Studies on genetic variability and screening for fibre yield components and biotic stress factors in tossa jute (Corchorus olitorius L.) germplasm under Terai region of West Bengal

Abstract

A study was carried out with 75 germplasm accessions along with two checks (JRO-524 and JRO-204) of tossa jute (Corchorus olitorius L.), over two years (2013 and 2014) at Instructional Farm of Uttar Banga Krishi Viswavidyalaya, Pundibari, Cooch Behar, West Bengal, India, for eight characters, out of which four were fibre yield components (plant height, basal diameter, green weight and fibre yield) and the remaining four were biotic stress components (incidence of yellow mite, semi looper, stem rot and root rot), affecting the fibre yield. The germplasm accessions differed significantly for plant height, fibre yield, the incidence of yellow mite, semi looper and stem rot. The highest fibre yielding accession was OIN-142 (17.15 g/plant) which performed significantly better than the two checks. The mean fibre yield of all the genotypes indicated that the fibre yield loss was more due to the incidence of stem rot and root rot rather than yellow mite and semi looper. The germplasm accession OIN-06, OIN-15, OIN-03, OIN-17, OIN-01, OIN-617, OIN-559 and OEX-09 were found to be tolerant towards stem rot incidence and the root rot incidence was low in OIN-93, OIN-86, OIN-25 and OIN-60. The genotypes were distributed in 12 clusters as per D2 analysis, out of which cluster-XII had the highest number of genotypes (40) followed by cluster-III (10) and cluster-I (9). The remaining 9 clusters had 2 genotypes each. The highest inter-cluster D2 value was found between cluster-III and cluster-IV (33.99) and the highest intra-cluster D2 value was found in cluster-I (35.90). The contribution to total divergence was higher by the four biotic factors namely yellow mite, semi looper, stem rot and root rot as compared to the fibre yield components. The greater difference between the GCV and PCV for the eight characters under study revealed the major role played by the environment in the expression of these characters which were further substantiated by the low heritability and genetic advance of the characters. Among the biotic factors, stem rot and root rot were found to decrease fibre yield significantly with increase in their incidence level. It was the negative association of stem rot and root rot with plant height which was the deciding factor in reducing the fibre yield drastically. On screening of the germplasm accessions by giving proper weightage to tolerance, higher fibre yield and genetic divergence, it was found that the genotypes OIN-03, OIN-06, OIN-15 and OIN-17 in cluster-I and the genotypes OIN-86 and OIN-93 in cluster-XII may be used in a hybridization programme, to enhance fibre yield along with tolerance to the two major biotic stress components, namely stem rot and root rot.