Search

Tomato leaf curl virus is a serious threat to an autumn-winter crop of tomato in North India, causing yield losses up to 90-100%. Therefore, nine resistant and one susceptible line (Punjab Chhuhara) of tomato were crossed in half-diallel fashion to develop 45 F1 hybrids. Parents and their hybrids were evaluated for yield and quality traits under natural epiphytotic field conditions. There were extensive differences in the performance of parental lines carrying similar and different resistance genes (Ty-X). Of three parental lines carrying Ty-2 gene, CLN 17 performed better than 2123D and 2123C in respect of mean and general combining ability (GCA) for total yield and fruit weight. Likewise, out of three parental lines incorporating two resistance genes (Ty-1 and Ty-2), the line CLN 138B had better mean values and GCA for total yield and fruit weight than CLN 138A and CLN 104. However, the parental line CLN 154 with three different resistance genes (Ty-1, Ty-2, Ty-3) showed the best GCA for total yield, and it was followed by genotype CLN 138B comprising of two resistance genes (Ty-1 and Ty-2). However, the parental lines carrying Ty-2 gene alone produced three useful hybrids expressing 19 to 28% heterosis over top parent for total yield. Four highly significant cross-combinations can be recommended for pedigree selection to develop superior inbred lines. The top parent CLN 154 yielding significantly higher than released varieties along with seven F1 hybrids manifesting 16 to 31% top parent heterosis for total yield can be recommended after multi-location evaluations. Overall, this study provides useful information on the successful leaf curl virus resistant gene combinations under the north-Indian conditions. [ABSTRACT FROM AUTHOR]

The present study examined the variation in survival, proportion of male morphotypes, female and male proportion, female reproductive status and tag losses in nine crosses from a complete (3 × 3) diallel mating of three populations of Macrobrachium rosenbergii in India. The populations originated from Gujarat (north-west), Kerala (south-west) and Odisha (east), representing different agro-ecological regions in India. Progeny from 60 families (4773 juveniles) were individually tagged and reared for 16-17 weeks in earthen ponds. Binary logistic regression was used to analyse the data. Survival rate was greatest (0.88) for Kerala × Odisha ( KO; the first letter represents the sire), whereas it was lowest (0.75) for both Kerala × Kerala ( KK) and Gujarat × Kerala ( GK). Significantly greater proportions of large male morphotypes were observed in KK cross and in combinations involving Kerala population. The highest proportion of immature females, as well as of non-berried females, was observed in the Odisha × Odisha ( OO) cross. Tag loss was greatest for KK (0.35) and lowest for GG (0.19). We found significant variations among crosses for all studied traits suggesting the possibility of including them in genetic improvement programmes of this species. [ABSTRACT FROM AUTHOR]