A.D. Munshi

RAPD markers for resistance to Alternaria solani (early blight) in cultivated tomato (Lycopersicon esculentum L.)

Summary An attempt was made to understand the genetics of resistance against Alternaria solani in tomato (Lycopersicon esculentum L. cv. ‘Megha’), and to develop molecular markers as an effective strategy to assist in the transfer of resistance. The F2 segregation pattern of a resistant susceptible (‘Megha’ ‘Pusa Gaurav’) cross revealed the trait to be governed by two recessive genes. Efforts were made to develop RAPD markers to these two recessive resistance genes. Out of 14 random primers that were polymorphic between the parents, two primers (OPG19 and OPE11) produced unique amplicons 1,350 bp and 1,300 bp in length, respectively, that co-segregated in repulsion phase (i.e., were linked to the susceptible disease reaction in F2 bulks). Single marker analysis also revealed significant differences between the marker genotypes of 75 F2 individuals, indicating a linkage between the disease reaction and the individual markers OPG191350 and OPE111300. A best-fit ratio of 9:3:3:1 between the two markers, OPG191350 and OPE111300, revealed that they were not linked to each other, suggesting that the markers were linked to two different loci governing the resistance trait. This is the first report of RAPD markers for resistance to Alternaria solani in tomato.

Estimating combining ability for yield and yield contributing traits in cucumber

A study was conducted on a 8 × 8 diallel set of cucumber excluding reciprocals to find out the extent of combining ability for yield and yield attributing characters. The magnitudes of variance due to general as well as specific combining ability were highly significant indicating the importance of both additive and non-additive gene action. Among parents, gynoecious line GBS-1(P1) showed maximum g.c.a effects in desirable direction for node number of first female flower, days to first female flower anthesis, days to fruit set from opening of first female flower, days to first fruit harvest, number of fruits per plant, and vine length. The parent P5 (Pusa Uday) exhibited highest positive g.c.a effect for fruit length, fruit diameter, average fruit weight and yield per plant. In order of merit the gynoecious hybrids P1 × P5 (GBS-1 × Pusa Uday) and P1 × P6 (GBS-1 × Punjab Naveen) followed by monoecious hybrid P3 × P5 (GS-4 × Pusa Uday), which exhibited highest s.c.a effects for number of characters including total fruit yield per plant. In case of yield and other yield contributing characters like node number of first female flower, days to first female flower anthesis, days to fruit set from opening of first female flower, days to first fruit harvest, number of fruits per plant and yield per plant where specific combining ability component of variance (s2s) is more than general combining ability component of variance (s2g), which indicated preponderance of non-additive gene action. Hence, an improvement programme based on heterosis breeding would be appropriate for improving different traits under study.

Profiling of Mineral Nutrients and Variability Study in Pumpkin (Cucurbita moschata) Genotypes

The present investigation was carried out to estimate the extent genetic variability and character association for fruit yield and nine mineral nutrients (sodium, potassium, calcium, magnesium, iron, manganese, copper, zinc and selenium) in 76 genotypes of pumpkin during spring–summer season of the year 2014. The experimental results revealed significant differences among the genotypes for all the traits under study. Based on mean performance, the genotypes DPU-6, DPU-26 and DPU-51-3 were found most promising for different mineral nutrients and fruit yield per plant. Further, high heritability estimates coupled with high genetic gain were observed for all the traits under study, which indicated that these traits are under additive gene effects and are more reliable for effective selection. The correlation coefficients (phenotypic and genotypic) among different minerals along with fruit yield per plant depict that fruit yield per plant has significantly positive association with calcium (0.187 and 0.216) and magnesium (0.149 and 0.155) content. Path coefficient analysis at genotypic level revealed that iron has maximum positive direct effect (0.374) on marketable fruit yield per plant, followed by calcium (0.198) and copper (0.037). Besides, maximum positive indirect effect of manganese (0.331) and copper (0.265) via iron was observed on the fruit yield per plant.

Transferability of sponge gourd EST-SSR markers for genetic diversity assessment of Luffa species

Genetic diversity was studied in 47 Luffa genotypes with 17 EST-SSR primers, which generated 34 alleles, ranging 1–2 loci per primer. Forty seven genotypes were broadly classified into two different clusters. ClusterI comprised of genotypes DRG-98, Utkal Tripti, DRG-6, Sel-102, Pusa Nasdar, Pusa Nutan, Arka Sujat, DRG-73, DRG-61, DRG-42 and DRG-50, while Cluster II consisted of 36 genotypes, respectively. EST-SSR primer C90830_G3was found to be highly informative with PIC value of 0.3750. The variability in the species could be creditedto introgression and selection as a result of long history of cultivation under varied climatic conditions. Thepresent data provide adequate evidence of the applicability of EST-SSR markers for diversity analyses, cultivaridentification and characterization of the Luffa germplasm.

Combining ability for yield and yield related traits and its relationship with gene action in cucumber

Combining ability studies was carried out to estimate general combining ability of 8 parents and specific combining ability of 28 crosses of cucumber for nine quantitative traits in 8 × 8 half-diallel mating design excluding reciprocals. The result revealed that the magnitude of σ2s were higher than the σ2g, predictability ratio (PR) was found to be less than 0.5 and average degree of dominance (ADD) was found to be > 1 for all the traits, indicating predominance of non-additive gene action and scope of heterosis breeding in improvement of different traits. The estimates of gca effects of parents showed that DC-1 was good general combiner for earliness, days to first fruit set, days to first fruit harvest and fruit diameter. For fruit length and average fruit weight, Kalyanpur Green was good general combiner. Pusa Uday showed the highest significant gca effect for number of fruits per plant and total yield per plant and second highest significant gca for average fruit weight. Majority of cross combinations recorded high sca effects and per se performance due to low × low, low × high or high × low parental gca status. The hybrid Pusa Uday × DC-1 exhibited high significant sca effects for days to first female flower opening, days to first fruit set, days to first fruit harvest, average fruit weight, number of fruits per plant and total yield per plant followed by Pusa Uday × Kalyanpur Green, Punjab Naveen × DC-1 for total yield per plant, hence can be further exploited for commercial cultivation after multi-location testing.

Characterisation of cultivated breeding lines of eggplant (Solanum melongena L.) and related wild Solanum species from India

ABSTRACT Immature fruit of cultivated species of eggplant (Solanum melongena L.) are commonly used as a summer vegetable in India. Rich morphological variation exists among the cultivated species of eggplant in different growing regions of the country. We have characterised 24 breeding lines of Solanum spp., including 20 eggplant cultivars and four wild species of eggplant, based on 13 morphological characters using Mahalonabis D2 statistics. All 24 breeding lines of Solanum spp., including the 20 eggplant cultivars and four wild species, were grouped into four clusters by agglomerative clustering. Cluster II and Cluster IV contained the most accessions (eight each), while Cluster I and Cluster III had four accessions each. The highest inter-cluster (D2) distance (158.33) was observed between Cluster I and Cluster II, followed by Cluster I and Cluster III (108.48), and Cluster II and Cluster IV (102.96), which indicated that accessions in Cluster I and Cluster II were more divergent than those in the other clusters. The highest intra-cluster distance (5.80) was observed in Cluster IV, with eight genotypes, and the lowest intra-cluster distance (2.21) was observed in Cluster II, also with eight genotypes. The intra-cluster distances in all four clusters were lower than the inter-cluster distances, which indicated that genotypes within the same cluster were closely related. Genotypes in Cluster IV had the maximum number of flowers per cluster (3.63), the highest number of fruit per cluster (3.25), and number of fruit per plant (208.63), which revealed that genotypes could be selected from Cluster IV for these characters. The first three principal components (PC1, PC2, and PC3) accounted 73.99% of the total variation among the 24 genotypes. These phenotypic data increase the feasibility of prioritising breeding lines in a crossing programme based on the uniqueness of their desirable morphological traits.