Combining ability for earliness, grain yield and its components in some bread wheat genotypes under the normal and late sowing dates

Abstract EN

The present investigation was conducted at the Agricultural Research Station, El- Gemmeiza, Egypt, during the two winter seasons of 2014 / 2015 and 2015/2016.

A half diallel cross analysis was made among eight parental bread wheat cultivars to study mean squares, mean performance and combining ability for days to heading, days to maturity, number of spikes/plant, number of grains/ spike, 1000-grain weight, grain yield/plant and protein content.

The parents and F1 crosses were grown in a randomized complete block design with three replicates and were sown under two sowing dates i.e., 20th November (normal sowing date) and 20th December (late sowing date).

Mean square due to parents, F1 crosses as well as general combining ability (GCA) and specific combining ability (SCA) were highly significant for all studied characters under both sowing dates.

The ratio of GCA/SCA variance was more than unity for each of days to heading, days to maturity, number of spikes/plant, number of grains/spike and protein content under the both sowing dates as well as 1000-grain weight under the late sowing one.

Otherwise, it was less than unity for 1000-grain weight under the normal sowing date.

Moreover, GCA/SCA ratio was near to unity for grain yield/plant under the two sowing dates.

The parental wheat cultivar Gemmeiza 12 and F1 crosses (Gemmeiza 7 × Gemmeiza 11), (Gemmeiza 7× Gemmeiza 12), (Gemmeiza 7 × Sids 12), (Gemmeiza 7 × Misr 1), (Gemmeiza 9 × Gemmeiza 11), (Gemmeiza 11 × Giza 168), (Gemmeiza 11 × Giza 171), (Gemmeiza 12 × Sids 12) and (Misr 1 × Giza 171) exhibited the lowest reduction percentage and HSI values in wheat grain yield.

Therefore, these genotypes were more tolerant to heat stress as created by late sowing date.

Whereas, the local parental cultivars Gemmeiza 7 and Misr 1 as well as the F1 crosses (Gemmeiza 7 × Gemmeiza 9), (Gemmeiza 9 × Gemmeiza 12), (Gemmeiza 9 × Misr 1), (Gemmeiza 9 × Giza 168), (Gemmeiza 9 × Giza 171), (Gemmeiza 11 × Gemmeiza 12), (Gemmeiza 12 × Misr 1), (Sids 12 × Giza 171) and (Giza 168 × Giza 171) offered the highest reduction percentage and HSI values.

So, these genotypes were more sensitive to late sowing date (heat stress).

The cultivars Gemmeiza 7, Gemmeiza 11 and sides 12 were the best general combiners for earliness characters.

Meanwhile, the cultivar Giza 171 was the best combiner for grain yield and its components.

Fourteen crosses exhibited highly significant and positive SCA effects for grain yield/plant under both sowing dates and were obtained from the three possible combinations between their respective parents of high×high, high×low and low × low GCA effects.