ABSTRACT

Forty eight potato genotypes were screened in two warm locations (Saminaka and Toro) and Kuru-a cool location all in the middle belt of Nigeria- in 1999 with a view to identifying progenitors with tolerance to heat stress. In each location the genotypes were laid out in a randomized complete block design with 3 replications and gross plot size of 9m2. Ten selected progenitors were used to constitute a crossing block in 2000 at Kuru. One hundred and forty nine hybrid progeny together with their parents and the check variety Desiree were evaluated in 2002 at Toro so as to identify and select transgressive segregates adapted to heat stress. The genotypes exhibited significant variability (p<O.001) for most traits assessed in all locations. There were also significant genotypes x environment interactions for most traits. Broadsence heritability for plant height, number of leaves, days to tuber initiation, days to maturity, and severity of early blight were high, while heritabilities for tuber yield per plant, and average tuber weight were relatively low. Correlation and regression analyses of tuber yield on other attributes showed in most cases positive relationships for plant emergence (P<0.01), number of stems per plant (P<0.05), plant height (P<0.01), number of leaves per plant (P<0.01), number of tubers per plant (P<0.05) and average tuber weight (P<0.05) and negative relationships for days to tuber initiation, and days to maturity. Partial correlation and path analysis revealed that number of tubers per plant, average tuber weight and to a lesser extent days to tuber initiation had the most direct effects on yield suggesting that these were important indices for tuber yield in potato. Twenty-seven hybrid genotypes exhibited better parent heterosis for tuber yield. Seventeen of these gave yields, which compared favourably with that of the check variety Desiree. These hybrids together with the eighteen parental genotypes, whose yields compared favourably with Desiree, are recommended for further evaluation as heat tolerant genotypes.