Chapter 12, Problem 2ITD

Summary Introduction

To review:

There are many varieties of rice that are tolerant or intolerant to floods. The true breeding-intolerant varieties are $\text{IR42\hspace{0.17em}and\hspace{0.17em}NB}$, while the true breeding-tolerant varieties are FR13A, BKNFR, and Kurk. The tolerant ones are crossed with the intolerant strains, which results in the F₁ generation, and then they are crossed with their intolerant parent. The crosses are as follows:

1. Results of the cross ${\text{F}}_1$ to intolerant parent:	Number of plants
	Tolerant (Alive)	Intolerant (Dead)	Total
$\left({\text{F}}_1\text{\hspace{0.17em}of\hspace{0.17em}IR42}\times \text{FR13A}\right)\times \text{IR42}$	$14$	$17$	$31$
$\left({\text{F}}_1\text{\hspace{0.17em}of\hspace{0.17em}IR42}\times \text{BKNFR}\right)\times \text{IR42}$	$15$	$10$	$25$
$\left({\text{F}}_1\text{\hspace{0.17em}of\hspace{0.17em}NB}\times \text{Kurk}\right)\times \text{NB}$	$21$	$35$	$56$

On the basis of the data given for the various crosses, justify that it supports that tolerance is a dominant trait with the help of genotypes and phenotypes.

Introduction:

A cross used to determine the phenotypes of parents is known as a test cross. The parent plant is crossed with the plant with the recessive genotype. If the ratio of dominant to recessive in the progeny is 3:1, the parent is true-breeding dominant, whereas if the ratio is $2:2\text{\hspace{0.17em}or\hspace{0.17em}}1:1$, the parent is heterozygous.