Screening of F1 progeny for selection of superior hybrids in mulberry (Morus spp.) - A simple approach Part II: Screening of transplants in relation to seedling size

Abstract

In continuation of studies on the effect of seed size on growth, made under part-I, the effect of seed size and seedling size are studied jointly by size-grading of seedlings in to three classes under each seed-size class, with 2700 F1 promising genotypes of two crosses. The combined population was screened in two steps, adopting comparison tree method. In step-1, transplanted seedlings (transplants) with closer spacing were screened based on shoot weight for a period of two crops and 487 genotypes were shortlisted based on higher superiority percent. In step-2, these 487 transplants were replanted with wider spacing and screened using three parameters for a period of four crops. In each crop, the genotypes which showed superiority percent value more than Minimum Selection Standard for the parameters studied, were shortlisted. Among 22 genotypes shortlisted finally, 18 have come from large seed-size class and the remaining four are also from long seedling-size class of medium seed-size class. This clearly established the importance of size-grading of seeds and seedlings in screening process. As the chance of getting any promising genotype from small seeds is remote they could be rejected before sowing and as it is also true with small seedlings they could be rejected at nursery stage screening. The tracking of juvenile performance of shortlisted genotypes indicated that, shoot length and root collar diameter are more reliable parameters for assessing the growth of seedlings at nursery. Comparison tree method is found to be highly useful for shortlisting of transplants in mulberry