasm Collection of the Brassica juncea

Aim: A renewed interest in glucosinolates (GSLs) as compounds with biocidal and anticarcinogenic activity demands evaluation of the available variability in germplasm collections. The objective of the present study was to evaluate a germplasm collection of the Brassica juncea for total content and profile of leaf and seed GSLs. Methods: A total of 366 entries of a RIL population derived from cross of NUDH-YJ-04 and RL-1359, were nondestructively analyzed by near-infrared reflectance spectroscopy by means of previously developed calibration equations. Out of 366 lines, 97 lines were selected on the basis of glucosinolate range and further analyzed by ultra performance liquid chromatography for total GSL content and the concentrations of individual components i.e. sinigrin, glucoiberin, epiprogoitrin, gluconapin, gluconasturtiin and gluconeobrassicin. Results and conclusion: The collection contained great variability for GSL content and profile. Remarkable variation in glucosinolate content and profiles from different tissues within one plant may reflect different control mechanism operating on the glucosinolate biosynthetic pathway in different tissues. In the present study no correlation has been observed in leaf and seed glucosinolates. NIRS screening followed by further HPLC analyses on preselected entries led to a fast and comprehensive evaluation of variability for total content and profile of seed GSLs, which represents an important advance in the evaluation of GSLs in Brassica germplasm.