Introgression of Cajanus platycarpus genome into cultivated pigeonpea, C. cajan

Summary Cajanus platycarpus, an incompatible wild species from the tertiary gene pool of pigeonpea (C. cajan (L.) Millspaugh), has many desirable characteristics for the improvement of cultivated varieties. To necessitate such transfers, embryo rescue techniques were used to obtain F₁ hybrids. The F₁ hybrids were treated with colchicine to obtain tetraploid hybrids, that were selfed to obtain F₂, F₃ and F₄ progenies. All of the hybrids and subsequent progenies had an intermediate morphology between the two parents. Backcrossing of the tetraploid hybrids with cultivated pigeonpea was not possible given embryo abortion, with smaller aborted embryos than those obtained in the F₀ parental cross.As a route of introgression, diploid F₁ hybrids were backcrossed with cultivated pigeonpea and BC₁ progeny obtained by in vitro culture of aborting embryos. BC₂ plants were obtained by normal, mature seed germination. Although embryo rescue techniques had to be used to obtain F₁ and BC₁ plants, it was possible to produce BC₂ and subsequent generations through direct mature seed. Every backcross to cultivated pigeonpea increased pollen fertility and the formation of mature seeds.Special project assistant till December, 2003.     

Intra species variation in Atylosia scarabaeoides (L.) Benth., a wild relative of pigeonpea (Cajanus cajan (L.) Millsp.)

Summary Atylosia scarabaeoides (L.) Benth., a wild relative of pigeonpea, possesses several useful genes which can be utilized for pigeonpea improvement. In the present study, 33 accessions of A. scarabaeoides were evaluated at ICRISAT Center during the 1987 rainy season for variation in some useful traits to identify parents for inter-generic hybridization. A large variation was observed for leaf components, seed size, pod length, seeds/pod, days to flowering, seed protein, sulphur amino acids, resistance to cyst nematode, phytophthora blight, sterility mosaic, fusarium wilt, pod borer, pod fly, and pod wasp. Only four accessions were found to have more than 28% protein content. Methionine and cystine contents were marginally higher than in pigeonpea but the variation was not large enough to utilize them in the breeding program. In A. scarabaeoides. accessions resistant to fusarium wilt, phytophthora blight, sterility mosaic, and cyst nematode were detected. Compared to pigeonpea, the A. scarabaeoides accessions were less susceptible to lepidopteran borer and were immune to pod fly damage. Accessions ICPW 89 and ICPW 111 in short- (100–120 days), and ICPW 94 and ICPW 118 in medium-duration (140–180 days) were identified as potential parents for use in inter-generic hybridization.ICRISAT Journal Article No. 967     

Variation for natural out-crossing in pigeonpea

Summary Several researchers have reported a considerable degree of natural out-crossing in pigeonpea from different environments. This paper reviews the subject with respect to the variation for natural out-crossability, pollinating vectors, extent of natural out-crossing, isolation specifications, and the possible utilization of natural out-crossing in pigeonpea improvement.ICRISAT Journal Article No. 831.     

RFLP analysis of cytoplasmic male-sterile lines of pigeonpea [Cajanus cajan (L.) Millsp.] developed by interspecific crosses

Total DNA from three putative cytoplasmic male sterile (CMS) progenies derived from crosses between the wild species Cajanus sericeus and the cultivated species Cajanus cajan, five C. cajan, one accession of C. sericeus and two genetic male sterile lines of pigeonpea were compared for their RFLP patterns using maize mitochondrial DNA (mtDNA) specific probes. Three putative cytoplasmic male sterile (CMS) progenies from the multiple cross genome transfer of pigeonpea lines (CMS 7–1, CMS 12–3, and CMS 33–1) showed hybridization patterns identical to that of C. sericeus when DNA was digested with EcoRI and HindIII and probed with maize mtDNA clones. The results suggested that these putative CMS progenies have the mitochondria of the female wild species parent. The hybridization patterns of the three male parental lines used in the development of the CMS progenies were similar in all the restriction enzyme-probe combinations except HindIII-atp6. The genetic male sterile lines, MS Prabhat and QMS 1 differed from each other in their hybridization pattern. The genomic DNA hybridization pattern of HindIII digested DNA from ICPL 87 differed from the other pigeonpea lines when probed with the maize mtDNA clones. The cluster analysis of the hybridization data suggested the occurrence of variation in the mitochondrial genome even among the cultivated species. This revised version was published online in July 2006 with corrections to the Cover Date.     

Genetics of a high-selfing trait in pigeonpea

Summary A true-breeding line characterized by free filaments of anthers and modified keel petal was derived from F₂ population of an intergeneric cross between Cajanus cajan (L.) Millsp. and Atylosia lineata W. & A. This variant, designated as partial cleistogamy, favours a high level of self-fertilization. The inheritance of this trait was studied in the F₁, F₂, F₃, and BC₁F₁ generations of three crosses. The results suggest that the partial cleistogamy trait is governed by a single recessive gene, designated as pct.     

Natural out-crossing in dwarf pigeonpea

Summary Natural out-crossing rate in pigeonpea was studied at ICRISAT Center using plant stature (tall plants in dwarf progenies) as the genetic marker. The data indicated natural out-crossing rates of 9.7% to 24.1% with a pooled value of 13.1% in the six populations studied. These data were comparable to earlier studies at the same site using stem colour and growth habit as genetic markers in tall pigeonpea cultivars thus suggesting that foraging of insect pollination vectors is not influenced by plant type. The implications of natural out-crossing on breeding and maintenance of genetic purity of cultivars is discussed.     

Inheritance of trichomes and resistance to pod borer (Helicoverpa armigera) and their association in interspecific crosses between cultivated pigeonpea (Cajanus cajan) and its wild relative C. scarabaeoides

The legume pod borer, Helicoverpa armigera, is one of the most devastating pests of pigeonpea. High levels of resistance to pod borer have been reported in the wild relative of pigeonpea, Cajanus scarabaeoides. Trichomes (their type, orientation, density and length) and their exudates on pod wall surface play an important role in the ovipositional behavior and host selection process of insect herbivores. They have been widely exploited as an insect defense mechanism in number of crops. In the present investigation, inheritance of resistance to pod borer and different types of trichomes (A, B, C and D) on the pod wall surface in the parents (C. cajan and C. scarabaeoides) and their F₁, F₂, BC₁ (C. cajan × F₁), and F₃ generations has been studied. Trichomes of the wild parents (high density of the non-glandular trichomes C and D, and glandular trichome B and low density of glandular trichome A) were dominant over the trichome features of C. cajan. A single dominant gene as indicated by the segregation patterns individually will govern each trait in the F₂ and backcross generation. Segregation ratio of 3 (resistant): 1 (susceptible) for resistance to pod borer in the F₂ generation under field conditions was corroborated with a ratio of 1:1 in the backcross generation, and the ratio of 1 non-segregating (resistant): 2 segregating (3 resistant: 1 susceptible): 1 non-segregating (susceptible) in F₃ generation. Similar results were obtained for pod borer resistance under no-choice conditions. Resistance to pod borer and trichomes associated with it (low density of type A trichome and high density of type C) are governed individually by a dominant allele of a single gene in C. scarabaeoides. Following backcrossing, these traits can be transferred from C. scarabaeoides into the cultivated background.     

Role of partial cleistogamy in maintaining genetic purity of pigeonpea

Summary Natural out-crossing in pigeonpea (Cajanus cajan (L.) Millsp.) leads to genetic deterioration and in certain environments the out-crossing may be as high as 70%. Studies with partially cleistogamous lines derived from an inter-generic cross indicated that average natural out-crossing in these lines was much lower (2.5%) than that reported earlier for pigeonpea (36.5%) at ICRISAT Center. Based on seed yield and disease resistance, potential parents such as ICPL 87154 in short-duration determinate, ICPL 87018 in short-duration indeterminate, and ICPL 87159 in medium-duration indeterminate groups have been identified for introgression of the partially cleistogamous trait into pigeonpea.     

Ineffectiveness of wrapped flower in inhibiting cross-fertilization in pigeonpea

Summary The wrapped flower character has been reported to inhibit out-crossing in pigeonpea in Australia. However, one of the wrapped flower lines gave an average of about 16% out-crossing at ICRISAT Center near Hyderabad, India. This level of out-crossing was not different from that in cultivars having normal (unwrapped) flowers. This suggests that the wrapped flower trait is not a dependable character for reducing out-crossing in pigeonpea.ICRISAT Journal Article No. 578.     

Possibility of genetic improvement of pigeonpea (Cajanus cajan (L.)Millsp.) utilizing wild gene sources

Summary Various wild relatives of pigeonpea,Cajanus cajan, namely some species ofAtylosia andRhynchosia, possess desirable characteristics that could be utilized for effecting genetic improvement of this crop. In total 73 cross combinations among two cultivars ofC. cajan and one accession each of eightAtylosia species and one ofRhynchosia were attempted. Twelve hybrids were obtained. Seven of these were analysed for F₁ fertility and their utility for agronomic improvement of theC. cajan. Fertility behaviour of the different F₁ hybrids varied and indicated that potential of gene transfer between the two genera,Atylosia andCajanus, was as good as within the genusAtylosia. From F₂ and F₃ families ofC. cajan × A. scarabaeoides andC. cajan × A. albicans, plants were selected with greater physiological efficiency and agronomic superiority. The prospects of transferring pod borer resistance and higher seed protein content from someAtylosia species to pigeonpea are discussed.     

RFLP variation and genetic relationships in cultivated cucumber

Summary Two sets of cucumber (Cucumis sativus L.) germplasm were used to determine the potential use of restriction fragment length polymorphisms (RFLPs) for estimating genetic relationships. Sixteen accessions [15 domesticated variety sativus and one feral variety hardwickii (PI 183967)] of diverse origin were used to assess RFLP variation in cucumber, and to determine if genetic relationships based on RFLPs were similar to those obtained by isozyme analysis. Additionally, 35 commercial lines or cultivars were surveyed to determine genetic relationships among and within common cucumber types (narrow genetic base). The 16 accessions were surveyed with 440 low copy clones from two libraries (Pst I partial genomic and cDNA) using two restriction enzymes. Data from a subset of 104 random (mapped and unmapped) and a set of 30 mapped RFLPs were used to estimate genetic relationships among the 16 cultigens. Variability was low among RFLPs (33% of all probes) and putative alleles ( 2.2 polymorphic fragments/probe). RFLP variation between sativus lines and hardwickii (21±4%) was greater than among sativus lines (12±2%). RFLPs among the 16 accessions revealed genetic relationships which agree with those obtained using isozymes. Genetic relationships estimated using mapped and unmapped RFLPs were similar. The 35 elite lines were surveyed using a set of 40 RFLPs from 3 libraries (Pst I and EcoR I partial genomic and cDNA) to evaluate the discriminatory value of RFLPs among and between commercial cucumber types. The RFLP-derived genetic relationships among this germplasm were in agreement with predictions based on fruit type and pedigree information. Thus, RFLPs are a useful addition to the morphological characters and isozyme loci currently used for taxonomic classification and plant variety protection of cucumber.     

玉米细胞质线粒体DNA RFLP分类研究

本实验用4个酶、4个探针组成16个酶/探针组合对玉米N、T、C、S、WBMs、801CMS等细胞质进行了线粒体DNA(mtDNA)RFLP分析。一方面对玉米细胞质mtDNARFLP分类方法进行研究，证明只要酶/探针技术体系合适，可以通过该方法对细胞质进行快速准确地分类；提出探针的选择是主要的，酶次之；认为PstⅠ/B30、HindⅢ/pBcmH3、BamHⅠ/pHJ2     

A mechanism for inhibiting cross-fertilization in pigeonpea (Cajanus cajan (L.) Millsp.)

Summary Natural out-crossing imposes considerable costs and inefficiencies in breeding, evaluation and commercialization of pigeonpea (Cajanus cajan (L.) Millsp.). This note reports identification of a modification of floral morphology which inhibits cross-fertilization. Floral morphology and possible mechanisms of action of this character are discussed.On leave from International Crops Research Institute for the Semi-Arid Tropics (ICRISAT). Hyderabad, India.     

Diversity in the wild potato species Solanum chacoense Bitt.

Summary The morphological and isozyme variation was studied in 22 accessions of Solanum chacoense from Paraguay and Argentina. Clear geographic groups were identified through the use of multivariate analyses. S. chacoense from mountain sites in Argentina could be readily distinguished from plains forms from Paraguay, on the basis of several correlated morphological characters. Three isozyme systems, namely phosphoglucose isomerase (PGI), glutamate-oxaloacetate transaminase (GOT) and peroxidase (PRX) were studied using starch gel electrophoresis. The banding patterns indicated that for each isozyme there were several loci, which were polymorphic. A genetic interpretation of one of the PGI loci was made, and indices of genetic diversity and genetic identity calculated. Principal components analysis, cluster analysis and genetic diversity indicated a close relationship between the geographical groups. These results are discussed in the context of in situ genetic conservation.     

Chloroplast-DNA variation in the wild and cultivated olives (Olea europaea L.) of Morocco

The male sterile plants that segregated in a BC₅F₂ of `C. sericeus × C. cajan var. TT-5' population were maintained by sib mating. The male sterile plants were crossed with ICPL-85012.Approximately 50% of the F₁ plants were sterile. F₂ plants derived from the fertile F₁ plants did not segregate for male sterility. The reciprocal hybrid i.e. ICPL-85012 × Fertile derivatives from C. sericeus × TT-5, did not express male sterility. However, among the 12 F₂ plant to row progenies, two segregated 25% male sterile plants and remaining 10 did not segregate. The segregation pattern in subsequent progenies revealed that the sterility was under control of a single recessive allele. Studies on the backcross and their BC₁F₂ and BC₁F₃progenies revealed another sterility gene which was found to be dominant in inheritance. This paper shows that what was thought to be cytoplasmic male sterility from C. sericeus cytoplasm is actually a single dominant gene possibly acting in concert with a single recessive gene to mimic cytoplasmic male sterility. This revised version was published online in July 2006 with corrections to the Cover Date.     

Relationships among ancestral species of sugarcane revealed with RFLP using single copy maize nuclear probes

Summary DNA restriction fragment length polymorphism (RFLP) analysis was performed on 50 wild and old cultivated sugarcane accessions. Ninety-four maize low copy nuclear DNA sequences of known chromosomal position were screened for hybridization to digested sugarcane genomic DNA blots. Seventy-five (80%) gave very strong hybridization signals and usually yielded many bands and detected profuse polymorphism. Twenty-nine probes and 36 probe/enzyme combinations were selected on the basis of the scorability of the banding profiles. A total of 1110 fragments were separately identified among the 50 genotypes. Multivariate analyses of the data allowed the separation of the three basic species, Saccharum spontaneum, S. robustum and S. officinarum, showed that S. spontaneum had structure which could be related to the geographic origin of the clones and supported current hypotheses on the origin of secondary species S. barberi and S. sinense. The use of more probes did not improve the resolution between the various species examined but identified a few key polymorphisms which were not accounted for by current phylogenetic hypotheses and can guide future analyses. RFLPs in sugarcane will be useful essentially for depicting the genomic constitution of modern varieties of interspecific origin.     

Genetic relationships between cultivated and wild olives of Corsica and Sardinia using RAPD markers

In order to ensure the genetic diversity of the Olea europaea complex,it is necessary to characterize the cultivated varieties and the wildpopulations. In the present study, we focused on the olives growing on twoMediterranean islands, Corsica and Sardinia. On these two islands, there areolives with many denominations, as well as forests of oleasters. Here, it wasproposed to determine the relationships among cultivated and wild olives.Some Italian denominations were studied in addition to assess the influenceof the mainland on the two islands in this respect.The 59 RAPD markers obtained showed the existence of manysynonymous, and homonymous. A dendrogram was constructed using theUPGMA method and a FCA was carried out. The results of these twoanalyses showed the existence of a genetic divergence between the oleastersand the cultivated varieties. They suggest that some of the Corsicanvarieties were probably selected from local wild forms, contrary to theSardinian varieties. They also show that there are feral forms growing onboth islands, which result from hybridization between oleasters andvarieties.     

Genetic analysis of phosphoglucoisomerase isozymes in cultivated and wild species of section Cepa in Allium

Phosphoglucoisomerase (PGI) was studied to establish the genetic system of the isozymes in section Cepa of Allium. The results of isozyme analyses using 15 cultivars and clones in two cultivated species A. fistulosum and A. cepa, eight strains in four wild species A. altaicum, A. galanthum, A. oschaninii and A. vavilovii and a total of 10 hybrids between A. fistulosum and A. cepa and between the cultivated and wild species revealed that: 1) PGI was a dimeric enzyme; 2) the two cultivated and four wild species had a common gene locus Pgi-1 where six alleles were identified; and 3) A. fistulosum had Pgi-1 ^F-1 and Pgi-1 ^F-2, A. cepa had Pgi-1 ^A-1 and Pgi-1 ^A-2, A. altaicum had Pgi-1 ^F-1, A. galanthum and A. vavilovii had Pgi-1 ^A-1, and A. oschaninii had Pgi-1 ^A-1, Pgi-1^O-1 and Pgi-1 ^O-1. The intra- and inter-specific polymorphisms of PGI isozymes are expected to be valuable tools for the genetics and practical utilization of the wild species in section Cepa.     

Species affinities between Cajanus cajan and some Atylosia species based on esterase isoenzymes

Summary Esterase isozymes were studied in seed extracts of Cajanus cajan and six Atylosia species by polyacrylamide gel electrophoresis and isoelectrofocusing. The isozyme patterns were stable and accession specific. Within the accessions of the Atylosia species, A. albicans and A. scarabaeoides showed three common bands indicating that they are more closely related to each other than to the other species. Of the accessions of Atylosia only A. cajanifolia shares the esterase isozyme of C. cajan and hence seems to be the closest wild relative of C. cajan.     

Inheritance pattern for pod lenghth and ovule number in wide crosses among Cajanus and Atylosia species

Summary Six interspecific/intergeneric F₂ populations involving two cultivars of C. cajan and five Atylosia species were scored for segregation patterns for pod length and ovule number. It was observed that for both characters the F₂ means and the ranges were correspondingly lower than the midparent values and the spread of the two parents. However, the intrageneric cross of A. lineata and A. scarabaeoides showed transgressive segregation for pod length and the F₂ mean and range were correspondingly larger than the midparent value and spread of the two parents, suggesting the usefulness of combining ability test for choice of suitable parents.