Eggplant (Solanum melongena L.) is a widely cultivated vegetable in India with enormous variability. Recent molecular techniques revealed three closely related but distinct Solanum species (S. melongena, S. incanum and S. insanum), with the Indian subcontinent being a domesticated centre. Spontaneous hybridization between S. insanum and S. melongena has led to the formation of naturally introgressed lines and limited studies are available to differentiate these genotypes using morphological key traits. Current study aimed to delineate naturally introgressed genotypes of Indian eggplant collections using morphological key traits for plant genetic resources (PGR) management and assess available genetic diversity. The study characterized a collection of 157 eggplant germplasm at ICAR-NBPGR, Regional Station, Kerala, and identified 30 naturally introgressed, 10 wild progenitors and 117 cultivated eggplants. The key morphological traits are prickliness (stem, petiole, calyx and pedicle), leaf base shape, fruit shape and size. Other fruit traits such as length, breadth and mesocarp texture could also provide some clues for delineating introgressed genotypes from S. insanum and S. melongena. Basic statistical analysis of six quantitative traits of 157 eggplant genotypes revealed the presence of considerable amount of variation (CV%) in which fruit length/breadth ratio showed higher variation (73.87) followed by fruit length (54.73) and average fruit weight (53.5). The frequency distribution of 14 qualitative traits revealed the presence of all character states among them. Key traits identified under study could provide clues to identify individual plants at field level to plant taxonomist/explorers and also to aid gene bank curators for PGR management.

Characterization of plant germplasm using molecular techniques is playing an increasingly important role in the management and utilization of plant genetic resources, but has its limitations in the screening of large numbers of accessions held in seed genebanks worldwide. Bulking individual plants from one accession or group to form a representative sample is a promising approach to widening the scope of a characterization, but it is not without technical problems in detecting genetic variation. This review was conducted to assess the technical pitfalls of bulking, and to evaluate the effectiveness of various bulking methods in the assessment of genetic variation and genetic relationships, and in the identification of plant germplasm. Clearly, some alleles, particularly those occurring at low frequency, may go undetected in a bulked sample, depending on the bulking methods and the molecular techniques used. As a result, genetic diversity estimates and genetic relationship inferences can be significantly biased. Germplasm identification may not be always reliable. Thus, it is imperative that the detection limit imposed by bulking be assessed for a newly initiated molecular germplasm characterization and bias be considered in interpretation of the resulting characterization data. Equally imperative is the need for continuous efforts of exploring efficient bulking procedures for the screening of large germplasm collections, particularly by the newly developed marker systems.